DESCRIPTION
Title of Invention
ELECTRIC-VEHICULAR CHARGE AND DISCHARGE DEVICE
Technical Field
[00011
The present invention relates to electric-vehicular charge and discharge devices and
particular to an electric-vehicular charge and discharge device to charge secondary
batteries of electric vehicles such as electric automobiles and allow the secondary
batteries to discharge stored electric charges to supply electricity to loads.
Background Art
[00021
Document 1 (JP 2010-239827 A) discloses an electric-automotive charger for charging
secondary batteries of electric vehicles such as electric automobiles.
[00031
The prior art disclosed in document 1 teaches that a communication earth line
connects a negative electrode of a control system power source of an
electric-automotive charger to an automotive body to enable data communication
between the charger and the electric automobile and this communication earth line is
grounded through a grounding line.
[00041
The electric-automotive charger includes a ground fault detector. The ground fault
detector includes a series circuit of resistors with the same resistance, a current
detector, and a controller. The series circuit is connected between positive and
negative charge lines. The current meter sequentially outputs a measurement of a
DC current flowing through the grounding line grounding a point between the
resistors. The controller compares the measurement of the current from the current
meter with a threshold to detect a ground fault in the electric-automotive charger and
a ground leakage in the electric automobile.
[00051
The aforementioned prior art can detect both a ground fault in the electric-automotive
charger and a ground leakage in the electric automobile while the electric automobile
is charged.
[00061
Recently, there have been developed systems for supply electricity from secondary
batteries of electric automobiles to loads other than the electric automobile (e.g.,
electric appliances in residences), so called V2H (Vehicle-to-Home) system.
[00071
However, when the electric automobile supplies electricity to loads outside the
automotive body, a ground fault may occur in a cable (charge and discharge cable)
connecting the electric-automotive charge and discharge device to the electric
automobile. The ground fault detector of the prior art disclosed in document 1
cannot detect such a ground fault. In more detail, in the prior art disclosed in
document 1, the secondary battery is not grounded, and thus the ground fault detector
can detect a ground leakage from the secondary battery to the automotive body but
cannot detect a ground fault in a cable outside the automotive body.
[00081
To safely supply electricity from the secondary batteries of the electric vehicles (such
as electric automobiles) to the loads outside the electric vehicles, it is necessary to
enable detection of a ground fault which has occurred in a load outside the electric
automobile (especially, a cable) while the secondary battery supplies electricity.
Summary of Invention
[00091
In view of the above insufficiency, the present invention has aimed to improve the
safety in power supply from a secondary battery of an electric vehicle to a load outside
the electric vehicle.
[00101
The electric-vehicular charge and discharge device of the first aspect in accordance
with the present invention includes a power converter, a grounding unit, a ground
fault detector, and a switcher. The power converter is interposed between an
external circuit and a pair of power terminals of a secondary battery unit provided to
an electric vehicle, and is configured to convert power between the external circuit
and the secondary battery unit. The grounding unit is configured to connect at least
one of the pair of power terminals of the secondary battery unit to a grounding point
to be connected to the power converter. The ground fault detector is configured to
determine whether a ground fault has occurred in a power supply path between the
power converter and the secondary battery unit. The switcher is configured to, when
the ground fault detector determines that a ground fault has occurred in the power
supply path, separate the secondary battery unit from the power supply path.
Loo1 1.1
According to the electric-vehicular charge and discharge device of the second aspect in
accordance with the present invention, in addition to the first aspect, the grounding
unit is configured to, when a ground fault has occurred in the power supply path,
connect at least one of the pair of power terminals of the secondary battery unit to the
grounding point so as to cause a difference between a current flowing through one of
the pair of power terminals and another current flowing through the other of the pair
of power terminals.
[00121
According to the electric-vehicular charge and discharge device of the third aspect in
accordance with the present invention, in addition to the first or second aspect, the
grounding unit includes a grounding line for connecting at least one of the pair of
power terminals of the secondary battery unit to the grounding point.
[00131
According to the electric-vehicular charge and discharge device of the fourth aspect in
accordance with the present invention, in addition to the third aspect, the grounding
unit includes a series circuit of two impedance components between the pair of power
terminals of the secondary battery unit. The grounding line connects a connection
point of the two impedance components to the grounding point. The two impedance
components have the same impedance.
[00141
According to the electric-vehicular charge and discharge device of the fifth aspect in
accordance with the present invention, in addition to the third or fourth aspect, the
electric-vehicular charge and discharge device further includes a selector. The
selector is configured to separate the grounding line from the grounding point while
the secondary battery unit is charged, and to connect the grounding line to the
grounding point and separate the power converter from the grounding point while the
secondary battery unit discharges.
[OO15 1
According to the electric-vehicular charge and discharge device of the sixth aspect in
accordance with the present invention, in addition to any one of the first to fifth
aspects, the electric-vehicular charge and discharge device further includes a cable
connecting the power converter to the pair of power terminals of the secondary battery
unit. The grounding unit and the ground fault detector are provided to the cable.
[00 161
According to the electric-vehicular charge and discharge device of the seventh aspect
in accordance with the present invention, in addition to any one of the first to fifth
aspects, the electric-vehicular charge and discharge device further includes: a cable
connecting the power converter to the pair of power terminals of the secondary battery
unit; and a plug connector configured to be detachably connected to a receptacle
connector of the electric vehicle. The cable has one end connected to the power
converter and the other end connected to the plug connector. The grounding unit
and the ground fault detector are provided to the plug connector.
[OO17 1
According to the electric-vehicular charge and discharge device of the eighth aspect in
accordance with the present invention, in addition to any one of the first to fifth
aspects, the electric-vehicular charge and discharge device further includes a cable
connecting the power converter to the pair of power terminals of the secondary battery
unit. The ground fault detector is provided to the cable. The grounding unit is
provided to the electric vehicle.
100 181
According to the electric-vehicular charge and discharge device of the ninth aspect in
accordance with the present invention, in addition to any one of the first to fifth
aspects, the grounding unit and the ground fault detector are provided to the electric
vehicle.
[00191
According to the electric-vehicular charge and discharge device of the tenth aspect in
accordance with the present invention, in addition to any one of the first to ninth
aspects, the ground fault detector is configured to, when acknowledging that a
difference between magnitudes of a current flowing through one of the pair of power
terminals and another current flowing through the other of the pair of power
terminals exceeds a predetermined threshold, determine that a ground fault has
occurred in the power supply path.
Lo0201
According to the electric-vehicular charge and discharge device of the eleventh aspect
in accordance with the present invention, in addition to any one of the first to tenth
aspects, the power converter is configured to perform a first conversion process to
convert power from the external circuit into predetermined first power and supply the
resultant first power to the pair of power terminals of the secondary battery unit, and
to perform a second conversion process to convert power from the pair of power
terminals of the secondary battery unit into predetermined second power and supply
the resultant second power to the external circuit.
[00211
According to the electric-vehicular charge and discharge device of the twelfth aspect
in accordance with the present invention, in addition to any one of the first to
eleventh aspects, the external circuit is an AC circuit connected to an AC power
source. The secondary battery unit includes a secondary battery. The pair of power
terminals are positive and negative electrodes of the secondary battery. The power
converter includes an AC/DC converter configured to convert AC power from the
external circuit into DC power suitable for the secondary battery unit and convert DC
power from the secondary battery unit into AC power suitable for the external circuit.
According to the electric-vehicular charge and discharge device of the thirteenth
aspect in accordance with the present invention, in addition to any one of the first to
eleventh aspects, the external circuit is an AC circuit connected to an AC power
source. The secondary battery unit includes a secondary battery and a charge and
discharge unit including the pair of power terminals. The charge and discharge unit
is configured to perform a charge process to charge the secondary battery with AC
power received by the pair of power terminals and to perform a discharge process to
convert power from the secondary battery into AC power and output the resultant AC
power from the pair of power terminals. The power converter includes an insulation
ACIAC converter configured to convert AC power from the external circuit into AC
power suitable for the secondary battery unit and convert AC power from the
secondary battery unit into AC power suitable for the external circuit.
Lo0231
According to the electric-vehicular charge and discharge device of the fourteenth
aspect in accordance with the present invention, in addition to any one of the first to
thirteenth aspects, the electric vehicle includes a switch for separation of the
secondary battery unit from the power supply path. The switcher is configured to,
when the ground fault detector determines that a ground fault has occurred in the
power supply path, control the switch to separate the secondary battery unit from the
power supply path.
Lo0241
According to the electric-vehicular charge and discharge device of the fifteenth aspect
in accordance with the present invention, in addition to the thirteenth aspect, the
charge and discharge unit includes a switch for separation of the secondary battery
unit from the power supply path. The switcher is configured to, when the ground
fault detector determines that a ground fault has occurred in the power supply path,
control the switch to separate the secondary battery unit from the power supply path.
Brief Description of the Drawings
Lo0251
FIG. 1 is a block diagram illustrating the electric-vehicular charge and discharge
device of the first embodiment;
FIG. 2 is a block diagram illustrating the electric-vehicular charge and discharge
device of the first embodiment;
FIG. 3 is a block diagram illustrating the electric-vehicular charge and discharge
device of the second embodiment;
FIG. 4 is a block diagram illustrating the electric-vehicular charge and discharge
device of the second embodiment;
FIG. 5 is a block diagram illustrating the electric-vehicular charge and discharge
device of the third embodiment;
FIG. 6 is a block diagram illustrating the electric-vehicular charge and discharge
device of the third embodiment;
FIG. 7 is a block diagram illustrating the electric-vehicular charge and discharge
device of the fourth embodiment;
FIG. 8 is a block diagram illustrating the electric-vehicular charge and discharge
device of the fourth embodiment;
FIG. 9 is a block diagram illustrating the electric-vehicular charge and discharge
device of the fifth embodiment;
FIG. 10 is a block diagram illustrating the electric-vehicular charge and discharge
device of the fifth embodiment;
FIG. 11 is a block diagram illustrating the electric-vehicular charge and discharge
device of the sixth embodiment; and
FIG. 12 is a block diagram illustrating the electric-vehicular charge and discharge
device of the sixth embodiment.
Description of Embodiments
Lo0261
The following detailed explanations referring drawings are made to embodiments of
charge and discharge devices for electric automobiles in accordance with the present
invention. Electric-vehicular charge and discharge devices according to the present
invention are not limited to the charge and discharge devices for electric automobiles,
but may be applicable to charge and discharge devices for electric vehicles including
electric automobiles.
100271
(FIRST EMBODIMENT)
As shown in FIGS. 1 and 2, a power distribution board (e.g., a residence power
distribution board) 6 is connected to an electricity system 5. A load (e.g., an electric
appliance in a residence) 7 and an electric-vehicular charge and discharge device
(hereinafter, referred to as "charge and discharge device") of the present embodiment
are connected to the electricity system 5 via the power distribution board 6 to receive
power from the electricity system 5.
As described above, the charge and discharge device of the present embodiment is
connected to an external circuit (the residence power distribution board 6 and the load
7). The electricity system 5 of the present embodiment is a system for AC power
supply. In summary, the external circuit is an AC circuit to be connected to an AC
power source (electricity system 5).
[00291
The charge and discharge device of the present embodiment is used for charge and
discharge of a secondary battery unit 44 provided to an electric vehicle (electric
automobile) 4.
[00301
The secondary battery unit 44 includes a secondary battery 40. The secondary
battery unit 44 further includes a pair of power terminals. The pair of power
terminals are used for charge and discharge of the secondary battery unit 44. The
pair of power terminals of the present embodiment are positive and negative
electrodes of the secondary battery 40.
[003 11
The charge and discharge device of the present embodiment includes a power
converter, a grounding unit, a ground fault detector, and a switcher.
LO0321
The power converter is interposed between the external circuit and the pair of power
terminals of the secondary battery unit 44 of the electric vehicle (electric automobile)
4, and is configured to convert power between the external circuit and the secondary
battery unit 44.
100331
The grounding unit connects at least one of the pair of power terminals of the
secondary battery unit 44 to a grounding point 8 to be connected to the power
converter.
roo341
The ground fault detector determines whether a ground fault has occurred in an
electric path (power supply path) between the power converter and the secondary
battery unit 44.
LO0351
The switcher is configured to separate the secondary battery unit 44 from the power
supply path when the ground fault detector determines that a ground fault has
occurred in the power supply path.
[00361
Hereinafter, the charge and discharge device of the present embodiment is described
in more detail.
Lo0371
FIGS. 1 and 2 show that the charge and discharge device of the present embodiment
includes a power conversion device 1, a cable 2, and a connector 3.
[00381
The cable 2 and the connector 3 constitute part of the electric path (power supply
path) between the power converter and the secondary battery unit 44.
[00391
The power conversion device 1 includes: a power conversion unit 10 serving as the
power converter; two impedance elements 11A and 11B; and a ground leakage circuit
breaker 13.
too401
The power conversion unit 10 is configured to perform bidirectional (reversible)
conversion between AC power and DC power. The power conversion unit 10 converts
AC power supplied from the electricity system 5 into DC power and supplies the
resultant DC power to the electric automobile 4. The power conversion unit 10
converts DC power supplied from the electric automobile 4 (secondary battery 40) into
AC power and supplies the resultant AC power to the load 7.
[00411
The power conversion unit 10 is configured to perform a first conversion process
(charge process) to convert power (AC power in the present embodiment) from the
external circuit into predetermined first power (DC power in the present embodiment)
and supply the resultant first power to the pair of power terminals of the secondary
battery unit 44. The power conversion unit 10 is configured to perform a second
conversion process (discharge process) to convert power (DC power in the present
embodiment) from the pair of power terminals of the secondary battery unit 44 into
predetermined second power (AC power in the present embodiment) and supply the
resultant second power to the external circuit. The first power is determined
according to the specification of the secondary battery 40 of the secondary battery unit
44. The second power is determined according to the specification of the electricity
system 5.
[00421
The power conversion unit 10 of the present embodiment includes an ACLDC
converter configured to convert AC power from the external circuit into DC power
suitable for the secondary battery unit 44 and convert DC power from the secondary
battery unit 44 into AC power suitable for the external circuit.
100431
The two impedance elements 11A and 11B are resistors having the same resistance.
The two impedance elements 11A and 11B are connected in series with each other
between DC side terminals of the power conversion unit 10.
100441
A connection point 11C of the impedance elements 11A and 11B is grounded via a
grounding line 12. In short, as shown in FIGS. 1 and 2, the connection point 11C is
connected to the grounding point 8 by the grounding line 12.
[00451
The ground leakage circuit breaker 13 compares a DC current (outward charge
current) outputted via the DC side positive terminal of the power conversion unit 10
with a DC current (return charge current) returned to the DC side negative terminal
of the power conversion unit 10. When a difference between these DC currents
exceeds a prescribed threshold, the ground leakage circuit breaker 13 determines that
a ground leakage has occurred, and breaks the electric path.
[00461
The cable 2 is a multicore cable including: a pair of power supply lines 20 and 21 for
supplying a DC current (a charge current and a discharge current); a grounding line
22 having one end grounded together with the connection point 11C of the impedance
elements 11A and 11B; a communication line (not shown); and an insulating sheath
(not shown) covering around these lines. The cable 2 has one end connected to the
power conversion device 1 (the ground leakage circuit breaker 13) and the other end
connected to the connector 3.
LO0471
The connector 3 is a plug connector configured to be detachably connected to a
receptacle connector 42 provided to the electric automobile 4. The connector 3
includes a ground fault detection unit 30 and impedance elements 31A and 31B. The
ground fault detection unit 30 and the impedance elements 31A and 31B are housed
in a casing of the connector 3.
[00481
These two impedance elements 31A and 31B are resistors having the same resistance.
These two impedance elements 31A and 31B are connected in series with each other
between terminals of the ground fault detection unit 30 to be connected to the electric
automobile 4. The grounding line 22 of the cable 2 is connected to a connection point
31C of the impedance elements 31A and 31B. In the present embodiment, the
impedance elements 31A and 31B and the grounding line 22 constitute the grounding
unit.
[00491
In the charge and discharge device of the present embodiment, the grounding unit
includes the two impedance elements 31A and 31B and the grounding line 22. The
two impedance elements 31A and 31B have the same impedance (resistance) and are
connected in series between the both electrodes of the secondary battery 40. The
grounding line 22 connects the connection point 31C of the impedance elements 31A
and 31B to the grounding point 8 of the power converter (power conversion unit) 10.
[00501
In other words, the grounding unit includes the grounding line 22 connecting at least
one of the pair of power terminals of the secondary battery unit 44 to the grounding
point 8.
[00511
Additionally, the grounding unit includes the series circuit of two impedance
components (impedance elements) 31A and 31B between the pair of power terminals
of the secondary battery unit 44. The grounding line 22 connects the connection
point 31C of the two impedance components (impedance elements) 31A and 31B to the
grounding point 8. The two impedance components (impedance elements) 31A and
31B have the same impedance.
[00521
In the present embodiment, each of the two impedance components is constituted by a
single impedance element. However, each impedance component is constituted by
not a single impedance element but two or more impedance elements. In brief, it is
only necessary that the two impedance components have the same impedance
(synthetic impedance).
[00531
The ground fault detection unit 30 measures currents individually flowing through
the power supply lines 20 and 21 of the cable 2, and, when a difference between the
magnitudes of the currents individually flowing through the power supply lines 20
and 21 is greater than a predetermined threshold, determines that a ground fault has
occurred. In brief, the ground fault detection unit 30 is configured to, when
acknowledging that a difference between the magnitudes of the current flowing
through one of the pair of power terminals and another current flowing through the
other of the pair of power terminals exceeds the predetermined threshold, determine
that a ground fault has occurred in the power supply path.
[00541
When detecting the ground fault, the ground fault detection unit 30 opens contacts 41
and 41 respectively interposed between one electrode of the secondary battery 40 and
the receptacle connector 42 and between the other electrode of the secondary battery
40 and the receptacle connector 42.
[00551
In summary, the ground fault detection unit 30 of the present embodiment serves as
the ground fault detector and the switcher.
[00561
Note that, these contacts 41 and 41 are provided to the electric automobile 4 in
advance for the purpose of protection of the secondary battery 40 from charging
abnormality. Contacts to be controlled by the ground fault detection unit 30 may be
provided to the connector 3.
[00571
In the present embodiment, the electric vehicle 4 includes the switch (contact) 41 for
separation of the secondary battery unit 44 from the power supply path (in particular,
the power supply lines 20 and 21 of the cable 2).
[00581
The ground fault detection unit (switcher) 30 is configured to, when determining that
a ground fault has occurred in the power supply path, control the switch 41 to
separate the secondary battery unit 44 from the power supply path.
[00591
Next, the operations of the charge and discharge device of the present embodiment
are described below.
[OO~O]
In the process of charging the electric automobile 4, AC power supplied from the
electricity system 5 is converted into DC power by the power conversion unit 10 and
the DC power is supplied to the electric automobile 4 through the cable 2 and the
connector 3. Thereby, the secondary battery 40 of the electric automobile 4 is
charged.
1006 11
When a ground fault has occurred in the power supply line 20 or 21 of the cable 2
during charging, the magnitude of the DC current outputted from the DC side positive
terminal of the power conversion unit 10 and flowing into the DC side negative
terminal of the power conversion unit 10 decreases by a magnitude of the ground fault
current.
[00621
Accordingly, the ground leakage circuit breaker 13 of the power conversion device 1
detects such a decrease in the DC current caused by the ground fault current, and
breaks the electric path. Hence, improvement of safety in charging is achieved.
LO0631
The following explanation is made to the operation of the charge and discharge device
of the present embodiment in supplying from the electric automobile 4 (discharging by
the secondary battery 40).
roo641
In the process of supplying electricity from the electric automobile 4, DC power
discharged from the secondary battery 40 is supplied to the power conversion device 1
through the connector 3 and the cable 2 and then converted into AC power by the
power conversion unit 10 of the power conversion device 1. The AC power converted
by the power conversion unit 10 is supplied to the load 7 through the power
distribution board 6.
[0065l
For example, it is assumed that a ground fault has occurred in the power supply line
20 of the cable 2 during the process of supplying electricity from the electric
automobile 4. According to this assumption, as indicated by the dashed arrow in FIG.
1, a ground fault current with the magnitude of Ig flows from the positive electrode of
the secondary battery 40 to a ground fault point (X) through the power supply line 20
of the cable 2.
[00661
Further, this ground fault current with the magnitude of Ig is divided into half
ground fault currents with the same magnitude of IgI2. One of the half ground fault
current with the magnitude of Ig12 flows to the negative electrode of the secondary
battery 40 through the grounding line 22 and the impedance element 31B, and the
other flows to the negative electrode of the secondary battery 40 through the
grounding line 12, the impedance element 11B, the ground leakage circuit breaker 13,
and the power supply line 21 of the cable 2.
When a difference between the magnitude of I of the current flowing through one
power supply line 20 and the magnitude of I-Igl2 of the current flowing through the
other power supply line 21, that is, the magnitude of Igl2 of the half ground fault
current is greater the predetermined threshold, the ground fault detection unit 30
determines that the ground fault has occurred, and opens the contact 41.
[00681
For example, it is assumed that a ground fault has occurred in the power supply line
21 of the cable 2 during the process of supplying electricity from the electric
automobile 4. According to this assumption, as indicated by the dashed arrow in FIG.
2, a ground fault current with the magnitude of Ig flows from the negative output
terminal of the power conversion device 1 to a ground fault point (X) through the
power supply line 21 of the cable 2.
[00691
Further, this ground fault current with the magnitude of Ig is divided into half
ground fault currents with the same magnitude of Igl2. One of the half ground fault
current with the magnitude of Igl2 flows to the negative electrode of the secondary
battery 40 through the grounding line 22 and the impedance element 31B, and the
other flows to the negative electrode of the secondary battery 40 through the
grounding line 12, the impedance element 11B, the ground leakage circuit breaker 13,
and the power supply line 21 of the cable 2.
[00701
When a difference between the magnitude of I of the current flowing through one
power supply line 20 and the magnitude of I-Igl2 of the current flowing through the
other power supply line 21, that is, the magnitude of Igl2 of the half ground fault
current is greater the predetermined threshold, the ground fault detection unit 30
determines that the ground fault has occurred, and opens the contact 41.
[0071.1
The charge and discharge device (electric-vehicular charge and discharge device) of
the present embodiment described above is an electric-vehicular charge and discharge
device configured to charge the secondary battery 40 of the electric vehicle 4 and allow
the secondary battery 40 to discharge stored electric charges to supply electricity to
the load 7 outside the electric vehicle 4. The charge and discharge device of the
present embodiment includes: the power converter (power conversion unit 10)
configured to perform bidirectional conversion between AC power and DC power; the
cable 2 constituting part of the electric path (power supply path) between the power
converter (power conversion unit 10) and the secondary battery 40; the grounding unit
configured to connect at least one of the electrodes of the secondary battery 40 to the
grounding point 8 of the power converter (power conversion unit 10); the ground fault
detector (ground fault detection unit 30) which is on the DC side of the power
converter (power conversion unit 10) and is configured to detect a ground fault in the
electric path while DC power is supplied from the secondary battery 40 to the power
converter (power conversion unit 10); and the switcher (ground fault detection unit
30) configured to open the contact 41 interposed in the electric path in response to
detection of a ground fault by the ground fault detector (ground fault detection unit
30).
[00721
In other words, the charge and discharge device of the present embodiment includes
the power converter (power conversion unit lo), the grounding unit, the ground fault
detector (ground fault detection unit 30), and the switcher (ground fault detection unit
30). The power converter (power conversion unit 10) is interposed between the
external circuit and the pair of power terminals of the secondary battery unit 44
provided to the electric vehicle 4, and is configured to convert power between the
external circuit and the secondary battery unit 44. The grounding unit is configured
to connect at least one of the pair of power terminals of the secondary battery unit 44
to the grounding point 8 to be connected to the power converter (power conversion
unit 10). The ground fault detector (ground fault detection unit 30) is configured to
determine whether a ground fault has occurred in the power supply path between the
power converter (power conversion unit 10) and the secondary battery unit 44. The
switcher (ground fault detection unit 30) is configured to, when the ground fault
detector (ground fault detection unit 30) determines that a ground fault has occurred
in the power supply path, separate the secondary battery unit 44 from the power
supply path.
[00731
Further in the charge and discharge device of the present embodiment, the grounding
unit (ground fault detection unit 30) is configured to, when a ground fault has
occurred in the power supply path between the power converter (power conversion
unit 10) and the secondary battery unit 44, connect at least one of the pair of power
terminals of the secondary battery unit 44 to the grounding point 8 so as to cause a
difference between a current flowing through one of the pair of power terminals and
another current flowing through the other of the pair of power terminals.
[0074:]
Further in the charge and discharge device of the present embodiment, the grounding
unit includes the grounding line 21 for connecting at least one of the pair of power
terminals of the secondary battery unit 44 to the grounding point 8.
[00751
Further in the charge and discharge device of the present embodiment, the ground
fault detector (ground fault detection unit 30) is configured to, when acknowledging
that a difference between magnitudes of a current flowing through one of the pair of
power terminals and another current flowing through the other of the pair of power
terminals exceeds a predetermined threshold, determine that a ground fault has
occurred in the power supply path.
[0076]
Further in the charge and discharge device of the present embodiment, the power
converter (power conversion unit 10) is configured to perform the first conversion
process (charge process) to convert power (in the present embodiment, AC power) from
the external circuit into the predetermined first power (in the present embodiment,
DC power) and supply the resultant first power to the pair of power terminals of the
secondary battery unit 44, and to perform the second conversion process (discharge
process) to convert power (in the present embodiment, DC power) from the pair of
power terminals of the secondary battery unit 44 into the predetermined second
power (in the present embodiment, AC power) and supply the resultant second power
to the external circuit.
[00771
Further in the charge and discharge device of the present embodiment, the external
circuit is an AC circuit connected to the AC power source (electricity system 5). The
secondary battery unit 44 includes the secondary battery 40. The pair of power
terminals are the positive and negative electrodes of the secondary battery 40. The
power converter includes the ACIDC converter configured to convert AC power from
the external circuit into DC power suitable for the secondary battery unit 44 and
convert DC power from the secondary battery unit 44 into AC power suitable for the
external circuit.
[0078]
Further in the charge and discharge device of the present embodiment, the grounding
unit includes the two impedance elements 31A and 31B and the grounding line 22.
The two impedance elements 31A and 31B have the same impedance and are
connected in series between the electrodes of the secondary battery 40. The
grounding line 22 connects the connection point 31C of the impedance elements 31A
and 31B to the grounding point 8 of the power converter (power conversion unit 10).
[00791
In other words, in the charge and discharge device of the present embodiment, the
grounding unit includes the series circuit of the two impedance components
(impedance elements) 31A and 31B between the pair of power terminals of the
secondary battery unit 44. The grounding line 22 connects the connection point 31C
of the two impedance components (impedance elements) 31A and 31B to the
grounding point 8. The two impedance components (impedance elements) 31A and
31B have the same impedance.
[0080]
As described above, in the present embodiment, the grounding line 22 connects the
connection point 31C of the impedance elements 31A and 31B is connected to the
grounding point 8 of the power conversion unit 10, and the ground fault detection unit
30 provided between the power conversion unit 10 and the impedance elements 31A
and 31B opens the contact 41 when detecting a ground fault occurring in at least one
of the power supply lines 20 and 21 of the cable 2.
LO08 1.1
Accordingly, even while the electric automobile 4 discharges, the charge and discharge
device of the present embodiment opens the contact 41 interposed in the electric path
to interrupt a DC current (charge current) when detecting a ground fault in the cable
2. Consequently, it is possible to improve the safety in supply of electricity from the
secondary battery 40 of the electric automobile 4 to the load 7.
[00821
As described above, the charge and discharge device of the present embodiment has
an advantageous effect on improvement of the safety in supply of power from the
secondary battery 40 provided to the electric vehicle 4 to the load 7 outside the electric
vehicle 4.
[0083l
Note that, in the present embodiment, the DC side terminals of the power conversion
unit 10 are grounded by use of the impedance elements 11A and 11B with the same
impedance, and the both electrodes of the secondary battery 40 are grounded by use of
the impedance elements 31A and 31B with the same impedance. The DC side
terminals of the power conversion unit 10 may be grounded directly without using
impedance elements. The both electrodes of the secondary battery 40 may be
grounded directly without using impedance elements.
[00841
However, when the grounding is made by use of the impedance elements 11A and 11B
and the other impedance elements 31A and 31B, a voltage of the cable 2 to the ground
can halve compared with a case in which no impedance element is used.
roo851
Further in the present embodiment, the grounding line 22 of the cable 2 constitutes
the grounding unit, and the ground fault detection unit 30 serving as the ground fault
detector and the impedance elements 31A and 31B constituting the grounding unit
are housed in the casing of the connector 3. Thereby, the grounding unit and the
ground fault detector are integrated with the cable 2.
[00861
Hence, in contrast to a case in which the electric automobile 4 includes the grounding
unit and the ground fault detector, it is possible to easily achieve the improvement of
the safety at lowered cost.
[0087l
Note that, the ground fault detection unit 30 and the impedance elements 31A and
31B may be integrated with the cable 2 in such a manner that the ground fault
detection unit 30 and the impedance elements 31A and 31B are housed in a
box-shaped casing interposed in the cable 2.
[0088l
Note that, the ground fault detection unit 30 serving as the ground fault detector may
be integrated with the cable 2 and the impedance elements 31A and 31B constituting
the grounding unit may be included in the electric automobile 4.
[00891
In the charge and discharge device of the present embodiment, the grounding unit
and the ground fault detector may be integrated with the cable 2. In other words,
the charge and discharge device of the present embodiment further includes the cable
2 connecting the power converter bower conversion unit 10) to the pair of power
terminals of the secondary battery unit 44. The grounding unit and the ground fault
detector are provided to the cable 2.
[00901
Alternatively, in the charge and discharge device of the present embodiment, the
cable 2 may include the plug connector (connector) 3 to be detachably connected to the
receptacle connector provided to the electric vehicle 4. The grounding unit and the
ground fault detector may be integrated with the plug connector 3. In other words,
the charge and discharge device of the present embodiment further includes: the cable
2 connecting the power converter (power conversion unit 10) to the pair of power
terminals of the secondary battery unit 44; and the plug connector 3 configured to be
detachably connected to the receptacle connector of the electric vehicle 4. The cable 2
has one end connected to the power converter (power conversion unit 10) and the
other end connected to the plug connector 3. The grounding unit and the ground
fault detector are provided to the plug connector 3.
[00911
Alternatively, in the charge and discharge device of the present embodiment, the
cable 2 may include the plug connector (connector) 3 to be detachably connected to the
receptacle connector provided to the electric vehicle 4. The ground fault detector
may be integrated with the cable 2 or the plug connector 3, and the grounding unit
may be included in the electric vehicle 4. In other words, the charge and discharge
device of the present embodiment further includes the cable 2 connecting the power
converter (power conversion unit 10) to the pair of power terminals of the secondary
battery unit 44. The ground fault detector is provided to the cable 2, and the
grounding unit is provided to the electric vehicle 4.
[00921
Alternatively, in the charge and discharge device of the present embodiment, the
grounding unit and the ground fault detector may be included in the electric vehicle 4.
In other words, in the charge and discharge device of the present embodiment, the
grounding unit and the ground fault detector are provided to the electric vehicle 4.
[00931
The present embodiment utilizes the contacts 41 and 41 provided to the electric
automobile 4 in advance for the purpose of protection of the secondary battery 40 from
charging abnormality. Accordingly, it is possible to simplify the structure of the
switcher and lower the cost of the switcher.
[00941
As described above, in the charge and discharge device of the present embodiment,
the switcher (ground fault detection unit 30) is configured to open the contact 41
provided to the electric vehicle 4.
[00951
In other words, the electric vehicle 4 includes the switch (contact) 41 for separation of
the secondary battery unit 44 from the power supply path. The switcher (ground
fault detection unit 30) is configured to, when the ground fault detector (ground fault
detection unit 30) determines that a ground fault has occurred in the power supply
path, control the switch 41 to separate the secondary battery unit 44 from the power
supply path.
[00961
(SECOND EMBODIMENT)
As shown in FIGS. 3 and 4, the charge and discharge device of the present
embodiment includes a selector switch 14. The selector switch 14 is provided to the
power conversion device 1 and is configured to ground any one of the grounding line
12 and the grounding line 22 of the cable 2. The configurations of the charge and
discharge device of the present embodiment other than the selector switch 14 are the
same as those of the first embodiment, and hence are designated by the same
reference numerals to omit their explanations.
[00971
The selector switch 14 includes one switching contact 14A connected to the grounding
line 12, the other switching contact 14B connected to the cable 2, and a common
contact 14C grounded.
[00981
While the power conversion unit 10 converts AC power into DC power (the secondary
battery 40 is charged), the selector switch 14 connects the common contact 14C to the
switching contact 14A, thereby separating the grounding line 22 of the cable 2 from
the grounding point 8 (see FIG. 3).
[00991
While the power conversion unit 10 converts DC power into AC power (the secondary
battery 40 discharges), the selector switch 14 connects the common contact 14C to the
switching contact 14B, thereby separating the grounding line 12 from the grounding
point 8 and connecting the grounding line 22 of the cable 2 to the grounding point 8
(see FIG. 4).
[o 1001
As described above, the charge and discharge device of the present embodiment
includes the selector (selector switch 14). The selector is configured to separate the
grounding line 22 from the grounding point 8 while the secondary battery 40 is
charged. Whereas, the selector is configured to connect the grounding line 22 to the
grounding point 8 and separate the power converter (power conversion unit 10) from
the grounding point 8 while the secondary battery 40 discharges.
[01011
In other words, the charge and discharge device of the present embodiment further
includes the selector (selector switch 14). The selector is configured to separate the
grounding line 22 from the grounding point 8 while the secondary battery unit 44 is
charged, and to connect the grounding line 22 to the grounding point 8 and separate
the power converter (power conversion unit 10) from the grounding point 8 while the
secondary battery unit 44 discharges.
[o 1021
According to the first embodiment, the grounding line 12 and the grounding line 22 of
the cable 2 are always connected to the grounding point 8. Hence, the ground fault
current with the magnitude of Ig caused by a ground fault in the cable 2 is separated
into currents individually flowing through the grounding lines 12 and 22. This may
cause a decrease in the ground fault current flowing through the ground fault
detection unit 30.
[01031
According to the present embodiment, while the secondary battery 40 discharges, the
grounding line 22 is connected to the grounding point 8 and the grounding line 12
(power conversion unit 10) is separated from the grounding point 8. The ground
fault current with the magnitude of Ig caused by a ground fault in the cable 2 cannot
flow into the grounding line 12. Therefore, it is possible to avoid a decrease in the
ground fault current flowing through the ground fault detection unit 30.
[01041
Thus, the present embodiment has an advantageous effect on improvement of ground
fault detection accuracy of the ground fault detection unit 30 relative to the first
embodiment. Further, while the secondary battery 40 is charged, the grounding line
22 of the cable 2 is separated from the grounding point 8 and only the grounding line
12 is connected to the grounding point 8. Also in the case of charging the secondary
battery 40, the ground fault current cannot flow into the grounding line 22.
Therefore, detection accuracy of the ground leakage circuit breaker 13 can be
improved.
[01051
(THIRD EMBODIMENT)
As shown in FIGS. 5 and 6, the charge and discharge device of the present
embodiment includes an impedance element 11 instead of the impedance elements
11A and 11B. The impedance element 11 is between the DC side negative terminal
of the power conversion unit 10 and the switching contact 14A. Further, the charge
and discharge device of the present embodiment includes an impedance element 31
instead of the impedance elements 31A and 31B. The impedance element 31 is
between the grounding line 22 and the negative electrode of the secondary battery 40.
[O 1061
In summary, only one side of each of the power conversion device 1 and the secondary
battery 40 of the present embodiment is grounded. The other configurations of the
present embodiment are the same as those of the second embodiment and hence are
designated by the same reference numerals to omit their explanations. Note that, it
is not always necessary to interpose the impedance element 11 between the grounding
line 12 and the switching contact 14A, and the grounding line 12 may be directly
connected to the switching contact 14A.
[01071
Also in the present embodiment, while the power conversion unit 10 converts AC
power into DC power (the secondary battery 40 is charged), the selector switch 14
connects the common contact 14C to the switching contact 14A, thereby separating
the grounding line 22 of the cable 2 from the grounding point 8 (see FIG. 5).
[o 1081
While the power conversion unit 10 converts DC power into AC power (the secondary
battery 40 discharges), the selector switch 14 connects the common contact 14C to the
switching contact 14B, thereby separating the grounding line 12 from the grounding
point 8 and connecting the grounding line 22 of the cable 2 to the grounding point 8
(see FIG. 6).
[O 1091
Also in the present embodiment, while the secondary battery 40 discharges, the
grounding line 22 is connected to the grounding point 8 and the grounding line 12
(power conversion unit 10) is separated from the grounding point 8. The ground
fault current with the magnitude of Ig caused by a ground fault in the cable 2 cannot
flow into the grounding line 12. Therefore, it is possible to avoid a decrease in the
ground fault current flowing through the ground fault detection unit 30.
[ollol
When the selector switch 14 is not provided and the DC side negative terminal of the
power conversion unit 10 is grounded through the grounding line 12 in a similar
manner to the first embodiment, a current always flows into the power supply line 21
and the grounding line 22 irrespective of occurrence of a ground fault. This may
cause a difference between the magnitudes of the currents individually flowing
through the power supply lines 20 and 21, and may result in false detection of a
ground leakage by the ground leakage circuit breaker 13 or ground fault by the
ground fault detection unit 30. Hence, when the only one side of the power
conversion device 1 is grounded, the selector switch 14 is necessary for prevention of
false detection by the ground leakage circuit breaker 13 and the ground fault
detection unit 30.
[01111
(FOURTH EMBODIMENT)
As shown in FIGS. 7 and 8, the power distribution board (e.g., the residence power
distribution board) 6 is connected to the electricity system 5. The load (e.g., the
electric appliance in a residence) 7 and the electric-vehicular charge and discharge
device (hereinafter, referred to as "charge and discharge device") of the present
embodiment are connected to the electricity system 5 via the power distribution board
6 to receive power from the electricity system 5.
[01121
The charge and discharge device of the present embodiment is used for charge and
discharge of a secondary battery unit 44A provided to the electric vehicle (electric
automobile) 4.
[01131
The secondary battery unit 44A includes the secondary battery 40 and a charge and
discharge unit (charge and discharge circuit) 43 including a pair of power terminals.
[O 1 14:l
The charge and discharge circuit 43 is configured to perform a charge process to
charge the secondary battery 40 with AC power received by the pair of power
terminals and to perform a discharge process to convert power (DC power) from the
secondary battery 40 into AC power and output the resultant AC power from the pair
of power terminals.
[01151
In the present embodiment, the electric automobile 4A includes the secondary battery
40, the charge and discharge circuit 43, the receptacle connector 42, and the pair of
contacts 41 between the charge and discharge circuit 43 and the receptacle connector
42, for example.
[Oll6l
The charge and discharge circuit 43 is configured to charge the secondary battery 40
with AC power supplied fiom the charge and discharge device, and to convert DC
power discharged from the secondary battery 40 into AC power and output the
resultant AC power to the charge and discharge device. For example, the charge and
discharge circuit 43 is a bidirectional ACIDC converter.
[01171
The charge and discharge device of the present embodiment includes the power
converter, the grounding unit, the ground fault detector, and the switcher.
[O 1181
The power converter is interposed between the external circuit and the pair of power
terminals of the secondary battery unit 44A of the electric vehicle (electric
automobile) 4A, and is configured to convert power between the external circuit and
the secondary battery unit 44A.
[01191
The grounding unit connects at least one of the pair of power terminals of the
secondary battery unit 44A to a grounding point 8 to be connected to the power
converter.
[o 1201
The ground fault detector determines whether a ground fault has occurred in the
power supply path between the power converter and the secondary battery unit 44A.
[01211
The switcher is configured to separate the secondary battery unit 44A from the power
supply path when the ground fault detector determines that a ground fault has
occurred in the power supply path.
lo1221
Hereinafter, the charge and discharge device of the present embodiment is described
in more detail.
lo1231
FIGS. 7 and 8 show that the charge and discharge device of the present embodiment
includes a power conversion device lA, the cable 2, and the connector 3.
lo1241
The cable 2 and the connector 3 constitute part of the electric path (power supply
path) between the power converter and the secondary battery unit 44A.
lo1251
The power conversion device 1A includes: a power conversion unit 10A serving as the
power converter; the two impedance elements 11A and 11B; and the ground leakage
circuit breaker 13.
Lo1261
The power conversion unit 10A is an insulation transformer or a bidirectional
insulation ACIAC converter, for example. The power conversion unit 10A electrically
insulates a circuit on an electricity system side (a power distribution board 6 side of
the power conversion unit 10A) and a circuit on non-electricity system side (an electric
automobile side of the power conversion unit 10A) from each other, and supplies AC
power between these circuits in a bidirectional manner.
[01271
The power conversion unit 10A is configured to perform a first conversion process
(charge process) to convert power (AC power in the present embodiment) from the
external circuit into predetermined first power (AC power in the present embodiment)
and supply the resultant first power to the pair of power terminals of the secondary
battery unit 44A. The power conversion unit 10A is configured to perform a second
conversion process (discharge process) to convert power (AC power in the present
embodiment) from the pair of power terminals of the secondary battery unit 44A into
predetermined second power (AC power in the present embodiment) and supply the
resultant second power to the external circuit. The first power is determined
according to the specification of the charge and discharge circuit 43 of the secondary
battery unit 44A. The second power is determined according to the specification of
the electricity system 5.
[01281
The power conversion unit 10A of the present embodiment includes an insulation
ACIAC converter configured to convert AC power from the external circuit into AC
power suitable for the secondary battery unit 44A and convert AC power from the
secondary battery unit 44A into AC power suitable for the external circuit.
[01291
The two impedance elements 11A and 11B are resistors having the same resistance.
The two impedance elements 11A and 11B are connected in series with each other
between the non-electricity system side terminals of the power conversion unit 10A.
[O 1301
The connection point 11C of the impedance elements 11A and 11B is grounded via the
grounding line 12. In short, as shown in FIGS. 7 and 8, the connection point 11C is
connected to the grounding point 8 by the grounding line 12.
[01311
The ground leakage circuit breaker 13 compares a current (outward charge current)
outputted via a first terminal of the non-electricity system side terminals of the power
conversion unit 10A with a current (return charge current) returned to a second
terminal of the non-electricity system side terminals of the power conversion unit 10A.
When a difference between these currents exceeds a prescribed threshold, the ground
leakage circuit breaker 13 determines that a ground leakage has occurred, and breaks
the electric path.
[01321
The cable 2 is a multicore cable including: the pair of power supply lines 20 and 21 for
supplying a current (a charge current and a discharge current); the grounding line 22
having one end grounded together with the connection point 11C of the impedance
elements 11A and 11B; the communication line (not shown); and the insulating
sheath (not shown) covering around these lines. The cable 2 has one end connected
to the power conversion device 1 (the ground leakage circuit breaker 13) and the other
end connected to the connector 3.
Lo1331
The connector 3 is a plug connector configured to be detachably connected to a
receptacle connector 42 provided to the electric automobile 4A. The connector 3
includes a ground fault detection unit 30 and impedance elements 31A and 31B. The
ground fault detection unit 30 and the impedance elements 31A and 31B are housed
in the casing of the connector 3.
[O 1341
These two impedance elements 31A and 31B are resistors having the same resistance.
These two impedance elements 31A and 31B are connected in series with each other
between terminals of the ground fault detection unit 30 to be connected to the electric
automobile 4A. The grounding line 22 of the cable 2 is connected to a connection
point 31C of the impedance elements 31A and 31B. In the present embodiment, the
impedance elements 31A and 31B and the grounding line 22 constitute the grounding
unit.
[O 1351
In the charge and discharge device of the present embodiment, the grounding unit
includes the two impedance elements 31A and 31B and the grounding line 22. The
two impedance elements 31A and 31B have the same impedance (resistance) and are
connected in series between the both electrodes of the secondary battery 40. The
grounding line 22 connects the connection point 31C of the impedance elements 31A
and 31B to the grounding point 8 of the power converter (power conversion unit 10A).
[01361
In other words, the grounding unit includes the grounding line 22 connecting at least
one of the pair of power terminals of the secondary battery unit 44A to the grounding
point 8.
[O 1371
Additionally, the grounding unit includes the series circuit of two impedance
components (impedance elements) 31A and 31B between the pair of power terminals
of the secondary battery unit 44A. The grounding line 22 connects the connection
point 31C of the two impedance components (impedance elements) 31A and 31B to the
grounding point 8. The two impedance components (impedance elements) 31A and
31B have the same impedance.
[O 1381
In the present embodiment, each of the two impedance components is constituted by a
single impedance element. However, each impedance component is constituted by
not a single impedance element but two or more impedance elements. In brief, it is
only necessary that the two impedance components have the same impedance
(synthetic impedance).
[O 1391
The ground fault detection unit 30 measures currents individually flowing through
the power supply lines 20 and 21 of the cable 2, and, when a difference between the
magnitudes of the currents individually flowing through the power supply lines 20
and 21 is greater than a predetermined threshold, determines that a ground fault has
occurred. In brief, the ground fault detection unit 30 is configured to, when
acknowledging that a difference between the magnitudes of the current flowing
through one of the pair of power terminals and another current flowing through the
other of the pair of power terminals exceeds the predetermined threshold, determine
that a ground fault has occurred in the power supply path.
[01401
When detecting the ground fault, the ground fault detection unit 30 opens contacts 41
and 41 respectively interposed between one electrode of the secondary battery 40 and
the receptacle connector 42 and between the other electrode of the secondary battery
40 and the receptacle connector 42.
[01411
In summary, the ground fault detection unit 30 of the present embodiment serves as
the ground fault detector and the switcher.
[O 1421
Note that, these contacts 41 and 41 are provided to the electric automobile 4A in
advance for the purpose of protection of the secondary battery 40 from charging
abnormality. Contacts to be controlled by the ground fault detection unit 30 may be
provided to the connector 3.
Lo1431
In the present embodiment, the electric vehicle 4A includes the switch (contact) 41 for
separation of the secondary battery unit 44A from the power supply path (in
particular, the power supply lines 20 and 21 of the cable 2).
[O 1441
The ground fault detection unit (switcher) 30 is configured to, when determining that
a ground fault has occurred in the power supply path, control the switch 41 to
separate the secondary battery unit 44A from the power supply path.
[01451
Next, the operations of the charge and discharge device of the present embodiment
are described below.
[O 1461
In the process of charging the electric automobile 4A, AC power supplied from the
electricity system 5 is transferred to the electric automobile 4A through the cable 2
and the connector 3. Thereby, the charge and discharge circuit 43 of the electric
automobile 4A charges the secondary battery 40.
[01471
When a ground fault has occurred in the power supply line 20 or 21 of the cable 2
during charging, the magnitude of the current outputted from the first terminal of the
non-electricity system side terminals of the power conversion unit 10A and flowing
into the second terminal of the non-electricity system side terminals of the power
conversion unit 10A decreases by a magnitude of the ground fault current.
[O 1481
Accordingly, the ground leakage circuit breaker 13 of the power conversion device 1A
detects such a decrease in the current caused by the ground fault current (i.e., an
unbalance between the outward and return currents), and breaks the electric path.
Hence, improvement of safety in charging is achieved.
[O 1491
The following explanation is made to the operation of the charge and discharge device
of the present embodiment in supplying from the electric automobile 4A (discharging
by the secondary battery 40).
[01501
In the process of supplying electricity from the electric automobile 4A, DC power
discharged from the secondary battery 40 is converted into AC power by the charge
and discharge circuit 43 and the resultant AC power is supplied to the load 7 through
the connector 3, the cable 2, and the power conversion device 1A.
[01511
For example, it is assumed that a ground fault has occurred in the power supply line
20 of the cable 2 during the process of supplying electricity from the electric
automobile 4A. According to this assumption, as indicated by the dashed arrow in
FIG. 7, a ground fault current with the magnitude of Ig flows from the first terminal
(upper terminal in the same drawing) of the charge and discharge circuit 43 to a
ground fault point (X) through the power supply line 20 of the cable 2.
[01521
Further, this ground fault current with the magnitude of Ip: is divided into half
ground fault currents with the same magnitude of 1~12. One of the half ground fault
current with the magnitude of Id2 flows to the second terminal (lower terminal in the
same drawing) of the charge and discharge circuit 43 through the grounding line 22
and the impedance element 31B, and the other flows to the second terminal of the
charge and discharge circuit 43 through the grounding line 12, the impedance element
11B, the ground leakage circuit breaker 13, and the power supplv line 21 of the cable
-2.
[01531
When a difference between the magnitude of I of the current flowing through one
power supply line 20 and the magnitude of I-Igl2 of the current flowing through the
other power supply line 21, that is, the magnitude of Igl2 of the half ground fault
current is greater the predetermined threshold, the ground fault detection unit 30
determines that the ground fault has occurred, and opens the contact 41.
[O 1541
For example, it is assumed that a ground fault has occurred in the power supply line
21 of the cable 2 during the process of supplying electricity from the electric
automobile 4A. According to this assumption, as indicated by the dashed arrow in
FIG. 8, a ground fault current with the magnitude of Ig flows from one output
terminal (lower terminal in the same drawing) of the power conversion device 1A to a
ground fault point (X) through the power supply line 21 of the cable 2.
Lo1551
Further, this ground fault current with the magnitude of Ig is divided into half
ground fault currents with the same magnitude of Igl2. One of the half ground fault
current with the magnitude of Igl2 flows to the second terminal of the charge and
discharge circuit 43 through the grounding line 22 and the impedance element 31B,
and the other flows to the second terminal of the charge and discharge circuit 43
through the grounding line 12, the impedance element llB, the ground leakage
circuit breaker 13, and the power supply line 21 of the cable 2.
[01561
When a difference between the magnitude of I of the current flowing through one
power supply line 20 and the magnitude of I-Igl2 of the current flowing through the
other power supply line 21, that is, the magnitude of Igl2 of the half ground fault
current is greater the predetermined threshold, the ground fault detection unit 30
determines that the ground fault has occurred, and opens the contact 41.
[O 1571
The charge and discharge device (electric-vehicular charge and discharge device) of
the present embodiment described above is an electric-vehicular charge and discharge
device suitable for the electric vehicle 4A. The electric vehicle 4A includes the
secondary battery 40 and the charge and discharge unit (charge and discharge circuit)
43. The charge and discharge unit (charge and discharge circuit) 43 is configured to
perform bidirectional conversion between AC power and DC power to charge the
secondary battery 40 and to allow the secondary battery 40 to discharge. The
electric-vehicular charge and discharge device suitable for the electric vehicle 4A is
configured to supply AC power to the charge and discharge circuit 43, and is
configured to receive AC power outputted from the charge and discharge unit (charge
and discharge circuit 43) and supply the received AC power to the load 7 outside the
electric vehicle 4A. The charge and discharge device of the present embodiment
includes: the insulation-type power converter (power conversion unit 10A) connected
to the AC electricity system 5 and configured to perform bidirectional conversion of
power; the cable 2 constituting part of the electric path between the power converter
(power conversion unit 10A) and the charge and discharge unit (charge and discharge
circuit 43); the grounding unit configured to connect at least one of the terminals of
the charge and discharge unit (charge and discharge circuit 43) to the grounding point
8 of the power converter (power conversion unit 10A); the ground fault detector
(ground fault detection unit 30) which is on the non-electricity system side of the
power converter (power conversion unit IOA) and is configured to detect a ground
fault in the electric path while AC power is supplied from the charge and discharge
unit (charge and discharge circuit 43) to the power converter (power conversion unit
10A); and the switcher (ground fault detection unit 30) configured to open the contact
41 interposed in the electric path in response to detection of a ground fault by the
ground fault detector (gound fault detection unit 30).
[O 1581
In other words, the charge and discharge device of the present embodiment includes
the power converter (power conversion unit lOA), the grounding unit, the ground fault
detector (ground fault detection unit 30), and the switcher (ground fault detection unit
30). The power converter (power conversion unit 10A) is interposed between the
external circuit and the pair of power terminals of the secondary battery unit 44A
provided to the electric vehicle 4, and is configured to convert power between the
external circuit and the secondary battery unit 44A. The grounding unit is
configured to connect at least one of the pair of power terminals of the secondary
battery unit 44A to the grounding point 8 to be connected to the power converter
(power conversion unit 10A). The ground fault detector (ground fault detection unit
30) is configured to determine whether a ground fault has occurred in the power
supply path between the power converter (power conversion unit 10A) and the
secondary battery unit 44A. The switcher (ground fault detection unit 30) is
configured to, when the ground fault detector (ground fault detection unit 30)
determines that a ground fault has occurred in the power supply path, separate the
secondary battery unit 44A from the power supply path.
[01591
Further in the charge and discharge device of the present embodiment, the grounding
unit (ground fault detection unit 30) is configured to, when a ground fault has
occurred in the power supply path between the power converter (power conversion
unit 10A) and the secondary battery unit 44A, connect at least one of the pair of
power terminals of the secondary battery unit 44A to the grounding point 8 so as to
cause a difference between a current flowing through one of the pair of power
terminals and another current flowing through the other of the pair of power
terminals.
[0160]
Further in the charge and discharge device of the present embodiment, the grounding
unit includes the grounding line 22 for connecting at least one of the pair of power
terminals of the secondary battery unit 44A to the grounding point 8.
[01611
Further in the charge and discharge device of the present embodiment, the ground
fault detector (ground fault detection unit 30) is configured to, when acknowledging
that a difference between magnitudes of a current flowing through one of the pair of
power terminals and another current flowing through the other of the pair of power
terminals exceeds a predetermined threshold, determine that a ground fault has
occurred in the power supply path.
Lo1621
Further in the charge and discharge device of the present embodiment, the power
converter (power conversion unit 10A) is configured to perform the first conversion
process (charge process) to convert power (in the present embodiment, AC power) from
the external circuit into the predetermined first power (in the present embodiment,
AC power) and supply the resultant first power to the pair of power terminals of the
secondary battery unit 44A, and to perform the second conversion process (discharge
process) to convert power (in the present embodiment, AC power) fiom the pair of
power terminals of the secondary battery unit 44A into the predetermined second
power (in the present embodiment, AC power) and supply the resultant second power
to the external circuit.
[01631
Further in the charge and discharge device of the present embodiment, the external
circuit is an AC circuit connected to the AC power source (electricity system 5). The
secondary battery unit 44A includes the secondary battery 40 and the charge and
discharge unit (charge and discharge circuit 43) including the pair of power terminals.
The charge and discharge unit (charge and discharge circuit 43) is configured to
perform the charge process to charge the secondary battery 40 with AC power
received by the pair of power terminals and to perform the discharge process to
convert power from the secondary battery 40 into AC power and output the resultant
AC power from the pair of power terminals. The power converter 10A includes the
insulation ACIAC converter configured to convert AC power from the external circuit
into AC power suitable for the secondary battery unit 44A and convert AC power from
the secondary battery unit 44A into AC power suitable for the external circuit.
[01641
Further in the charge and discharge device of the present embodiment, the grounding
unit includes the two impedance elements 31A and 31B and the grounding line 22.
The two impedance elements 31A and 31B have the same impedance (resistance) and
are connected in series between the both terminals of the charge and discharge unit
(charge and discharge circuit 43). The grounding line 22 connects the connection
point 31C of the impedance elements 31A and 31B to the grounding point 8 of the
power converter (power conversion unit 10A).
[01651
In other words, in the charge and discharge device of the present embodiment, the
grounding unit includes the series circuit of the two impedance components
(impedance elements) 31A and 31B between the pair of power terminals of the
secondary battery unit 44A. The grounding line 22 connects the connection point
31C of the two impedance components (impedance elements) 31A and 31B to the
grounding point 8. The two impedance components (impedance elements) 31A and
31B have the same impedance.
[o 1661
As described above, in the present embodiment, the grounding line 22 connects the
connection point 31C of the impedance elements 31A and 31B is connected to the
grounding point 8 of the power conversion unit 10A, and the ground fault detection
unit 30 provided between the power conversion unit 10A and the impedance elements
31A and 31B opens the contact 41 when detecting a ground fault occurring in at least
one of the power supply lines 20 and 21 of the cable 2.
Lo1671
Accordingly, even while the electric automobile 4A discharges, the charge and
discharge device of the present embodiment opens the contact 41 interposed in the
electric path to interrupt a current (charge current) when detecting a ground fault in
the cable 2. Consequently, it is possible to improve the safety in supply of electricity
from the secondary battery 40 of the electric automobile 4A to the load 7.
[01681
As described above, the charge and discharge device of the present embodiment has
an advantageous effect on improvement of the safety in supply of power from the
secondary battery 40 provided to the electric vehicle 4A to the load 7 outside the
electric vehicle 4A.
[01691
Note that, in the present embodiment, the non-electricity system side terminals of the
power conversion unit 10A are grounded by use of the impedance elements 11A and
11B with the same impedance, and the both terminals of the secondary battery 40
(charge and discharge circuit 43) are grounded by use of the impedance elements 31A
and 31B with the same impedance. The non-electricity system side terminals of the
power conversion unit 10 may be grounded directly without using impedance elements.
The both terminals of the secondary battery 40 (charge and discharge circuit 43) may
be grounded directly without using impedance elements.
[01701
However, when the grounding is made by use of the impedance elements 11A and 11B
and the other impedance elements 31A and 31B, a voltage of the cable 2 to the ground
can halve compared with a case in which no impedance element is used.
to1711
Further in the present embodiment, the grounding line 22 of the cable 2 constitutes
the grounding unit, and the ground fault detection unit 30 serving as the ground fault
detector and the impedance elements 31A and 31B constituting the grounding unit
are housed in the casing of the connector 3. Thereby, the grounding unit and the
ground fault detector are integrated with the cable 2.
[01721
Hence, in contrast to a case in which the electric automobile 4A includes the
grounding unit and the ground fault detector, it is possible to easily achieve the
improvement of the safety at lowered cost.
[01731
Note that, the ground fault detection unit 30 and the impedance elements 31A and
31B may be integrated with the cable 2 in such a manner that the ground fault
detection unit 30 and the impedance elements 31A and 31B are housed in a
box-shaped casing interposed in the cable 2.
[01741
Note that, the ground fault detection unit 30 serving as the ground fault detector may
be integrated with the cable 2 and the impedance elements 31A and 31B constituting
the grounding unit may be included in the electric automobile 4A.
[01751
In the charge and discharge device of the present embodiment, the grounding unit
and the ground fault detector may be integrated with the cable 2. In other words,
the charge and discharge device of the present embodiment further includes the cable
2 connecting the power converter (power conversion unit 10A) to the pair of power
terminals of the secondary battery unit 44A. The grounding unit and the ground
fault detector are provided to the cable 2.
[O 1761
Alternatively, in the charge and discharge device of the present embodiment, the
cable 2 may include the plug connector (connector) 3 to be detachably connected to the
receptacle connector provided to the electric vehicle 4A. The grounding unit and the
ground fault detector may be integrated with the plug connector 3. In other words,
the charge and discharge device of the present embodiment further includes: the cable
2 connecting the power converter (power conversion unit 10A) to the pair of power
terminals of the secondary battery unit 44A; and the plug connector 3 configured to be
detachably connected to the receptacle connector of the electric vehicle 4A. The cable
2 has one end connected to the power converter (power conversion unit 10A) and the
other end connected to the plug connector 3. The grounding unit and the ground
fault detector are provided to the plug connector 3.
[O 1771
Alternatively, in the charge and discharge device of the present embodiment, the
cable 2 may include the plug connector (connector) 3 to be detachably connected to the
receptacle connector provided to the electric vehicle 4a. The ground fault detector
may be integrated with the cable 2 or the plug connector 3, and the grounding unit
may be included in the electric vehicle 4A. In other words, the charge and discharge
device of the present embodiment further includes the cable 2 connecting the power
converter (power conversion unit 10A) to the pair of power terminals of the secondary
battery unit 44A. The ground fault detector is provided to the cable 2, and the
grounding unit is provided to the electric vehicle 4A.
[01781
Alternatively, in the charge and discharge device of the present embodiment, the
grounding unit and the ground fault detector may be included in the electric vehicle
4A. In other words, in the charge and discharge device of the present embodiment,
the grounding unit and the ground fault detector are provided to the electric vehicle
4A.
[01791
The present embodiment utilizes the contacts 41 and 41 provided to the electric
automobile 4A in advance for the purpose of protection of the secondary battery 40
from charging abnormality. Accordingly, it is possible to simplify the structure of the
switcher and lower the cost of the switcher. Note that, instead of the contacts 41 and
41, the charge and discharge circuit 43 of the electric automobile 4A may be
configured to separate the secondary battery 40 from the power supply lines 20 and
21.
[01801
As described above, in the charge and discharge device of the present embodiment,
the switcher (ground fault detection unit 30) is configured to open the contact 41
provided to the electric vehicle 4A.
[01811
In other words, the electric vehicle 4A includes the switch (contact) 41 for separation
of the secondary battery unit 44A from the power supply path. The switcher (ground
fault detection unit 30) is configured to, when the ground fault detector (ground fault
detection unit 30) determines that a ground fault has occurred in the power supply
path, control the switch 41 to separate the secondary battery unit 44A from the power
supply path.
Alternatively, the switcher (ground fault detection unit 30) may be configured to open
a contact (not shown) of the charge and discharge unit (charge and discharge circuit
43).
[01831
In other words, the charge and discharge unit (charge and discharge circuit 43)
includes the switch (not shown) for separation of the secondary battery 40 from the
power supply path. The switcher (ground fault detection unit 30) is configured to,
when the ground fault detector (gound fault detection unit 30) determines that a
ground fault has occurred in the power supply path, control the switch of the charge
and discharge unit (charge and discharge circuit 43) to separate the secondary battery
40 from the power supply path.
[01841
(FIFTH EMBODIMENT)
As shown in FIGS. 9 and 10, the charge and discharge device of the present
embodiment includes the selector switch 14. The selector switch 14 is provided to
the power conversion device 1A and is configured to ground any one of the grounding
line 12 and the grounding line 22 of the cable 2. The configurations of the charge
and discharge device of the present embodiment other than the selector switch 14 are
the same as those of the fourth embodiment, and hence are designated by the same
reference numerals to omit their explanations.
[01851
The selector switch 14 includes one switching contact 14A connected to the grounding
line 12, the other switching contact 14B connected to the cable 2, and a common
contact 14C grounded.
[01861
While the secondary battery 40 is charged, the selector switch 14 connects the
common contact 14C to the switching contact 14A, thereby separating the grounding
line 22 of the cable 2 from the grounding point 8 (see FIG. 9).
[01871
While the secondary battery 40 discharges, the selector switch 14 connects the
common contact 14C to the switching contact 14B, thereby separating the grounding
line 12 from the grounding point 8 and connecting the grounding line 22 of the cable 2
to the grounding point 8 (see FIG. 10).
[01881
As described above, the charge and discharge device of the present embodiment
includes the selector (selector switch 14). The selector is configured to separate the
grounding line 22 from the grounding point 8 while the secondary battery 40 is
charged. Whereas, the selector is configured to connect the grounding line 22 to the
grounding point 8 and separate the power converter (power conversion unit 10A) from
the grounding point 8 while the secondary battery 40 discharges.
[0189l
In other words, the charge and discharge device of the present embodiment further
includes the selector (selector switch 14). The selector is configured to separate the
grounding line 22 from the grounding point 8 while the secondary battery unit 44A is
charged, and to connect the grounding line 22 to the grounding point 8 and separate
the power converter (power conversion unit 10A) from the grounding point 8 while the
secondary battery unit 44A discharges.
[01901
According to the fourth embodiment, the grounding line 12 and the grounding line 22
of the cable 2 are always connected to the grounding point 8. Hence, the ground fault
current with the magnitude of Ig caused by a ground fault in the cable 2 is separated
into currents individually flowing through the grounding lines 12 and 22. This may
cause a decrease in the ground fault current flowing through the ground fault
detection unit 30.
[O 19 11
According to the present embodiment, while the secondary battery 40 discharges, the
grounding line 22 is connected to the grounding point 8 and the grounding line 12
(power conversion unit 10A) is separated from the grounding point 8. The ground
fault current with the magnitude of Ig caused by a ground fault in the cable 2 cannot
flow into the grounding line 12. Therefore, it is possible to avoid a decrease in the
ground fault current flowing through the ground fault detection unit 30.
[01921
Thus, the present embodiment has an advantageous effect on improvement of ground
fault detection accuracy of the ground fault detection unit 30 relative to the fourth
embodiment. Further, while the secondary battery 40 is charged, the grounding line
22 of the cable 2 is separated from the grounding point 8 and only the grounding line
12 is connected to the grounding point 8. Also in the case of charging the secondary
battery 40, the ground fault current cannot flow into the grounding line 22.
Therefore, detection accuracy of the ground leakage circuit breaker 13 can be
improved.
[01931
(SIXTH EMBODIMENT)
As shown in FIGS. 11 and 12, the charge and discharge device of the present
embodiment includes the impedance element 11 instead of the impedance elements
11A and 11B. The impedance element 11 is between the second terminal of the
non-electricity system side terminals of the power conversion unit 10A and the
switching contact 14A. Further, the charge and discharge device of the present
embodiment includes the impedance element 31 instead of the impedance elements
31A and 31B. The impedance element 31 is between the grounding line 22 and the
second terminal of the charge and discharge circuit 43.
[O 1941
In summary, only one side of each of the power conversion device 1A and the
secondary battery 40 of the present embodiment is grounded. The other
configurations of the present embodiment are the same as those of the fifth
embodiment and hence are designated by the same reference numerals to omit their
explanations. Note that, it is not always necessary to interpose the impedance
element 11 between the grounding line 12 and the switching contact 14A, and the
grounding line 12 may be directly connected to the switching contact 14A.
[01951
Also in the present embodiment, while the secondary battery 40 is charged, the
selector switch 14 connects the common contact 14C to the switching contact 14A,
5 thereby separating the grounding line 22 of the cable 2 from the grounding point 8
(see FIG. 11).
[0196l
While the secondary battery 40 discharges, the selector switch 14 connects the
10 common contact 14C to the switching contact 14B, thereby separating the grounding
line 12 from the grounding point 8 and connecting the grounding line 22 of the cable 2
to the grounding point 8 (see FIG. 12).
[01971
15 Also in the present embodiment, while the secondary battery 40 discharges, the
grounding line 22 is connected to the grounding point 8 and the grounding line 12
(power conversion unit 10A) is separated from the grounding point 8. The ground
fault current with the magnitude of Ig caused by a ground fault in the cable 2 cannot
flow into the grounding line 12. Therefore, it is possible to avoid a decrease in the
20 ground fault current flowing through the ground fault detection unit 30.
[O 1981
When the selector switch 14 is not provided and one of the non-electricity system side
terminals of the power conversion unit 10 is grounded through the grounding line 12
25 in a similar manner to the fourth embodiment, a current is always flows into the
power supply line 21 and the grounding line 22 irrespective of occurrence of a ground
fault. This may cause a difference between the magnitudes of the currents
individually flowing through the power supply lines 20 and 21, and may result in false
detection of a ground leakage by the ground leakage circuit breaker 13 or ground fault
30 by the ground fault detection unit 30. Hence, when the only one side of the power
conversion device 1A is grounded, the selector switch 14 is necessary for prevention of
false detection by the ground leakage circuit breaker 13 and the ground fault
detection unit 30.
CLAIMS
1. An electric-vehicular charge and discharge device, comprising:
a power converter interposed between an external circuit and a pair of power
terminals of a secondary battery unit provided to an electric vehicle and configured to
convert power between the external circuit and the secondary battery unit;
a grounding unit configured to connect at least one of the pair of power
terminals of the secondary battery unit to a grounding point to be connected to the
power converter;
a ground fault detector configured to determine whether a ground fault has
occurred in a power supply path between the power converter and the secondary
battery unit; and
a switcher configured to, when the ground fault detector determines that a
ground fault has occurred in the power supply path, separate the secondary battery
unit from the power supply path.
2. The electric-vehicular charge and discharge device according to claim 1, wherein
the grounding unit is configured to, when a ground fault has occurred in the
power supply path, connect at least one of the pair of power terminals of the
secondary battery unit to the grounding point so as to cause a difference between a
current flowing through one of the pair of power terminals and another current
flowing through the other of the pair of power terminals.
3. The electric-vehicular charge and discharge device according to claim 1, wherein
the grounding unit includes a grounding line for connecting at least one of the
pair of power terminals of the secondary battery unit to the grounding point.
4. The electric-vehicular charge and discharge device according to claim 3, wherein:
the grounding unit includes a series circuit of two impedance components
between the pair of power terminals of the secondary battery unit;
the grounding line connects a connection point of the two impedance
components to the grounding point; and
the two impedance components have the same impedance.
5. The electric-vehicular charge and discharge device according to claim 3, further
comprising a selector configured to separate the grounding line from the grounding
point while the secondary battery unit is charged, and to connect the grounding line to
the grounding point and separate the power converter from the grounding point while
the secondary battery unit discharges.
6. The electric-vehicular charge and discharge device according to claim 1, further
comprising a cable connecting the power converter to the pair of power terminals of
the secondary battery unit,
the grounding unit and the ground fault detector being provided to the cable.
7. The electric-vehicular charge and discharge device according to claim 1, further
comprising:
a cable connecting the power converter to the pair of power terminals of the
secondary battery unit; and
a plug connector configured to be detachably connected to a receptacle
connector of the electric vehicle,
the cable having one end connected to the power converter and the other end
connected to the plug connector, and
the grounding unit and the ground fault detector being provided to the plug
connector.
8. The electric-vehicular charge and discharge device according to claim 1, further
comprising a cable connecting the power converter to the pair of power terminals of
the secondary battery unit,
the ground fault detector being provided to the cable, and
the grounding unit being provided to the electric vehicle.
9. The electric-vehicular charge and discharge device according to claim 1, wherein
the grounding unit and the ground fault detector are provided to the electric
vehicle.
10. The electric-vehicular charge and discharge device according to claim 1, wherein
the ground fault detector is configured to, when acknowledging that a
difference between magnitudes of a current flowing through one of the pair of power
terminals and another current flowing through the other of the pair of power
terminals exceeds a predetermined threshold, determine that a ground fault has
occurred in the power supply path.
11. The electric-vehicular charge and discharge device according to claim 1, wherein
the power converter is configured to perform a first conversion process to
convert power from the external circuit into predetermined first power and supply the
resultant first power to the pair of power terminals of the secondary battery unit, and
to perform a second conversion process to convert power from the pair of power
terminals of the secondary battery unit into predetermined second power and supply
the resultant second power to the external circuit.
12. The electric-vehicular charge and discharge device according to claim 1, wherein:
the external circuit is an AC circuit connected to an AC power source;
the secondary battery unit includes a secondary battery;
the pair of power terminals are positive and negative electrodes of the
secondary battery; and
the power converter includes an ACIDC converter configured to convert AC
power from the external circuit into DC power suitable for the secondary battery unit
and convert DC power from the secondary battery unit into AC power suitable for the
external circuit.
13. The electric-vehicular charge and discharge device according to claim 1, wherein:
the external circuit is an AC circuit connected to an AC power source;
the secondary battery unit includes a secondary battery and a charge and
discharge unit including the pair of power terminals;
the charge and discharge unit is configured to perform a charge process to
charge the secondary battery with AC power received by the pair of power terminals
and to perform a discharge process to convert power from the secondary battery into AC power output the resultant AC power from the pair of power terminals; and the power converter includes an insulation AC/AC converter configured to convert AC power from the external cireuit into AC power suitable for the secondary battery unit and convert AC power from the secondary battery unit into AC power suitable for the external circuit.
14.The electric vehicular charge and discharge device according to claim I, wherein; the electric vehicle includes a switch for separation of the secondary battery unit from the power supply path: and the switcher is configured to, when the ground fault detector determines that a ground fault has occurred in the power supply path, control the switch to separate the secondary battery unit from the power supply path.
15. The electric vehicular charge and discharge device according to claim 13, wherein; the charge and discharge unit includes a switch for separation of the secondary battery unit from the power supply path:and
the switcher is configured to when the ground fault detector determines that a ground fault has occurred in the power supply path, control the switch to separate the secondary battery unit from the power supply path.