1. A feeder voltage stabilizer with power storage, the stabilizer connected to a direct-current feeder circuit, comprising: a power storage element5 ; power conversion means provided between the feeder circuit and the power storage element; voltage detection means which detects a voltage corresponding to a feeder voltage at a connection point of 10 the feeder circuit; means for detecting energy stored in the power storage element; and control means which adjusts charge and discharge power of the power storage element based on values detected by the 15 voltage detection means and the means for detecting energy, wherein the control means comprises means for causing the power conversion means to charge and discharge the power storage element to reduce a difference between a voltage command value and a value detected by the voltage detection 20 means, and wherein the voltage command value is monotonically increased relative to the energy within a normal operating range of the power storage element. 30 Amended Claims under PCT Article 19

2. The feeder voltage stabilizer with power storage according to claim 1, wherein the power conversion means is a bidirectional chopper. 5

3. The feeder voltage stabilizer with power storage according to claim 1 or claim 2, wherein the power conversion means comprises a filter circuit which includes at least one reactor and at least one 10 capacitor at a connection point of the power conversion means and the direct-current feeder circuit, and wherein the voltage corresponding to the feeder voltage is a terminal voltage of the capacitor. 15 4. The feeder voltage stabilizer with power storage according to any one of claims 1 to 3, wherein the power storage element is a rechargeable battery. 20 5. The feeder voltage stabilizer with power storage according to claim 4, wherein means for detecting energy of the rechargeable battery calculates a charging rate of the rechargeable battery. 25 31 Amended Claims under PCT Article 19

6. The feeder voltage stabilizer with power storage according to any one of claims 1 to 3, wherein the power storage element is an electric double-layer capacitor. 5

7. The feeder voltage stabilizer with power storage according to claim 6, wherein means for detecting energy of the electric double-layer capacitor comprises voltage detection means 10 which detects a terminal voltage of the capacitor.

8. The feeder voltage stabilizer with power storage according to any one of claims 1 to 3, wherein the power storage element is a flywheel. 15

9. The feeder voltage stabilizer with power storage according to claim 8, wherein means for detecting energy of the flywheel comprises a function of detecting a rotational speed of the 20 flywheel.

10. A method for controlling a feeder voltage stabilizer with power storage, the stabilizer connected to a direct-current feeder circuit, comprising: 25 a power storage element; 32 Amended Claims under PCT Article 19 power conversion means provided between the feeder circuit and the power storage element; voltage detection means which detects a voltage corresponding to a feeder voltage at a connection point of the feeder circuit5 ; means for detecting energy stored in the power storage element; and control means which adjusts charge and discharge power of the power storage element based on values detected by the 10 voltage detection means and the means for detecting energy, wherein the control means comprises means for causing the power conversion means to charge and discharge the power storage element to reduce a difference between a voltage command value and a value detected by the voltage detection 15 means, and wherein the voltage command value is monotonically increased relative to the energy within a normal operating range of the power storage element. 20 11. The method for controlling a feeder voltage stabilizer with power storage according to claim 10, wherein the power conversion means is a bidirectional chopper. 33 Amended Claims under PCT Article 19

12. The method for controlling a feeder voltage stabilizer with power storage according to claim 10 or claim 11, wherein the power conversion means comprises a filter circuit which includes at least one reactor and at least o5 ne capacitor at a connection point of the power conversion means and the direct-current feeder circuit, and wherein the voltage corresponding to the feeder voltage is a terminal voltage of the capacitor. 10

13. The method for controlling a feeder voltage stabilizer with power storage according to any one of claims 10 to 12, wherein the power storage element is a rechargeable 15 battery, wherein means for calculating a charging rate of the rechargeable battery is provided, and wherein the voltage command value is monotonically increased relative to the charging rate. 20

14. The method for controlling a feeder voltage stabilizer with power storage according to any one of claims 10 to 12, wherein the power storage element is an electric 25 double-layer capacitor, 34 Amended Claims under PCT Article 19 wherein means for detecting a terminal voltage of the capacitor is provided, and wherein the voltage command value is monotonically increased relative to the terminal voltage of the capacitor. 5

15. The method for controlling a feeder voltage stabilizer with power storage according to any one of claims 10 to 12, wherein the power storage element is a flywheel, 10 wherein means for detecting a rotational speed of the flywheel is provided, and wherein the voltage command value is monotonically increased relative to the rotational speed of the flywheel.

TITLE OF INVENTION
POWER-STORING VOLTAGE STABILIZER AND METHOD FOR CONTROLLING
SA5 ME
FIELD OF THE INVENTION
[0001]
The present invention relates to a voltage stabilizer
10 which is connected to a direct current (DC) feeder for
electric railroads, particularly, to such a voltage
stabilizer with power storage means.
BACKGROUND ART
15 [0002]
Electric trains having a regenerative brake, namely,
regenerative trains are recently used in electric railway
systems. During deceleration, the regenerative brake
converts the kinetic energy of a train to electric energy by
20 an inverter on the train. An electricity feeding system
supplies DC power from an electrical substation to a train
through a feeder when the train accelerates, and absorbs
regeneration power from a regenerative train through the
feeder when the train decelerates. If there is an
25 accelerating train near a regenerative train, regeneration
3
power is consumed as acceleration energy of that train,
which saves the energy of the electricity feeding system.
However, if there is no accelerating train near a
regenerative train, a filter capacitor of the regenerative
train is charged and the voltage at the pantograph of th5 e
regenerative train rises. In this case, braking changes
from the regenerative brake to a mechanical brake to protect
the train from overvoltage. This change causes a negative
effect on comfortability of passengers and energy saving
10 performance.
[0003]
In JP 11-91415, a voltage stabilizer with power
storage is disclosed in which surplus electric power is
stored in a power storage element and discharged as energy
15 when driving a train. JP 2001-260719 discloses a control
method of a power converter to control the power of a power
storage element. In such methods, charging is performed if
a feeder voltage is above or equal to a predetermined
charging-control setting voltage, and discharging is
20 performed if the feeder voltage is below or equal to a
predetermined discharging-control setting voltage.
[0004]
Furthermore, in JP 4238190B, a control method of a
power converter is described in which the state of charge of
25 power storage means is adjusted by charging and discharging
4
to a feeder if the feeder voltage is between a chargingcontrol
setting voltage and a discharging-control setting
voltage.
DOCUMENT LIS5 T
PATENT DOCUMENT
[0005]
PATENT DOCUMENT 1: JP 11-91415
PATENT DOCUMENT 2: JP 2001-260719
10 PATENT DOCUMENT 3: JP 4238190B
[0006]
Equipment for electric railroads such as above voltage
stabilizer with power storage is typically installed in an
electric substation where the area for installation is
15 limited, e.g., under elevated railroad tracks or at the side
of railroad tracks, because of restriction of available land
owned by a party who introduces such equipment.
Consequently, in some situations, a voltage stabilizer with
power storage having large rated power needs to be built up
20 of plural voltage stabilizers having power storage (each of
which will hereinafter be referred to as a single
stabilizer) and the single stabilizers need to be
distributed and placed within one electric substation.
[0007]
5
The above-mentioned power converter includes a
bidirectional chopper, a sensor to detect the voltage and
current of the circuit, and a waveform controller. The
waveform controller inputs an output signal of the voltage
and current sensor and an output signal of a batte5 ry
controller which detects the state of charge of a power
storage element, and outputs a signal for driving the
bidirectional chopper.
If the above-mentioned single stabilizers are controlled by
10 a single waveform controller, it is required to lay plural
signal lines which connect voltage and current sensors and
the battery controllers included in the respective
stabilizers and the waveform controller, requiring
countermeasures against noise and disconnection and
15 increasing work-hours of wiring work.
[0008]
Meanwhile, if a voltage stabilizer is configured to
include plural single stabilizers each having a waveform
controller, the power converters in the single stabilizers
20 each detect a feeder voltage with their built-in voltage
sensors and adjust the charge and discharge power of a power
storage element based on the detected voltage value.
Consequently, a charging start time and a discharging start
time differ among the respective single stabilizers due to
25 detection errors of the voltage sensors. Difference in such
6
times causes accumulating difference in electric charge to
be charged and discharged and, as a result, there occurs
disparity among the states of charge of the power storage
elements of the respective single stabilizers. When such
state of charge disparity increases, it causes 5 ses a decrease in
the rate of utilization of the respective single stabilizers.
Especially, in a case where the power storage elements are
rechargeable batteries, the batteries will stay at a high
state of charge or a low state of charge for longer time,
10 causing an early deterioration of the batteries.
SUMMARY OF INVENTION
TECHNICAL PROBLEM
[0009]
15 In view of the circumstances discussed above, the
present invention proposes a voltage stabilizer and a method
for controlling the same, enabling a reduction in state of
charge disparity among single stabilizers installed in one
electric substation.
20
SOLUTION TO PROBLEM
[0010]
A voltage stabilizer of the present invention includes
a power storage element and a power converter provided
25 between a feeder and the power storage element, wherein a
7
waveform controller in the power converter includes setting
voltage correction means which monotonically increases a
charging-control setting voltage and a discharging-control
setting voltage relative to a state of charge of the power
storage element. Thereby, it is possible to achieve 5 e a
solution to the problem discussed above.
ADVANTAGEOUS EFFECTS OF INVENTION
[0011]
10 In a single stabilizer which detects a higher feeder
voltage than other single stabilizer does because of
detection errors of voltage sensors, the feeder voltage
increases earlier due to surplus regeneration power and
charging starts earlier than in other single stabilizer,
15 resulting in a higher state of charge than in other single
stabilizer. Since, in response to an increase in the state
of charge, a control setting voltage in the single
stabilizer is corrected higher by the setting voltage
correction means of the present invention, time to start
20 charging when the feeder voltage increases is delayed and,
thus, state of charge disparity among single stabilizers can
be reduced.
[0012]
Furthermore, according to the present invention, a
25 controller is not needed which collects a quantity of status
8
of each single stabilizer and, therefore, it is unnecessary
to lay plural signal lines connecting voltage and current
sensors and a battery controller included in respective
single stabilizers with a waveform controller therein and
wiring work can be simplified5 .
BRIEF DESCRIPTION OF DRAWINGS
[0013]
Figure 1 is a diagram explaining a voltage stabilizer
10 with power storage according to a first embodiment of the
present invention.
Figure 2 is a diagram explaining a structure of a
single stabilizer according to the first embodiment of the
present invention.
15 Figure 3 is a block diagram depicting detail of
calculation by a waveform controller in the single
stabilizer according to the first embodiment of the present
invention.
Figure 4 is a diagram explaining a calculation to
20 calculate a correction signal to correct a voltage to start
charging and a voltage to start discharging depending on the
state of charge of the single stabilizer according to the
first embodiment of the present invention.
Figure 5 is a diagram explaining an example of change
25 of the voltage to start charging and the voltage to start
9
discharging in relation to the state of charge of a single
stabilizer according to the first embodiment of the present
invention.
Figure 6 is a diagram explaining an operation of the
voltage stabilizer with power storage according to 5 the first
embodiment of the present invention.
DESCRIPTION OF EMBODIMENTS
FIRST EMBODIMENT
10 [0014]
With reference to Fig. 1, a first embodiment of the
present invention is described.
[0015]
A voltage stabilizer 1 with power storage of the
15 present invention is connected to a feeder 6 and a rail 7.
The feeder 6 and the rail 7 are connected to a rectifier 5.
The rectifier 5 is connected to a power system 3 via a
transformer 4 and supplies DC power to a train which is not
depicted in Fig. 1 when the train accelerates.
20 [0016]
When the above train performs a regenerative operation
for deceleration, the voltage at the pantograph of the train
increases, which results in an increase in a feeder voltage
with respect to the rail 7 (hereinafter referred to as a
25 feeder voltage). The voltage stabilizer 1 with power
10
storage has functions to suppress an increase of the feeder
voltage by detecting the increase of the feeder voltage
vfeeder and charging a rechargeable battery which will be
described later and to suppress a decrease of the feeder
voltage by detecting the decrease of the feeder voltag5 e
occurring when the train accelerates and discharging the
battery.
[0017]
The voltage stabilizer 1 with power storage includes a
10 circuit breaker 2 and single stabilizers 1_a and 1_b. The
single stabilizers 1_a and 1_b are connected with each other
in parallel at their connection points to the circuit
breaker 2 and the rail 7.
[0018]
15 The single stabilizers 1_a and 1_b have an identical
structure, detecting increase and decrease of the feeder
voltage with a voltage sensor included in each single
stabilizer, charging and discharging a rechargeable battery
included in each single stabilizer, and changing currents
20 idc_a and idc_b flowing in from the feeder 6.
[0019]
With reference to Fig. 2, a single stabilizer 1_a is
described.
[0020]
11
The single stabilizer 1_a mainly includes a
bidirectional chopper 80_a, a rechargeable battery 30_a, a
battery controller 40_a, and a waveform controller 100_a.
Based on detected values by voltage and current sensors in
the bidirectional chopper 80_a and the state of charge 5 of
the battery 30_a detected by the battery controller 40_a,
the waveform controller 100_a calculates gate signals
GateP_a and GateN_a as driving signals of IGBT assembly in
the bidirectional chopper 80_a and outputs the gate signals
10 to the bidirectional chopper 80_a, implementing charging and
discharging of the battery 30_a. The charge and discharge
power of the battery 30_a is equal to power to and from the
feeder 6, when loss in the bidirectional chopper 80_a is
ignored. The feeder voltage can be stabilized by properly
15 charging and discharging the battery 30_a.
[0021]
The bidirectional chopper 80_a includes a boost
reactor 30L_a, an IGBT assembly 10_a, a filter reactor 20L_a
which prevents a ripple component produced by switching of
20 the IGBT assembly from flowing out to the feeder 6, and a
filter capacitor 20C_a. The IGBT assembly 10_a includes a
series circuit of IGBT modules 10m_a and 10n_a in each of
which an IGBT and a diode are connected in inverse parallel.
[0022]
12
The single stabilizer 1_a includes a voltage sensor
50PT_a which detects a voltage of the filter capacitor 20C_a,
a current sensor 51CT_a which detects a current of the boost
reactor 30L_a, and a voltage sensor 52PT_a which detects a
terminal voltage of the battery 30_a. Output signals of th5 e
above sensors are input to the waveform controller 100_a.
Output signals of the current sensor 51CT_a and the voltage
sensor 52PT_a are also input to the battery controller 40_a.
The battery controller 40_a calculates the state of charge
10 SOC_a of the battery 30_a based on the output signals of
these sensors and outputs a resulting value to the waveform
controller 100_a.
[0023]
Although the state of charge SOC_a of the battery 30_a
15 is calculated by the battery controller 40_a in the present
embodiment, the state of charge may be calculated within the
waveform controller 100_a. Although in the present
embodiment, the battery controller 40_a calculates the state
of charge SOC_a by using the output signals of the current
20 sensor 51CT_a which detects a current flowing through the
boost reactor and the voltage sensor 52PT_a which detects
the terminal voltage of the battery, the similar effect is
obtained by employing a voltage sensor and a current sensor
which are used only by the battery controller 40_a.
25 [0024]
13
With reference to Fig. 3, calculation operations which
are executed by the waveform controller 100_a are described.
[0025]
Calculation of the waveform controller 100_a mainly
includes a voltage control command value calculator 15005 a
that calculates a voltage control command value Vabs2 for
charging operation and a voltage control command value
Vdisc2 for discharging operation of the single stabilizer
1_a; a system control calculator 1004a that decides which
10 operation is performed of charging operation through the
bidirectional chopper, discharging operation through the
bidirectional chopper, and suppress standby operation in
which switching of the IGBT modules is deactivated and the
voltage stabilizer 1 stands by with switching of the
15 bidirectional chopper 80_a deactivated until a timing for
the voltage stabilizer 1 to operate; a current command value
calculator 1100a that calculates a charging current command
value to the battery 30_a; a current controller 1200a that
calculates a voltage command value vref which the IGBT
20 assembly 10_a should output to the battery 30_a according to
the current command value; and a gate signal generator that
generates gate signals GateP_a and GateN_a for driving the
IGBT modules 10m_a and 10n_a based on the voltage command
value vref.
25 [0026]
14
The system control calculator 1004a inputs Vabs2 and
Vdisc2, which are outputs of the voltage control command
value calculator 1500a, and a filter capacitor voltage
vline_a; calculates a calculation flag ABS_ENABLE of a
voltage controller 1007a for charging, which will 5 be
described later, a calculation flag DISC_ENABLE of a voltage
controller 1008a for discharging, and a gate deblocking flag
GateENBALE of the IGBT assembly; and outputs these flags to
the current command value calculator 1100a, the current
10 controller 1200a, and the gate signal generator 1300a.
[0027]
Specifically, if vline_a is higher than or equal to
Vabs2, ABS_ENBALE is set to 1, and if vline_a is lower than
Vabs2, ABS_ENBALE is set to 0. If vline_a is lower than or
15 equal to Vdisc2, DISC_ENABLE is set to 1, and if vline_a is
higher than Vdisc2, DISC_ENABLE is set to 0.
[0028]
GateENABLE is set to 1 if both or either of the above
ABS_ENBALE and DISC_ENABLE is 1, and set to 0 if both
20 ABS_ENBALE and DISC_ENABLE are 0.
[0029]
The current command value calculator 1100a inputs
output signals Vabs2 and Vdisc2 from the voltage control
command value calculator 1500a, a filter capacitor voltage
25 detected value vline_a, and the outputs ABS_ENBALE and
15
DISC_ENABLE of the system control calculator 1004a, and
calculates a charging current command value for the battery
30_a.
[0030]
A subtracter 1005a calculates a difference between th5 e
voltage command value Vabs2 for charging and the capacitor
voltage detected value vline_a and outputs the difference to
the voltage control calculator 1007a for charging. Moreover,
a subtracter 1006a calculates a difference between the
10 voltage command value Vdisc2 for discharging and the
capacitor voltage detected value vline_a and outputs the
difference to the voltage control calculator 1008a for
discharging.
[0031]
15 The voltage control calculator 1007a for charging,
which is a proportional integrator, performs a proportional
integral calculation on an output of the subtracter 1005a if
the calculation flag ABS-ENABLE is 1 and outputs zero if
ABS-ENABLE is 0.
20 [0032]
The voltage control calculator 1008a for discharging,
which is also a proportional integrator, performs a
proportional integral calculation on an output of the
subtracter 1006a if the calculation flag DISC_ENABLE is 1
25 and outputs zero if DISC_ENABLE is 1.
16
[0033]
Outputs of the voltage control calculator 1007a for
charging and the voltage control calculator 1008a for
discharging are added by an adder 1011a and the result is
output to the current controller 1200a as a charging curre5 nt
command value for the battery 30_a.
[0034]
In the current controller 1200a, a difference between
the above charging current command value and a detected
10 current value ibat_a of the boost reactor is calculated by a
subtracter 1012a and the difference is output to a current
control calculator 1013a.
[0035]
The current controller 1013a inputs the above
15 difference and a flag GateENABLE output from the system
control calculator 1004a. The current controller 1013a,
which is a proportional integrator, performs a proportional
integral calculation on an output of the subtracter 1012a if
GateENABLE is 1 and outputs the result to an adder 1015a.
20 It outputs zero to the adder 1015a if GateENABLE is 0.
[0036]
A terminal voltage detected value vbat_a of the
battery 30_a is input to a low-pass filter 1014a. The lowpass
filter 1014a eliminates a ripple component due to
25 switching and outputs the output to the adder 1015a.
17
[0037]
The adder 1015a calculates a sum of an output of the
current controller 1013a and an output of the low-pass
filter 1014a and outputs the sum to the gate signal
generator 1300a as an output voltage command value vref fo5 r
the IGBT assembly 10_a.
[0038]
The gate signal generator 1300a includes a carrier
generator 1016a for generating a carrier tri which is a
10 triangular wave, and a comparator 1017a. The comparator
1017a inputs a voltage command value vref, tri, and the flag
GateENABLE which is output by the system control calculator
1004a.
[0039]
15 If the flag GateENABLE is 1, the comparator compares
the voltage command value vref and the carrier tri to
determine which is larger, generates a gate signal, and
outputs the gate signal to the IGBT assembly 10_a. If
GateENABLE is 0, the comparator outputs a gate signal to
20 make both the IGBT modules 10m_a and 10n_a OFF to the IGBT
assembly 10_a.
[0040]
By the calculation operations described above, if the
filter capacitor voltage detected value vline_a becomes
25 larger than the voltage command value Vabs2 for charging,
18
the single stabilizer 1_a can control the charging current
of the battery 30_a to make vline_a equal to Vabs2; if
vline_a becomes smaller than the voltage command value
Vdisc2 for discharging, the stabilizer 1 can control the
discharging current of the battery 30_a to make vline_5 a
equal to Vdisc2; and if vline_a is between Vabs2 and Vdisc2,
the stabilizer 1 can deactivate switching of the IGBT
assembly 10_a and stand by.
[0041]
10 Then, the voltage control command value calculator
1500a which is a novelty of the present invention is
described.
[0042]
The voltage control command value calculator 1500a of
15 the present embodiment includes calculation means which
inputs the state of charge SOC_a of the battery 30_a and
corrects a voltage command value so that a voltage command
value Vabs2 for charging and a voltage command value Vdisc2
for discharging is monotonically increased relative to the
20 state of charge within a normal operating range of the state
of charge. This calculation operation makes it possible to
suppress disparity between the states of charge of the
rechargeable batteries of the single stabilizers 1_a and 1_b
whose controllers are independent with each other. It can
25 be expected to improve the rate of utilization of the
19
batteries and avoid shortening the lifespans of the
batteries.
[0043]
A specific calculation of the voltage control command
value calculator 1500a is describe5 d.
[0044]
The voltage control command value calculator 1500a
includes a voltage command value correction calculator 1001a
and adders 1002a and 1003a. By adding a correction term
10 vref_hos calculated by the voltage command value correction
calculator 1001a to Vabs and Vdisc which are given values,
the voltage control command value calculator 1500a
calculates a new voltage command value Vabs2 for charging
and a new voltage command value Vdisc2 for discharging, and
15 outputs these voltage command values to the current command
value calculator 1100a and the system control calculator
1004a.
[0045]
With reference to Fig. 4, an internal calculation
20 operation of the voltage command value correction calculator
1001a is described.
[0046]
The state of charge SOC_a of the battery 30_a is
output to a subtracter 10011a which subtracts SOC1 from it,
20
and the difference is output to an upper and lower limiter
10012a.
[0047]
The upper and lower limiter 10012a inputs an output of
the subtracter 10011a, limits it to a value equal to o5 r
larger than zero and equal to or lower than SOC, and
outputs the limited value to a multiplier 10013a. The
multiplier 10013a multiples an output of the upper and lower
limiter 10012a by a predetermined positive value K, thus
10 calculating a voltage command value correction term vref_hos.
[0048]
Here, SOC1 and SOC are predefined values and SOC1 is
set equal to or lower than a lower limit value of the normal
operating range. If a lithium ion battery is used for the
15 rechargeable battery, it is preferable to define an
operating range of the state of charge so that, taking the
battery lifespan into consideration, the lower limit is
equal to or higher than 20% and the upper limit is equal to
or lower than 80%. In this case, SOC1 is set equal to or
20 lower than 20% and the sum of SOC1 and SOC is set equal to
or higher than 80%.
[0049]
Through this correction calculation, the state of
charge SOC_a, the voltage command value Vabs2 for charging,
25 and the voltage command value Vdisc2 for discharging become
21
to exhibit a proportional characteristic, as is represented
in Fig. 5. This characteristic meets a purpose of
preventing disparity between the states of charge of the
batteries of the respective single stabilizers due to
detection errors of the voltage sensors to detect th5 e
capacitor voltage provided in the single stabilizers 1_a and
1_b. If an excessive correction is made to a voltage
command value in relation to the state of charge, the stable
range of the feeder voltage greatly changes depending on the
10 state of charge of the battery, leading to a risk to impair
the original function of the voltage stabilizer. Therefore,
it is preferable that a voltage command value correction
term vref_hos is set to be two to three times of an assumed
detection error of the voltage sensor. Specifically, the
15 given constant K should be selected so that the correction
term is set equal to or lower than 10% of the rated feeder
voltage.
[0050]
With reference to Fig. 6, operation of the voltage
20 stabilizer 1 with power storage of the present invention is
described.
[0051]
A graph in Fig. 6 represents, in order from top to
bottom, feeder voltage vfeeder at a point closest to the
25 voltage stabilizer 1; current idc_a flowing in the single
22
stabilizer 1_a from the feeder 6; the state of charge SOC_a
of the battery 30 of the single stabilizer 1_a; current
idc_b flowing in the single stabilizer 1_b from the feeder
6; and the state of charge SOC_b of the battery of the
single stabilizer 1_b. As an initial condition, SOC_a an5 d
SOC_b are assumed to be 50%, equal with each other. Solid
lines in the graph represent waveforms of operation
according to the present embodiment and waveforms
represented by dashed lines are waveforms when a calculation
10 is not executed to correct a voltage command value depending
on the state of charge.
[0052]
Furthermore, Fig. 6 represents the waveforms of
operation in a case where a voltage sensor for detecting the
15 capacitor voltage in the single stabilizer 1_a detects a
higher voltage than a voltage sensor for detecting the
capacitor voltage in the single stabilizer 1_b does.
[0053]
The feeder voltage increases because of a regenerative
20 operation of the train and the feeder voltage vfeeder
reaches a voltage control command value vf2 for charging of
the single stabilizer 1_a at time t1. The single stabilizer
1_a receives power from the feeder 6 by charging the battery
30_a, thus stabilizing the voltage. The current idc_a is a
23
positive value as the single stabilizer 1_a receives power
from the feeder 6.
[0054]
The single stabilizer 1_a continues charging until
time t2 when the feeder voltage decreases to a value lowe5 r
than the voltage control command value for charging, and
meanwhile the battery state of charge SOC_a increases.
[0055]
As the train accelerates, the feeder voltage vfeeder
10 decreases and becomes lower than a voltage control command
value vf3 for discharging of the single stabilizer 1_b at
time t3. The single stabilizer 1_b detects a decrease in
the capacitor voltage and supplies power to the feeder 6 by
discharging the battery, thus stabilizing the voltage. The
15 current idc_b is a negative value as the single stabilizer
1_b supplies power to the feeder 6.
[0056]
The single stabilizer 1_b continues discharging until
time t4 when the feeder voltage increases a value higher
20 than the voltage control command value vf3 for discharging,
and meanwhile the battery state of charge SOC_b decreases.
[0057]
In response to the change in the states of charge
mentioned above, the voltage control command value Vabs2 for
25 charging and the voltage control command value Vdisc2 for
24
discharging of the single stabilizer 1_a are corrected to
higher values, and the voltage control command value for
charging and the voltage control command value for
discharging of the single stabilizer 1_b are corrected to
lower values. In consequence, the differences decrease 5 of
the voltage control command values for charging and the
voltage control command values for discharging between the
single stabilizers 1_a and 1_b. As a result, charging and
discharging to stabilize the feeder voltage after time t5
10 are performed so that power is evenly distributed between
the single stabilizers 1_a and 1_b.
[0058]
If no correction is made of the voltage control
command value for charging and the voltage control command
15 value for discharging depending on the state of charge,
charging is performed again by the single stabilizer 1_a for
a period from time t5 to time t6 and discharging is
performed by the single stabilizer 1_b for a period from
time t7 to time t8. In consequence, disparity continues to
20 grow between the states of charge of the batteries of the
single stabilizers 1_a and 1_b.
[0059]
In the voltage stabilizer 1 with power storage of the
present embodiment, it is possible to suppress state of
25 charge disparity between the single stabilizers by making
25
correction of voltage control command values depending on
the state of charge.
[0060]
In the present embodiment, a correction term of a
voltage control command value for charging and a voltag5 e
control command value for discharging in relation to the
state of charge is assumed to be a value proportional to the
state of charge. The same effect as the present invention
can be expected even if the correction term may be a value
10 obtained by reference to a table or an exponential value of
the state of charge as long as it monotonically increases.
[0061]
In the present embodiment, voltage stabilizer includes
a battery as a power storage element. Alternatively, an
15 electric double-layer capacitor or a flywheel may be
included instead of the battery.
[0062]
When an electric double-layer capacitor is used as a
power storage element, the same effect as the present
20 invention is obtained by assuming as the state of charge a
normalized value of the energy stored in the capacitor by
the energy stored in the capacitor at a rated voltage.
Since the energy stored in the capacitor is proportional to
the square of the capacitor’s terminal voltage, the energy
25 stored in the capacitor may be calculated, a voltage sensor
26
to detect the capacitor voltage being included, from an
output of the sensor.
[0063]
When a flywheel is used as a power storage element,
the same effect as the present invention is obtained 5 by
assuming as the state of charge a normalized value of the
energy stored in the flywheel by the kinetic energy that the
flywheel stores at the rated rotational speed. Since the
kinetic energy stored in the flywheel is proportional to the
10 square of the rotational speed, the energy stored in the
flywheel may be calculated, a sensor to detect the
rotational speed or the rotational phase angle of the
flywheel being included, from the sensor.
[0064]
15 In the present embodiment, the terminal voltage of the
filter capacitor is assumed to be under voltage control.
Alternatively, a voltage between P and N terminals of the
single stabilizer may be under voltage control.
[0065]
20 According to the present invention, even in a case
where plural voltage stabilizers having power storage are
installed adjacently to one another, it is possible to
prevent state of charge disparity between the respective
voltage stabilizers. Therefore, it is possible to improve
27
utilization rate of the batteries and avoid aging
deterioration of the batteries.
[0066]
Furthermore, because communication between waveform
controllers is not required, it is possible to avo5 id
increase in work-hours of wiring work.
EXPLANATION OF REFERENCE CHARACTERS
[0067]
10 1: Voltage stabilizer
2: Circuit breaker
3: Power system
4: Transformer
5: Rectifier
15 6: Feeder
7: Rail
1a, 1b: Single stabilizers
80_a: Bidirectional chopper
30_a: Battery
20 40_a: Battery controller
100_a: Waveform controller
20L_a: Filter reactor
20C_a: Filter capacitor
10_a: IGBT assembly
25 10m_a, 10n_a: IGBT module
28
30L_a: boost reactor
50PT_a, 52PT_a: Voltage sensors
51CT_a: Current sensor
1100a: Current command value calculator
1200a: Current controlle5 r
1300a: Gate signal generator
1004a: System control calculator
1500a: Voltage control command value calculator
1001a: Voltage command value correction calculator
10 1007a, 1008a: Voltage control calculators
1013a: Current control calculator
1016a: Carrier generator
1017a: Gate signal calculator
10012a: Upper and lower limiter
15 10013a: Multiplier
29
Amended Claims under PCT Article 19

WE CLAIM:
1. A feeder voltage stabilizer with power storage, the
stabilizer connected to a direct-current feeder circuit,
comprising:
a power storage element5 ;
power conversion means provided between the feeder
circuit and the power storage element;
voltage detection means which detects a voltage
corresponding to a feeder voltage at a connection point of
10 the feeder circuit;
means for detecting energy stored in the power storage
element; and
control means which adjusts charge and discharge power
of the power storage element based on values detected by the
15 voltage detection means and the means for detecting energy,
wherein the control means comprises means for causing
the power conversion means to charge and discharge the power
storage element to reduce a difference between a voltage
command value and a value detected by the voltage detection
20 means, and
wherein the voltage command value is monotonically
increased relative to the energy within a normal operating
range of the power storage element.
30
Amended Claims under PCT Article 19
2. The feeder voltage stabilizer with power storage
according to claim 1,
wherein the power conversion means is a bidirectional
chopper.
5
3. The feeder voltage stabilizer with power storage
according to claim 1 or claim 2,
wherein the power conversion means comprises a filter
circuit which includes at least one reactor and at least one
10 capacitor at a connection point of the power conversion
means and the direct-current feeder circuit, and
wherein the voltage corresponding to the feeder
voltage is a terminal voltage of the capacitor.
15 4. The feeder voltage stabilizer with power storage
according to any one of claims 1 to 3,
wherein the power storage element is a rechargeable
battery.
20 5. The feeder voltage stabilizer with power storage
according to claim 4,
wherein means for detecting energy of the rechargeable
battery calculates a charging rate of the rechargeable
battery.
25
31
Amended Claims under PCT Article 19
6. The feeder voltage stabilizer with power storage
according to any one of claims 1 to 3,
wherein the power storage element is an electric
double-layer capacitor.
5
7. The feeder voltage stabilizer with power storage
according to claim 6,
wherein means for detecting energy of the electric
double-layer capacitor comprises voltage detection means
10 which detects a terminal voltage of the capacitor.
8. The feeder voltage stabilizer with power storage
according to any one of claims 1 to 3,
wherein the power storage element is a flywheel.
15
9. The feeder voltage stabilizer with power storage
according to claim 8,
wherein means for detecting energy of the flywheel
comprises a function of detecting a rotational speed of the
20 flywheel.
10. A method for controlling a feeder voltage
stabilizer with power storage, the stabilizer connected to a
direct-current feeder circuit, comprising:
25 a power storage element;
32
Amended Claims under PCT Article 19
power conversion means provided between the feeder
circuit and the power storage element;
voltage detection means which detects a voltage
corresponding to a feeder voltage at a connection point of
the feeder circuit5 ;
means for detecting energy stored in the power storage
element; and
control means which adjusts charge and discharge power
of the power storage element based on values detected by the
10 voltage detection means and the means for detecting energy,
wherein the control means comprises means for causing
the power conversion means to charge and discharge the power
storage element to reduce a difference between a voltage
command value and a value detected by the voltage detection
15 means, and
wherein the voltage command value is monotonically
increased relative to the energy within a normal operating
range of the power storage element.
20 11. The method for controlling a feeder voltage
stabilizer with power storage according to claim 10,
wherein the power conversion means is a bidirectional
chopper.
33
Amended Claims under PCT Article 19
12. The method for controlling a feeder voltage
stabilizer with power storage according to claim 10 or claim
11,
wherein the power conversion means comprises a filter
circuit which includes at least one reactor and at least o5 ne
capacitor at a connection point of the power conversion
means and the direct-current feeder circuit, and
wherein the voltage corresponding to the feeder
voltage is a terminal voltage of the capacitor.
10
13. The method for controlling a feeder voltage
stabilizer with power storage according to any one of claims
10 to 12,
wherein the power storage element is a rechargeable
15 battery,
wherein means for calculating a charging rate of the
rechargeable battery is provided, and
wherein the voltage command value is monotonically
increased relative to the charging rate.
20
14. The method for controlling a feeder voltage
stabilizer with power storage according to any one of claims
10 to 12,
wherein the power storage element is an electric
25 double-layer capacitor,
34
Amended Claims under PCT Article 19
wherein means for detecting a terminal voltage of the
capacitor is provided, and
wherein the voltage command value is monotonically
increased relative to the terminal voltage of the capacitor.
5
15. The method for controlling a feeder voltage
stabilizer with power storage according to any one of claims
10 to 12,
wherein the power storage element is a flywheel,
10 wherein means for detecting a rotational speed of the
flywheel is provided, and
wherein the voltage command value is monotonically
increased relative to the rotational speed of the flywheel.