Field of the Invention
The present invention relates to a power distribution
device and a power distribution system using the same and,
more particularly, to a power distribution device and a
power distribution system that have the function of
distributing a DC power supplied from a DC power source to
loads.
Background of the Invention
Conventionally, a power distribution system for
distributing an AC power and a DC power in a building such
as a house, a store or an office building, is disclosed in,
e.g., Patent Document 1. The power distribution system is a
grid-connected system that includes a DC power generation
equipment such as a solar photovoltaic power generation
apparatus, as a private power station, installed in a
building. The power distribution system converts a DC power
outputted from the DC power generation equipment into an AC
power, and performs a grid connection of the AC power
converted from the DC power of the DC power generation
equipment and a commercial power source (an AC power system)
supplied from an electric power company.
Such a grid-connected system employs a configuration

where a DC power generated by the DC power generation
equipment is converted into an AC power by a power converter
(a power conditioner) and is cooperated with the commercial
power source serving as an AC power source. Further, the
grid-connected system enables a surplus power to reversely
flow into the commercial power source (so-called electric
power selling) when a power supplied from the DC power
generation equipment exceeds the power consumed by loads
within a building.
Furthermore, as a power distribution system for
supplying a DC power to a DC load device, there is proposed
a power supply system in, e.g., Patent Document 2. In the
power supply system, a DC power supply unit communicates
with a terminal device of the DC load device and a power-
feeding control unit compares power reception information
notified by the terminal device with operational power
information stored in an operation information memory, and
controls an output voltage to supply the DC load device with
a proper voltage and current.
In such power distribution system for distributing the
DC power, multiple power sources including a DC power
generation equipment such as a solar photovoltaic power
generation apparatus or a fuel cell, a battery, a commercial
power source and the like, may be used. Therefore, it is
necessary to provide a power distribution system suitable to
these multiple power sources. In this case, typically, an

output converter such as a DC/DC converter or an AC/DC
converter is provided for each of the power sources, and
outputs a DC power with a specific voltage level.
As described above, if there are used multiple power
sources, the output converter such as a DC/DC converter or
an AC/DC converter is required in order to distribute a
power from the power sources. Thus, it is necessary to
simplify and make safe the management of the plurality of
power sources, such as installation and maintenance. In
particular, since a plurality of heat-generating output
converters is provided on a distribution board, a problem of
heat dissipation property arises in a DC distribution board,
unlike an AC distribution board.
Recently, there are provided an AC input terminal from
an AC power source, a DC input terminal from a DC power
source such as solar cells, and a DC output terminal
connected to DC device all together in the distribution
board. An erroneous connection between the terminals may
lead to damage of devices and a serious accident, and cause
danger.
Furthermore, a power distribution system disclosed in
Patent Document 3 adopts a configuration for controlling the
output of a secondary battery or solar cells so that a power
converter or AC/DC converter can be operated at maximum
conversion efficiency. Besides, in the power distribution
system of Patent Document 3, multiple AC/DC converters are

used depending on an amount of a power supplied to a load.
In the power distribution system of Patent Document 3,
however, if the amount of the power supplied to the load
varies due to, e.g., an increase of a load or a replacement
of a load, the existing power converter cannot supply enough
power to the load. Further, in a power distribution system
having a specification where a power conversion efficiency
increases with an increase in the amount of the power
supplied to a load, a power conversion efficiency may lower
due to a significant change in the amount of the power
supplied to the load.
Such problem can be solved by changing the
specification of the power distribution system in accordance
with the load. In this case, the entire power distribution
system has to be replaced. As a result, the existing power
distribution system needs to be discarded, thereby causing
an increase in cost.
[Related Art Documents]
[Patent Document 1] Japanese Patent Application
Publication No. 2003-284245
[Patent Document 2] Japanese Patent Application
Publication No. 2009-159690
[Patent Document 3] Japanese Patent Application
Publication No. 2009-153301

Summary of the Invention
In view of the above, the present invention provides a
power distribution device and a power distribution system
for DC power that are easy to install and maintain. Further,
the present invention provides a power distribution device
that has excellent heat dissipation properties and rises
less in temperature. Furthermore, the present invention
provides a safe power distribution device capable of
preventing an error connection.
Additionally, the present invention provides a power
distribution device capable of easily changing a
specification of a power distribution system.
In accordance with a first aspect of the present
invention, there is provided a power distribution device,
including: a DC power source DC/DC converter connected to a
DC power source; an AC/DC converter connected to an AC power
source; and a DC load line connected to a DC load, wherein
the DC/DC converter and the AC/DC converter are accommodated
in a single container, and the DC load line is drawn from
the container.
Further, the power distribution device includes: a
battery; a battery DC/DC converter connected to the battery;
and a protection circuit connected to at least one of the DC
power source DC/DC converter, the battery DC/DC converter,
and the AC/DC converter.

With this configuration, handling is easy because
elements necessary to supply power from the DC power source
is formed into a single unit and accommodated in the
container. Handling becomes further easier because the
installation or maintenance of the elements may be performed
at one place.
Preferably, the DC power source DC/DC converter, the
battery DC/DC converter, and the AC/DC converter are
arranged horizontally side-by-side with a predetermined gap.
With such configuration, since the heat generating
first and the second DC/DC converters and the AC/DC
converter are arranged side by side, it is possible to
enhance heat dissipation. Further, since a heat dissipation
plate or a heat dissipation fin is disposed between the
converters, heat dissipation property may be increased.
The battery may be disposed so that the battery is not
placed above the DC power source DC/DC converter, the
battery DC/DC converter, and the AC/DC converter.
Accordingly, the heat dissipation property can be
excellently maintained without being lowered.
The battery may be detachably installed in the
container.
With such configuration, since the battery is
detachable, maintenance is easy when the battery needs to be
replaced due to deterioration of the battery or scale-up of
the device.

Further, the battery DC/DC converter may be connected
to the battery by a connector.
By doing so, since the second DC/DC converter is
connected to the external battery by the connector, the
battery can be easily removed.
Further, the power distribution device may includes: a
control unit for controlling outputs of the DC power source
DC/DC converter, the batter DC/DC converter, and the AC/DC
converter; a display unit for displaying status of power
supply; and a manipulation unit for manipulating an ON/OFF
of each of the DC power source, AC power source, and the
protection circuit.
With this configuration, since the control unit, the
display unit, and the manipulation unit are provided on the
outer surface of the container of the power distribution
device, workability is excellent.
Furthermore, the power distribution device may
include: a first terminal block for connecting a first line
to the DC load; and a second terminal block for connecting a
second line from the DC power source; wherein at least one
of shapes and colors of the first and the second terminal
blocks and colors of the first and the second lines are
distinguishable from each other.
With such configuration, an erroneous connection can
be avoided, and a high-reliability connection can be
achieved.

In accordance with a second aspect of the present
invention, there is provided a power distribution system
including the power distribution device as described above,
and a terminal for additionally installing a battery.
Accordingly, a battery having, e.g., a high output
capacity is easily added as needed.
The power distribution system may further include
battery units each including a battery and a battery DC/DC
converter.
Accordingly, the battery can be easily added if
necessary.
Further, the power distribution system may include a
plurality of the above-described power distribution device.
With this configuration, it is possible to provide a
compact power distribution system capable of reliably
driving high performance equipments.
In accordance with a third aspect of the present
invention, there is provided a power distribution device,
including: module devices each including a power converter
for converting an input power into a desired output power,
wherein the module devices are accommodated in a single
container, each having an external dimension having a preset
unit size or corresponding to the dimension in which
multiple module devices each having the preset unit size are
arranged in parallel.
Further, the power distribution device includes a main

path electrically connected to the module devices, for
including a power line and a communications line, wherein a
power is supplied from the module devices to a load via a
power supply line connected to the main path; and wherein
each of the module devices includes a connection hole
connected to the main path, a body detachably installed to
the main path via the connection hole, and an internal
circuit accommodated in the body and connected to the main
path, the internal circuit having a function of autonomously
controlling an output power so that a power needed for the
load can be supplied to the load and a function of operating
in accordance with an external instruction via the
communications line.
With such configuration, the power converter is
modularized as the module device, including the body having
an external size equivalent to a unit size or equivalent to
the multiple module devices each having the unit size, the
multiple module devices being arranged horizontally side-by-
side; and the internal circuit connected to the main path.
Accordingly, the additional installation or the replacement
of a power converter can be easily performed. Further,
there is an advantage in that a specification of the power
distribution system may be easily changed depending on the
loads.
Furthermore, the internal circuit of the module device
has the function of autonomously controlling an output power

so that a power equivalent to the power required by each of
the loads is supplied to the load. Accordingly, a power can
be supplied to the load by a module device only by
connecting the module device to the main path. Besides, the
internal circuit of the module device also has the function
of operating in accordance with an external instruction via
the communications line. Accordingly, it is also possible
to perform a complicated control based on an external
instruction.
In the power distribution device, at least two module
devices of the module devices connected to the main path may
form a converter group, and a sum of output currents
outputted from the module devices of the converter group may
be supplied to the load as a total output current; each of
the module devices having a power conversion efficiency
depending on an amount of the output current, the power
distribution device may further include: an efficiency
storage unit which previously stores a relationship between
an output current and a conversion efficiency for each of
the module devices; a pattern storage unit which previously
stores allocation patterns each indicating a rule for
allocating the total output current to each of the module
devices of the converter group; a total output instruction
unit for instructing a total output current to be outputted
from the converter group; a allotment determination unit for
selecting one from the allocation patterns stored in the

pattern storage unit as an application pattern using the
total output current instructed by the total output
instruction unit and the conversion efficiency stored in the
efficiency storage unit; and an allocation control unit for
controlling the output of each of the module devices so that
the total output current is allocated to each of the module
devices based on the selected application pattern.
Preferably, the allotment determination unit
calculates a sum of input powers of the entire converter
group when the output currents are allocated to the module
devices of the converter group based on each of the
allocation patterns stored in the pattern storage unit, the
sum of the input powers being calculated by using the
conversion efficiency stored in the efficiency storage unit
with respect to each of the allocation patterns. Further,
the allotment determination unit may select an allocation
pattern having a minimum sum of the input powers as the
application pattern.
With this configuration, since the total output
current is allocated based on application patterns, power
conversion efficiency in all the multiple module devices
forming each the converter group is increased as compared
with the case where the total output current is not
allocated based on application patterns. Consequently, it
is possible to reduce a loss during power conversion in the
entire power distribution device.

In the power distribution device, each of the module
devices of the converter group may be formed of a switching
power supply in which a relationship between the output
current and the conversion efficiency varies depending on an
oscillation control mode thereof, and the allotment
determination unit may select the application pattern using
the conversion efficiency corresponding to the oscillation
control mode.
By doing so, it is possible to select as a application
pattern an allocation pattern where a sum of input power is
minimum regardless of a oscillation control mode of a module
device, and the power conversion efficiency is increased in
the multiple module devices included in the converter group
as a whole.
Further, the power distribution device may be employed
in a power distribution system including solar cells, a
battery and a power conditioner having a function of
converting a DC power into an AC power, the module devices
serving as a power converter may be provided between the
battery and the power conditioner. Furthermore, the power
converter may be connected to the main path, input powers
from the solar cells and the battery to the power
conditioner, and reversely flow a surplus power provided in
at least one of the solar cells and the battery into a
commercial power system via the power conditioner.
With such configuration, since power from solar cells

and a battery is inputted to the power conditioner, the
power conditioner is shared by the solar cells and the
battery. Thus, even when a surplus power is present in the
output power from the solar cells and the battery, the
surplus power can be made to flow reversely into the
commercial power system via the power conditioner.
In the power distribution device, further, the power
conditioner may be provided between the solar cells and the
commercial power system, and the power converter may be
provided between the solar cells and the main path, and the
power converter bi-directionally may convert a power between
the solar cells and the battery, and reversely flow the
surplus power of the battery into the commercial power
system via the power conditioner.
In this case, the power converter can perform a
bidirectional power conversion between the solar cells and
the main path. Thus, the power converter may output the
power generated by the solar cells to the main path at
normal times and perform the reverse flow of a surplus power
into the commercial power system when the battery outputs
the surplus power. Further, the power converter provided
between the solar cells and the main path may be realized
using a single bidirectional module device or two
unidirectional module devices.
Effect of the invention

With the power distribution device of the present
invention, when a power is supplied to a DC device from a DC
power source such as solar light power generation or a fuel
cell, and a commercial power source, the supply of the power
can be easily manipulated and can be executed using one unit.
Furthermore, with the power distribution device of the
present invention, a power converter can be easily added or
replaced because the power converter is modularized as a
module device formed of a body having a external dimension
equivalent to a unit size, and an internal circuit connected
to a main path. Accordingly, there is an advantage in that
a specification of the power distribution system can be
easily changed depending on the loads.
Brief Description of the Drawings
The objects and features of the present invention will
be apparent from the following description of embodiments
when taken in conjunction with the accompanying drawings, in
which:
Fig. 1 is a schematic diagram showing an appearance of
a power distribution device in accordance with an embodiment
1 of the present invention;
Fig. 2 is a perspective view showing the distribution
board of the power distribution device in accordance with

the embodiment 1 of the present invention;
Fig. 3 is a block diagram showing configuration of the
power distribution system in accordance with the embodiment
1 of the present invention;
Fig. 4 is a block diagram showing configuration of a
power distribution system in accordance with an embodiment 2
of the present invention;
Fig. 5 is a block diagram showing configuration of a
power distribution system in accordance with an embodiment 3
of the present invention;
Fig. 6 is a block diagram showing configuration of a
power distribution system in accordance with an embodiment 4
of the present invention;
Fig. 7 is a schematic block diagram showing another
configuration example of the power supply apparatus in the
power distribution system shown in Fig. 6;
Fig. 8 is a conversion efficiency-output current
characteristic diagram of the module device used in the
power distribution system shown in Fig. 6;
Fig. 9 is a schematic block diagram of principle parts
of the power distribution system shown in Fig. 6;
Fig. 10 is a block diagram showing configuration of a
power distribution system in accordance with an embodiment 5
of the present invention;
Fig. 11 is a schematic circuit diagram showing
configuration of a module device used in the power

distribution system shown in Fig. 10; and
Fig. 12 is a diagram showing the appearance of the
module device used in the power distribution system shown in
Fig. 12.
Detailed Description of the Preferred Embodiments
Embodiments of the present invention will be described
in detail below with reference to the accompanying drawings
that form a part hereof. The same reference numerals will
be assigned to the same or similar components throughout the
drawings, and redundant descriptions thereof will be omitted.
In the embodiments described below, although a power
distribution device in accordance with the present invention
is applied to a detached house, the present invention is not
limited thereto. The power distribution system in
accordance with the present invention may also be applied to
each house of a multi-family house or each office of an
office building.
Fig. 1 is a schematic diagram showing the appearance
of a power distribution device in accordance with an
embodiment 1 of the present invention; Fig. 2 is a
perspective view showing the distribution board of the power
distribution device in accordance with the embodiment 1 of
the present invention; and Fig. 3 is a block diagram showing
configuration of the power distribution system in accordance

with the embodiment 1 of the present invention.
The power distribution system of the present
embodiment is applicable to a hybrid power distribution
system that has solar cells and a battery and can distribute
an AC and DC power.
The power distribution device is provided as a DC
distribution board 110 (see Fig. 3) and accommodated in a
container 100. The power distribution device, as shown in
Figs. 1 to 3, includes a first DC/DC converter (hereinafter,
referred to as a "solar cell converter") 111 connected to
solar cells 101 as a DC power source, an AC/DC converter 113
connected to a commercial power source (an AC power system)
105 as an AC power source, a battery 102, and a second DC/DC
converter (hereinafter, referred to as a "battery
converter") 112 connected to the battery 102.
The power distribution device further includes
protectors 116, that is, protection circuits connected to
the solar cell converter 111, the battery converter 112 and
the AC/DC converter 113, and power distribution paths 107
for DC load drawn from the container 100 that defines the DC
distribution board 110. In the embodiment, although the
protectors 116 is connected to all of the solar cell
converter 111, the battery converter 112 and the AC/DC
converter 113, the protectors may be connected to at least
one of the solar cell converter 111, the battery converter
112 and the AC/DC converter 113.

The solar cell converter 111, the battery converter
112, and the AC/DC converter 113 are arranged horizontally
side-by-side with a predetermined gap therebetween, and heat
dissipation fins 400 are provided between the solar cell
converter 111, the battery converter 112, and the AC/DC
converter 113, as shown in Fig. 2.
As shown in Fig 1, the battery 102 is accommodated in
a battery casing 220 and is detachably installed to the
container 100 using a fixing unit 122. Further, the battery
may be directly connected to the board of the battery
converter 112, and may be connected to the board of the
battery converter 112 using a connector 132. In such a
connector connection, maintenance becomes easier when the
battery needs to be replaced due to deterioration or scale-
up. Furthermore, installation and separation are easy
because a connection to an external battery is performed
using the connector connection. In addition, the battery
converter 112 may also be connected to the board of the
distribution board using a connector, as will be described
later.
In the meantime, a power distribution system using the
power distribution device, as shown in Fig. 3, includes an
AC distribution board 104 for distributing an AC power to an
AC load device (not shown) via an AC power distribution path
106, and the DC distribution board 110 as a DC power
distribution device for distributing a DC power to DC loads

via the DC power distribution paths 107. The AC
distribution board 104 has input terminals connected to the
commercial power source 105 (the AC power source) and a
power conditioner 103 and has output terminals connected to
the AC power distribution path 106 and the DC distribution
board 110. The AC distribution board 104 branches an AC
power outputted from the commercial power source 105 or the
power conditioner 103 and outputs AC power to the AC power
distribution path 106 and the DC distribution board 110.
The solar cells 101 and the battery 102 are provided
as the DC power sources of the power distribution system.
In the embodiment, the battery 102 is installed on the DC
distribution board 110, but the battery 102 may be
externally added and used as an additional power source. An
example in which the battery 102 is externally added will be
descixbed later. The solar cells 101 receive a solar light,
generate a solar power by converting the energy of the solar
light into electricity by the photovoltaic effect, and
output a DC power, and form a part of a solar power
generation apparatus as an example of a DC power generation
equipment.
The battery 102 includes a secondary battery capable
of being charged with a DC power and discharging the DC
power. The DC distribution board 110 has input terminals
connected to the solar cells 101 and the AC distribution
board 104, and has output terminals connected to the DC

power distribution paths 107. The DC distribution board 110
includes the solar cell converter 111, the battery converter
112, and the AC/DC converter 113, as output converters.
Further, the DC distribution board 110 includes a control
unit 114 and a display unit 115.
An output line of the solar cells 101 branches into
two, and is connected to the power conditioner 103 and the
solar cell converter 111 in the DC distribution board 110.
The power conditioner 103 converts a DC power outputted from
the solar cells 101 into an AC power synchronized with the
phase of the commercial power source 105. The power
conditioner 103 outputs the AC power to reversely flow into
the commercial power source 105.
The solar cell converter 111 includes a DC/DC
converter. The converter 111 converts a DC power outputted
from the solar cells 101 into a DC power having a desired
voltage level, and outputs the DC power having the desired
voltage level. The battery converter 112 includes a DC/DC
converter. The converter 112 converts a DC power outputted
from the battery 102, into a DC power having a desired
voltage level, and outputs the converted DC power to charge
the battery 102. The AC/DC converter 113 converts an AC
power supplied from the AC distribution board 104 into a DC
power having a desired voltage level, and outputs the DC
power.
The power conditioner 103 includes a boosting chopper

circuit (not shown) for boosting the DC power outputted from
the solar cells 101, an inverter (not shown) for converting
the DC power boosted by the boosting chopper circuit into a
sinusoidal AC power synchronized with the phase of the AC
power system, an inverter control circuit (not shown) for
controlling the inverter to adjust the AC power, and a grid
connection protection device.
Like a so-called household distribution board (a
household board), the AC distribution board 104 is provided
in a box having a door, and includes a main breaker (not
shown) whose primary side is connected to the commercial
power source 105, and multiple branch breakers into which a
conduction bar (not shown) branches. The conduction bar is
connected to a secondary side of the main breaker. Further,
an output line of the power conditioner 103 is connected to
the AC distribution board 104 and the commercial power
source 105 in the box. Furthermore, the AC power
distribution path 106 is connected to the secondary sides of
the branch breakers, so that the AC power is supplied to the
AC load device within the house via the AC power
distribution path 106.
Like the AC distribution board 104, the DC
distribution board 110 is accommodated in the container 100
having a door. Further, the output of the commercial power
source 105 via the AC distribution board 104 and the output
of the solar cells 101 are respectively inputted to the

AC/DC converter 113 and the DC/DC solar cell converter 111,
so that the DC power is supplied to DC load devices 207 via
the power distribution paths 107.
In the DC distribution board 110, each of the solar
cell converter 111 and the battery converter 112 includes,
e.g., a switching regulator, and converts the voltage level
of the DC power outputted from each of the solar cells 101
and the battery 102 into a.desired voltage level. The solar
cell converter 111 and the battery converter 112 perform a
constant voltage control (feedback control) by detecting an
output voltage and increasing or decreasing the output
voltage so that the detected output voltage becomes
identical to a target voltage.
The AC/DC converter 113 includes a switching regulator,
an inverter and the like, rectifies an AC voltage and
outputs a DC voltage. The AC/DC converter 113 converts the
AC power outputted from the AC distribution board 104 into a
DC power having a desired voltage level by performing a
constant voltage control on the output voltage through
feedback control. The output terminals of the solar cell
converter 111, the battery converter 112, and the AC/DC
converter 113 are connected in parallel to the DC power
distribution paths 107 via the protectors 116 such as
current fuses.
In the DC power distribution paths 107, Protection
circuits (not shown) may be installed externally when

necessary. Thus, from among the DC powers having desired
voltage levels converted by the solar cell converter 111,
the battery converter 112 and the AC/DC converter 113, a DC
power is supplied to DC load devices 207 via the DC power
distribution paths 107.
The control unit 114 is formed of an information
processing device including, e.g., a microcomputer, and
controls the operations of the parts of the DC distribution
board 110. The control unit 114 controls the turning ON/OFF
and an output voltage of each of the solar cell converter
111, the battery converter 112, and the AC/DC converter 113.
The control unit 114 also controls the display unit 115.
The display unit 115 includes a liquid crystal display
device, and displays a variety of information including an
operating status of the DC distribution board 110, using
characters, numerals, and images, based on an instruction
from the control unit 114. Further, a manipulation unit 300
is provided through which an operating status, an abnormal
state, measurement items, a timer and the like, are set and
an abnormal history is displayed.
Here, the abnormal history may include a voltage of
the solar cells, a voltage of the battery, an AC voltage,
and an output power immediately before an abnormality occurs,
and the time when the abnormality occurred. Further, the
above settings may be performed using not only a
manipulation unit provided in the DC distribution board 110

but also a remote manipulation unit (a remote controller or
a personal computer in the house), or may be performed
through a DLC (DC power line communications) terminal 310.
Meanwhile, the power conditioner 103 may have a normal
reverse flow function for a power generated by the solar
light, a night battery charging function, and a day battery
discharging function. Accordingly, the power conditioner
103 may usefully utilize both the power generated using the
solar light and the power charged at night.
Further, since the reverse flow of the power
discharged from the battery into an AC power system is not
permitted, it is necessary to change the discharged power
depending on a use situation of the load devices. For
example, a power flowing in the power system may be detected
by a power reception detection unit provided in a reception
point of the power system, and a control for preventing the
reverse flow may be performed so that no power is reversely
flowed from the battery.
With this configuration, handling is easy because
elements necessary to supply a power from the DC power
source are formed into a single unit as the DC distribution
board and can be accommodated in the container. Further,
handling becomes easier because installation and maintenance
can be performed in one place.
In the present embodiment, the solar cell converter
111, the battery converter 112, and the AC/DC converter 113

which are accompanied by the generation of heat are arranged
in parallel to each other in the same plane, as shown in
Figs. 1 and 2, thereby achieving excellent heat dissipation.
Besides, since heat dissipation plates or the heat
dissipation fins 400 are disposed between the converters, it
is possible to further improve the heat dissipation.
Further, the battery 102 is disposed so that it is not
placed over any of the solar cell converter 111, the battery
converter 112, and the AC/DC converter 113. Accordingly,
the heat dissipation of the solar cell converter 111, the
battery converter 112, and the AC/DC converter 113 can be
excellently maintained without being hindered by the
existence of the battery 102.
Furthermore, the battery can be freely mounted on and
removed from the container. Accordingly, maintenance is
easy even when the battery needs to be replaced due to
deterioration or scale-up.
In the present embodiment, the control unit 114
controls which one of the solar cell converter 111, the
battery converter 112, and the AC/DC converter 113 outputs
power, and the display unit 115 displays the power supply
status. Further, by using the manipulation unit 300, the
ON/OFF of the DC or AC power source or of the protectors 116
as the protection circuits can be controlled. Therefore,
operability is excellent.
In the present embodiment, the DC/DC battery converter

112 is connected to the battery 102 by the connector.
Accordingly, the DC/DC battery converter 112 can be easily
mounted and removed even when it is connected to an external
battery. Further, even when a battery needs to be replaced
due to deterioration or scale-up, maintenance is easy
because the battery 102 is detachably connected to the DC/DC
battery converter 112.
In order to avoid erroneous connections, it is
preferred that a first terminal block 307 connected to the
DC power distribution paths 107 for the DC load devices 207,
a second terminal block 301 connected to a power
distribution path 201 from the DC power source, and a third
terminal block 305 connected to the AC power distribution
path 2 05 from the AC power source are different from each
other in shape or color, and colors of the power
distribution paths are distinguishable from each other. If
the shapes of the terminal blocks are different such that
the terminal blocks cannot be erroneously connected, it
becomes safer.
(Embodiment 2)
An embodiment 2 of the present invention in which an
additional battery is installed will be described below.
Fig. 4 shows the block diagram of a power distribution
system in accordance with the embodiment 2. As shown in Fig.
4, a connector 200 for a battery may be provided in a DC
distribution board 110, and an external battery 102S may be

connected to the DC distribution board 110 via the connector
200 for a battery. Since the other elements of the power
distribution system shown in Fig. 4 are the same as those of
the power distribution system shown in Fig. 3, descriptions
thereof will be omitted. In the present embodiment, the
manipulation unit is not provided, and manipulation is
performed through the DLC terminal using a remote
manipulation unit (not shown).
With such configuration, if a capacity of solar cells
is increased by, e.g., addition and renovation, an
additional battery may be installed in accordance with the
capacity of the solar cells.
(Embodiment 3)
Next, an embodiment 3 of the present invention where
an additional battery unit is installed will be described
below.
Although only the battery is added in the embodiment 2,
a battery unit 210 including a battery converter 112S and
the external battery 102S is provided as a single unit and
connected to a DC distribution board 110 in the present
embodiment. Fig. 5 shows a block diagram of a power
distribution system in accordance with the present
embodiment. As shown in Fig. 5, a connector 211 is provided
in the DC distribution board 110, such that the battery unit
210 is externally connected to the DC distribution board 110
via the connector 211.

If the battery unit 210 is externally provided as
described above, the battery 102 and the battery converter
112 within the DC distribution board 110 may be omitted.
Since the other elements of the power distribution system
shown in Fig. 5 are the same as those of the power
distribution system shown in Fig. 3, descriptions thereof
will be omitted.
With such configuration, even when the capacity of the
battery converter is insufficient, an additional battery
unit can be installed, and therefore the limitations imposed
on a design can be significantly reduced.
As described above, in accordance with the present
embodiment, the battery unit including the battery and the
DC/DC battery converter is detachably provided, and the
installation of an additional battery becomes easy.
Furthermore, since the connector 211 is provided as a
terminal for additional battery, it becomes easier to
install an additional battery such as a high capacity
battery whenever necessary.
Further, the power distribution system in accordance
with the present invention may have a configuration which
includes a plurality of power distribution systems
constituted by the combination of the power distribution
systems of the embodiments 1 to 3.
(Embodiment 4)
A power distribution system in accordance with an

embodiment 4 of the present invention will be described
below with reference to Figs. 6 to 9. As shown in Fig. 6,
the power distribution system of the embodiment 4 includes a
power supply apparatus 1 (a power distribution device) which
converts a DC power from a battery 3 and solar cells 4 and
an AC power from a commercial power source AC into a desired
DC power and outputs the converted DC power, and a
controller 8 provided in the outside of the power supply
apparatus 1. The power distribution device may further
include the battery 3, and the display unit and the
manipulation unit (not shown) described in connection with
the embodiment 1. The battery 3, the display unit, and the
manipulation unit may be accommodated in the container 100
shown in Fig. 1.
The power distribution system supplies a current
outputted from the power supply apparatus 1 to multiple
loads (not shown) via power supply lines 5. The loads
connected to the power supply lines 5 are DC loads driven by
DC power, e.g., LED illuminations or alarms in a house.
Further, an AC power supply line 7 is connected to the
commercial power source AC via an AC distribution board 6,
and an AC load (not shown) driven by an AC power are
connected to the power supply line 7. Accordingly, a power
can be supplied to both the DC loads and the AC load.
The power supply apparatus 1 includes power converters
which converts respective input powers into desired output

powers. In the present embodiment, the power converters
include a bidirectional AC/DC converter provided between the
commercial power source (the AC distribution board 6) AC and
the power supply lines 5 for converting an AC power into DC
power and vice versa, a DC/DC converter for stepping up or
down the output of the solar cells 4, a bidirectional DC/DC
converter for charging and discharging the battery (a
secondary battery) 3, and a DC/DC converter for stepping
down a voltage.
The power supply apparatus 1 is accommodated in a
board unit 10. Specifically, power converters forming a
part of the power supply apparatus 1 as described above are
disposed in the board unit 10 as module devices 2a to 2d
(hereinafter, simply referred to "module devices 2" if they
are not specially distinguished from one another) and the
module devices 2 are connected to bus lines (main paths) 11
provided within the board unit 10. Here, the DC power
supply lines 5 are divided into two systems of a high
voltage system (e.g., DC 350 V) and a low voltage system
(e.g., DC 48 V). Further, the power supply line 5 of the
high voltage system is directly connected to the bus line 11,
and the power supply line 5 of the low voltage system is
connected to the bus line 11 via a DC/DC step-down converter
as the module device 2d.
In the present embodiment 4, all of the module devices
2 included in the power supply apparatus 1 have the same

external dimension and shape as shown in Fig. 12. For
example, an internal circuit 2-2 is installed in a body 2-1
having a preset unit dimension in respective module devices.
The board unit 10 includes further an installation space
(not shown) where a module device 2 having a unit dimension
may be additionally installed, and a connection part (not
shown) through which the module device 2 is connected to a
bus line 11.
Further, a connection part 2-3 for connecting to the
bus line 11 is provided at the body of the module device 2,
and the connection parts have a common shape and arrangement
in all the module devices 2. Thus, any module device 2 may
be detachably attached in an empty installation space of the
board unit 10, and can be connected to the bus line 11.
In addition to the connection part for the bus line 11,
each of the module devices 2 is provided with a connection
terminal (not shown) for connecting to the commercial power
source (the AC distribution board 6) AC, the solar cells 4,
or the battery 3. Accordingly, lines from the AC
distribution board 6, the solar cells 4, and the battery 3
are connected to the respective connection terminals of the
module devices 2 in the board unit 10.
The bus line 11 includes a power supply line 11a and a
communications line lib. In each of the module device 2,
the connection part may be provided separately or commonly
for the power line 11a and the communications line lib. In

the present embodiment, the power supply apparatus 1
includes a communications interface 12 connected to the
communications line lib of the bus line 11 in the board unit
10. The communications interface 12 is connected to an
external device. Accordingly, communications is possible
between the external device and each of the module devices 2
connected to the communications line lib. Further, voltage
of DC 350 V i 10 V is supplied to the power line 11a.
The internal circuit of each of the module devices 2
is connected to the bus line 11, and has the function of
autonomously controlling an output power so that a power
required from a load is supplied to the load and the
function of operating based on an instruction inputted from
the outside via the communications line lib. That is, in
the power supply apparatus 1, when the module devices 2 are
connected to the bus line 11, the module devices 2
independently start operating without having to do set
specially, so that a power is supplied to the load. Further,
the operation of each of the module devices 2 may also be
externally controlled through communications with a
controller via the communications interface 12, which will
be described later.
In the present embodiment, while operating in an
autonomous control, the module device 2 monitors a voltage
on the power line 11a in order to check a demand from a load
and determines the amount and direction of the output based

on the voltage. That is, the module device 2 determines the
amount and direction of the output by estimating that a
power supplied to the load is insufficient when the voltage
on the power line 11a drops and a surplus power is present
in the power supplied to the load when the voltage rises.
For example, the module device 2a provided between the
commercial power source AC and the power supply line 5 and
formed of an AC/DC converter converts an AC power from the
commercial power source AC into a DC power and outputs the
DC power when voltage on the power line 11a is lower than
350 V. The module device 2a converts a DC power into an AC
power to reversely flow (electric power selling) to the
commercial power source AC when the voltage on the power
line 11a is 350 V or higher.
The module device 2c formed of a DC/DC converter for
performing the charging and discharging of the battery 3
discharges the battery 3 when the voltage on the power line
11a is below a threshold value (e.g., 350 V) and charges the
battery 3 when the voltage on the power line 11a is the
threshold value or higher. The module device 2b formed of a
DC/DC converter for stepping up or down an output of the
solar cells 4 performs Maximum Power Point Tracking (MPPT)
control. Since the output of the solar cells 4 generally
varies depending on a time zone, the operational
characteristic of each module device 2 may be changed
according to the time zone.

As described above, with the power supply apparatus 1,
since a variety of the power converters can be accommodated
in and connected to the board unit 10 as the module devices
2. Therefore, a power converter may be added as an element
in accordance with the capacity of a load as shown in, for
example, Fig. 7. As compared with the example of Fig. 6,
the example of Fig. 7 further includes a module device 2e
serving as an AC/DC converter for the commercial power
source AC, a module device 2f serving as a DC/DC converter
for the solar cells 4, a module device 2g serving as a
bidirectional DC/DC converter for the charging and
discharging of the battery 3, and a module device 2h serving
as a DC/DC converter for the power supply line 5 of the high
voltage system.
With the power supply apparatus 1 of the present
embodiment 4, the additional installation or replacement of
the module devices 2 may be easily made when a load is added
or replaced. Further, the specification of the power supply
apparatus 1 may be easily changed in accordance with a load.
Accordingly, when a load is added or replaced, the entire
power distribution system need not to be replaced, i.e., the
existing power distribution system need not to be discarded
as in the prior art, thereby suppressing a rise in expenses.
[0031] (Invention 2)
Further, although all the module devices 2 have been
described to have a common external unit dimension, the

present invention is not limited thereto. At least one of
the module devices 2 may have a dimension corresponding to
two or more module device 2 having the unit dimension. In
this case, such a module device 2 may be attached to an
installation space corresponding to two or more module
devices 2 each having the unit dimension.
Referring to Fig. 6, from among the multiple module
devices 2a to 2d attached to the board unit 10, the module
devices 2a, 2b, and 2c serve as a converter group and output
a power to the power line 11a of the bus line 11. In the
present embodiment, although the converter group includes
three module devices, it may include two or more module
devices. The sum of the output currents outputted from the
module devices 2a, 2b, and 2c forming the converter group is
supplied to loads as the total output current.
In the present embodiment, each of the module devices
2a, 2b, and 2c is a so-called switching power source device,
and has a conversion efficiency-output current
characteristic in which power conversion efficiency changes
in accordance with the amount of'output current, as shown in
Fig. 8. Further, each of the module devices 2a, 2b, and 2c
is configured to have a conversion efficiency-output current
characteristic (a conversion efficiency curve) in which the
conversion efficiency becomes maximum when the output
current has a maximum efficiency value Ip smaller than a
rating current value.

That is, the power conversion efficiency of the module
device 2 becomes maximum when the output current has the
maximum efficiency value Ip, and decreases as the output
current increases or decreases from the maximum efficiency
value Ip. For the sake of simplification, it is assumed
that all the module devices 2a, 2b, and 2c included in the
converter group have a same conversion efficiency-output
current characteristic.
Furthermore, it is hereinafter assumed that the output
of the solar cells 4 and the remaining capacity of the
battery 3 are sufficient. For example, an output of the
solar cells 4 actually decreases at night and, accordingly,
a current outputted from the module device 2b as a DC/DC
converter for stepping up or down the output from the solar
cells 4 is restricted within a limit based on the output of
the solar cells 4. That is, the outputs of the module
devices 2b and 2c is limited based on the output of the
solar cells 4 and the remaining capacity of the battery 3,
respectively, and a shortfall in the outputs is made up for
by the module device 2a.
Referring to Fig. 6, the controller 8 provided
externally is connected to the communications line lib of
the bus line 11 via the communications interface 12. The
controller 8 monitors the current outputted from each
module device 2, the remaining capacity of the battery 3,
and the power consumed by a load, and controls the

operations of the respective module devices 2a, 2b, and 2c.
To this end, the controller 8 is provided with a
communications function that enables data transmission via
the communications interface 12 between the module devices
2a, 2b, and 2c.
Configurations of the controller 8 and the module
devices 2a, 2b, and 2c are described below with reference to
Fig. 9.
Each of the module devices 2a, 2b, and 2c includes a
communications unit 21 for communicating with the controller
8, a current control circuit 24 for converting an input
power into a desired power and outputting the desired power,
and an output control unit 23 for performing a feedback
control on the current control circuit 24. In Fig. 9, an
internal configuration of the module device 2a is shown, and
the other module devices 2b and 2c have the same
configuration as the module device 2a.
The controller 8 includes a communications unit 81 for
communicating with the module devices 2a, 2b, and 2c; and a
total output instruction unit 82 for determining a total
output current that needs to be outputted from the converter
group. The total output instruction unit 82 determines a
total output current that needs to be outputted from the
module devices 2a, 2b, and 2c of the converter group based
on the remaining capacity and charging/discharging ability
of the battery 3, the operating status (the amount of power

generation) of the solar cells 4, and the current consumed
by a load, which are obtained via the communications unit 81.
Further, the controller 8 includes an efficiency-
storage unit 83 for previously storing a correspondence
between a conversion efficiency and an output current with
respect to each of the module devices 2a, 2b, and 2c; and a
pattern storage unit 84 for previously storing a plurality
of allocation patterns indicating rules of allocating a
total output current to the module devices 2a, 2b, and 2c.
Furthermore, the controller 8 includes a allotment
determination unit 85 for determining which allocation
pattern among the multiple allocation patterns stored in the
pattern storage unit 84 is used in allocating the total
output current; and an allocation control unit 86 for
issuing an instruction to allocate the total output current
according to the allocation pattern selected by the
allotment determination unit 85.
In the present embodiment, there is stored an
efficiency table such as Table 1 for indicating the
correspondence between the output current and the conversion
efficiency based on the conversion efficiency-output current
characteristic shown in Fig. 8. In Table 1, power
conversion efficiencies corresponding to output currents are
shown as the output currents increase by a pitch of 0.1 A up
to the rating current value (e.g., 4.0 A) of the module
devices 2a, 2b, and 2c. In the present embodiment, when

output current from each of the module devices 2a, 2b, and
2c is a maximum efficiency value Ip, e.g., 2.0 A, the power
conversion efficiency of each of the module devices 2a, 2b,
and 2c reaches a maximum (75%). A description is now given
based on Table 1 of the efficiency table.

The allocation patterns stored in the pattern storage
unit 84 designates how the total output current from the
converter group is allocated to the respective multiple
module devices 2a, 2b, and 2c included in the converter
group when the total output current is outputted. That is,
the allocation pattern represents the rule for determining
an amount of an output current to be outputted from each of
the module devices 2a, 2b, and 2c included in the converter
group in order to obtain a desired total output current from
the converter group.
In the present embodiment 4, the pattern storage unit
84 stores six allocation patterns, e.g., No. 1 to No. 6, as
shown in Table 2 below. Further, the allocation patterns of
No. 1 to No. 6 are only an example, and one or more of the

allocation patterns may be used as allocation patterns or
another allocation pattern may be used.



Each of the allocation patterns in Table 2 is
described below. The ^allotment example' at the right end
column of Table 2 indicates an example of a current value
allocated to each of the module devices 2a, 2b, and 2c
according to each allocation pattern when the total output
current is 5.0 A.

The six types of the allocation patterns No. 1 to No.
6 are chiefly classified an uneven pattern of No. 1 and No.
2, a full balance pattern of No. 3 and No. 4, and a semi-
balance pattern of No. 5 and No. 6.
Firstly, in the uneven patterns of Nos. 1 and 2, the
output current, i.e., the maximum efficiency value Ip at
which conversion efficiency is at a maximum is allocated to
at least one of the module devices 2 of the converter group
and the remaining output current of the total output current
is allocated to one of the module devices 2. As a result,
in the uneven pattern, it is concerned that each of the
module devices 2a, 2b, and 2c operates at a high conversion
efficiency.
In the uneven patterns of Nos. 1 and 2, the remaining
output current is differently handled between the first
pattern of No. 1 and the second pattern of No. 2. That is,
in the first pattern, the remaining output current is
allocated to a module device 2 other than module devices 2
to which the output current of the maximum efficiency value
Ip has already been allocated.
Accordingly, if the remaining output current is the
maximum efficiency value Ip or lower, an output current
below the maximum efficiency value Ip is outputted from the
module devices 2 to which the remaining output current has
been allocated. For example, if the total output current is
5.0 A, 2 A, 2 A, and 1 A as the output current are allocated

to the module devices 2a, 2b, and 2c, respectively, in the
allocation pattern No. 1.
Further, in the second pattern, the remaining output
current is allocated to either one of the module devices 2
to which the output current of the maximum efficiency value
has already been allocated. Accordingly, an output current
greater than the maximum efficiency value Ip is outputted
from the module device 2 to which the remaining output
current has been allocated. For example, if the total
output current is 5.0 A, 3 A, 2 A and 0 A of the output
current are allocated to the module devices 2a, 2b, and 2c,
respectively, in the allocation pattern No. 2.
Meanwhile, the full balance pattern Nos. 3 and 4 are
patterns for allocating a uniform output current to all the
module devices 2a, 2b, and 2c of the converter group so that
a difference between output currents of the module devices
2a, 2b, and 2c can be minimized. For example, in the full
balance pattern, the amount of the total output current is
divided by the number of the module devices 2a, 2b, and 2c
included in the converter group, and an output current is
allocated to each of the module devices 2a, 2b, and 2c based
on the result of the division. In the full balance pattern,
it is concerned that the operations of the module devices 2a,
2b, and 2c are balanced, without consideration of the
conversion efficiency of each of the module devices 2a, 2b,
and 2c.

In the full balance pattern Nos. 3 and 4, it is
different whether the output currents uniformly allocated to
the module devices 2a, 2b and 2c is to be calculated in a
decimal level or an integer level. That is, in the uniform
type pattern of No. 3, the total output current is allocated
to all the module devices 2a, 2b, and 2c in such a way that
the output current allocated to each of the module devices
2a, 2b, and 2c becomes uniform in a decimal level (e.g.,
rounded off to first decimal point).
In this case, even if a remaining output current of
the total output current which is not allocated below the
decimal point occurs, the remaining output current is also
allocated to all the module devices 2a, 2b, and 2c as
equally as possible up to one decimal place. For example,
if the total output current is 5.0 A, 1.7 A, 1.7 A, and 1.6A
of the output current are allocated to the respective module
devices 2a, 2b, and 2c in the allocation pattern of No. 3.
In the residual type pattern of No. 4, the total
output current is allocated to all the module devices 2a, 2b,
and 2c so that the output currents of the each module
devices 2a, 2b, and 2c becomes uniform in an integer level.
Further, if there is a remaining output current, only the
integer part of the remaining output current is allocated to
all of the module devices 2a, 2b, and 2c as uniform as
possible. For example, if the total output current is 5.0 A,
the output currents of 2 A, 2 A, and 1 A are allocated to

the module devices 2a, 2b, and 2c, respectively, in the
residual type pattern of No. 4.
Further, if there is a decimal part of the remaining
output current, the remaining output current of the decimal
part is allocated to one of the module devices 2. In this
case, it is preferred that the remaining output current of
the decimal part is allocated to a module device which power
conversion efficiency becomes higher when the remaining
output current of the decimal part is allocated thereto.
Furthermore, in the semi-balance pattern Nos. 5 and 6,
the total output current is allocated to some (e.g., two) of
the module devices 2 included in the converter group such
that a difference between output currents of the module
devices 2 which are allocated is reduced. For example, the
amount of a total output current is divided by the number of
the module devices 2 to which an output current is allocated,
and the resultant value of the division is allocated to each
of the module devices 2. For this reason, in the semi-
balance pattern, at least one of the module devices 2 stops
operating.
The allocation control unit 86 controls the respective
module devices 2 not only to output an amount of the
allocated output current, but also to stop the operation as
described above. Here, a relationship between the uniform
type pattern of No. 5 and the residual type pattern of No. 6
is the same as that between the full balance pattern Nos. 3

and 4, and thus a description thereof is omitted.
Accordingly, for example, if the total output current
is 5.0 A, 2.5 A, 2.5 A and 0 A of the output current are
allocated to the module devices 2a, 2b and 2c, respectively,
in the pattern of No. 5, and 3 A, 2 A and 0 A of the output
current are allocated to the module devices 2a, 2b and 2c,
respectively, in the pattern of No. 6.
In the meantime, the allotment determination unit 85
of the controller 8 calculates the sum (hereinafter,
referred to as a ,total input power') of input powers
inputted to the module devices 2a, 2b, and 2c of the
converter group in the case where the total output current
is allocated using one of the six types of allocation
patterns stored in the pattern storage unit 84.
Further, the allotment determination unit 85
calculates a power conversion efficiency (hereinafter,
referred to as a 'total conversion efficiency') of the
converter group as a whole based on a relationship between
the total input power and the sum (hereinafter, referred to
as a 'total output power') of the output powers of the
module devices 2a, 2b, and 2c included in the converter
group; and determines an allocation pattern having a maximum
total conversion efficiency. The allocation pattern having
the maximum total conversion efficiency calculated as
described above is used to practically allocate the total
output current, and such an allocation pattern used in

allocating is also referred to as an "application pattern"
hereinafter.
More specifically, the allotment determination unit 85
first receives an instruction including a total output
current value from the total output instruction unit 82 and
calculates an output current of each of the module devices
2a, 2b, and 2c included in the converter group when the
total output current is allocated according to an allocation
pattern. Further, the allotment determination unit 85 reads
a power conversion efficiency of the respective module
devices 2a, 2b, and 2c from the efficiency table stored in
the efficiency storage unit 83 based on the calculated
output current of the respective module devices 2a, 2b, and
2c.
Accordingly, the output current and the conversion
efficiency of each of the module devices 2a, 2b, and 2c are
obtained, and input powers of the respective module devices
2a, 2b, and 2c can be calculated using the output current
and the conversion efficiency and a known output voltage
(voltage supplied to a power line) . The sum of the input
powers of the module devices 2a, 2b, and 2c that have been
calculated as described above becomes the total input power,
and the total conversion efficiency can be calculated from
the relationship between the total input power and the known
total output power. The allotment determination unit 85
stores the calculated total conversion efficiency

corresponding to each of the allocation patterns in a
temporal memory unit (not shown).
The allocation control unit 86 is informed of an
application pattern (one of the allocation patterns)
selected by the allotment determination unit 85 as described
above. The allocation control unit 8 6 informed of the
application pattern starts to allocate a total output
current based on the application pattern by calculating an
amount of an output current that needs to be output from
each of the module devices 2a, 2b, and 2c. The allocation
control unit 86 sends a current instruction indicative of
the calculated output current to each of the module devices
2a, 2b, and 2c via the communications unit 81.
In each of the module devices 2a, 2b, and 2c which
have received the current instruction via the communications
unit 21 from the controller 8 (the allocation control unit
86), the output control unit 23 controls the current control
circuit 24 based on the current instruction. Accordingly,
the output current designated by the current instruction is
outputted from each of the module devices 2a, 2b, and 2c.
The controller 8 selects an application pattern
whenever the amount of the total output current exceeds a
specific tolerance limit, and reallocates a total output
current to the module devices 2a, 2b, and 2c. However, the
present invention is not limited thereto, and the selection
of an application pattern and the reallocation of a total

output current may be regularly performed.
With the above configuration, an output current
equivalent to an amount allocated each of the module devices
2a, 2b, and 2c based on an application pattern is outputted
from each of the module devices 2a, 2b, and 2c included in
the converter group. Here, the application pattern is an
allocation pattern selected from among plural types of
allocation patterns so that the total conversion efficiency
is at the maximum. Accordingly, when the application
pattern is applied, the power conversion efficiency of the
module devices 2a, 2b, and 2c included in the converter
group as a whole is improved. Consequently, it is possible
to reduce a loss occurring during power conversion of the
converter group, thereby improving the power conversion
efficiency in the entire power supply apparatus.
With the embodiment 4, since the module devices 2a, 2b,
and 2c included in the converter group all have a common
conversion efficiency-output current characteristic, the
total conversion efficiency of the converter group is
constant even though an output current determined by an
application pattern is allocated to any of the module
devices 2a, 2b, and 2c. That is, as long as a combination
of output currents to be allocated complies with that in the
applied allocation pattern, the total conversion efficiency
does not change regardless whether each allocated output
current is allocated to either module device among the

module device 2a, 2b, and 2c. For example, in the
allocation pattern of No. 1 in which 2 A, 2 A, and 1 A of
output currents are allocated when a total output current is
5 A, the total conversion efficiency is the same even when
the output current of 1 A is allocated to either one of the
module devices 2a, 2b, and 2c.
As an modified example of the present embodiment 4,
the allotment determination unit 85 may includes a
combination determination unit (not shown) for determining a
combination of output currents that have to be allocated to
and a unique allocation unit (not shown) for determining the
module devices 2a, 2b, and 2c to which the respective output
currents are allocated. With this configuration, the
combination determination unit first determines a
combination of output currents at which the total conversion
efficiency is a maximum based on an allocation pattern, and
the unique allocation unit determines an allocation pattern
including a module device to which an output current will be
allocated as an application pattern.
In this case, the unique allocation unit may randomly
determine a module device to which an output current is
allocated. It is however preferred that priority be given
to the module devices 2a, 2b, and 2c and that the output
current be assigned in order of higher priorities first.
Here, the priority is not fixedly determined, but may be
flexibly determined not to overburden some of the module

devices 2a, 2b, and 2c.
For example, the controller 8 may include an
accumulation monitoring unit (not shown) for monitoring an
accumulated value of the amount of output current in each of
the module devices 2a, 2b, and 2c; and a priority
determination unit (not shown) for determining a priority
based on the monitoring result of the accumulation
monitoring unit.
The accumulation monitoring unit monitors the output
currents of the respective module devices 2a, 2b, and 2c of
the converter group and manages the accumulated value Ah of
the output current amounts using a table. The accumulation
is executed regularly (e.g., once per second). Further, the
accumulation of the output current amounts may be executed
by each of the module devices 2a, 2b, and 2c. The priority
determination unit determines the priority of each of the
module devices 2a, 2b, and 2c such that a priority is higher
as an accumulated value is smaller. The priorities may be
regularly updated.
With such configuration in which a target to which an
output current is allocated is determined based on the
priority of each of the module devices 2a, 2b, and 2c,
larger output currents are sequentially allocated to the
module devices 2a, 2b, and 2c in the order of having smaller
accumulated values of the output currents. Accordingly, a
difference in the output current amount between the module

devices 2a, 2b, and 2c can be reduced. That is, since the
multiple module devices 2a, 2b, and 2c can be made uniformly
in the operation ratio by equally distributing the operating
time thereof, it is possible to prevent overburdening some
of the module devices 2a, 2b, and 2c.
Accordingly, a reduction in the lifespan due to the
exploitation of some of the module devices 2a, 2b, and 2c
can be avoided, and the period over which the power
distribution system may continue to be used without
replacement of the module devices 2a, 2b, and 2c, becomes
longer.
Meanwhile, the conversion efficiency-output current
characteristic (the conversion efficiency curve) of each of
the module devices 2a, 2b, and 2c may be changed depending
on the oscillation control mode of switching in each of the
module devices 2a, 2b, and 2c. For example, if the output
of each of the module devices 2a, 2b, and 2c is controlled
by using a Pulse Width Modulation (PWM), the conversion
efficiency-output current characteristic is changed as the
switching frequency changes. Further, if a burst control in
which an oscillation period for executing the PWM control
and an oscillation stop period for stopping the output are
alternately repeated is performed, the conversion
efficiency-output characteristic varies depending on a
change in the timing of the burst control.
For that reason, it is preferred that the controller 8

can previously store the conversion efficiency-output
characteristics corresponding to the oscillation control
modes with respect to each of the module devices 2a, 2b, and
2c, and, when the oscillation control mode is changed,
select a conversion efficiency-output characteristic
corresponding to the changed oscillation control mode.
In the embodiment 4, an example in which the
conversion efficiency-output characteristics of the module
devices 2a, 2b, and 2c are stored in the efficiency storage
unit 83 in the form of the efficiency table has been
described, but the present invention is not limited thereto.
For example, an operation equation indicating a relationship
between output current and conversion efficiency may be
stored in the efficiency storage unit 83. In this case, the
allotment determination unit 83 may calculate the conversion
efficiency of each of the module devices 2a, 2b, and 2c
using a corresponding operation equation.
(Embodiment 5)
Next, a power distribution system in accordance with a
embodiment 5 of the present invention will be described with
reference to Fig. 10. The power distribution system of the
embodiment 5 is different from the power distribution system
of the embodiment 4 in that a surplus power of a battery 3
can be reversely flowed into the commercial power source AC
(the commercial system).
Referring to Fig. 10, solar cells 4 are connected to

an AC distribution board 6 via a power conditioner 9 which
converts a DC into an AC. Therefore, the surplus power of
the solar cells 4 is converted into an AC power through the
power conditioner 9 and then reversely flowed (electric
power selling) into the commercial system.
In the present embodiment, a power supply apparatus 1
includes a module device 2a' provided between the commercial
power source AC and a power line 11a, the module device 2a'
serving .as an AC/DC converter for converting an AC power
into a DC power; a module device 2b' as a bidirectional
DC/DC converter provided between the solar cells 4 and the
power line 11a; and a module device 2c as a bidirectional
DC/DC converter provided between a battery 3 and the power
line 11a.
The module device 2b' provided between the solar cells
4 and the power line 11a includes a first full bridge
circuit having first to fourth switching elements Ql to Q4,
and a second full bridge circuit having fifth to eighth
switching elements Q5 to Q8 . Further, the first and the
second full bridge circuit are almost symmetrical to each
other and have a transformer Tl interposed therebetween, as
shown in Fig. 11, for example. A serial circuit of an
inductor LI and a capacitor CI is inserted between an output
terminal of the first full bridge circuit and the
transformer Tl.
Thus, when the battery 3 is charged, the first full

bridge circuit is operated so that an output VI (voltage
across a smoothing capacitor CIO) of the solar cells 4 is
transferred to the battery 3 via the transformer Tl and
parasitic diodes of the second full bridge circuit. Further,
when the battery 3 is discharged, the second full bridge
circuit is operated, so that an output V2 (a voltage across
the smoothing capacitor C20) of the battery 3 is transferred
to the power conditioner 9 via the transformer Tl and
parasitic diodes of the first full bridge circuit.
The power supply apparatus 1 further includes a
controller 8 including a CPU and the like and a display unit
13 capable of displaying various information, the controller
8 and the display unit 13 being provided in a board unit 10.
The controller 8 and the display unit 13 are connected to
the module devices 2 via communications line lib.
Connection terminals 15 for power distribution are connected
to the power line 11a via a circuit protector 14. Further,
connection terminals 16 for communications are connected to
the controller 8 .
As described above, since the module device 2b'
provided between the solar cells 4 and the power line 11a
serves as a bidirectional DC/DC converter, the output of the
solar cells 4 can be used to charge the battery 3. Further,
when there is a surplus power in the output of the solar
cells 4, the surplus power is reversely flowed from the
battery 3 to the commercial power source AC via the power

conditioner 9.
That is, the power conditioner 9 is shared by the
solar cells 4 and the battery 3 because powers from the
solar cells 4 and the battery 3 are inputted to the power
conditioner 9. Accordingly, when a sufficient output is
obtained from the solar cells 4, e.g., during the daytime,
the battery 3 is charged by the output of the solar cells 4.
Further, when the output of the solar cells 4 is reduced,
the power can be reverse flowed from the battery 3 to the
commercial power source AC.
In the present embodiment 5, an example in which the
single module device 2b' serves as the bidirectional DC/DC
converter provided between the solar cells 4 and the power
line 11a has been described, but the present invention is
not limited thereto. For example, the bidirectional power
conversion may be realized between the solar cells 4 and the
battery 3 using two module devices each serving as a
unidirectional DC/DC converter.
The other elements and functions are the same as those
of embodiment 4, and description thereof is omitted.
(Embodiment 6)
Hereinafter, a power distribution system in accordance
with an embodiment 6 of the present invention will be
described. The power distribution system of the embodiment
6 is different from the power distribution system of
embodiment 4 in that at least one of multiple module devices

2a, 2b, and 2c included in a converter group has a different
conversion efficiency-output characteristic (conversion
efficiency curve).
That is, in the present embodiment 6, a total
conversion efficiency is changed not only by a combination
of output currents allocated to the respective module
devices 2a, 2b, and 2c, but also by a combination of the
module devices 2a, 2b, and 2c to which the respective output
currents is allocated. For example, in the allocation
pattern of No. 1 described in the embodiment 4, if the total
output current of 5 A is allocated into 2 A, 2 A, and 1 A,
the total conversion efficiency varies depending on whether
output current of 1 A will be allocated to which of the
module devices 2a, 2b, and 2c.
In the present embodiment 6, patterns (hereinafter
referred to as xlow-ranking patterns') into which the six
types of allocation patterns of No. 1 to No. 6 (hereinafter,
referred to as ^high-ranking patterns') shown in Table 2 as
described in the embodiment 4 are further subdivided are
used as allocation patterns, the low-ranking patterns being
classified based on target module devices to which the
output currents are allocated. The allotment determination
unit 85 calculates total conversion efficiency for each of
the allocation patterns further subdivided as described
above and selects an allocation pattern at which the total
conversion efficiency is at the maximum as an application

pattern.
A detailed example is described below. In this
example, it is assumed that the three module devices 2a, 2b,
and 2c of the converter group have different conversion
efficiency-output characteristics and the power conversion
efficiency is at a maximum (maximum efficiency values Ip are
2 A, 3 A, 4 A) when output currents are 2 A, 3 A, and 4 A,
respectively.
The allotment determination unit 85 receives an
instruction on the total output current and calculates the
total conversion efficiency for each of the allocation
patterns in which the six types of high-ranking patterns of
No. 1 to No. 6 are further subdivided into multiple low-
ranking patterns. For example, assuming that the total
output current is 7 A, the uneven pattern of No. 1 is
subdivided into three types of low-ranking patterns
according to whether an output current having a maximum
efficiency value Ip is allocated to which of the three
module devices 2a, 2b, and 2c.
That is, in a first low-ranking pattern, 2 A, 3 A, and
2 A of output currents are allocated to the module devices
2a, 2b, and 2c, respectively; in a second low-ranking
pattern, 0 A, 3 A, and 4 A are allocated to the module
devices 2a, 2b, and 2c, respectively; and, in a third low-
ranking pattern, 2 A, 1 A, and 4 A are allocated to the
module devices 2a, 2b, and 2c, respectively. The allotment

determination unit 85 calculates the total conversion
efficiency for each of the first to third low-ranking
patterns.
With the above-describe present embodiment 6, although
a converter group includes the module devices 2a, 2b, and 2c
each having different conversion efficiency-output
characteristics, the conversion efficiency for the entire
converter group can be improved. In addition, since the
low-ranking patterns further subdivided by taking into
consideration the target to which an output current is
allocated can be used, a selectable range is broadened when
an allocation pattern having a maximum total conversion
efficiency, as compared to the case where only high-ranking
patterns are used,. Consequently, the total output current
can be allocated according to a more suitable application
pattern in terms of total conversion efficiency.
The other elements and functions are the same as those
of the embodiment 4, and description thereof is omitted.
As the above, although the power converters have been
described as module devices 2 in embodiments 4 to 6, devices
(e.g., power measurement devices) other than the power
converters may be modularized and then installed to power
supply apparatus 1 as the module devices 2.
While the invention has been shown and described with
respect to the embodiments, the present invention is not
limited thereto. It will be understood by those skilled in

the art that various changes and modifications may be made
without departing from the scope of the invention as defined
in following claims.

WE CLAIM:
1. A power distribution device, comprising:
a DC power source DC/DC converter connected to a DC
power source; .
an AC/DC converter connected to an AC power source;
and
a DC load line connected to a DC load,
wherein the DC/DC converter and the AC/DC converter
are accommodated in a single container, and the DC load line
is drawn from the container.
2. The power distribution device of claim 1, further
comprising:
a battery;
a battery DC/DC converter connected to the battery;
and
a protection circuit connected to at least one of the
DC power source DC/DC converter, the battery DC/DC converter,
and the AC/DC converter.
3. The power distribution device of claim 2, wherein the
DC power source DC/DC converter, the battery DC/DC converter,
and the AC/DC converter are arranged parallel to each other
with a specific gap in a same plane.

4. The power distribution device of claim 3, wherein the
battery is disposed so that the battery is not placed above
the DC power source DC/DC converter, the battery DC/DC
converter, and the AC/DC converter.
5. The power distribution device of any one of claims 2
to 4, wherein the battery is detachably installed in the
container.
6. The power distribution device of claim 5, wherein the
battery DC/DC converter is connected to the battery by a
connector.
7 . The power distribution device of any one of claims 2
to 6, further comprising:
a control unit for controlling outputs of the DC power
source DC/DC converter, the batter DC/DC converter, and the
AC/DC converter;
a display unit for displaying status of power supply;
and
a manipulation unit for manipulating an ON/OFF of each
of the DC power source, AC power source, and the protection
circuit.
8 . The power distribution device of any one of claims 2
to 7, further comprising:

a first terminal block for connecting a first line to
the DC load; and
a second terminal block for connecting a second line
from the DC power source;
wherein at least one of shapes and colors of the first
and the second terminal blocks and colors of the first and
the second lines are distinguishable from each other.
9. A power distribution system comprising the power
distribution device of any one of claims 2 to 8, and a
terminal for additionally installing a battery.
10. The power distribution system of claim 9, further
comprising battery units each including a battery and a
battery DC/DC converter.
11. A power distribution system in which a plurality of
the power distribution device of any one of claims 2 to 8 is
arranged.
12. A power distribution device, comprising:
module devices each including a power converter for
converting an input power into a desired output power,
wherein the module devices are accommodated in a
single container, each having an external dimension having a
preset unit size or corresponding to the dimension in which

multiple module devices each having the preset unit size are
arranged in parallel.
13. The power distribution device of claim 12, further
comprising a main path electrically connected to the module
devices, for including a power line and a communications
line,
wherein a power is supplied from the module devices to
a load via a power supply line connected to the main path;
and
wherein each of the module devices includes a
connection hole connected to the main path, a body
detachably installed to the main path via the connection
hole, and an internal circuit accommodated in the body and
connected to the main path, the internal circuit having a
function of autonomously controlling an output power so that
a power needed for the load can be supplied to the load and
a function of operating in accordance with an external
instruction via the communications line.
14. The power distribution device of claim 13, wherein:
at least two module devices of the module devices
connected to the main path form a converter group, and a sum
of output currents outputted from the module devices of the
converter group is supplied to the load as a total output
current;

each of the module devices has a power conversion
efficiency depending on an amount of the output current,
the power distribution device further comprising:
an efficiency storage unit which previously stores a
relationship between an output current and a conversion
efficiency for each of the module devices;
a pattern storage unit which previously stores
allocation patterns each indicating a rule for allocating
the total output current to each of the module devices of
the converter group;
a total output instruction unit for instructing a
total output current to be outputted from the converter
group;
a allotment determination unit for selecting one from
the allocation patterns stored in the pattern storage unit
as an application pattern using the total output current
instructed by the total output instruction unit and the
conversion efficiency stored in the efficiency storage unit;
and
an allocation control unit for controlling the output
of each of the module devices so that the total output
current is allocated to each of the module devices based on
the selected application pattern,
wherein the allotment determination unit calculates a
sum of input powers of the entire converter group when the
output currents are allocated to the module devices of the

converter group based on each of the allocation patterns
stored in the pattern storage unit, the sum of the input
powers being calculated by using the conversion efficiency
stored in the efficiency storage unit with respect to each
of the allocation patterns, and
wherein the allotment determination unit selects an
allocation pattern having a minimum sum of the input powers
as the application pattern.
15. The power distribution device of claim 14, wherein:
each of the module devices of the converter group is
formed of a switching power supply in which a relationship
between the output current and the conversion efficiency
varies depending on an oscillation control mode thereof; and
the allotment determination unit selects the application
pattern using the conversion efficiency corresponding to the
oscillation control mode.
16. The power distribution device of claim 13, wherein the
power distribution device is employed in a power
distribution system comprising solar cells, a battery and a
power conditioner having a function of converting a DC power
into an AC power,
wherein the module devices serving as a power
converter are provided between the battery and the power
conditioner, and

wherein the power converter is connected to the main
path, inputs powers from the solar cells and the battery to
the power conditioner, and reversely flows a surplus power
provided in at least one of the solar cells and the battery
into a commercial power system via the power conditioner.
17. The power distribution device of claim 16, wherein:
the power conditioner is provided between the solar
cells and the commercial power system, and the power
converter is provided between the solar cells and the main
path, and
wherein the power converter bi-directionally converts
a power between the solar cells and the battery, and
reversely flows the surplus power of the battery into the
commercial power system via the power conditioner.

ABSTRACT

A power distribution device includes a direct current
power source DC/DC converter connected to a direct current
power source, and an AC/DC converter connected to an
alternating current power source. The direct current power
source DC/DC converter and the AC/DC converter are
accommodated in a single container from which a DC load
supply line is led out.