JPH08331776A - Dc power source system - Google Patents

Abstract

PURPOSE: To provide a DC power source system capable of supplying a required minimum of load by converting the output of a storage battery to AC power by high efficiency even when the storage battery having small capacity is mounted as an emergency power source. CONSTITUTION: In a DC power source system, a storage battery 7 having small capacity is connected to the output terminal of a DC power source 1 made of a solar cell via a charge/discharge controller 6, a small-capacity inverter 8 having lower rated output than that of a main inverter 2 is connected between the controller 6 and the battery 7, and an emergency plug socket 9 is connected to the output terminal of the inverter 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC power supply system in which a DC power supply such as a solar cell is connected to a commercial power system via an inverter.

[0002]

2. Description of the Related Art In recent years, a DC power supply system has been put into practical use in which solar cells are installed in homes, factories or areas and are connected to a commercial power grid of a power company, and surplus power of the solar cells flows backward to the commercial power grid. Has been converted.

In this type of DC power supply system, solar cells are connected to a commercial power system via an inverter,
A home load is connected to the output terminal of the inverter. As a result, the output of the solar cell is converted from direct current to alternating current,
The AC power is supplied to the commercial power system and home loads.

In the conventional DC power supply system, the operation of the inverter is stopped when a power failure occurs in the commercial power system due to a disaster or lightning strike. In order to effectively use the power generated by the solar cells, it is considered to operate the inverter independently with the grid connection to the commercial power system disconnected and supply the power from the solar cells to the household load. .

Further, as shown in FIG. 4, in order to cover the required power at night when a power failure occurs, a DC power source (1) and an inverter are used.
A charge / discharge control circuit (62) is interposed between (2), and the charge / discharge control circuit (62) charges the storage battery (71).
During the daytime, the electric power obtained by the independent operation of the inverter (2) is supplied to the domestic load (5), and the surplus power charges the storage battery (71) and discharges the storage battery (71) at night. By doing so, a method of supplying the electric power to the domestic load (5) is being studied. In this case, as the storage battery (71), a relatively small amount of electric power (for example, 1
It is sufficient to have a capacity capable of covering 100 to 500 W) for a short period of about 10 hours including nighttime.

[0006]

However, in the conventional DC power supply system shown in FIG. 4, the output of the storage battery (71) is charged and discharged while the breaker (4) is opened due to the occurrence of a disaster or the like. Input to the inverter (2) via the control circuit (62),
Thus, when the AC power obtained from the inverter (2) is supplied to the domestic load (5), the output of the storage battery (71) is 100 to 500 W as described above, and the rated output of the inverter (2) itself (for example, 3 to Since it is much smaller than 5 kW, the operating efficiency of the inverter (2) will be significantly reduced.

FIG. 5 exemplifies the efficiency characteristics of an inverter. High efficiency exceeding 90% can be obtained at the rated output, but when the output falls below 20%, the proportion of fixed loss increases. , The efficiency drops sharply.
Therefore, in the DC power supply system of FIG.
In 1), it is necessary to have a capacity that is obtained by adding the loss due to the decrease in efficiency to the required power. For example, when the efficiency is reduced to 30%, the storage battery (71) needs a capacity of 1000 WH in order to cover the power of 300 WH. However, when the capacity of the storage battery (71) is increased in this way, there is a possibility that the storage battery (71) cannot be charged in one day.

An object of the present invention is to provide a DC power supply system capable of converting the output of the storage battery into AC power with high efficiency and supplying it to the load even when the storage battery having a small capacity is equipped. .

[0009]

A DC power supply system according to the present invention has a DC power supply (1) in the basic configuration shown in FIG.
Storage battery of small capacity through the charge / discharge control circuit (6) at the output end of
(7) is connected, and a small capacity inverter (8) whose rated output is lower than that of the main inverter (2) is connected to the output terminal of the storage battery (7), and the output terminal of the small capacity inverter (8) is connected. The emergency outlet (9) is connected to.

In another configuration shown in FIG. 2, the charge / discharge control circuit (61) has a DC input terminal and an AC input terminal, and the DC input terminal is an output terminal of the DC power source (1) via the relay (10). On the other hand, the AC input terminal is connected to the power line between the main inverter (2) and the commercial power system (3).

In still another configuration shown in FIG. 3, the output terminal of the small capacity inverter (8) is connected to the emergency outlet (9) through the first relay (11) and the first relay (1).
The power line between the 1) and the emergency outlet (9) and the power line between the main inverter (2) and the commercial power system (3) are the second
They are connected to each other via relays (12).

In each of the above constructions, specifically, the rated output of the small capacity inverter (8) corresponds to the capacity of the storage battery (7). Incidentally, instead of the emergency outlet (9), it is possible to equip a switch equipped to automatically supply the output of the small capacity inverter (8) to a part of the domestic load (5).

[0013]

In the basic configuration shown in FIG. 1, a DC power source
The storage battery (7) is charged by the electric power obtained from (1). When the output of the DC power supply (1) drops, the storage battery
DC power obtained by discharging (7) is supplied to the small capacity inverter (8). At this time, by starting the small capacity inverter (8) and connecting the minimum required load to the emergency outlet (9), the AC power obtained from the small capacity inverter (8) will It will be supplied from the power outlet (9) to the minimum load required.

In another configuration shown in FIG. 2, during normal interconnection operation, the relay (10) is opened and the AC power from the commercial power system (3) is supplied to the AC input terminal of the charge / discharge control circuit (61). Then, the storage battery (7) is charged. And when a power outage occurs,
By closing the relay (10) and supplying the electric power obtained from the DC power supply (1) to the DC input terminal of the charge / discharge control circuit (61), the storage battery
Charge (7). When the output of the DC power supply (1) drops, the DC power from the storage battery (7) is supplied to the small capacity inverter (8), and the AC power obtained from the small capacity inverter (8) passes through the emergency outlet (9). It will be supplied to the minimum required load.

In still another configuration shown in FIG. 3, during normal interconnection operation, the first relay (11) is opened and the second relay (12) is closed to supply AC power from the commercial power system (3). Supply to the emergency outlet (9) via the second relay (12).
This makes it possible to use the emergency outlet (9) not only in an emergency. At this time, DC power supply (1)
The storage battery (7) is charged with the electric power obtained from the battery. Then, when the output of the DC power supply (1) decreases, the DC power obtained by discharging the storage battery (7) is supplied to the small capacity inverter (8). At this time, if the first relay (11) is closed and the second relay (12) is opened, the AC power obtained from the small capacity inverter (8) can be supplied to the first relay (11) and the emergency outlet (9). ) Will be supplied to the minimum required load.

In any of the above constructions, the DC power obtained from the small capacity storage battery (7) is converted into AC by the small capacity inverter (8), so that the conversion efficiency is high. Here, if the rated output of the small capacity inverter (8) is made to correspond to the capacity of the storage battery (7), the maximum conversion efficiency can be obtained.

[0017]

According to the DC power supply system of the present invention, when a power failure occurs, the output of a small-capacity storage battery can be converted into AC power with high efficiency and supplied to the minimum load required.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Three examples in which the present invention is applied to a solar cell power generation system will be described in detail below with reference to the drawings. First Embodiment In the solar cell power generation system shown in FIG. 1, a DC power source (1) composed of solar cells is connected to a commercial power system (3) via a main inverter (2), and the main inverter (2) ) And the commercial power system (3), a breaker (4) is interposed, and a domestic load (5) is connected between the output end of the main inverter (2) and the breaker (4).

A charge / discharge control circuit is provided at the output end of the DC power supply (1).
A small-capacity storage battery (7) is connected via (6), and a small-capacity inverter (8) is connected to the connection point between the charge / discharge control circuit (6) and the storage battery (7). An emergency outlet (9) is connected to the output terminal of (8).

At the time of normal interconnection operation in which the main inverter (2) is started and the breaker (4) is closed, the DC power source is used.
The DC power obtained from (1) is converted into AC by the main inverter (2), the AC power is supplied to the domestic load (5), and the surplus power is reversely flowed to the commercial power system (3). It The surplus power generated by the DC power supply (1) is supplied to the storage battery (7) by the charge / discharge control circuit (6), and the storage battery (7) is charged. At this time, small capacity inverter (8)
Is shut down and the emergency outlet (9) is unusable.

When a power failure occurs in the commercial power system (3) due to a disaster or the like, the breaker (4) is opened and the main inverter (2) shifts to the self-sustained operation mode. DC power supply
During the day when output is obtained from (1), DC power supply (1)
Is supplied to the storage battery (7) by the charge / discharge control circuit (6), and the storage battery (7) is charged.

On the other hand, when no output is obtained from the DC power source (1) at night, etc., the self-sustained operation of the main inverter (2) is stopped and the small capacity inverter (8) is started. As a result, the DC power obtained by discharging the storage battery (7) is converted into AC by the small capacity inverter (8) and supplied to the emergency outlet (9). Therefore, by connecting the minimum required load such as lighting equipment and television receiver to the emergency outlet (9),
The AC power obtained from the small capacity inverter (8) can be supplied to these minimum required loads.

In the above solar battery power generation system, the capacity of the storage battery (7) is set to a value required to operate the minimum electric appliances required in the event of a disaster, and a small capacity with a rated output corresponding to the capacity. By equipping the inverter (8), the storage battery (7) can be fully charged in the daytime of the day, and since the small capacity inverter (8) is operated near the rated output point. , Its conversion efficiency is high.

Second Embodiment The solar cell power generation system shown in FIG. 2 is equipped with a charging / discharging control circuit (61) having a DC input terminal and an AC input terminal, and the charging / discharging control circuit (61) is provided. The output terminal of the DC power supply (1) is connected to the DC input terminal of the relay via the relay (10), and the AC input terminal of the charge / discharge control circuit (61) is connected to the main inverter (2).
And the commercial power system (3).

During normal interconnection operation, main inverter (2)
While the relay starts, the relay (10) is opened and the AC power obtained from the main inverter (2) is supplied to the household load (5) and the charge / discharge control circuit (61). The storage battery (7) is charged. Also, when the output of the DC power supply (1) is reduced, AC power obtained from the commercial power system (3) is supplied to the domestic load (5) via the breaker (4) and the charge / discharge control circuit (61). Is supplied to the AC input end of the storage battery
(7) is charged.

When a power failure occurs in the commercial power system (3) due to a disaster or the like, the breaker (4) is opened and the main inverter (2) shifts to the self-sustained operation mode. Also, the relay
(10) is closed. During the daytime, the output of the DC power supply (1) is supplied to the charge / discharge control circuit (6) via the relay (10), and the storage battery (7) is charged thereby.

On the other hand, when the output decreases at night or the like, the self-sustained operation of the main inverter (2) is stopped and the small capacity inverter (8) is started. As a result, the DC power from the storage battery (7) is supplied to the small capacity inverter (8), and the AC power output from the small capacity inverter (8) passes through the emergency outlet (9) to the minimum load required. Supplied.

Also in the solar cell power generation system of FIG.
By equipping the small-capacity inverter (8) with a rated output corresponding to the small-capacity storage battery (7), it is possible to sufficiently charge the storage battery (7) and operate the small-capacity inverter (8) with high efficiency. Moreover, especially in the solar cell power generation system of FIG. 2, since the relay (10) is opened during normal interconnection operation, the DC power supply
The output voltage of the solar cell as (1) is not affected by the voltage of the storage battery (7), and the maximum power point tracking operation becomes possible.

Third Embodiment A solar cell power generation system shown in FIG. 3 is a small capacity inverter.
The emergency outlet (9) is connected to the output terminal of (8) via the first relay (11), and the power line between the first relay (11) and the emergency outlet (9) and the main inverter (2) are connected. ) And the electric power between the breaker (4) are connected to each other via the second relay (12).

During normal interconnection operation, the main inverter
While starting (2), the first relay (11) is opened and the second relay (12) is closed. This allows the main inverter
AC power from (2) or commercial power system (3)
It is supplied to the domestic load (5) via (4) and is supplied to the emergency outlet (9) via the second relay (12). As a result, it becomes possible to use the emergency outlet (9) not only in an emergency. At this time, the electric power obtained from the DC power supply (1) is supplied to the storage battery (7) by the charge / discharge control circuit (6), and the storage battery (7) is charged.

When a power failure occurs in the commercial power system (3) due to a disaster or the like, the breaker (4) is opened and the main inverter (2) shifts to the self-sustained operation mode. Also, the first relay (11) is closed and the second relay (12) is opened. During the daytime, the output of the DC power supply (1) is supplied to the storage battery (7) by the charge / discharge control circuit (6), and the storage battery (7) is charged.

When the output of the DC power supply (1) drops, the self-sustained operation of the main inverter (2) is stopped and the small capacity inverter (8) is started. As a result, the DC power from the storage battery (7) is supplied to the small capacity inverter (8), and the AC power output from the small capacity inverter (8) is supplied to the first relay (11).
After that, the power is supplied to the emergency outlet (9) and the power of the minimum load required is covered.

Similarly, in the solar battery power generation system shown in FIG. 3, a small capacity inverter (8) having a rated output corresponding to a small capacity storage battery (7) is provided to sufficiently charge the storage battery (7). It is possible to operate the small capacity inverter (8) with high efficiency.

In any of the solar cell power generation systems shown in FIGS. 1 to 3, the small capacity inverter (8) is operated independently from the main inverter (2).
The specifications of (8) can be selected regardless of the specifications of the main inverter (2), and free design is possible. DC power supply
Since an emergency power system different from the main power system from (1) to the commercial power system (3) is configured, the emergency power system is
It is not subject to legal restrictions on the main power system, and it is possible to simplify auxiliary equipment.

The above description of the embodiments is for explaining the present invention, and should not be construed as limiting the invention described in the claims or limiting the scope. The configuration of each part of the present invention is not limited to the above-mentioned embodiment, and it goes without saying that various modifications can be made within the technical scope described in the claims. For example, the emergency outlet of the above embodiment
Instead of (9), it is also possible to equip a switching device or the like that can automatically supply the output of the small capacity inverter (8) to a part of the domestic load (5). Further, in the above-described embodiment, the main inverter has the self-sustained operation mode, but the main inverter can be applied to a solar cell power generation system having no self-sustained operation mode.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a first embodiment of a DC power supply system using a solar cell.

FIG. 2 is a block diagram showing a configuration of a second embodiment of the same.

FIG. 3 is a block diagram showing a configuration of a third embodiment of the above.

FIG. 4 is a block diagram showing a configuration of a conventional DC power supply system.

FIG. 5 is a graph showing a characteristic of conversion efficiency of an inverter.

[Explanation of symbols]

 (1) DC power supply (2) Main inverter (3) Commercial power system (4) Breaker (5) Household load (6) Charge / discharge control circuit (7) Storage battery (8) Small capacity inverter (9) Emergency outlet

Claims (4)

[Claims] 1. In a DC power supply system in which a DC power supply is connected to a commercial power system via a main inverter and a domestic load is connected between the main inverter and the commercial power system, an output terminal of the DC power supply is provided. A storage battery is connected via the charge / discharge control circuit, and at the output end of the storage battery,
A direct-current power supply system characterized in that a small-capacity inverter having a rated output lower than that of the main inverter is connected, and an emergency outlet means is connected to the output terminal of the small-capacity inverter. 2. The charging / discharging control circuit has a DC input terminal and an AC input terminal, the DC input terminal is connected to the output terminal of a DC power source via relay means, while the AC input terminal is connected to a main inverter and commercial power. The DC power supply system according to claim 1, which is connected to a power line between grids. 3. The output terminal of the small capacity inverter is connected to the emergency outlet means via the first relay means, and the power line between the first relay and the emergency outlet, the main inverter and the commercial power system. The power line between
The DC power supply system according to claim 1, wherein the DC power supply systems are connected to each other via relay means. 4. The DC power supply system according to claim 1, wherein the rated output of the small capacity inverter corresponds to the capacity of the storage battery.