JP3147724B2 - Distributed power supply - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a power generation apparatus using a solar cell or the like, which is connected to a commercial power system, and
The present invention relates to a distributed power supply that supplies power to an emergency load together with a storage battery by causing a power generator to operate independently when an abnormality occurs in the commercial power system.

[0002]

2. Description of the Related Art In a facility such as a hospital or a school, a distributed power supply may be used in order to save energy. In the distributed power supply system, a power generation device using a solar cell or the like is installed in the facility, and the DC power generated by the power generation device is converted into AC by an inverter (DC / AC converter) and connected to a commercial power system. It supplies to the load (general load) in the facility. Even when an abnormality such as a power failure occurs in the commercial power system due to a disaster or the like, the distributed power supply unit operates the power generation device independently and converts the DC power of the power generation device into AC using an inverter. Load (independent operation load)
There is something that can be supplied to. Further, in a power generation device using a solar cell or the like, the generated power fluctuates according to the amount of solar radiation and the like. Therefore, during this self-sustaining operation, a storage battery is provided along with the power generation device so that power can be stably supplied.

FIG. 3 shows a conventional configuration example of the distributed power supply device.
Shown in In this distributed power supply, the output of a solar cell array 1 as a power generator and the output of a storage battery 3 are commonly connected to a DC input of an inverter 4. A general load 6 is connected to the AC output of the inverter 4 via an electromagnetic contactor 5, and an independent operation load 8 is connected via an electromagnetic contactor 7. The general load 6 is also supplied with AC power from a commercial power system via a power receiving point 11. A charger 14 is connected to the storage battery 3, and the power receiving point 11
The AC power supplied from the commercial power system via the AC power supply and the AC power supplied from the AC output of the inverter 4 via the electromagnetic contactor 5 are converted into DC and supplied to the storage battery 3, thereby providing the storage battery 3. Is charged when the storage battery 3 is normal.

In the above-mentioned distributed power supply device, when the commercial power system is normal, the electromagnetic contactor 7 is turned off and the electromagnetic contactor 5 is turned on, and the DC power generated by the solar cell array 1 is converted into AC by the inverter 4. Then, the AC power is supplied to the general load 6 by the interconnection operation with the commercial power system. Also, when the commercial power system is abnormal, the electromagnetic contactor 7 is turned on and the electromagnetic contactor 5 is turned off, and the DC power generated by the solar cell array 1 and the storage battery 3 when the generated power is insufficient are discharged. The obtained DC power is converted into AC by the inverter 4, and the AC power is converted into the independent operation load 8 by the independent operation.
To supply. When the power generated by the solar cell array 1 is insufficient and the storage battery 3 discharges, the DC power is also supplied to the storage battery 3 when the power generated by the solar cell array 1 becomes sufficiently large next time. Recovery charging is performed.

[0005]

However, in the above-mentioned conventional distributed power supply device, since the solar cell array 1 and the storage battery 3 are always connected in parallel, the terminal voltage fluctuates or unnecessary charge / discharge current is generated. There was a problem that the storage battery 3 could not be maintained in an appropriate state. Further, when the solar cell array 1 and the storage battery 3 are always connected in parallel, there is a problem that the power of the storage battery 3 may flow backward.

Further, the above-mentioned distributed power supply device operates the inverter 4 by maximum power tracking control (hereinafter, referred to as “MPPT control”) when the commercial power system is normal, so that the power generated by the solar cell array 1 is effectively used. Should be available. However, when such MPPT control is performed, the output voltage of the solar cell array 1 constantly fluctuates. Therefore,
If the storage batteries 3 are always connected in parallel, there is a problem that the inverter 4 cannot be operated by the MPPT control.

The present invention has been made in view of the above circumstances, and controls the inflow of a charging current to a storage battery to keep the storage battery in an optimum state and to control the MP of the inverter.
It is an object of the present invention to provide a distributed power supply device that enables operation by PT control.

[0008]

In order to solve the above-mentioned problems, a first aspect of the present invention provides a power generator for generating DC power, a storage battery for storing and supplying DC power, and Occasionally, the DC power generated by the power generator is converted into AC and connected to a commercial power system to be supplied to a general load, and the DC power output from the power generator and / or the storage battery when the commercial power system is abnormal. And a DC-to-AC converter that supplies AC to the self-sustained operating load, the output of the power generator is connected to the DC input of the DC-AC converter, and the output of the storage battery is A direct current of the DC / AC converter is switched via a switching circuit capable of switching between a state in which the charge / discharge current of the storage battery is cut off, a state in which only the discharge current is conducted, and a state in which only the charge / discharge current or the charge current is conducted. This switching circuit is connected to an input, and includes a parallel circuit of a diode and a first switch, which is in a forward direction with respect to the discharge current of the storage battery, and a series circuit of a resistor for limiting inrush current and a second switch. The circuit in which the third switch and the third switch are connected in parallel comprises a circuit connected in series, and when the commercial power system is normal, the switching circuit is switched to a state in which the charge / discharge current of the storage battery is cut off, In the event of an abnormality, first, the second switch is closed, the discharge current of the storage battery is conducted through the resistor, and then the third switch is closed,
Switching circuit control means is provided for conducting the discharge current of the storage battery without passing through the resistor, and thereafter, when the terminal voltage of the storage battery drops, switching the switching circuit to a state in which the first switch is closed to conduct the charge / discharge current. It is characterized by having.

According to a second aspect of the present invention, there is provided a power generator for generating DC power, a storage battery for storing and supplying DC power,
When the commercial power system is normal, the DC power generated by the power generator is converted into AC and connected to the commercial power system to be supplied to a general load, and when the commercial power system is abnormal, these power generators and / or storage batteries And a DC-to-AC converter that converts output DC power to AC and supplies the AC power to a self-sustained operating load, wherein the output of the power generator is connected to the DC input of the DC-AC converter, and the storage battery Output of the DC / AC converter through a switching circuit capable of switching between a state in which the charge / discharge current of the storage battery is interrupted, a state in which only the discharge current is conducted, and a state in which only the charge / discharge current or the charge current is conducted. The switching circuit is connected to an input and includes a parallel circuit of a diode and a first switch, which is in a forward direction with respect to a discharge current of the storage battery, a resistor for limiting inrush current, and a third switch. A parallel circuit of a second switch is composed of series-connected circuit, the normal state of the commercial power system,
The switching circuit is switched to a state in which the charging / discharging current of the storage battery is interrupted. When the commercial power system is abnormal, first, the second switch is closed, the discharging current of the storage battery is passed through the resistor, and then the third switch is opened. Switching circuit control for closing the first switch to allow the discharge current of the storage battery to conduct without passing through the resistor, and then, when the terminal voltage of the storage battery drops, closing the first switch to conduct the charging / discharging current. Means are provided.

According to the first and second aspects of the present invention, when the commercial power system is normal, the switching circuit is switched to a state in which the charging / discharging current of the storage battery is cut off, so that only the power generated by the power generator is converted to DC / AC. The power can be supplied to the device to perform an interconnection operation with the commercial power system. In this case, since the storage battery is disconnected, the DC / AC converter can be operated by the MPPT control.

When the commercial power system is abnormal, first, the second switch is closed to supply the discharge current from the storage battery to the DC / AC converter to start the operation. Moreover, at the start of the operation, the discharge current from the storage battery is supplied via the resistor, so that a large inrush current can be prevented from flowing through the DC / AC converter. Then, after the DC / AC converter starts operating, by closing the third switch, the discharge current from the storage battery can be directly supplied.

Further, even when the operation of the DC / AC converter is started, it is possible to prevent the charging current from flowing from the power generator into the storage battery by the diode, so that the storage battery is always kept in an appropriate state, and It is also possible to prevent the power of the storage battery from flowing backward. Then, only when the terminal voltage of the storage battery is reduced by the supply of the discharge current, the charging current from the power generation device can be supplied to the storage battery by closing the first switch.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

1 and 2 show an embodiment of the present invention. FIG. 1 is a circuit block diagram showing a configuration of a distributed power supply device, and FIG. 2 is a partial circuit showing another configuration of a switching circuit. It is a block diagram.

In this embodiment, a distributed power supply device using a solar cell, which is installed in a facility such as a hospital or a school, will be described. In this facility, a solar cell array 1 is installed as a power generation device in a place where sunlight is irradiated, such as outdoors or on a roof. The solar cell array 1 has a large number of planarly arranged solar cells that generate DC power by receiving sunlight. The solar cell array 1 includes a switching circuit 2
A storage battery 3 is also provided via the storage battery. The storage battery 3 via the positive output of the solar cell array 1 and the switching circuit 2
Is connected to the DC input of the inverter 4.
The inverter 4 is a stationary DC / AC converter that converts DC power into AC.

The switching circuit 2 includes an electromagnetic contactor 2a (first
Switch) and a parallel circuit of a diode 2b and an electromagnetic contactor 2
The circuit in which an electromagnetic contactor 2e (third switch) is connected in parallel to a series circuit of c (second switch) and a resistor 2d is connected in series. Therefore, all the electromagnetic contactors 2a, 2
When c and 2e are OFF, the storage battery 3 is disconnected from the solar cell array 1 and the inverter 4, and the charge / discharge current is cut off. When only the electromagnetic contactor 2c is turned ON, the discharge current of the storage battery 3 is supplied to the inverter 4 via the resistor 2d and the diode 2b.
Only the discharge current flows to the resistor 2d while being limited. Next, when the electromagnetic contactor 2e is turned on, the discharge current of the storage battery 3 is supplied to the inverter 4 via the diode 2b, and only the discharge current flows without being limited to the resistor 2d. When the electromagnetic contactor 2a is also turned on, the discharge current of the storage battery 3 is directly supplied to the inverter 4, and the charging current from the solar cell array 1 is supplied to the storage battery 3, so that the charging / discharging current is reduced. It becomes a flowing state.

The AC outputs of the inverter 4 are connected to general loads 6 and 6 via an electromagnetic contactor 5, and are connected to an independent operation load 8 via an electromagnetic contactor 7.
In addition, the AC output of the inverter 4 is connected to a self-contained shared load 10 via the electromagnetic contactors 5 and 7 and the electromagnetic switching contactor 9. The general loads 6 and 6 are general loads in a facility used when the commercial power system is normal, and are provided between the general loads 6 and 6 and the electromagnetic contactor 5 from a power receiving point 11 of the commercial power system. By connecting the distribution line, power is also supplied from this commercial power system. A system interconnection protection relay 12 is connected between the general loads 6 and 6 and the electromagnetic contactor 5,
Detects abnormality in the commercial power system and turns on the electromagnetic contactors 5 and 7
/ OFF and switching of the electromagnetic switching contactor 9 can be controlled. The self-sustaining operation load 8 is an emergency load in a facility used when an abnormality occurs in the commercial power system. The interconnected independent shared load 10 is a load in a facility commonly used when the commercial power system is normal and abnormal.

A relay circuit 13 is connected between the storage battery 3 and the switching circuit 2 so that the terminal voltage of the storage battery 3 can be detected to control ON / OFF of the electromagnetic contactor 2a of the switching circuit 2. Has become. The DC output of the charger 14 is connected between the storage battery 3 and the switching circuit 2. The battery charger 14 converts AC power supplied via the distribution line from the power receiving point 11 and AC power supplied from the AC output of the inverter 4 via the electromagnetic contactor 5 to DC and supplies the DC to the storage battery 3. This is a charging circuit for supplying the electric power corresponding to the self-discharge of the storage battery 3 when the commercial power system is normal.

The operation of the distributed power supply having the above configuration will be described. When the commercial power system is normal, the grid interconnection protection relay 1
2 turns on the electromagnetic contactor 5 and turns on the electromagnetic contactor 7
The FF is set, and the electromagnetic switching contactor 9 is switched to the general load 6 side. Further, the electromagnetic contactors 2a, 2c, 2e of the switching circuit 2 are all turned off, and the storage battery 3 is disconnected. Then
The DC power generated by the solar cell array 1 is supplied to the inverter 4
Is converted to AC by the electromagnetic contactor 5 and the general load 6,6
, And is further supplied to the interconnection independent shared load 10 via the electromagnetic switching contactor 9, so that the interconnection operation with the commercial power system is performed. Therefore, the general loads 6 and 6 and the interconnected independent shared load 10 receive power from the solar cell array 1 when the generated power during the day is sufficient, and the amount of solar radiation is small even at night or during the day. Therefore, when the generated power is insufficient, the shortage of power is supplied from the commercial power system via the power receiving point 11. In this case, the storage battery 3
Is separated from the solar cell array 1 and the inverter 4 by the switching circuit 2 so as not to be affected by the fluctuation of the output voltage of the solar cell array 1.
The operation can be performed by the PPT control.

When an abnormality occurs in the commercial power system due to, for example, a power failure, the grid interconnection protection relay 12 detects the abnormality,
The operation of the inverter 4 is stopped, and the electromagnetic contactor 5 is stopped.
To OFF. Then, first, the electromagnetic contactor 2c of the switching circuit 2 is turned on to supply the discharge current of the storage battery 3 via the resistor 2d and the diode 2b to restart the operation of the inverter 4. After a few seconds, the electromagnetic contactor 2e is turned on to supply the discharge current of the storage battery 3 to the inverter 4 via only the diode 2b, and the electromagnetic contactor 7 is turned on.
The electromagnetic switching contactor 9 is switched to the independent operation load 8 side. Then, the inverter 4 starts the self-sustaining operation, converts the DC power generated by the solar cell array 1 or the DC power supplied from the storage battery 3 into AC, and supplies the AC to the self-sustaining operation load 8 and the interconnected self-supporting shared load 10. Become like When the operation of the inverter 4 is restarted, the discharge current of the storage battery 3 is supplied through the resistor 2d for only the first few seconds, so that a large inrush current can be prevented from flowing. When the independent operation is started in this way, the independent operation load 8 and the interconnected independent shared load 10 receive power supply from the solar cell array 1 when the power generated during the day is sufficient, and the power is supplied at night or during the day. When the generated power is insufficient due to a small amount of solar radiation even in the middle, the shortage of power is supplied from the storage battery 3.

When the commercial power system is abnormal, the storage battery 3
Is connected to the solar cell array 1 and the inverter 4 via the switching circuit 2.
Connected to. However, the switching circuit 2 includes an electromagnetic contactor 2a
Remains OFF, the discharge current from the storage battery 3 flows out, but the charging current is cut off by the diode 2b. Therefore, this storage battery 3 is
Also, when connected to the inverter 4, it is usually possible to prevent the charging current from flowing from them.

When the terminal voltage of the storage battery 3 drops below a predetermined value due to discharge, the relay circuit 13 detects this and turns on the electromagnetic contactor 2a of the switching circuit 2. For example, when the storage battery 3 is a lead storage battery, the relay circuit 13 turns on the electromagnetic contactor 2a when the terminal voltage of each cell of the storage battery 3 drops to 2.10 V or less. Then, since the storage battery 3 is directly connected to the output of the solar cell array 1 by bypassing the diode 2b, if the power generated by the solar cell array 1 is sufficiently large, a charging current flows into the storage battery 3 to perform charging. Will be When the terminal voltage of the storage battery 3 recovers to a predetermined value or more by this charging, the relay circuit 13
Detects this and turns off the electromagnetic contactor 2a of the switching circuit 2.
To complete charging. When the storage battery 3 is a lead storage battery as described above, the relay circuit 13 returns the electromagnetic contactor 2a to OFF when the terminal voltage of each cell of the storage battery 3 rises to 2.45V or more. Thereafter, each time the storage battery 3 is discharged and the terminal voltage falls below a predetermined value, charging is performed by the same operation.

Therefore, according to the distributed power supply of this embodiment, the storage battery 3 is disconnected by the switching circuit 2 when the commercial power system is normal, so that the inverter 4 is connected to the MPPT.
It operates by control, and the power generated by the solar cell array 1 can be used effectively. When the commercial power system is abnormal, the charging current is cut off by the diode 2b of the switching circuit 2, so that the storage battery 3 is always kept in an appropriate state and the power of the storage battery 3 is prevented from flowing backward. it can. Furthermore, when this commercial power system is abnormal,
Only when the storage battery 3 has discharged to a certain extent or more, the charging current from the solar cell array 1 can be supplied to the storage battery 3 via the switching circuit 2 to perform charging.

FIG. 2 shows another example of the configuration of the switching circuit 2. The switching circuit 2 includes a parallel circuit of an electromagnetic contactor 2a (first switch) and a diode 2b, a parallel circuit of an electromagnetic contactor 2e (third switch) and a resistor 2d, and an electromagnetic contactor 2c. Connected to. Also in the case of this switching circuit 2,
When the commercial power system is normal, the electromagnetic contactors 2a, 2c, 2e
Is turned off, the storage battery 3 can be disconnected. Further, when the commercial power system is abnormal, if the electromagnetic contactor 2c is first turned on, the discharge current of the storage battery 3 is reduced by the resistor 2d.
Is supplied via After a few seconds, the electromagnetic contactor 2e
Is turned on, the discharge current of the storage battery 3 can be supplied directly to the inverter 4. Then, when the electromagnetic contactor 2a is turned on, the diode 2b is bypassed, and a charging current flows from the solar cell array 1 to the storage battery 3 to perform charging. That is, in the case of the switching circuit 2 shown in FIG. 2, the same effect is obtained by switching ON / OFF of the electromagnetic contactors 2a, 2c and 2e by the same control as in the case of the switching circuit 2 shown in FIG. Obtainable.

[0025]

As is apparent from the above description, according to the distributed power supply of the present invention, when the commercial power system is abnormal,
Since the storage battery is connected to the DC / AC converter by the switching circuit in a state where only the discharge current flows, the storage battery can always be kept in an appropriate state, and the power of the storage battery can be prevented from flowing backward. Also, when the commercial power system is normal, the storage battery is disconnected by the switching circuit, so that the DC / AC converter can be operated by MPPT control, and the power generated by the power generator can be used to the maximum extent.

[Brief description of the drawings]

FIG. 1, showing an embodiment of the present invention, is a circuit block diagram illustrating a configuration of a distributed power supply device.

FIG. 2, showing an embodiment of the present invention, is a partial circuit block diagram illustrating another configuration of the switching circuit.

FIG. 3 is a circuit block diagram showing a conventional example and showing a configuration of a distributed power supply device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Solar cell array 2 Switching circuit 2a Electromagnetic contactor 2b Diode 2c Electromagnetic contactor 2d Resistor 2e Electromagnetic contactor 3 Storage battery 4 Inverter 6 General load 8 Independent operation load 11 Receiving point of commercial power system

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-6-178461 (JP, A) JP-A-1-103128 (JP, A) JP-A-4-2511531 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) H02J 7/35 H02J 7/00

Claims (2)

(57) [Claims] 1. A power generator for generating DC power, a storage battery for storing and supplying DC power, and when the commercial power system is normal, the DC power generated by the power generator is converted into AC and connected to the commercial power system. And a DC / AC converter that converts the DC power output from the power generator and / or the storage battery to AC and supplies the AC power to the self-sustained operation load when the commercial power system is abnormal. In the power supply unit, the output of the power generator is connected to the DC input of the DC / AC converter, and the output of the storage battery is in a state in which the charge / discharge current of the storage battery is interrupted, a state in which only the discharge current is conducted, and a state in which the charge / discharge current Alternatively, the switching circuit is connected to the DC input of the DC / AC converter via a switching circuit capable of switching between a state in which only the charging current is conducted, and the switching circuit is connected in a forward direction to the discharging current of the storage battery. The parallel circuit of the diode and the first switch, the series circuit of the inrush current limiting resistor and the second switch, and the circuit in which the third switch is connected in parallel are connected in series. When the commercial power system is normal, the switching circuit is switched to a state in which the charge / discharge current of the storage battery is cut off. When the commercial power system is abnormal, the second switch is closed first, and the battery is discharged through the resistor. The current is conducted, then the third switch is closed, and the discharge current of the storage battery is conducted without passing through the resistor. After that, when the terminal voltage of the storage battery drops, the first switch is closed to reduce the charge / discharge current. A distributed power supply device, comprising: switching circuit control means for switching a switching circuit to a conductive state. 2. A power generator for generating DC power, a storage battery for storing and supplying DC power, and when the commercial power system is normal, the DC power generated by the power generator is converted into AC and connected to the commercial power system. And a DC / AC converter that converts the DC power output from the power generator and / or the storage battery to AC and supplies the AC power to the self-sustained operation load when the commercial power system is abnormal. In the type power supply device, the output of the power generator is connected to the DC input of the DC / AC converter, and the output of the storage battery is in a state of interrupting the charge / discharge current of the storage battery, a state of conducting only the discharge current, and a state of charging / discharging current. Or, a state in which only the charging current is conducted is connected to the DC input of the DC / AC converter via a switching circuit capable of switching, and the switching circuit is connected to the forward direction with respect to the discharge current of the storage battery. Circuit consisting of a parallel circuit of a diode and a first switch, a parallel circuit of a resistor for limiting inrush current and a third switch, and a circuit in which a second switch is connected in series. At times, the switching circuit is switched to a state in which the charge / discharge current of the storage battery is interrupted. In the event of an abnormality in the commercial power system, the second switch is first closed, the discharge current of the storage battery is passed through the resistor, and then the third switch is turned on. A switch that closes the switch and conducts the discharge current of the storage battery without passing through the resistor, and then, when the terminal voltage of the storage battery drops, switches the switching circuit to a state where the first switch is closed and the charge and discharge current is conducted. A distributed power supply device provided with circuit control means.