JPH08256436A - Solar power generation system - Google Patents

Abstract

PURPOSE: To positively detect the individual operation of an inverter without generating a power loss. CONSTITUTION: In a solar power generation system where an inverter 22 for converting a DC power generated by a solar cell 21 to AC is joined to a system power supply 23 by a system interconnection device 24, the inverter 22 monitors the individual operation of the inverter 22 due to a system separation using a voltage detection circuit 31 or a frequency detection circuit 32. Then, the system separation is generated, the phase jump or the frequency fluctuation of a system voltage is detected by the voltage detection circuit 31 or the frequency detection circuit 32 and the detection signal is directly transmitted to an output control circuit 33. A control signal is transmitted to a main circuit 28 by the output control circuit 33, thus decreasing the output of the inverter 22.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solar power generation system, and more specifically, it converts a direct current power generated by a solar cell into an alternating current by an inverter and connects the inverter to a system power source by a system interconnection device to form a load. The present invention relates to a solar power generation system that supplies electric power.

[0002]

2. Description of the Related Art In a solar power generation system, an inverter 2 for converting DC power generated in a solar cell 1 into AC power is connected to a system power supply 5 by a system interconnection device 4 via a distribution board 3 as shown in FIG. Power is supplied from the solar cell 1 and the system power supply 5 to the load 6 by making them system. The distribution board 3
Is equipped with a system interconnection switch 7 that can be opened based on a command from the system interconnection device 4, as described later.

The grid interconnection device 4 functions as an interface for connecting the solar cell 1 and the inverter 2 to the grid power supply 5, and the inverter 2 and the distribution board 3 are based on the grid voltage and frequency. Sends a predetermined command to.

That is, the voltage and frequency of the system are detected in the vicinity of the interconnection point, which is the system interconnection switch 7 of the distribution board 3, and the system interconnection device 4 operates the inverter 2 and the electricity distribution device based on the detected measurement signal. A control and operation signal is output to the panel 3, the inverter 2 is operated / stopped based on this control signal, and the system interconnection switch 7 of the distribution board 3 is turned on by the operation signal.
I'm trying to turn it off.

[0005] For example, when a system power failure occurs due to a system disconnection due to construction, if the solar cell 1 and the inverter 2 are still connected, the inverter 2 operates independently and the solar cell 1 in the construction section. There is a risk that a reverse power flow will occur when the power generated by the power generator is added, and there is a risk of electric shock to the construction worker.

Therefore, in order to prevent the electric shock accident, the islanding operation of the inverter 2 due to the grid disconnection is detected, the inverter 2 is quickly stopped based on the detection signal, and the grid interconnection switch of the distribution board 3 is detected. It is necessary to shut off 7. Generally, there are two types of methods for detecting the islanding operation of the inverter 2 due to the grid disconnection, a passive method and an active method.

The passive system is an inverter 2 based on a grid disconnection.
Is to detect the phase jump of the system voltage that occurs during the independent operation of the. Here, in the completely balanced state in which the output power of the inverter 2 and the power consumption of the load 6 are equal, no change occurs in the system at the time of disconnection, and therefore, the passive method cannot detect.

Therefore, in the active system, the output power of the inverter 2 is constantly fluctuated by the occurrence of disturbance to break the perfect balance state, and the phase jump or the frequency fluctuation of the system voltage is induced at the time of the islanding operation of the inverter 2 by the system out-of-line operation. This is to detect this.

The detection of the islanding operation of the inverter 2 by the active method is specifically carried out based on the configuration shown in FIG. FIG. 7 shows the output of the inverter when the system disconnection occurs in a state where the system is constantly changed due to the occurrence of disturbance. Also,
FIG. 8 is a flowchart showing an algorithm for stopping the inverter by detecting the islanding operation due to the grid disconnection.

That is, while the output of the inverter 2 is constantly changed by the disturbance generator 11 of the grid interconnection device 4, the islanding operation of the inverter 2 due to the grid disconnection is monitored. And
When a system disconnection occurs, a phase jump or frequency fluctuation of the system voltage at that time is detected by the voltage detection circuit 12 or the frequency detection circuit 1.
3 and sends this detection signal to the output control circuit 15 via the timer circuit 14.

The timer circuit 14 confirms that the phase jump or frequency fluctuation of the system voltage has continued for a predetermined time to prevent malfunction, and then the output control circuit 15 to the main circuit 16
To quickly stop the inverter 2 and disconnect the inverter 2 from the system by shutting off the system interconnection switch 7 of the distribution board 3 based on the operation signal output from the protection circuit 17.

[0012]

By the way, in the solar power generation system, an active system in which the inverter output is constantly fluctuated by the occurrence of disturbance is adopted as a method for detecting the isolated operation of the inverter 2. Constantly changing, power loss of 5 to 10% or more always occurs.

Further, in the case where a plurality of solar cells 1 and inverters 2 are installed, it is difficult to obtain the desired effect because the fluctuations caused by the disturbance generated in the inverter output interfere with each other by the distributed power sources. Moreover, if a large number of solar cells 1 and inverters 2 are grid-connected, it is predicted that a large reactive power component generated by the total output of the large number of inverters 2 will adversely affect the system.

Therefore, the present invention has been proposed in view of the above problems, and an object thereof is to provide a photovoltaic power generation system capable of surely detecting an isolated operation of an inverter without generation of power loss. To do.

[0015]

As a technical means for achieving the above object, the present invention connects an inverter for converting DC power generated in a solar cell to an AC power by a grid interconnection device. In the solar power generation system, the inverter detects an islanding operation by a grid disconnection by a voltage or frequency detection circuit, directly operates an output control circuit based on the detection signal, and outputs an inverter output by the output control circuit. It is characterized by decreasing.

[0016]

In the photovoltaic power generation system according to the present invention, since the inverter is provided with the output control circuit that reduces the output when the grid disconnection occurs, it is not necessary to constantly change the inverter output due to the occurrence of disturbance, so that the power loss is eliminated. Does not occur, there is no interference between systems, and moreover,
Since the disturbance generating part of the system interconnection device can be omitted, the system interconnection device can be made compact and lightweight.

[0017]

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

As in the conventional case, the solar power generation system of the present invention includes, as shown in FIG. 2, an inverter 22 for converting the direct current power generated in the solar cell 21 into an alternating current, the solar cell 21, the inverter 22 and the system power supply 23. It is composed of equipment of the grid interconnection device 24 that functions as an interface for coupling. In this embodiment, the inverter 22 and the grid interconnection device 24 are incorporated into a distribution board 25.

That is, the distribution board 25 has a system interconnection device 24 connected to the system power source 23 via an internal system interconnection switch 26, the system interconnection device 24 and the solar cell 21.
And an inverter 22 connected to each of them, and a transmission cable for transmitting a connection cable, a measurement signal, a control signal, and an operation signal between the system interconnection switch 26, the system interconnection device 24, and each equipment device of the inverter 22. Use the cable for internal wiring. Therefore, in this solar power generation system, the grid interconnection switch 26, the grid interconnection device 24, and the inverter 22.
Since the respective equipments of the above are connected by the internal wiring of the distribution board 25, the external wiring is connected to the system power supply 23, the solar cell 21 and the load 2.
7 need only be connected to the distribution board 25, and external wiring can be simplified and the system can be made compact.

The load 27 supplied with power from the solar cell 21 or the system power supply 23 is connected to the distribution board 25 near the inverter side of the system interconnection switch 26, as in the conventional case.
The system interconnection device 24 sends a predetermined command to the inverter 22 and the system interconnection switch 26 based on the voltage and frequency of the system inside the distribution board 25. That is, the distribution board 2
The voltage and frequency of the system are detected in the vicinity of the interconnection point, which is the system interconnection switch 26 of No. 5, and control and operation signals are output to the inverter 22 and the distribution board 25 based on the detected measurement signals. Based on the above, the inverter 22 is operated / stopped, and the system interconnection switch 26 of the distribution board 25 is turned on / off by an operation signal.

Here, in order to detect the islanding operation of the inverter 22 due to the grid disconnection, the inverter 22 of the photovoltaic power generation system according to the present invention has a circuit configuration as shown in FIG. Incidentally, FIG. 3 shows the inverter output when the system disconnection occurs in the present invention. Further, an algorithm for detecting the islanding operation due to the grid disconnection and stopping the inverter in the present invention is shown in the flowchart of FIG.

The inverter 22 monitors the islanding operation of the inverter 22 due to the grid disconnection by the voltage detection circuit 31 or the frequency detection circuit 32. Then, when the system disconnection occurs, the voltage detection circuit 31 or the frequency detection circuit 32 detects the phase jump or the frequency fluctuation of the system voltage at that time, and the detection signal is directly sent to the output control circuit 33. The output control circuit 33 sends a control signal to the main circuit 28 to decrease the output of the inverter 22.

When the reduction of the inverter output by the output control circuit 33 becomes, for example, 1/2, 1/3, etc., the voltage drop detection relay [U
VR] is operated, the inverter 22 is stopped by the operation of UVR, and the system interconnection switch 26 of the distribution board 25 is operated based on the operation signal output from the protection circuit 34.
Is cut off to disconnect the inverter 22 from the system.

In this way, by immediately executing the reduction of the inverter output by the output control circuit 33 from the detection of the isolated operation by the voltage detection circuit 31 or the frequency detection circuit 32, the inverter 2 can be operated within a predetermined time from the time when the grid is disconnected.
2 can be stopped.

In the above description, the output signal of the voltage detection circuit 31 or the frequency detection circuit 32 is directly output to the output control circuit 33.
However, a timer circuit is inserted between the voltage detection circuit 31 or the frequency detection circuit 32 and the output control circuit 33, and the phase jump or frequency fluctuation of the system voltage is caused by the timer circuit for a predetermined time. The output control circuit 33 may be operated after continuing the operation.

In the above embodiment, the inverter 2
2 and the case where the grid interconnection device 24 is incorporated into the distribution board 25 have been described, but the present invention is not limited to this, and is also applied to the inverter 2 configuring the conventional solar power generation system shown in FIG. Of course it is possible.

[0027]

According to the photovoltaic power generation system of the present invention, the inverter is provided with the output control circuit that reduces the output when the islanding operation occurs due to the grid disconnection, so that there is no power loss and there is no power loss between the systems. Interference in
Moreover, since the disturbance generator can be omitted from the system interconnection device, the system interconnection device can be made smaller and lighter.

[Brief description of drawings]

FIG. 1 is a circuit block diagram illustrating an inverter having a circuit configuration for detecting an isolated operation, for explaining an embodiment of the present invention.

FIG. 2 is a circuit block diagram showing an inverter and a grid interconnection device incorporated in a distribution board.

FIG. 3 is a characteristic diagram showing an output of an inverter when a grid disconnection occurs in the present invention.

FIG. 4 is a flowchart showing an algorithm of the present invention for detecting an islanding operation due to a grid disconnection and stopping the inverter.

FIG. 5 is a circuit block diagram showing each facility device that constitutes a conventional photovoltaic power generation system.

FIG. 6 is a circuit block diagram showing an inverter having a circuit configuration for detecting islanding operation.

FIG. 7 is a characteristic diagram showing an inverter output when a conventional system disconnection occurs.

FIG. 8 is a flow chart showing a conventional algorithm for stopping the inverter by detecting islanding due to grid disconnection.

[Explanation of symbols]

 21 solar cell 22 inverter 23 system power supply 24 system interconnection device 25 distribution board 31 voltage detection circuit 32 frequency detection circuit 33 output control circuit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takaya Miura 3-3-22 Nakanoshima, Kita-ku, Osaka City, Osaka Prefecture Kansai Electric Power Co., Inc.

Claims (1)

[Claims] 1. In a photovoltaic power generation system in which an inverter that converts direct current power generated by a solar cell into an alternating current is connected to a system power supply by a system interconnection device, the inverter comprises:
Photovoltaic power generation characterized by detecting an isolated operation due to a grid disconnection by a voltage or frequency detection circuit, directly operating an output control circuit based on the detection signal, and decreasing the inverter output by the output control circuit system.