JPS6366143B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a grid-connected inverter disconnection device for disconnecting inverters connected to a power distribution line when the power distribution line is stopped.

As is well known, when power obtained from a solar power generation device or fuel cell is supplied to a distribution line via an inverter, the inverter must be disconnected from the distribution line in the event of an accident or work power outage on the distribution line, and the power supply to the distribution line must be stopped. Need to stop.

Conventionally, when connecting a small hydropower generator or the like to a power distribution line, a transfer cutoff method is used to stop power supply to the power distribution line in the event of an accident or the like. However, when a large number of small-capacity solar power generation devices are connected to a distribution line system, it is economically disadvantageous to apply this method to each device.

This invention was made based on the above circumstances, and its purpose is to be able to reliably disconnect the inverter from the distribution line when the distribution line is stopped, and to provide an economically advantageous way to disconnect the inverter from the distribution line when the line is stopped. The present invention aims to provide a grid-connected inverter disconnection device.

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

In FIG. 1, the power distribution line 11 is branched by a connecting line 1, and a commercial frequency sine wave signal is supplied to a synchronizing signal shaping circuit 12 via this connecting line 1, as shown in FIG. 2a. This synchronous signal shaping circuit 1
2 is synchronized with the input sine wave signal in Fig. 2b.
As shown in the figure, a synchronization signal consisting of a square wave is generated at the same frequency. This generated synchronization signal is supplied to the phase shift circuit 13, and the phase shift circuit 13
In this case, the phase of the input synchronizing signal is advanced by 180 degrees as shown in FIG. 2c. By doing so, it is possible to prevent the output of the inverter 15 from being fed back positively, although the details will be described later. The synchronization signal output from this phase shift circuit 13 is supplied to an oscillation circuit 14. This oscillation circuit 14 is a well-known synchronous oscillator, and when the synchronizing signal is supplied, it oscillates at the same frequency as the synchronizing signal, and when the supply of the synchronizing signal is stopped, the frequency is lower than the frequency of the synchronizing signal by about 5 Hz. It is configured to self-oscillate at a low unique frequency. The output signal of this oscillation circuit 14 is supplied to an inverter 15. This inverter 1
5 is operated by the output signal of the oscillation circuit 14,
For example, it converts the output power of a DC power source 16, such as a solar cell, into AC power. Therefore, when the distribution line 11 is normal, the inverter 15 is driven by the same signal as the product frequency supplied from the oscillation circuit 14, and generates AC power with the same phase as the commercial frequency. . Electric power generated in this inverter 15 is supplied to the distribution line 11 via an inverter bus 17 and a closed circuit breaker 18. Further, a frequency detection circuit 19 is connected to the inverter bus bar 17 . This frequency detection circuit 19 detects the frequency change of the AC power output from the inverter 15 and controls the circuit breaker 18. That is, when the distribution line 11 is normal, the inverter 15
AC power at the same frequency as the commercial frequency is being output, and in this state, the circuit breaker 18 is controlled to remain closed. On the other hand, distribution line 1
1 stops as shown by ABN in Figure 2a, the synchronization signal shaping circuit 1 stops as shown in Figure 2b.
2. Since a synchronizing signal cannot be obtained from the phase shift circuit 13, the oscillation circuit 14 begins to oscillate at its own frequency _t2 , which is 5 Hz lower than the commercial frequency _t1 , as shown in FIG. 2d. Therefore, the frequency of the AC power output from the inverter 15 also decreases, and the frequency detection circuit 19 detects this frequency change. Therefore, the circuit breaker is opened by the control signal output from the frequency detection circuit 19,
Inverter 15 is disconnected from power distribution line 11 .

According to the above configuration, the oscillation circuit 14 is connected to the distribution line 11
In addition to synchronizing with the system frequency of the distribution line 11
When the circuit breaker stops, it is possible to output a signal with a frequency slightly lower than the grid frequency, and the frequency detection circuit 19 detects a change in the output frequency of the inverter 15 controlled by the output signal of the oscillation circuit 14, and the circuit breaker 18 is activated. It's in control. Therefore, distribution line 1
As soon as inverter 1 becomes stopped, inverter 1
5 can be disarranged.

Further, since the above configuration is relatively simple and inexpensive, it is suitable for small-scale solar power generation devices and the like.

Next, the reason why the phase shift circuit 13 advances the phase of the synchronization signal output from the synchronization signal shaping circuit 12 by 180 degrees will be explained. That is, when the power of the distribution line 11 is stopped, the synchronization signal shaping circuit 12 continues to output the synchronization signal as shown in FIG. 2b even at the time of the stop. Therefore, if the oscillation circuit 14 is directly driven by the synchronization signal output from the synchronization signal shaping circuit 12 without providing the phase shift circuit 13, the oscillation circuit 14 will not oscillate when the power of the distribution line 11 is stopped. The frequency is the same as before the power to the distribution line 11 was stopped.

Therefore, the output AC power of the inverter 15 driven by the output of this oscillation circuit 14 is also transmitted to the distribution line 1.
The output of the inverter 15 is shaped by the synchronizing signal shaping circuit 12 via the circuit breaker 18 and used to drive the oscillation circuit 14. That is, in the absence of the phase shift circuit 13, when the power of the distribution line 11 is stopped, the inverter 15, the circuit breaker 18, the synchronization signal shaping circuit 1
2. A positive feedback loop consisting of the oscillation circuit 14 and the inverter 15 is constructed. For this reason, the output frequency of the inverter 15 is maintained at the frequency before the power stoppage of the distribution line 11, and the frequency detection circuit 19 cannot detect the change in the output frequency of the inverter 15, and the frequency of the output frequency of the distribution line 11 is maintained. Stoppage is no longer detected.

However, in the phase shift circuit 13, the synchronous signal shaping circuit 1
By advancing the phase of the synchronization signal output from 2 by 180 degrees, when the power on the distribution line 11 is stopped, the oscillation is started half a cycle of the synchronization signal earlier than at the time of the stop, as shown in Figure 2c. Since the supply of the synchronizing signal to the circuit 14 is stopped, the oscillation circuit 14 can perform an oscillation operation at its own frequency. Therefore, the output frequency of the inverter 15 also changes, the frequency detection circuit 19 detects the change in the output frequency of the inverter 15, and power stoppage of the distribution line 11 is detected.

As detailed above, according to the present invention, it is possible to reliably disconnect the inverter from the distribution line when the distribution line is stopped, and moreover, an economically advantageous system for disconnecting the interconnected inverter from the distribution line when the line is stopped is provided. Can be provided.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing one embodiment of a grid-connected inverter disconnection device when a line is stopped according to the present invention, and FIG.
The figure is a waveform diagram shown to explain the operation of FIG. 1. 11... Distribution line, 12... Synchronous signal shaping circuit,
13... Phase shift circuit, 14... Oscillation circuit, 15...
Inverter, 18...breaker, 19...frequency detection circuit.

Claims (1)

[Claims] 1. Means for extracting the system frequency of the distribution line and generating a signal synchronized with it, means for advancing the phase of the synchronization signal outputted from this means by 180 degrees, and outputting a signal with the same frequency as the phase-shifted synchronization signal. At the same time, an oscillator capable of oscillating a signal with a unique frequency slightly different from the synchronizing signal when the synchronizing signal stops, an inverter driven by the output signal of this oscillator, and an intervening device between the inverter and the distribution line. and a circuit breaker which is normally closed and supplies the output of the inverter to the distribution line, and a means to which the output of the inverter is supplied and detects a frequency change of the output voltage to set the circuit breaker in a cut-off state. A grid-connected inverter disconnection device when a line is stopped, characterized by the following.