JPS6362987B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a reclosing device for an AC-DC parallel system.

Conventionally, there has been a device of this type as shown in FIG. In the figure, 1a, 1b, 1c, 1d are generators, 2a, 2b, 2c, 2d are disconnectors that connect each generator to the grid, 3a, 3b are bus bars, 4a,
4b is an AC/DC converter, 5a and 5b are line breakers, 6a and 6b are transformers installed on the line side of the breakers 2a and 2b, and 7a and 7b are transformers installed on the generator side. 8a and 8b are synchronization input devices.

Next, the operation will be explained. If we consider the case where an accident occurs on the AC line in Figure 1 and the cable breakers 5a and 5b are tripped, we assume that the system is in a system where the load amount is less than the amount of power generation (here, we assume a system with generators 1a and 1b). ) increases the frequency, while the other decreases the frequency. In particular, when the difference between the amount of power generation and the amount of load is large, the frequency rise is also large, and a system protection device such as a frequency relay (not shown) may cause a disconnection 2.
The generators 1a and 2b are tripped, the generators 1a and 1b are disconnected from the grid, and the governor operates to reduce the load to no-load operation, and then wait for the grid to be restored.
On the other hand, on the grid side, after the accident disappeared,
A is sequentially introduced to charge the line. The synchronization devices 8a and 8b know that the grid has been restored by the line-side transformers 6a and 6b, and synchronize the generator-side transformer 7.
a, 7b and the line-side transformers 6a, 6b detect the frequency difference, phase difference, and voltage difference on both sides of the breaker, send control signals to the generator governor and AVR, and check that the phase difference and voltage difference are within the allowable range. When the circuit enters the state, a closing command is issued to the shield circuit breakers 2a and 2b, and the re-closing is completed. After reclosing, the output of each generator will be increased to restore the original state.

Conventional reclosing devices are configured as described above, so in the event of an accident, all generators can be disconnected from the line to bring them all to a standstill, and even when adjusting the frequency and voltage during reclosing, Since the control target is a generator with a large inertia constant, it has the disadvantage that it takes an extremely long time to complete reclosing.

This invention was made in order to eliminate the drawbacks of the conventional ones as described above. By controlling the power of the parallel DC system, frequency and phase matching can be performed without disconnecting the generators, and it can be done in a short time. The purpose of the present invention is to provide an automatic re-closing device that can re-close the circuit at the same time.

An embodiment of the present invention will be described below with reference to the drawings. In Fig. 2, 1a, 1b, 1c, and 1d are generators, 2a, 2b, 2c, and 2d are cutouts, and 3
a, 3b are busbars, 4a, 4b are AC/DC converters, 5
a and 5b are the cutoffs. These elements are the first
Since it is the same as that shown in the figure, its explanation will be omitted. Further, 9a and 9b are transformers, 10 is an automatic synchronization device, 11 and 12 are frequency detection devices, and 1
3 and 14 are adders that add with the polarities shown; 15 is a frequency control circuit; 16 is a power command value; 17 is a control device that controls the firing angle of the AC/DC converter 4a based on the output of the adder 14; and 18 is a voltage - It is a function generator that has hysteresis characteristics in its frequency characteristics.

Next, the operation will be explained. After an accident occurs on an AC line and the shield breakers 5a and 5b trip, one of the shield breakers 5a and 5b (assumed to be 5b here) is forcibly turned on after a certain period of time. In this state, AC voltage is input to the frequency detection devices 11, 12 and the automatic synchronization device 10 through the transformers 9a, 9b provided on both sides of the other breaker 5a. The outputs of the frequency detection devices 11 and 12 are supplied to an adder 13, the difference between them is calculated, and the output indicating the calculation result is the voltage -
The signal is input to the frequency control circuit 15 via a function generator 18 having a hysteresis characteristic in its frequency characteristics. This function generator 18 sets a target value so as to have a predetermined frequency difference in order to shorten the time until reclosing, and after overshooting, changes the target value so as to have a frequency difference of the opposite polarity. This frequency control circuit 15 outputs a signal necessary to correct the power command value 16 so that the detected frequency difference disappears. This correction is performed by the adder 14, and the corrected power command value is supplied to the control device 17, which controls the firing angle of the AC/DC converter 14 based on its output, thereby increasing or decreasing the power transmitted in the DC system. Then, the frequencies on both sides of the breaker 5a are made to match each other. Automatic synchronization input device 10
detects the voltage difference, frequency difference, and phase difference on both sides of the sheath breaker 5a, and gives a closing command to the sheath breaker 5a when these differences are within an allowable range.
In addition, the automatic synchronous closing device 10 is generally designed so that even if there is a slight frequency difference or phase difference, the circuit breaker can be closed by adjusting the timing of the closing command. By setting the conditions to turn on the cylindrical circuit breaker 5a before this occurs, it is possible to reclose the circuit in a short time. The frequency control circuit may include only a simple proportional element, or depending on the nature of the control system, compensation may be added using a delay element or a lead element.

In each of the above-mentioned embodiments, the shingle breaker 5b is used as the advance closing end, but the other windshield breaker 5a may be used as the leading end. Further, although the case where the power command value 16 is corrected has been shown, if the DC power transmission power can be controlled, the current command value or the voltage command value may be corrected.

As described above, according to the present invention, since the power transmitted in the parallel DC system is controlled, frequency and phase matching can be performed without disconnecting the generators, and thus the circuit can be reclosed in a short time. ,
This has the effect of minimizing system disturbances and supply disruptions in the event of an accident.

[Brief explanation of drawings]

Figure 1 is a block diagram of a conventional automatic reclosing device.
FIG. 2 is a block diagram of an automatic reclosing device according to one embodiment of the present invention. 1a to 1d... Generator, 2a to 2d... Edge breaker, 3a, 3b... Bus bar, 4a, 4b... AC/DC converter, 5a, 5b... Edge breaker, 9a, 9b...
...Transformer, 10...Automatic synchronization device, 11,1
2... Frequency detection device, 13, 14... Adder,
15... Frequency control device, 17... Control device, 1
8...Function generator. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. An AC/DC parallel system, first and second cable breakers provided on the AC lines of this AC/DC parallel system, and two cable breakers connected to both sides of the first cable breaker, respectively.
an automatic synchronization device that closes the first circuit breaker when the output voltage, frequency, and phase of each transformer fall within a predetermined tolerance range; and an output frequency of each transformer. two frequency detection devices for detecting the frequency of An automatic reclosing device comprising a frequency control circuit that outputs a necessary signal and a control circuit that is supplied with a corrected power command value and corrects the power transmitted on a DC line.