JPH0154926B2 - - Google Patents

Description

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

Conventionally, there has been a device of this type as shown in FIG. In the figure, 1a, 1b, 1c, 1
d is a generator; 2a, 2b, 2c, and 2d are disconnectors that connect each of the generators 1a to 1d to the grid; 3a, 3
b is a bus bar, 4a, 4b are AC/DC converters, 5a, 5
b is a line breaker, 6a, 6b is a line breaker 2
Transformers installed on the line side of a and 2b, 7a and 7
b is a transformer installed on the generator side, and 8a and 8b are synchronization 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 trip, we will assume that the system has a load less than the amount of power generated (in Figure 1, this is assumed to be 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 the system protection devices such as frequency relays (not shown) cause the disconnection 2a, 2b
is tripped, the generators 1a and 1b are disconnected from the grid, and the governor operates to bring them into a no-load operating state, after which they wait for the grid to be restored. On the other hand, on the grid side, after the accident disappears, the breakers 5a and 5b
are applied sequentially to charge the AC line. The automatic synchronizers 8a and 8b know that the grid has been restored by the transformers 6a and 6b on the line side, and switch the transformer 7 on the generator side.
A, 7b and the transformers 6a, 6b on the line side detect the frequency difference, phase difference, and voltage difference on both sides of the shield breakers 2a, 2b, and control the governors of the generators 1a, 1b and the AVR.
(not shown), and when the phase difference and voltage difference are within the allowable range, the shield breakers 2a, 2
Issue a closing command to b and complete re-closing.

After reclosing, the output of each generator will be increased to restore the original state.

The conventional reclosing method is configured as described above, so in the event of an accident, all generators are disconnected at once, resulting in a complete shutdown state, and the inertia constant is also required when adjusting the frequency and voltage during reclosing. The drawback was that it took an extremely long time to complete reclosing, as it controlled a large generator. Accidents on power transmission lines are often temporary, and it is not desirable to disconnect generators every time an accident occurs, as is the case with conventional systems.After an accident occurs, it is not desirable to disconnect generators and restore the system immediately. That was what was hoped for.

The present invention has been made in order to eliminate the drawbacks of the conventional ones as described above, and after recovery from an AC line accident, one side of the disconnector is re-energized, and the frequency deviation on both sides of the other side of the disconnector is corrected. The purpose of this invention is to provide a device that can control the transmitted power of a parallel DC system based on voltage deviation, quickly match the frequency, phase, and AC voltage, and reclose the circuit by turning on the other disconnector.

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 2, the same symbols as in FIG. 1 indicate the same or corresponding parts, 9a and 9b are transformers, 200
100a and 100b are voltage detectors; 17 is a control device for controlling the firing angle of the AC-DC converter; 300 is the frequency difference output from the frequency difference detector 200 and the voltage detector; 100
This is a control device which inputs the deviation of the outputs of outputs 100a and 100b, a voltage deviation reference signal (ΔVref), and a frequency deviation reference signal (Δfref), and outputs a signal for correcting the frequency deviation and voltage deviation to the control device 17. Note that a voltage deviation detector is constituted by the voltage detectors 100a and 100b and an adder that adds their outputs with opposite polarities.

FIG. 3 is a diagram illustrating FIG. 2.

Next, the operation will be explained. After a transient accident occurs on the AC line and the shield breakers 5a and 5b trip, the shield cutter at one end is forcibly closed after a certain period of time. (In Figure 2, it is assumed that the cutter 5b is turned on. Also, the accident has been resolved at this time.)
Transformers 9a, 9 provided at both ends of the shield breaker 5a
The AC voltage is input to the frequency difference detector 200 and the voltage detectors 100a, 100b through b, and the frequency deviation signal (Δf) and the voltage detectors 100a, 100
A voltage difference signal (ΔV) obtained by passing the output of signal b through an adder is input to the control device 300. The control device 300 compares voltage and frequency deviation tolerance values ΔVref, Δfref input in advance with the difference signals (Δf), (ΔV). Here, if Δf>Δfref, a DC transmission power correction signal such that 0<Δf≦Δfref is output to the control device 17. Based on the correction signal, the DC transmission power is passed through the control device 17 to control the firing angle of the AC-DC converter 4a. If the frequency deviation Δf ₁ after the control is (O<Δf ₁ ≦Δfref), the voltage phase difference angle between both ends of the shingle breaker 5a is 1/Δf ₁
It changes between -180° - 0° - 180° in the form of a trigonometric function with the period of [see]. The known synchronization conditions for insulators and disconnectors require that voltage deviation and voltage phase difference angle deviation be within a certain value. Therefore, on the condition that the frequency deviation reaches Δf ₁ , the reactive power consumed by the AC-DC converter 4a is changed by changing the DC voltage without changing the DC transmitted power, and the voltage is changed to the known voltage. The AC voltage is controlled based on the relationship of reactive power, and the voltage deviation is controlled to be ΔV ₁ ΔVref.

FIG. 3 is a diagram illustrating the relationship between DC power P and reactive power consumption Q to explain one example of the above control. Initially, if DC power transmission is continued at point a and ΔV>ΔVref>O, by lowering the DC voltage V _D , the consumed reactive power moves from Q ₃ to Q ₄ and increases to point b. Due to the increase in reactive power, ``decreases''.
Vref>'' The above control is continued until V>O is satisfied. Furthermore, in the above control, the DC power is not changed because the DC current Id is increased by decreasing the DC voltage V <sub>D.</sub> If ``Vref>''V>O is established, a closing command is output at the timing when the periodically changing voltage phase difference angle becomes 0° when the main contact of the disconnector closes. It becomes possible to input synchronously.

In the above embodiment, the DC voltage is controlled, but the DC current may also be controlled. Further, the frequency deviation may be a differential value of the voltage phase difference angle deviation.

As described above, according to the present invention, the frequency difference is reduced by the DC power transmitted by the DC line, the DC voltage or current is controlled so that the DC power does not change, and the AC voltage deviation is made minute. Since the generator and the disconnector are turned on synchronously, the circuit can be reclosed quickly, and the generator can be turned on again without disconnecting the generator.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a conventional example, FIG. 2 is a diagram showing an embodiment of the present invention, and FIG. 3 is a diagram explaining an embodiment of the present invention. 1a, 1b, 1c, 1d... Generator, 2a, 2
b, 2c, 2d, 5a, 5b...Shiya disconnection, 3
a, 3b... Bus bar, 4a, 4b... AC/DC converter, 6a, 6b, 7a, 7b, 9a, 9b... Transformer, 17... Control device, 200... Frequency difference detector, 100a, 100b... ...voltage detector, 30
0...control device; the same reference numerals in the drawings indicate the same or corresponding parts.

Claims (1)

[Claims] 1 Installed at one end of an AC line in an AC/DC parallel system,
A first breaker that is tripped in the event of an accident on the AC line; a second breaker installed at the other end of the AC line that is tripped in the event of an accident on the AC line;
A Noshiya disconnector, two transformers that respectively derive the voltages on both sides of the first Shiya disconnector, a frequency difference detector that detects the frequency deviation of the voltages derived by each of the transformers, and each of the above transformers. A voltage deviation detector detects the deviation of the voltage derived by the frequency difference detector, and the frequency difference detector corrects the transmitted power of the DC line according to the frequency difference, and the condition is that the frequency difference is within a certain tolerance value. , a control device that corrects the reactive power consumption of the DC line according to the voltage difference of the voltage deviation detector, and outputs a closing command to the first breaker when the voltage difference falls within an allowable range. An automatic reclosing device characterized by comprising: