SU1757015A1 - Method of control over voltage in power network - Google Patents

Abstract

The method of regulating the voltage in the electrical network. Summary of the invention: in order to reduce the deadband to a value equal to the adjustment step, the method prohibits the execution of a reverse command when issuing the corresponding initial command in the event that the voltages leave the deadband. The voltage is then measured at a controlled point and, if it is greater than the voltage after increasing or less after decreasing it, the prohibition is removed. 1 il.

Description

The invention relates to electrical networks and can be used to control the voltage of power transformers that supply power lines.

A known method of regulating the voltage of transformers is that, when the voltage overflows at a controlled point, beyond the deadband, it gives out a signal to the switching device of the transformer turns, which, reducing the voltage at the output of the transformer, returns it to the deadband. If the voltage at the controlled point decreases and becomes less than the lower limit of the dead zone, the switching device will increase the voltage, putting it into the dead zone,

In the known method for preventing the effect of overshoot and creating conditions for the stable operation of the regulator, the zone

insensitivity is taken over the voltage regulation step. In some cases, this zone can reach 150% of the voltage control step. Such a large deadband, as compared with the control stage, impairs the quality of the voltage control.

In order to improve the quality of voltage regulation, it is desirable to reduce the dead zone at which the regulator does not work.

The purpose of the invention is to improve the quality of voltage regulation by reducing the dead zone to a value equal to the voltage regulation step, and to eliminate the overshoot effect.

This goal is achieved by the fact that at the time of increasing (decreasing) voltage, it is prohibited to decrease (increase) voltage and over time,

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sufficient for sustained operation of the transformer winding switches, additionally, the voltage is not measured at the controlled point and, if it is greater than the voltage after the increase, or less after its decrease using the transformer winding switch, the prohibition is removed.

So, for example, when the voltage goes out at a controlled point, beyond the upper (lower) boundary of the dead zone, equal to the voltage control level of a transformer, a command is given to lower (raise) the voltage. This command causes a decrease (increase) in voltage by one level. At the same time, the drop in voltage change commands is remembered, in this case, a decrease (increase) in voltage and a prohibition on issuing a reverse command is created, i.e. teams do not increase the voltage,

If we suggest that the execution of a command to reduce (increase) the voltage at the controlled point did not enter the dead zone and is even higher (lower) than the upper (lower) border of the dead zone, then the next low voltage increase (increase) command previous performance. Such a decrease (increase) will occur until the voltage of the controlled point enters the dead zone. In this case, the created Prohibition does not affect the execution of the command to decrease (increase), the tach as it was created on the reverse command, namely the voltage increase (decrease) command. Such a situation is also possible when, for any reason, when executing the initial command to decrease (increase) the voltage, the voltage at the controlled point decreases (increases) and enters the lower (upper) limit of the insensitivity zone.

In this case, since the voltage at the controlled point did not remain in the dead zone and went beyond the lower one (the top one should follow the command to increase (decrease) the voltage. However, since when issuing the initial command to decrease (increase) the voltage was the prohibition of reduction (increase) was introduced, then the command to increase (decrease) the voltage will not follow.

The next step is to follow the voltage change at the controlled point after the initial command, i.e. commands for lowering (raising) voltage,

If the voltage at the controlled point remains unchanged, then it is natural that no voltage change commands will follow.

If the voltage starts to increase, then no decrease command will follow until it (if it happens) exceeds the upper limit of the deadband.

If, however, the voltage after processing the first command, in our case, the decrease command (increase) becomes less than the lower limit of the deadband, and with further control over the voltage change, you will be relieved that it begins to decrease further, then the prohibition created will be removed and command to increase the voltage is issued.

Thus, the chain t of the offered method is achieved by imposing a ban on executing a reverse command when issuing a corresponding initial command in the event of a voltage coming out of the dead zone, and monitoring further voltage changes after the initial command has been performed.

The drawing shows a diagram of the implementation of the method.

On input 1, current 8 of the power line, D of which voltage is controlled, is supplied to current sensor 2 (DT). The voltage from this sensor output is proportional to the voltage drop from the beginning of the transmission line to a point with a constant controlled voltage. The voltage from the DT 2 output goes to one of the inputs of the voltage isolation unit 3 at the controlled point of the line by electric lines. The second input of the unit 3 to the input 4 receives voltage from the voltage transformer. Unit 3 allocates the difference between the voltage on the busbars of the supply transformer and the voltage drop in the transmission line to a controlled point with a constant voltage. Essentially, the actual voltage at the controlled point is removed from the output of the block 3, depending on the load current of the transmission line. This voltage is fed to the input of block 5 voltage comparison. Block 5 compares the input voltage with the voltage of the upper and lower limits of the deadband. In this case, if the actual voltage at the controlled point exceeds the upper limit, the signal is on the upper output of block 5. If the equipment is less than the lower limit of the dead zone, the signal on the lower output of the block 5

The signals from the outputs of the comparator unit 5 are fed to the time delay elements b and 7, which are necessary to prevent voltage regulation during a short-term change. The delay time of occurrence of signals at their outputs is 1-2 minutes. The output signals of the elements b and 7 are received on the elements 8 and 9 of the ban. If there are no signals from the corresponding elements MEMORY 10 and 11 on the prohibition inputs of elements 8 and 9, the signals will pass to the actuators

12 and 13. At the same time, when actuating the actuating element 12, the signal at input 14 will go to the coil voltage of the transformer. When element 13 is triggered, the signal at input 15 will increase the voltage of the transformer. Simultaneously, the signals from the executive elements 12 and

13 includes, respectively, MEMORY 11 and 10. The output signals of the memory through the element OR 16 are received from the input element 17 of the delay. The delay time is chosen sufficient for the final operation of the switching device of the turns of the transformer winding from the moment the signal at output 14 or 15 appears. It depends on the drive of this device and may take several seconds.

The signal from the delay element 17 is fed to the input of the control unit 18 for changing the input voltage coming from the block 3. At the same time, the signals at the outputs a or b can appear only when the enabling signal comes from the delay element 17. The signal at output a of block 18 appears if there is an enable signal with delay element 17 and if the voltage from block 3 changes at the input of block 18 in the direction of increasing. If the voltage at the input of block 18 coming from block 3. changes in the direction of decreasing, then the signal is sent at output b. If the voltage across the output of block 18 does not change, then there will be no signals at both outputs a and b.

The appearing signals at the outputs a and b of block 18 return the elements of Memory 10 and 11 to their initial states.

Consider the implementation of the method with counter voltage control. Suppose that in the power line, and therefore on the input 1, an increase in current occurred. At the same time, the voltage at the DT 2 output will increase, which is proportional to the voltage drop to a point with a constant controlled voltage. If we assume that the voltage from the voltage transformer at input 4 has not changed, then from block 3, the difference between its input signals will decrease

voltages A decrease in voltage at the output of block 3 also means a decrease in voltage at a controlled point of the transmission line. The voltage from block 3 enters block 5, where it is sregshe

0 with the upper and lower boundaries of the dead zone,

Suppose that the voltage at the controlled point of the transmission line decreased to such a value that it became

5 is less than the lower limit of the deadband. In this case, the signal from the lower output of block 5 is fed to the input of the delay element 17,

If within one to two min / g (time

0 the delay of element 7) the signal at the lower output of the block 5 does not disappear, then the signal is received from the output of the prohibition element 9. For this case, it will be assumed that the inhibit signal from Memory 11 is missing. it

5 will cause a signal to appear at the input and, therefore, at the output of the actuating element 13, which sends a command to the input 15 to increase the voltage. At the same time, the signal from item 13 will turn on Memory 10.

0 From the output of the element Memory 10, a prohibition signal on the prohibition element 8 and a signal on one of the inputs of the element OR 16. The signal from the output of the delay element 17 is generated after a time corresponding to the stable operation of the switching device 5 turns of the transformer windings,

Suppose that with the occurrence of a signal at input 15, switching occurs

0 turns of the transformer winding and the transformer voltage will increase. An increase in voltage at the output of the transformer (at input 4) will naturally cause an increase in voltage at the controlled point

5 power lines (at the output of block 5). Suppose that with an increase in the voltage s at a controlled point, it will go beyond the upper limit of the dead zone. This will cause a signal in the upper

0 output of block 5. After a time delay, the signal arrives at the input of element 8 However, the signal is not output at the output, because the prohibiting input contains a signal from Memory 10. The investigator 5 will not receive a signal at input 14 to reduce the voltage and will not follow the effect of overshoot.

Next, you should follow the voltage change at the input of the block 18 - the control unit for the change of the input voltage.

If the voltage at the monitored point after the appearance of the signal at input 15 remains unchanged, then there will be no signals from the a and b outputs of block 18. If the voltage at the output of block 3 (the voltage at the controlled point) decreases and goes beyond the lower limit of the dead zone, the signal will turn on at the lower output of block 5 and through elements 7, 9 and 13 and further along the bypass 15 will increase the voltage.

If the voltage at the output of block 18 after the occurrence of the signal from the delay element 17 begins to increase, then the memory of the signal a now r of the output of block 18 will be reset. When executing the command for the increase, the voltage at the controlled point has gone beyond the upper boundary of the zone insensitivity. This caused the appearance of a signal at the upper output of block 5 and, respectively, at the input of prohibition elements 8 and delay 6, Earlier, when an overvoltage at a controlled point above the upper limit of the dead zone when executing the increase command was caused by the inaccuracy of the coil switching device the signal through the element 8 of the ban is not passed. The reason for this is a ban on Memory 10.

Now, when the subsequent increase in voltage at the controlled point is due to the mode of the power line and there is no inhibitory signal from the Memory 10 element, the signal will pass through the prohibition element 9. The actuating element 12 will operate and the signal at input 14 will pass to reduce the voltage.

Similarly, the method is implemented if, due to a change in the mode of the transmission line, the voltage at the controlled point extends beyond the upper limit of the deadband.

The positive effect of the application of the proposed method is to improve the quality of voltage regulation in electric networks.

Claims (1)

Invention Formula A method of controlling voltage in an electrical network containing a voltage-controlled transformer under load using a turn switch, consisting in measuring the voltage at the control point of the network and comparing it with the voltage of the upper and lower limits of the deadband and, for example, pressure is higher than the upper limit of the insensitivity zone, then it is reduced, if the voltage is less than the voltage of the lower limit of the deadband, it is increased, characterized in that, in order to improve the quality voltage control, at the time of increasing (decreasing) voltage, prohibiting a decrease (increase) in voltage and after a time sufficient for the stable operation of the transformer winding switch, the voltage at the controlled point is also measured and, if it is greater than After increasing or less after decreasing it using the turns of the transformer winding, the prohibition is removed.