JPH0256685B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in an automatic power factor control device that controls turning on and off of a capacitor provided for improving the power factor in a power consumer.

Automatic power factor control devices turn on or turn off capacitors in order to appropriately compensate for delayed reactive power generated by loads, and are increasingly being used by large customers such as factories. ing. By the way, in general, load fluctuations of consumers are
There are short-period components and long-period components. If the automatic power factor control device is made to follow load fluctuations of short-period components, the number of times the switch will open and close becomes excessive, which is not preferable. Generally, it is desirable to judge whether to connect or disconnect a capacitor based on the average reactive power value for about 5 minutes. In addition, in order to prevent the generation of abnormal voltage due to the residual charge of the capacitor, the interval between charging and discharging the same capacitor is 5 minutes if the discharge element that discharges the residual charge is a resistor, and 5 minutes if the discharge element is a reactor. It is necessary to provide a delay time of seconds. Conventionally, capacitors were turned on and off when the reactive power was out of the appropriate range for a certain period of time. Therefore, even if the voltage is significantly out of the appropriate range, it is necessary to wait for a certain period of time to turn on or turn off the capacitor, which has the disadvantage that, for example, in the case of a delay, delayed reactive power is accumulated.

An object of the present invention is to solve the above-mentioned problems and to provide an automatic power factor that is capable of appropriately changing the waiting time in response to reactive power that is out of the appropriate range without being affected by load fluctuations of short-period components. The purpose of the present invention is to provide a control device.

In order to achieve this objective, the present invention stores the reactive power obtained at each fixed time, averages the reactive power from the latest one to the previous predetermined time, and calculates the average reactive power at each fixed time. and a means for calculating the average reactive power given to the control means, a storage means for storing the number of the capacitor which has been cut off, and an elapsed time of the cut-off state, and a means for calculating the average reactive power given to the control means, a storage means for storing the number of the capacitor which has been cut off, and an elapsed time of the cut-off state, and a means for calculating the average reactive power to be given to the control means, and a storage means for storing the number of the capacitor that has been cut off and the elapsed time of the cut-off state. The present invention is characterized in that it includes a capacitor closing interval determining means that causes the control means to wait for a closing command to be issued until the elapsed time of the cut-off state exceeds a predetermined delay time.

Hereinafter, the present invention will be explained in detail based on illustrated embodiments.

FIG. 1 is a circuit diagram showing a typical installation example of an automatic power factor control device. A transaction meter current transformer 2 is connected to the distribution line 1, and further connected to a management meter transformer 5 via a disconnector 3 and a main disconnector 4. The load (not shown) is the branch breaker 6 to 8.
and are connected via transformers 9-11. Capacitors 12 to 14 for power factor improvement are connected to switches 15 to 17.
and are connected via series reactors 18-20. Discharge resistor 2 in parallel with capacitors 12 to 14
1 to 23 are connected. The input side of the automatic power factor control device 24 is connected to the current transformer 5 for management instruments, and the output side thereof is connected to the controller 25. The controller 25 drives the switches 15 to 17 to open and close, and the output means of the automatic power factor control device 24 directly controls the switches 15 to 17.
It is not necessary if 17 can be controlled.

FIG. 2 shows a front panel 27 of an automatic power factor control device 26, which is one embodiment of the present invention. 28～
31 is the reactive power on the lag side, the lag side in the appropriate range,
A control status indicator light that lights up when it is on the advance side or the advance side of the appropriate range, and also blinks to indicate the normal operation of the automatic control in the test mode, 3
2 is a mode setting switch for setting automatic mode, manual mode, or test mode; 33 to 35;
numerals 36 to 38 are manual switches for turning on and off the capacitors, and 39 to 41 are capacitor capacity setting devices for setting the capacitance of the capacitor (in VA).

As shown in FIG. 3, the main part of the automatic power factor control device 26 is composed of a central processing unit 42. The configuration of the central processing unit 42 is equivalently represented by its functional blocks a to j. The automatic power factor control device 26 includes a voltage transformer 43 and a current transformer 44, which are connected to the management voltage transformer 5. The sensor 45 detects a zero cross point and a current value based on a voltage signal representing the load voltage inputted from the instrument transformer 43 and a current signal representing the load current inputted from the current transformer 44. An output relay 46 is provided for each capacitor.

First, when the power switch (not shown) is turned on for the first time after installation, the sensor 45 detects the zero cross point and determines the power frequency in the area.
It is determined in block a whether it is 50HZ or 60HZ, and the automatic control process is set to proceed in synchronization with this. At the same time, it is checked whether the sensor 45 is normal. In block b, timekeeping is performed by using the power supply frequency as a clock pulse.

To explain the operation when the automatic mode is set by the mode setting switch 32, execution of automatic control processing is instructed in block c of FIG. The automatic control process is performed as shown in the flowchart of FIG. The sensor 45 outputs a current value every second, for example, and the central processing unit 42 calculates the average value (effective value) of the current value over several tens of seconds. The phase difference is detected by the central processing unit 42 based on the zero cross point output from the sensor 45 for each cycle of the power supply frequency, and the average value over several tens of seconds is similarly calculated.
These correspond to block d in FIG. The load voltage is treated as a constant and does not fluctuate, and based on the current value and phase difference, the reactive power is
is calculated and stored every 10 seconds or more).
Furthermore, the reactive powers VAR ₁ to _{VAR o} from the latest one to the one a predetermined number n times ago are averaged and
The average reactive power is calculated every time. That is, this average reactive power is a value obtained by absorbing short-period components in t×n time. The fixed time t and the predetermined number of times n are determined so that the t×n time is, for example, 5 minutes.
Calculating the average reactive power requires only a few cycles of the power supply frequency and corresponds to block e in FIG. block f
In this case, a load current pattern for one or two days is created by storing current values, and day and night are divided according to the load current pattern. block g
In this case, different appropriate ranges are set for day and night. In block h, the elapsed time since the last control and whether the previous control was on or off are stored for each capacitor. In block i, if the calculated average reactive power is within the set appropriate daytime range or nighttime range, it is determined that it is unnecessary to turn on or off the capacitor, and the output relay 46 is energized or de-energized. The state is maintained as is. If the average reactive power is out of the appropriate daytime range or nighttime range, it is determined that the capacitor needs to be turned on or off. When it is determined that the capacitors are to be shrunken, a shunt command is immediately output to the output relay corresponding to the capacitor in the order to be shrunken. When making a decision to make a capacitor, it is checked in block j whether a predetermined delay time (for example, 5 minutes) or more has elapsed since the capacitor in the order to be made was last cut off. If the predetermined delay time or more has not elapsed, the output of the input command is deferred until the predetermined delay time has elapsed. The automatic control processing routine shown in FIG. 4 is executed at regular time intervals t. If the average reactive power falls within the appropriate range as a result of turning on and off the capacitor, the control status indicator light 29 or 30 lights up.

In this embodiment, whether or not it is necessary to turn on or cut off the capacitor is determined from the average reactive power over t×n time, so there is no need to respond to short-period components. In addition, the decision to turn on or cut off is made at fixed time intervals t, and the turn-on command is output after the waiting time is subtracted by the elapsed time of the cutoff state up to that point, so the load of long-period components is Improves quick response to fluctuations.

In the illustrated embodiment, block i in FIG. 3 corresponds to the control means of the present invention, and block h corresponds to the storage means.

In the illustrated embodiment, the current value, phase difference, and reactive power are calculated, but the present invention is not limited to this, and information may be obtained from a separately installed reactive power meter. In addition, the capacitor input/decompression memory (block h) only needs to store at least the number of the decremented capacitor and the elapsed time of the decremented state.

As explained above, according to the present invention, the reactive power obtained at each fixed time is stored, and the reactive power from the latest to the previous predetermined time is averaged to calculate the average reactive power at each fixed time. and a means for calculating the average reactive power given to the control means, a storage means for storing the number of the capacitor which has been cut off, and an elapsed time of the cut-off state, and a means for calculating the average reactive power given to the control means, a storage means for storing the number of the capacitor which has been cut off, and an elapsed time of the cut-off state, and a means for calculating the average reactive power to be given to the control means, and a storage means for storing the number of the capacitor that has been cut off and the elapsed time of the cut-off state. Since a capacitor closing interval judgment means is provided that causes the control means to wait for a closing command to be issued until the elapsed time of the disconnection state exceeds a predetermined delay time, the capacitor closing interval can be determined within an appropriate range without being affected by load fluctuations of short-period components. The waiting time can be changed appropriately according to the reactive power that is outside the range.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing a typical installation example of an automatic power factor control device, Fig. 2 is a front view showing a front panel of an embodiment of the present invention, Fig. 3 is a block diagram, and Fig. 4 is a circuit diagram showing a typical installation example of an automatic power factor control device. It is also a flowchart. 12-14... Capacitor, 15-17... Switch, 21-23... Discharge resistor, 26... Automatic power factor control device, 28-31... Control status indicator, 32... Mode setting switch , 42...Central processing unit, 45...Sensor, 46...Output relay, a to j...Function block.

Claims (1)

[Claims] 1. In an automatic power factor control device equipped with a control means that determines and instructs whether to turn on or off a capacitor based on reactive power, the reactive power obtained at a certain time period is stored, and the reactive power obtained from the latest one is an average reactive power calculating means for calculating an average reactive power at each predetermined period of time by averaging the reactive power up to and giving the average reactive power to the control means; and a number of the capacitor being cut off;
a storage means for storing the elapsed time of the shrunken state and a storage means for storing the elapsed time of the shrunken state; and a storage means for storing the elapsed time of the shrunken state, and when it is determined that the capacitor is turned on, the control means continues to issue a closing command until the elapsed time of the shrunken state of the capacitor reaches a predetermined delay time or more. An automatic power factor control device characterized in that it is provided with means for determining a capacitor closing interval that causes the user to wait.