JPH0256686B2 - - 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 installed in a power consumer for improving the power factor.

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-scale consumers such as factories. ing. Some conventional automatic power factor control devices
As shown in the figure, adjustment lines L ₁ and L ₂ are set on the leading side and the lagging side of reactive power, and the adjustment lines
The turning on and turning off of capacitors _C1 to _C3 is controlled so that the reactive power falls within the appropriate range surrounded by L1 _{and L2} . +C ₁ , +C ₂ , +C ₃ are capacitors
It represents the input of _C1 to _C3 , and _-C3 represents the disconnection of the capacitor _C3 . In this control method, the adjustment line
Since L ₁ and L ₂ are set to constant reactive power,
When the reactive power increases or decreases continuously, there is a problem in that the capacitor does not respond quickly to turning on or turning off the capacitor. If the interval between the adjustment lines L ₁ and L ₂ is narrowed, the response will be faster, but this is not possible because it would also respond to short-period component load fluctuations.

Other _conventional automatic power factor _control devices _, as _shown in _{FIG .} There is. Compared to the one shown in FIG. 1, this makes the response faster when there is a continuous increase or a continuous decrease, but it is still insufficient.

In other words, when the reactive power increases (continuously decreases), capacitors C ₁ to C ₃ are successively turned on (shrinked), but the adjustment line at that time is continuously turned on (shrinked). Since the adjustment line is the same as the one when there is no flow, the responsiveness when the inputs (shrinking) are continuous is the same as the responsiveness when the loading (shrinking) is not consecutive. Responsiveness when the inputs (or interruptions) are not continuous cannot be very fast considering short-period component load fluctuations, so in the end, the response when the inputs (or interruptions) are continuous is not very fast either. , is insufficient to reduce reactive power.

The purpose of the present invention is to solve the above-mentioned problems, and to provide an automatic system that can quickly respond when reactive power continuously increases or decreases, and does not respond to short-period component load fluctuations. An object of the present invention is to provide a power factor control device.

In order to achieve this object, the present invention provides an appropriate range selection means that selects a different appropriate range depending on whether the previous control was turned on or off. The adjustment line is set to a line where the advance power factor becomes a predetermined value, and the advance side adjustment line in the appropriate range of power failure selected by the previous shear failure is set to a line where the advance power factor is greater than the advance side adjustment line in the appropriate range at the time of turning on. It is characterized in that the delay side adjustment line for the proper range for turning on and the shrinking time is set at a line that is a predetermined reactive power distance from each advance side adjustment line on the lag side.

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

FIG. 3 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 C ₁ to _{C 3} for power factor improvement are connected via switches 12 to 14 and series reactors 15 to 17.
Discharge resistor 18-2 in parallel with capacitor _C1 - _C3
0 is connected. The input side of the automatic power factor control device 21 is connected to the voltage transformer 5 for management instruments, and the output side thereof is connected to the controller 22. The controller 22 drives the switches 12 to 14 to open and close, and the output means of the automatic power factor control device 21 directly controls the switches 12 to 1.
It is not necessary if 4 can be controlled.

FIG. 4 shows a front panel 24 of an automatic power factor control device 23, which is an embodiment of the present invention. 25～
28 indicates that the reactive power is on the lagging side, the appropriate range at the time of sagging,
A control status indicator light that lights up when the input is in the proper range and on the advance side, and also blinks to indicate the normal operation of automatic control in the test mode, 29
is a mode setting switch to set to automatic mode, manual mode, or test mode; 30 to 32 are indicator lights that are provided separately for capacitors C ₁ to _{C 3} and light up when they are turned on; 33 to 35 are capacitors C ₁ to C ₃ 36 to 38 are capacitor capacity setting devices for setting the capacitance (unit: VA) of the capacitors C ₁ to C ₃ .

As shown in FIG. 5, the main part of the automatic power factor control device 23 is composed of a central processing unit 39. The configuration of the central processing unit 39 is equivalently represented by its functional blocks a to g. The automatic power factor control device 23 incorporates a voltage transformer 40 and an alternator 41, which are connected to a management voltage transformer 5. The sensor 42 detects the zero-crossing point and the current value based on a voltage signal representing the load voltage inputted from the instrument transformer 40 and a current signal representing the load current inputted from the current transformer 41. Output relay 43 is a capacitor
It is provided for each of C ₁ to _{C 3} .

First, when the power switch (not shown) is turned on for the first time after installation, the sensor 42 detects the zero cross point and the power frequency in the area is determined.
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 42 is normal. In block b, timekeeping is performed by using the power supply frequency as a clock pulse.

The operation when the automatic mode is set by the mode setting switch 29 will be explained. In block c of FIG. 5, execution of automatic control processing is instructed. The automatic control process is performed as shown in the flowchart of FIG. The sensor 42 outputs a current value every second, for example, and the central processing unit 39 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 39 based on the zero cross point output from the sensor 42 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 that does not vary, and the reactive power is calculated from the current value and the phase difference. This calculation requires only a few cycles of the power supply frequency and corresponds to block e in FIG.

In block f, if the previous capacitor control was ON, the appropriate range at the time of ON is selected, and if it was OFF, the appropriate range at the time of OFF is selected. These appropriate ranges are shown in FIG. The advance side adjustment line La in the appropriate range at the time of turning on is determined to be a line where the advance power factor becomes a predetermined value. Similarly, the lagging side adjustment line Lb is
It is determined by moving the leading side adjustment line La in parallel to the lag side by a predetermined reactive power adjustment width W. However, from the point X where it intersects with zero reactive power, the line of zero reactive power becomes the delay side adjustment line. As a result, the appropriate range at the time of injection is the area between the adjustment lines La and Lb. It is preferable that the adjustment width W is set to about 150% of each capacitor capacity. Therefore, when the capacitances of the capacitors C ₁ to _{C 3} are different, the adjustment width W will be different for each capacitor.

The advance side adjustment line Lc of the appropriate range for heat interruption is:
It is determined to be a line with a leading power factor greater than the leading side adjustment line La. Similarly, the lagging side adjustment line
Ld is the adjustment width W from the leading side adjustment line Lc to the delayed side.
It is determined that the object is moved in parallel. As a result, the appropriate range for shrunken time becomes the area between the adjustment lines Lc and Ld.

If the reactive power calculated in block e is within the selected appropriate range, the capacitor is turned on.
It is determined that the disconnection is unnecessary, and the energized and de-energized states of the output relay 43 are maintained as they are. If the reactive power is out of the appropriate range, it is determined that it is necessary to turn on or turn off the capacitors, and the output relays corresponding to the capacitors C ₁ to _{C 3} in the order of turning on or turning off are energized. or de-energized. This stage corresponds to block g in FIG. 5, and is completed in, for example, ten or more cycles of the power supply frequency. As a result, if the reactive power falls within the appropriate range, the control status indicator light 26 or 27 lights up.

When the load increases continuously, as shown in FIG. 7, capacitor _C1 is first turned on, thereby selecting the appropriate range at the time of turning on. Therefore, from now on, every time the delayed reactive power reaches the delayed adjustment line Lb, the capacitors C ₂ and C ₃ are sequentially turned on. After that, if the load decreases continuously, the reactive power will increase and the adjustment line will increase.
When La is reached, capacitor C ₃ is turned off, thereby selecting the appropriate range for the cut-off period. From then on,
Each time the advancing reactive power advances and reaches the adjustment line Lc,
Capacitors C ₂ and C ₁ are cut off in sequence. In this way, when the reactive power increases or decreases continuously, the leading side adjustment line is Lc and the lagging side adjustment line is Lb, so the adjustment width of the appropriate range is apparently narrower than W. and the response will be quick. In addition, if the loading and unshrinking are not continuous,
Since the adjustment width W within the appropriate range is ensured, it does not respond to load fluctuations of short-period components.

According to this embodiment, during times when the load is heavy, no lagging reactive power is generated, so power charges can be reduced, and during times when the load is light, almost no leading reactive power is generated. , it is possible to prevent an increase in the receiving voltage.

In the illustrated embodiment, the current value, phase difference, and reactive power are calculated, but the invention is not limited to this. Information may also be obtained from a separate no-current wattmeter or ammeter. good.

As explained above, according to the present invention, an appropriate range selection means is provided for selecting a different appropriate range depending on whether the previous control was turned on or off, and the advanced side of the appropriate range at the time of turning selected depending on the previous turning on is provided. adjustment line
Set La to the line where the leading power factor is a predetermined value,
The advance side adjustment line Lc of the appropriate range for shear failure, selected by the previous shear failure, is set to a line that has a lead power factor larger than the advance adjustment line La of the appropriate range at the time of closing, and Since the lagging side adjustment lines Lb and Ld in the appropriate range are set to lines that are separated from the respective leading side adjustment lines La and Lc by a predetermined reactive power W on the lagging side, when the reactive power increases or decreases continuously. It is possible to respond quickly to load fluctuations with short period components, and it is possible to avoid responding to load fluctuations with short period components.

[Brief explanation of drawings]

Figures 1 and 2 are diagrams explaining a conventional automatic power factor control system, Figure 3 is a circuit diagram showing a typical installation example of an automatic power factor control device, and Figure 4 is an embodiment of the present invention. 5 is a block diagram, and FIG. 6 is a flowchart.
FIG. 7 is a diagram showing an appropriate range according to an embodiment of the present invention. 12-14...Switch, 23...Automatic power factor control device, 39...Central processing unit, 43...Output relay, _C1 - _C3 ...Capacitor, a-g...Function block, La... ...Adjustment line on the advance side of the appropriate range at the time of injection, Lb...Adjustment line on the lag side of the appropriate range at the time of injection, Lc...Adjustment line on the advance side of the appropriate range at the time of frost failure, Ld...Delay of the appropriate range at the time of frost failure Side adjustment line, W...Adjustment width.

Claims (1)

[Claims] 1. In an automatic power factor control device equipped with a control means that determines whether to turn on or turn off a capacitor and issues a command when the reactive power is out of the appropriate range, the power factor control device is equipped with a control means that determines whether to turn on or turn off a capacitor when the reactive power is out of the appropriate range. Proper range selection means is provided to select the range, and the advancing side adjustment line La of the appropriate range at the time of input selected by the previous input is provided.
is set to a line where the advance power factor becomes a predetermined value, and the advance side adjustment line Lc in the appropriate range for shear failure selected by the previous shear failure is set to a line where the advance power factor is larger than the advance side adjustment line La in the appropriate range at the time of turning on. The lagging side adjustment lines Lb and Ld of the appropriate range at the time of input and during the cooling time are set as the lines that will become the rate, and the respective advancing side adjustment lines
An automatic power factor control device characterized in that a predetermined reactive power W is set on a line separated from La and Lc on the lag side.