JPH0261049B2 - - 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, when the active power is large under heavy load, the power is often in the delayed reactive power region except immediately after the capacitor is turned on, so that the effective use of power may not be sufficient. Furthermore, during light loads where the active power is small, the active power is often in the advanced reactive power region except immediately after the capacitor is cut off, so that problems such as an increase in the receiving voltage may occur.

Other _conventional automatic power factor _control devices _, as _shown in _{FIG .} ,
When the load is heavy, the reactive power is made to be on the leading side as much as possible, and when the load is light, the reactive power is made to be on the lagging side as much as possible. However, even with this,
This is insufficient to prevent the occurrence of lagging reactive power during the day and leading reactive power at night. In other words, when operating during the day under the load condition just before capacitor _C3 is turned on, delayed reactive power is generated, reducing the power factor of the entire power system and reducing the power output to power consumers. Increase electricity rates through a rate rate system. Further, when the capacitor C ₁ is operated at night under a load condition just before it is cut off, reactive reactive power is generated, causing an increase in the receiving voltage.

SUMMARY OF THE INVENTION An object of the present invention is to provide an automatic power factor control device that solves the above-mentioned problems and can prevent the generation of lagging reactive power during the day and leading reactive power at night.

In order to achieve this object, the present invention sets a reactive power region on the leading side of the zero reactive power adjustment line as the daytime appropriate range, and sets a reactive power region on the advanced side of the zero reactive power adjustment line as the nighttime appropriate range during the day. The present invention is characterized in that a day/night appropriate range setting means is provided for setting a reactive power region on the lag side of the adjustment line.

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. Loads (not shown) are branch breakers 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 opens and closes the switches 12 to 14, and is not necessary when the output means of the automatic power factor control device 21 can directly control the switches 12 to 14.

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 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, 2
9 is a mode setting switch for setting automatic mode, manual mode, or test mode; 30 to 32;
are provided separately for capacitors C ₁ to _{C 3} and are indicator lights that light up when the capacitors are turned on. 33 to 35 are indicator lights for 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 h. The automatic power factor control device 23 includes a voltage transformer 40 and a current transformer 41, which are connected to the voltage and current transformer 5 for management. 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 50.
Hz or 60 Hz is determined in block a, 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, time is measured by using the power supply frequency as a clock pulse, and the clock in block b is set or corrected by the time counting process performed in block c. This will be explained using the flowcharts shown in FIGS. 6 and 7.

As shown in FIG. 6, automatic control processing (8th
A part of the time counting process (details will be described later) and a part of the time counting process are performed sequentially within one cycle of the power frequency, and the automatic control process and the time counting process proceed in parallel as the cycles of the power frequency continue. In the time counting process, as shown in FIG. 7, the power supply frequency is counted, and the current value is stored in block d every time a specified number is counted (for example, 40 minutes). This current value blocks the current value output from the sensor 42 every second.
In block d, it was averaged over several tens of seconds, and in block d, it was averaged over several tens of minutes. A load current pattern as shown in FIG. 9 is created from the stored current values, and day and night can be estimated from this pattern. That is, first, the following four conditions are considered.

(1) The light load condition continues for the specified time or more (between t ₂ and t ₃ ) (2) Following the condition (1), the heavy load condition continues for the specified time or more ( (between t ₃ and t ₄ ) (3) The load (maximum value - minimum value) must be greater than or equal to the specified value. (4) The time (t ₁ - t ₃ ) must be within the specified value range. All of these conditions are met. If filled, time
Set t ₁ or t ₃ as a reference time representing the start of daytime (8:00 AM to 10:00 PM), estimate the current time from this reference time, and set or correct the clock in block b. do. Thereby, it is possible to automatically distinguish between day and night, and it is possible to eliminate the need for power outage compensation for the watch.

In block c, a suitable daytime range _S1 is set in the advanced reactive power region during the daytime, and a suitable nighttime range _S2 is set in the delayed reactive power region at night. As shown in Fig. 10, the appropriate daytime range S ₁ is defined by the adjustment line L ₁ set to a value corresponding to 120 to 150% of the capacity of one capacitor and the adjustment line L ₀ of zero reactive power.
The appropriate night range _S2 is the area between the adjustment line _L2 and the adjustment line _L0 . In addition,
If the capacitances of capacitors C ₁ to C ₃ are the same, the adjustment lines L ₁ and L ₂ will be common to each capacitor, but if the capacitances are different, the adjustment lines L ₁ and L ₂ will be different accordingly. The appropriate ranges S ₁ and S ₂ also vary depending on the capacitance of the capacitors in the order in which they are turned on or turned off.

The operation when the automatic mode is set by the mode setting switch 29 will be explained. In block f 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 e 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 g in FIG. If the calculated reactive power is within the set appropriate daytime range _S1 or nighttime range _S2 , it is determined that it is unnecessary to turn on or off the capacitor, and the output relay 43 is energized or de-energized. The state is maintained as is. If the reactive power is out of the appropriate daytime range _S1 or the appropriate nighttime range _S2 , it is determined that it is necessary to turn on or turn off the capacitors, and the capacitors _C1 to _C3 that are in the order to be turned on or off are determined to be necessary. The corresponding output relay is energized or de-energized. This stage corresponds to block h 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 S ₁ or S ₂ ,
The control status indicator light 26 or 27 lights up.

FIG. 10 shows the states in which the capacitors C ₁ to _{C 3} are turned on and off. During the day, when the reactive power exceeds the adjustment line L ₀ and becomes even slightly on the lagging side, the capacitors are turned on in the order of C ₁ → C ₂ → C ₃ ,
When the adjustment line L1 or _more is on the leading side, the capacitors are cut off in the reverse order. Therefore, during the daytime, delayed reactive power is no longer generated, contributing to improving the power factor of the entire power system, and making it possible to use electric power sufficiently effectively. Furthermore, since the current power factor rate system targets only delayed reactive power during the day, it is possible to reduce power rates. At night, when the reactive power exceeds the adjustment line L ₀ and becomes even slightly on the leading side, the capacitors C ₃ to C ₁ are cut off, and when the reactive power reaches the lag side beyond the adjustment line L ₂ , the capacitors are turned on. Therefore, at night, advanced reactive power is not generated, and an increase in the receiving voltage can be prevented.

Note that the load is light during the daytime from 12:00 to 13:00, but it is preferable to prohibit turning on and off the capacitor during this time to reduce the number of times the switch is opened and closed.

In the illustrated embodiment, the current value, phase difference, and reactive power are calculated, but the invention is not limited to this, and information may be obtained from a separately installed reactive power meter or ammeter. . Further, the determination of day and night is not limited to the one based on the load current pattern, but may be based on a clock or an external signal.

As explained above, according to the present invention, in the daytime, the reactive power region on the advanced side of the zero reactive power adjustment line is set as the daytime appropriate range, and in the night, the reactive power region is set as the nighttime appropriate range. Since the day/night appropriate range setting means for setting the reactive power region on the lagging side of the adjustment line is provided, it is possible to prevent the generation of lagging reactive power in the daytime and leading reactive power in the nighttime. By not generating delayed reactive power during the day, it is possible to contribute to improving the power factor of the entire power system, and it is possible to reduce electricity charges for electricity consumers based on the power factor rate system. Furthermore, by not generating advanced reactive power at night, it is possible to prevent an increase in the received power voltage. Note that the power factor rate system does not apply to delayed reactive power at night, so although delayed reactive power is generated at night, power rates will not increase. Therefore, it is possible to contribute to improving the power factor of the entire power system, and it is also possible to prevent adverse effects such as an increase in the receiving voltage.

[Brief explanation of the drawing]

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, FIGS. 6 to 8 are flowcharts, FIG. 9 is a diagram of a load current pattern according to an embodiment of the present invention, and FIG. 10 is a diagram showing day and night patterns. It is a figure showing an appropriate range. 12-14...Switch, 23...Automatic power factor control device, 39...Central processing unit, 43...Output relay, _C1 - _C3 ...Capacitor, a-h...Function block, _L0 ~ _L2 ...Adjustment line, _S1 ...Appropriate daytime range, _S2 ...Appropriate nighttime range.

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 reactive power is adjusted to zero during the day as the appropriate range. A day/night appropriate range setting means is provided for setting a reactive power area on the leading side of the line, and setting a reactive power area on the lagging side of the zero reactive power adjustment line as the night appropriate range at night. Automatic power factor control device.