JPH0731562B2 - Power system power factor correction device - Google Patents

Description

The present invention relates to a device for automatically improving the power factor of a power system.

Conventionally, power factor improvement in a customer power system has been performed by automatic power factor control or automatic reactive power control, but a load (for example, a thyristor converter) that needs to supply large lag reactive power to the system is connected. In such a case, the tripping of the capacitor bank is frequently performed. Further, there is a problem that the control device must be replaced each time to change the control method.

The present invention eliminates the above-mentioned drawbacks, suppresses the disturbance given to the electric power system as much as possible, and also performs the power factor control and the reactive power control by the same device by simply changing the power factor setting. It is an object of the present invention to provide a power factor correction device capable of doing so.

The present invention will be described below based on illustrated embodiments. FIG. 1 shows an embodiment of the present invention. The allowable reactive power computing circuit 1 is provided with a target set power factor (Pf
s) and the grid power (W3φ) detected from the grid is input,
The reactive power corresponding to the set power factor is calculated as the allowable reactive power (VarS). In addition, the system reactive power calculation circuit 3
The system power factor (Pf) detected from the system and the system power (W _{3 φ} ) are input and the system reactive power (Var) is constantly calculated.
Further, the system power factor (Pf) is also input to the polarity stabilizing circuit 4 to determine the delay or advance power factor. If the polarity is delayed, the contact lag of the signal selection switch 9 is closed and the adjustment is invalid. The adjusted reactive power (ΔVar) calculated as the difference between the system reactive power (Var) and the allowable reactive power (Vars) is input from the power calculation circuit 5 to the dead zone determination circuit 6. When the adjusted reactive power (ΔVar) exceeds the dead zone setting value (ΔSC), an appropriate combination of capacitor banks is selected from the capacitor operation table 7 and output as a closing / tripping command for each bank. When the polarity determination circuit 4 determines that the power factor is the advance power factor, the contact lead is closed this time, and the grid reactive power (Var) is input to the capacitor operation table 7.
A combination of capacitor banks is selected so as to reduce the reactive power, and output for each bank as a closing / closing command. In particular, the dead zone determination circuit 8 is inserted on the closing command side, thereby suppressing frequent closing and tripping of the capacitor bank. It should be noted that the capacitor operating table 7 is constantly input with the operating and failure states of the capacitor, and the data contents read in advance in the operating table are updated. In addition, the dead zone determination circuit 6,8
Corresponds to the dead zone setting device 10, where the upper and lower limits of the dead zone width are set.

Next, the control operation for improving the power factor by the above configuration will be described.

First, when the automatic power factor control method is adopted, the set power factor (Pfs) is set to a desired value other than 1 by the power factor setting device 2, and the dead zone setting value (ΔSC) is set to, for example, the minimum capacitor bank capacity. Select and set about 60%. As a result, as shown in FIG. 2, automatic power factor control of the electric power system is carried out so that the power factor falls within the band-shaped range indicated by the diagonal line determined by the set power factor (Pfs) (Pfs ≠ 1) and the dead band width (ΔSC).

On the other hand, in order to switch from the above-mentioned automatic power factor control operation to automatic reactive power control operation, the set power factor of the power factor setting device 2 is set to 1 and the dead zone setting width (ΔSC) is set to, for example, the setting width in FIG. Select twice as many. As a result, as shown in FIG. 3, the automatic reactive power control is performed so that it falls within the diagonal band range. Moreover, in either of the systems shown in FIGS. 2 and 3, the dead zone ΔSC can be set to prevent the capacitor bank from being frequently turned on and off.

As described above, according to the present invention, the power factor control can be performed by simply changing the power factor setting in the same device from the device configuration that can perform only one of the power factor control and the reactive power control in the related art. Control, reactive power control, or combined control of both control methods is also possible. Moreover, by setting the dead zone, it is possible to suppress high-frequency tripping and tripping of the capacitor bank and prevent transient disturbances in the system, and its practical effect is extremely large.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of the present invention, and FIGS. 2 and 3 are control characteristic diagrams of automatic power factor control and automatic reactive power control according to FIG. 1, respectively. 1 ... Allowable reactive power calculation circuit, 2 ... Power factor setting device, 3 ...
… System reactive power calculation circuit, 4 …… Polarity judgment circuit, 5 ……
Adjustment reactive power calculation circuit, 6,8 ... Dead band judgment circuit, 7 ...
… Capacitor operation table, 9… Signal selection switch.

Claims (1)

[Claims] 1. A power factor setting means for setting a target value of the power factor,
A permissible reactive power calculating means for calculating permissible reactive power from the set power factor set in the setting means and the grid power detected from the grid, and grid reactive power from the grid power factor detected from the grid and the grid power. A system reactive power calculation means for
Adjusting reactive power calculating means for calculating adjusted reactive power by comparing the allowable reactive power calculated by the allowable reactive power calculating means with the system reactive power calculated by the grid reactive power calculating means, and the adjusting reactive power calculating means Based on the adjusted reactive power calculated by the means, the operating capacitor table for generating and tripping the power factor improving capacitor bank, and the adjusted reactive power calculated by the adjusted reactive power calculating means are preset. A power factor improving device for a power system, comprising: dead zone determination means for applying the adjusted reactive power to the operating capacitor table when the dead zone set value is exceeded.