JP4341625B2 - Calculation method in reactive power compensator - Google Patents

Description

  The present invention relates to a compensation reactive power calculation method in a reactive power compensator that is linked to a power system and suppresses voltage fluctuations of the power system.

FIG. 3 shows a general example of the reactive power compensator.
The reactive power compensator 1 is connected between the system impedance 3 and the load 4 of the power system to which the load 4 is connected from the power system 2 through the system impedance 3 and compensates for the reactive power generated from the load 4. . The reactive power compensator 1 includes a thyristor 5, a reactor 6, a capacitor 7, and the like. Reference numeral 13 denotes a control device of the reactive power compensator 1.

  As an operation of the reactive power compensator 1, the reactive power generated by the load 4 is compensated. Here, when the reactive power generated by the load 4 is Qf, the reactive power of the reactive power compensator 1 is Qt, and the reactive power of the system is Qs, the reactive power compensator 1 is controlled so that Qt = Qf. The reactive power of the system is Qs = 0, and the voltage fluctuation of the system voltage can be suppressed.

An example of a control device for the reactive power compensator is shown in FIG.
This is because the reactive power detector 10 detects the reactive power Q from the detected system voltage Vs and the load current If, and the result obtained by multiplying the reactive power Q by the gain by the coefficient unit or the multiplier 11 is the firing angle. This is input to the regulator 12, where a firing angle command α for firing the thyristor is calculated, and reactive power is compensated based on this.

As the reactive power detector 10, for example, an example disclosed in Patent Document 1 is shown in FIG.
This is composed of a phase shifter 14, multipliers 15 and 16, integrators 17, 18, and 23, a sample and hold unit 19, an adder / subtractor 20, a divider 21 and a setter 22, and the detected system voltage Vs and The reactive power Q is finally calculated from the load current if and the like. The calculation method will be described below.

First, e0 having the same phase as the system voltage Vs and e90 delayed by 90 ° are obtained by the phase shifter. if, e0 and e90 are defined as in the following equations (1) to (3), respectively.
e0 = √2Ecos θ (1)
e90 = √2Esin θ (2)
if = √2I cos (θ−φ) (3)
The reactive power instantaneous value q is calculated by multiplying e90 and if.
q = e90 × if = E · I {sinφ + sin (2θ−φ)} (4)

The equation (4) is integrated from θ = 0 to obtain the equation (5) in equation (1).

The active power instantaneous value p is obtained by multiplying e0 and if.
p = e0 × if = E · I {cos φ + cos (2θ−φ)} (6)
1/2 of the active power instantaneous value p and 1/2 at the time of θ = 0, that is, p ₍ θ _{= 0)} / 2 are calculated as in the following equations (7) and (8).
p / 2 = E · I {cos φ + cos (2θ−φ)} / 2 (7)
p ₍ θ _{= 0)} / 2 = E · I cos φ (8)

When the above expression (5) + expression (7) −expression (8) is calculated, the expression (9) in Expression 2 is obtained.

Thereby, the reactive power Q is calculated | required like the following (3) Formula (10).

Japanese Patent Publication No. 06-025955

As described above, in order to calculate the reactive power Q, all cannot be calculated with an instantaneous value, and there is a problem that a value at θ = 0 of the active power instantaneous value p is required. Therefore, when the load current if changes, the change is not reflected, and an error is included in the calculation of the reactive power Q, so that sufficient compensation cannot be performed.
Accordingly, an object of the present invention is to make it possible to follow reactive power that changes from moment to moment and to improve compensation performance.

In order to solve such a problem, in the invention of claim 1, in the reactive power compensator connected to the power system and suppressing the voltage fluctuation of the power system,
To the integral value of the reactive power instantaneous value, adds the value obtained by multiplying the gain in the active power instantaneous value, the calculation result obtained by dividing the angle of the integration interval, by subtracting the calculation result obtained by dividing the effective power at an angle interval of integration In calculating the reactive power amount, the active power is obtained by dividing the calculation result obtained by subtracting the value obtained by multiplying the instantaneous value of the reactive power by the gain from the integral value of the instantaneous value of the active power by the angle of the integration interval. Features.

In the invention of claim 2, in the reactive power compensator connected to the power system and suppressing the voltage fluctuation of the power system,
When calculating the reactive power amount by adding the value obtained by multiplying the active power instantaneous value by the gain to the integral value of the reactive power instantaneous value and dividing the calculation result obtained by subtracting the active power by the angle of the integration interval , The active power is obtained by dividing a calculation result obtained by subtracting a value obtained by multiplying an instantaneous value of a reactive power by a gain from an integral value of an instantaneous value of an active power by an angle of an integration interval .

  According to this invention, it is possible to improve the compensation performance by devising the calculation of the reactive power so as to be able to follow the reactive power that changes every moment.

FIG. 1 is a block diagram showing an embodiment of the present invention.
The reactive power detector 10 is changed from that shown in FIG. 5 as shown in FIG. 1, that is, a divider 24, a multiplier 25, an adder 26, a subtractor 27, a gain element 28, and an integrator 29 compared to FIG. The point which added etc. is the feature.

The calculation is performed as follows. First, the detected system voltage Vs and the load current if are input, and e0 having the same phase as the system voltage Vs and e90 delayed by 90 ° are obtained by the phase shifter. if, e0 and e90 are defined as in the following equations (1 ′) to (3 ′).
e0 = √2Ecos θ (1 ′)
e90 = √2Esin θ (2 ′)
if = √2I cos (θ−φ) (3 ′)
The reactive power instantaneous value q is calculated by multiplying e90 and if.
q = e90 × if = E · I {sinφ + sin (2θ−φ)} (4 ′)

The equation (4 ′) is integrated from θ = 0 to obtain the equation (5 ′) of equation (4).

The active power instantaneous value p is obtained by multiplying e0 and if.
p = e0 × if = E · I {cos φ + cos (2θ−φ)} (6 ′)
1/2 of the active power instantaneous value p is calculated.
p / 2 = E · I {cos φ + cos (2θ−φ)} / 2 (7 ′)
Up to this point, the process is exactly the same as in FIG.

Next, the equation (7 ′) is integrated from θ = 0 to obtain the equation (11) of Formula 5.

Calculate 1/2 of the reactive power instantaneous value q,
q / 2 = E · I {sinφ + sin (2θ−φ)} / 2 (12)
Is calculated and the following expression (13) is obtained.

It can be seen that Expression (13) in Expression 6 is transformed into Expression (14) in Expression 7 and becomes an effective power amount.

Accordingly, the reactive power Q is expressed as the following equation (15) by substituting the equation (14) instead of p ₍ θ _{= 0)} / 2 in the above equation (10).

The above equation (15) can be transformed into equation (16). This indicates that the multiplier 25 can be omitted from FIG. 1 and the position of the divider 21 can be changed to configure as shown in FIG.

  As described above, in the conventional example, the reactive power amount is calculated using the active power amount at θ = 0, so that the followability with respect to the load that changes momentarily is low, but in the present invention, an instantaneous value is used. This makes it possible to follow the reactive power of the load that changes from moment to moment, so that an advantage of improving the compensation performance can be obtained.

Block diagram showing an embodiment of the present invention The block diagram which shows the modification of FIG. Configuration diagram showing a typical power system The block diagram which shows the specific example of the control apparatus of FIG. The block diagram which shows the specific example of the reactive power detector provided in the control apparatus of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Reactive power compensator, 2 ... Power system, 3 ... Inductance, 4 ... Load, 5 ... Thyristor, 6 ... Reactor, 7 ... Capacitor, 8 ... PT (transformer), 9 ... CT (8 current transformer), DESCRIPTION OF SYMBOLS 10 ... Reactive power detector, 11, 28 ... Gain element, 12 ... Firing angle control circuit, 13 ... Control apparatus, 14 ... Phase shifter, 15, 16, 25 ... Multiplier, 17, 18, 23, 29 ... Integrator: 19 ... Sample and hold device, 20 ... Adder / subtractor, 21, 24 ... Divider, 22 ... Setter, 26 ... Adder, 27 ... Subtractor.

Claims (2)

In the reactive power compensator connected to the power system and suppressing the voltage fluctuation of the power system,
To the integral value of the reactive power instantaneous value, adds the value obtained by multiplying the gain in the active power instantaneous value, the calculation result obtained by dividing the angle of the integration interval, by subtracting the calculation result obtained by dividing the effective power at an angle interval of integration In calculating the reactive power amount, the active power is obtained by dividing the calculation result obtained by subtracting the value obtained by multiplying the instantaneous value of the reactive power by the gain from the integral value of the instantaneous value of the active power by the angle of the integration interval. An arithmetic method in a reactive power compensator as a feature. In the reactive power compensator connected to the power system and suppressing the voltage fluctuation of the power system,
When calculating the reactive power amount by adding the value obtained by multiplying the active power instantaneous value by the gain to the integral value of the reactive power instantaneous value and dividing the calculation result obtained by subtracting the active power by the angle of the integration interval , The active power is obtained by dividing a calculation result obtained by subtracting a value obtained by multiplying an instantaneous value of a reactive power by a gain from an integral value of the instantaneous value of the active power, and dividing the result by an angle of the integration interval. method.

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