JPS603728A - Reactive power controller - Google Patents

Abstract

PURPOSE:To prevent the bad influence from exerting upon a power generation system by taking the variation of a compensating reactive power value due to the variance of the frequency of an AC bus into consideration to exercise a high-precision reactive power compensating control for the variance of the frequency. CONSTITUTION:A converting circuit 50 is connected to an AC bus 11, which is connected to an AC power supply system 10, AC-DC converters 9a and 9b, and plural parallel capacitors SC, through an AC voltage transformer 12. A DC voltage proportional to the frequency of the input voltage is generated by this circuit 50, and this output is inputted to a function generator 65, and a deviation between the output of the generator 65 and an effective compensating capacity Q1 is obtained by an adder 60. Meanwhile, a reactive power value QD of capacitors SC is calculated by a required reactive power detecting circuit 70, and the output of the adder 60 and the power value QD are applied to an operation command discriminating circuit 80 through an adder 75. The output of the adder 60 and the power value QD are compared with each other by the circuit 80, and the comparison result is applied to an SC control circuit 85 to perform a high-precision reactive power compensation in case of the variance of the frequency.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a reactive power control device for an AC-DC converter in DC power transmission.

Conventionally, the first reactive power control device for the Eri AC-DC converter station
The configuration shown in the figure and the control operation shown in FIG. 2 have been proposed. 1. In Fig. 1, 1°2 is a converter transformer with a tap changer (hereinafter referred to as a transformer), 3, 4.5
are respectively parallel capacitors SC1 or F13 in this example
It is a breaker that opens and closes two parallel capacitors SC1, SC2, and 8C3;
+9b is an AC-DC converter and a 10JIi AC power supply system. FIG. 2 is an operating characteristic diagram showing the control operation of the @i column capacitor SC in #I, where the horizontal axis is the power P transmitted by DC power transmission, and the compensation is disabled at a certain power value. Power q is represented on the vertical axis.

The operation of the conventional reactive power control device mentioned above will be briefly described below. In the AC-DC exchange station, AC-DC converters 9a + 9b, which are constructed of mercury or thyristor valves, are used as one means for obtaining DC power. By controlling the ignition phase of the mercury or silice valves of the AC-DC converters 9a and 9b, the magnitude of the direct R power to be sent is controlled. In normal operation, the III transfer device side performs constant current control, and the inverter side performs constant voltage control, and the DC current 1d and DC voltage V are determined by each control. d&r-
DC power P calculated by Pp□=VdXId 11
0 is being transmitted. Direct current being transmitted 1dc
and the reactive power QDO consumed by the AC-DC converters 9a and 9b.
The relationship between .

Q p O= I d c x W −-+11 However,
Edo: No-load DC voltage (1) Force) It is clear that the reactive power QDO increases in proportion to the DC transmitted power PDOK. Therefore, as shown in Fig. 2, in response to an increase in the transmitted power P, the necessary pre-compensation dynamic force q is set in advance and the transmitted power P at each level is calculated in advance.
Depending on the value of DO, the parallel capacitor sc, which is the source of reactive power q, is turned on or off as shown in FIG. In response to this control operation, the front dynamic power control is performed by controlling the opening/closing of each of the circuit breakers 3.4.5.

Since the conventional reactive power control device is configured with one or more devices, it has the following drawbacks. In other words, is there a parallel conductor in conventional control operation? The precondition is that the compensation capacity of the SC remains constant. Therefore, the compensation of two parallel capacitors sc, ffl g, t QQ is 5, as is well known, 1
It can be expressed by equation 21.

Qa = ωCV2...-121 However, ω: Fundamental angular frequency (2πf) C: Capacitance ■: AC line voltage 1R@Scenery QC is a function of the frequency f of the AC system. Therefore, if the frequency f is not equal to the rated value, 1c will be in either an undercompensation or overcompensation state (7J), and appropriate compensation control cannot be performed. In this way, in conventional control operations, the output value of reactive power of the AC power supply system 1o shown in Fig. 1, which can respond to fluctuations in frequency f, is varied, and this causes a serious disturbance to the entire power generation system. It has flaws. This drawback is particularly noticeable in independent direct current transmission from power plants.

This invention eliminates the drawbacks of the conventional ones as mentioned above.
By taking into account the frequency fluctuations caused by the busy schedule, we can respond to the frequency fluctuations. circle. □
, □□1e7o. The purpose of the present invention is to provide a reactive power control device that can perform the following steps.

An embodiment of the present invention will be described below with reference to the drawings. Third
In the figure, 11 indicates a bus bar to which the AC-DC converters 9 a y 9 b and the parallel capacitor SC are connected. 12Fi voltage transformer (hereinafter referred to as PT) that transforms AC voltage, 5O
A conversion circuit that converts the frequency of the Fi bus 11 into an amount of electricity proportional to it, 60.75 is an adder, 65 is a function generator,
Reference numeral 70 indicates a required reactive power detection circuit, 80 indicates an operation command discrimination circuit, and 85 indicates an SC control circuit for outputting a plurality of parallel capacitors SC and a cut-off command.

The operation of this embodiment will be explained with reference to FIGS. 4 and 5. In Fig. 3, the frequency f of the first bus 11 is rated 1.
The case where +9− f 1 is explained.

The AC voltage of bus 11 is transformed into PT12,
The signal is input to the conversion circuit 50. In the conversion circuit 50, the frequency f
outputs a DC voltage output signal having a magnitude proportional to . This DC voltage output signal is input to the function generator 65. In the function generator 65.

As shown in Fig. 4, the output value of the effective supplementary R capacitance Q1 of the parallel capacitor SC corresponding to the rated frequency f
Output to 0. -10,000, the adder 61) outputs the deviation from the rated effective compensation capacity IQ□. Therefore, at the frequency of busbar 11, sword 1, etc., which is now rated Sen f1.

) Ju, R, the output signal of the device 60 becomes zero.

- In the required reactive power detection circuit 70, the DC power PDO
The reactive power value QD to be compensated using 5ctc of parallel capacitors is calculated and output.

This output signal is input to the adder 75, but no! .

Since the output signal of the adder 60 is zero, the output value of the output signal of the PJr required/invalid torque detection circuit 70 is inputted to the operation command discrimination circuit 80VC. In the operation command discrimination circuit 80, the output 1i1- of the adder 75 and the current parallel capacitor S
A control f111 signal for closing or opening each parallel capacitor SC is output via the SC control circuit 85, and the closing or opening of the parallel capacitor SC is performed as specified. reactive power compensation control is completed.

A case in which the frequency f of the bus bar 11 decreases from fl to flK will be briefly described. Bus line 11 sword 1 et al PT12 conversion circuit 5
A DC voltage signal corresponding to the frequency fL is input to the function generating circuit 65 via the frequency fL. On the other hand, the function generating circuit 65 outputs an effective complementary R reactive power value QL of the parallel capacitor SC corresponding to the input frequency fL. As shown in FIG. 4, since there is a magnitude relationship between Q and Q□, the output signal of the adder 60 is ΔQ=QL−Q1, and 1m− of ΔQ has a negative value. Therefore, the output value of adder T5 is QD - ΔQ
Since ΔQ has a negative polarity, it has a larger value than when the frequency f of the AC bus 11 is fl. Therefore, a value larger than the actually required compensating reactive power is input to the operation command discriminating circuit 800 Å force signal, and a DC power value smaller than that when one frequency f is f□, for example, the 5th V
! A control command for the parallel capacitor SC is output from the SC control circuit 85 at a DC power value P1 of 4. The extent of this is as described above and 7 corresponds to the reduction ΔQK of the effective compensation thermodynamic power, so that the necessary compensation amount can always be obtained. In the above embodiment, even when the frequency f rises to fH, the control command for the parallel capacitor SC is set to S with a larger DC power value than when the frequency f1 is used for the same operation.
It is understood that the necessary complements 17 to I are always obtained as shown by the solid line in FIG. 5.

Note that the broken line in FIG. 5 represents the case where the present invention is not applied.

In other words, the control operation for determining the amount of compensation for reactive power and force by a conventional reactive power control device is illustrated for reference.
It is clear from the figure that if the present invention is applied, more appropriate complementary 1R control of reactive power can be achieved.

Incidentally, in the above embodiment, a case has been described in which opening/closing is performed using a breaker such as a parallel capacitor SC, but the same effects as in the above embodiment can also be obtained with an fc stationary front power compensator using a thyristor or the like.

As described above, with the reactive power control device of the present invention, if 1 ton is used,
Since the structure is configured to take into account changes in the compensation reactive power value due to frequency fluctuations of the AC bus, it is possible to generate thermodynamic power that does not cause any disturbance to the power supply system with high precision in lv hours per frequency f. A compensatory control operation is obtained.

Especially when combined with a static pre-dynamic force compensator.

The effect is so remarkable that the compensation of the effect power by the parallel capacitor is always appropriate, and there is no unfavorable influence on the power generation system.

[Brief explanation of the drawing]

FIG. 1 is a system configuration diagram showing an example of the system configuration of an AC-DC converter station having a reactive power control device, and FIG. 2 is an explanatory diagram showing the control operation of a conventional reactive power control device. FIG. 3 is a block configuration diagram showing the configuration of a reactive power control device according to an embodiment of the present invention, FIG. 4 is a characteristic diagram showing the relationship between frequency and effective compensation capacity of the parallel capacitor in the device of the embodiment of FIG. FIG. 5 is an explanatory diagram showing the relationship between DC power and reactive power in the apparatus of the embodiment shown in FIG. 1.2...Transformer for converter with tap changer. 3.4.5... Parallel capacitor switching breaker, SC
:SC1, SC2, SC3...Parallel capacitor, 10
...AC power system, 11...AC bus, 12...
AC voltage transformer, 50... Conversion circuit, 60.75...
・Adder, TO... Required reactive power detection circuit, 80...
- Operation command discrimination circuit, 85...SC control circuit. Agent Masuo Oiwa 2 Figure q fLf+ fH C 1. ,□ 1

Claims (1)

[Claims] In a reactive power control device that adjusts the reactive power of an AC power system by using phase adjustment equipment when mutually converting power between AC power and DC power for DC power transmission, The phase modulating equipment is controlled in accordance with an output signal corrected by adding a change in the compensation capacity of the phase modulating equipment due to a fluctuation in the frequency of the AC power system to the power value after power conversion. reactive power control device.