JP3447933B2 - Control device for reactive power compensator - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention comprises a thyristor control reactor, a thyristor control capacitor, and the like, and compensates for reactive power of a power system to stabilize the system and suppress voltage fluctuations. The present invention relates to a control device of a reactive power compensating device. 2. Description of the Related Art In a power system or the like in which power is supplied from a system power source such as a substation to a load through a system bus, a large-capacity arc furnace, a train load, a steel rolling load, or the like that causes a system voltage fluctuation due to a reactive power fluctuation. For a variable load, a reactive power compensator is provided between the system power supply and the variable load to compensate for the reactive power caused by the variable load. The following is a description of an equivalent circuit of the general system No. 3 with reference to FIG. In the figure, (Vs)
Is system power supply, (Xs) is system impedance, (CT
a) is a load current detection current transformer, (PTa) is a system voltage detection transformer, (T) is a system interconnection transformer, (1) is a variable load, (2) is a system bus, and (3) Is a separately-excited reactive power compensator. [0003] The load (1) generates reactive power of an arc furnace or the like, and is connected to a system power supply (V) through a system bus (2).
s). The reactive power compensator (3) is connected to the system power supply (Vs) in parallel with the load (1) via the system impedance (Xs) by connecting to the system bus (2) via the transformer (T). . Then, a compensation current having a reactive current component (reactive power) having an opposite phase to the reactive current component (reactive power) of the load (1) is generated, and the reactive current component of the load (1) is canceled out by the reactive current component of the compensation current. And a control unit for setting the compensation current to an optimum value according to the reactive current component of the load (1). [0004] The reactive power compensator (3) has a TCR (T
Hystertor Controlled React
or) type and TSC (Thyristor Switch)
edCapacitor) type. The TCR type has a configuration in which a TCR that generates a lagging reactive power and a filter (FC) that generates a leading reactive power are connected in parallel to a system bus (2), and the TCR connects a transformer and a series reactor. (Or a high impedance transformer) and a thyristor. The filter (FC) includes a phase-advancing capacitor and a series reactor that absorbs harmonics of the bus (2) by resonance with the capacitor. [0005] Reactive power (Qa) due to load fluctuations
, The reactive power (Qt) generated by the TCR is increased or decreased by phase control of the thyristor to make (Qa + Qt) constant, and at the same time, the power factor is increased by the constant advanced reactive power (-Qc) generated by the phase-advancing capacitor. Improve and continuously compensate for reactive power fluctuations in the system. In the case of the TCR type, a command value is output once every half cycle to set the control angle, and the phase of the reactor current is continuously controlled to compensate for the reactive power fluctuation. In the TSC type, a plurality of phase-advancing capacitors connected in parallel to the load (1) are controlled on and off by a thyristor switch to the system power supply (2) to generate a step-like phase-advanced reactive power to reduce the reactive power fluctuation of the system. Compensate step by step. At this time, TSC
In the case of the type, the capacitors are grouped into several stages according to the reactive power fluctuation to be compensated, and the capacitors are turned on and off so as to be controlled stepwise. In order to perform finer control, the number of groups of capacitors may be further increased. The control unit receives the outputs of the current transformer (CTa) and the transformer (PTa), calculates the load current and the system voltage, and outputs a firing pulse for output command to the thyristor of the reactive power compensator (3). It is continuously transmitted, and the output of the reactive power (Q) for compensating the leading and lagging phases is controlled. [0006] According to the above configuration, the bus voltage or the load current is detected by the transformer (PTa) and the current transformer (CTa), and when the reactive power fluctuation or voltage fluctuation of the system due to the load fluctuation is detected, they are suppressed. Compensated reactive power (Q) is separately excited S
Output from the VC (3) to the system bus (2) via the transformer (T), the reactive power (Q) for compensation cancels out and compensates for the reactive power (Qa) due to load fluctuation. Here, when compensating for the voltage fluctuation of the system bus (2) by the separately excited type reactive power compensator (3), for some reason, for example, the distance between the device and the system bus (2) is long, When the completion is not performed with the system bus (2) in the intended device, for example, as shown in FIG.
The installation line of the reactive power compensator (3) is a control voltage detection bus (4), and a transformer (PTb) is connected to the detection bus (4) to compensate by the voltage (Vr) at the detection point (B). [0008] The problem to be solved is that the voltage (V) of the control voltage detection bus (4) different from the system bus (2) in the compensation by the reactive power compensator (3).
r), a voltage difference (ΔV = Z ・) between the system bus (2) and the impedance of the transformer (T).
I, where Z: impedance of transformer, I: SVC
This is a point that an error occurs in the voltage compensation amount in the case of voltage control. An object of the present invention is to correct the voltage drop due to the impedance between the two buses when the installation bus of the reactive power compensator (3) different from the system bus (2) is used as the control voltage detection bus (4). It is an object of the present invention to provide a control device for a reactive power compensating device. According to the present invention, a compensation current connected between a system power supply and a load and having a reactive current component having an opposite phase to the reactive current component of the load is generated, and In a control device of a reactive power compensator that cancels out a reactive current component by a reactive current component of the compensation current and stabilizes a system and suppresses voltage fluctuation, a control voltage detection is performed on an installation bus of the reactive power compensator that is different from a system bus. When using a bus,
A correction control circuit for outputting a voltage correction signal obtained by removing a harmonic component from a current obtained by combining the absolute values of the respective phase currents of the detected bus current with a low-pass filter and multiplying the current by a predetermined impedance equivalent value. And the reactive power is compensated by correcting the voltage drop caused by the impedance between the detection bus and the system bus with the correction signal. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a control device for a reactive power compensator according to the present invention will be described below with reference to FIGS. In the figure, the same parts as those shown in FIG. 4 are denoted by the same reference numerals, and description thereof will be omitted. The difference is that, as shown in FIG. 1, a correction control circuit (5) is connected to a reactive power compensator installation bus serving as a control voltage detection bus (4) via a current transformer (CTb) and a transformer (PTb). That is the addition. As shown in FIG. 2, the correction control circuit (5) includes an absolute value circuit (Ya) (Yb) (Yc), a summation circuit (Sa), a low-pass filter (6), and a gain adjustment unit ( 7) and an adder (8). The absolute value circuit (Ya) (Y
b) (Yc) is each phase current (Iu) of the detected bus current (SVC output current) (I) detected from the current transformer (CTb)
(Iv) Absolute value of (Iw) (Iu ′) (Iv ′) (I
w ′) is output. The sum circuit (Sa) calculates the phase current (I
u) Absolute value of (Iv) (Iw) (Iu ′) (Iv ′)
A current (Ia) obtained by combining (Iw ′) is output. The low-pass filter (6) outputs a current (Ib) obtained by removing harmonic components from the combined current (Ia). The gain adjuster (7) outputs a voltage signal (Va) obtained by multiplying the current (Ib) by a predetermined impedance equivalent value (Z) to correct the impedance drop of the transformer (T). The adder (8) is an absolute value (Vu ') of each phase voltage (Vu) (Vv) (Vw) of the detection bus detected by the transformer (PTb) from the detection point (B) of the control voltage detection bus (4). (Vv ′) and (Vw ′) are added to the sum circuit (Sb).
And sends a correction signal (Vo) obtained by adding the combined voltage (detected bus voltage) (Vr) combined with the voltage signal (Va) to the reactive power control unit. The operation of the present invention based on the above configuration will now be described. First, when the installation bus of the reactive power compensator (3) different from the system bus (2) is used as the control voltage detection bus (4), the correction control circuit (5) calculates the detection bus current (I) of the detection bus (4). A correction signal (Vo) obtained by adding a voltage signal (Va) obtained by removing a harmonic component and multiplying by a predetermined impedance equivalent value (Z) and a detected bus voltage (Vr) is output and sent to the reactive power control unit. . Thereby, the reactive power compensation voltage is corrected by compensating the detected bus voltage (Vr) for the voltage drop generated by the transformer (T). According to the present invention, in the reactive power fluctuation compensation by the reactive power compensator, when the installation bus of the reactive power compensator different from the system bus is used as the control voltage detection bus,
A correction control circuit is added to the reactive power compensator to compensate for the voltage drop due to the impedance between the two buses. Therefore, even if the system voltage is not directly detected from the system bus, the bus for installing the reactive power compensator of a different bus is required. The reactive voltage compensator can be controlled while compensating for the above-mentioned voltage drop with the detected voltage.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a main circuit configuration diagram showing an embodiment of a control device of a reactive power compensator according to the present invention. FIG. 2 is a circuit block diagram showing a correction control circuit according to the present invention. FIG. 3 is an equivalent circuit diagram showing a general system of a reactive power compensator. FIG. 4 is an equivalent circuit diagram showing a general system of the reactive power compensator when the installation bus of the reactive power compensator different from the system bus is used as a control voltage detection bus. [Description of Signs] 1 Fluctuating load 2 System bus 3 Reactive power compensator 4 Control voltage detection bus 5 Correction control circuit T Grid interconnection transformer CTb Current transformer PTb Transformer

Continuation of the front page (72) Inventor Takeshi Yoshida 47, Umezu Takaune-cho, Ukyo-ku, Kyoto-shi, Japan Nissin Electric Co., Ltd. (56) References , U) (58) Field surveyed (Int. Cl. ⁷ , DB name) H02J 3/00-5/00

Claims (1)

(57) [Claim 1] A reactive current of a load, which is connected between a system power supply and a load, generates a compensation current having a reactive current component of a phase opposite to that of the reactive current of the load, and In the control device of the reactive power compensator for compensating the component by the reactive current component of the compensation current, when the installation bus of the reactive power compensator different from the system bus is used as the control voltage detection bus , each phase of the detected bus current is used. Electric
A low-pass filter removes harmonic components from the current obtained by synthesizing the absolute value of the current, and outputs a voltage correction signal multiplied by a predetermined impedance equivalent value, and outputs a voltage correction signal between the detection bus and the system bus. A control device for a reactive power compensator, wherein the reactive signal is compensated by correcting the voltage drop caused by the impedance component with the correction signal.