JPH03122705A - Static type reactive power compensating device - Google Patents

Abstract

PURPOSE:To effectively secure the control capacity of the static type reactive volt-ampers compensating device (SVC) by providing the SVC with a control means for setting up a state expanding the width of a dead zone band only by the time sufficient for operating the voltage control of a voltage regulator other than an SVC to reduce the output of the SVC and then returning the width of the dead zone band to the width used for normal operation. CONSTITUTION:A variable non-sensitive band 14 is added to a deviation signal between a control object voltage Vref and an AC system voltage Vs. The dead zone band of the variable dead zone band 14 is normally set up to zero or a comparatively nallow value and the width is expanded periodically or based upon a control signal. In the normal operation state, the state (b) expanding the dead zone band from the zero state (a) is set up, the state (b) is held only by the time sufficient for operating the voltage control of the voltage regulator other than the SVC and then the deat zone band is returned to the zero state (c). Consequently, the control capactity of the SVC can be secured so that voltage variation can be suppressed at the time of suddenly changing a load by the reduction of the current of the SVC.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention (Field of Industrial Application)] The present invention relates to a static var power compensator installed in a system in which a voltage regulator is provided on a railway line.

(Prior Art) Figures 5(a) and 5(c) are a single-line diagram of a well-known power system in which a voltage regulator is installed on the line and a functional explanatory diagram of the voltage regulator. In the single line diagram a), a load 103a is connected to a line 104 connected to a substation 101.

103b, 103c, 104d, and 103e, and an L voltage regulator 10 to adjust the voltage of each load terminal.
2a and 102b are shown. Generally, in a power system, a voltage regulator is provided at an appropriate position on the line depending on the impedance of the line and the size of the load in order to keep the terminal voltage of the load terminal within a specified voltage fluctuation range. If there is no voltage regulator, the voltage at each point on the line can be determined by sequentially taking loads from the substation as load a, load b, load C, load d, and load e, as shown in Figure 5 (b). The voltage decreases as it approaches the load e, but when there is a voltage regulator, the voltage at each part of the line increases where the voltage regulator is installed, as shown in Figure 5 (C). The voltage at the terminals of the load e, etc., is maintained at a voltage close to that at the substation terminals.

On the other hand, when a large capacity load that undergoes sudden load fluctuations is connected to a line, voltage fluctuations on the line will also increase, but in general, the operating time of conventional voltage regulators is required to adjust the voltage against sudden voltage fluctuations. In recent years, static var power compensators (hereinafter referred to as SvC) have been installed.

FIG. 6 shows a schematic configuration diagram and a control block of the SVC, and particularly shows a configuration example in which a thyristor device consisting of anti-parallel connections of thyristors is used to control the current flowing through the reactor. SvC includes a transformer 1 connected to an AC system 8, a reactor 2 connected in series to the transformer 1, a thyristor device 3 connected in series to the reactor 2, and a filter 4 connected in series to the transformer 1 and in parallel to the reactor 2. , an instrument transformer 5 that detects the AC system voltage Vs, a current transformer 6 that detects the SVC output current Is, an SvC switch 9 that connects the SvC to the AC system 8, and a filter 4 connected to the SvC bus 7. A filter switch 10 is provided.

The thyristor device 3 is composed of a forward thyristor U and a reverse thyristor X.

In FIG. 7, 8 indicates the voltage between the electrodes of the thyristor device 3;
Iu and Ix are in the order of the thyristor device 3, respectively.

These are the waveforms of the positive and negative currents flowing through the reverse direction thyristors U and X.

The magnitudes of the firing angles αU and αX of the thyristor device 3 control the magnitudes of the currents Iu and Ix flowing through the thyristors U and X.

FIG. 6 also shows a control block diagram of a conventional SvC device applied to such SvC. Control target voltage Vref,
The voltage deviation signal ΔV is calculated from the AC detection voltage Vs and the value obtained by multiplying the SvC output current Is by 1 using the coefficient multiplier 11.
--- Calculated based on the formula (1). The compensation state dynamic power determining circuit 12 determines the reactive power Q to be compensated for in the SvC so that this voltage deviation signal ΔV becomes zero, and obtains the V-1 characteristic as shown in the characteristic diagram of FIG. Compensated reactive power Q
In order to output , the firing angle α of the thyristor device 3 is determined by the reactive power/firing angle conversion circuit 13 . As described above, the SvC adjusts the AC voltage at its connection point.

FIG. 9 shows a single-line diagram of a power system in which a large capacity load that undergoes rapid load fluctuations is connected to a line, and voltage fluctuations due to the influence of the load are suppressed by SvC. In FIG. 9, there is a sudden change load 105, which is a large capacity load that causes sudden load changes, at the end of the line in FIG. 5, and a 5VC 106 is provided in parallel with or near the sudden change load.

(Problem to be Solved by the Invention) General loads other than sudden changing loads also have load fluctuations, although the changes are slow in terms of time. Since SvC has a faster control response than other voltage regulators, SvC operates even when voltage fluctuations occur due to general load fluctuations, and SvC
Voltage regulators other than C did not function, and the SvC device capacity needed to be able to suppress voltage fluctuations including loads other than sudden changes.

In other words, if the SvC capacity is determined by considering only the suddenly changing load, the SvC will also operate to suppress voltage fluctuations due to changes in loads other than the suddenly changing load, and the SvC capacity will be insufficient when the sudden changing load changes. There was a problem.

The present invention has been made to solve the above-mentioned problems, and provides a static var power compensator that performs control to ensure the control capacity of the SVC so as to suppress voltage fluctuations during sudden load changes. The purpose is to

[Structure of the Invention] (Means for Solving the Problems) The present invention provides a dead zone in the deviation signal between the control target voltage Vref of the SvC and the AC system voltage Vs, and operates the voltage control of a voltage regulator other than the SvC. The control means is provided for reducing the output of the SvC with the width of the dead zone widened for a sufficient period of time, and then returning the width of the dead zone to the width during constant operation.

(Function) With the above means, the SvC device of the present invention makes it possible to secure the control capacity of SvC so that voltage fluctuation can be suppressed when the load fluctuates suddenly.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a control block diagram of an SvC device according to an embodiment of the present invention.

Comparing FIG. 1 with the control block diagram of FIG. 6 which shows the prior art, a variable dead zone 14 is added to the deviation signal between V ref and AC system voltage Vs. FIG. 2 shows changes in the width of the dead zone of the variable dead zone 14 and changes in the V-I characteristic of SvC. The dead band width of the variable dead band 14 is normally set to zero or relatively narrow, and is increased periodically or with a control signal.

The states of the dead zone in Fig. 2 range from state a where the dead zone width is zero under constant operation, state b where the dead zone width is widened, and state Sv.
It is shown that after holding for a sufficient time to operate the voltage control of the voltage regulators other than C, the dead band width returns to the state BC where it is zero. To explain the state of SvC according to changes in the state of the dead zone, in state a, the operating point of SvC is the V-1 characteristic of sVc and the voltage characteristic Vs of the circuit to which SVC is connected.
(OLD). By widening the width of the dead zone, the V-I characteristic of the SvC becomes step-like as shown in the figure, and as shown by the operating point of the SvC in the figure above, the output of the SvC is reduced and the SVC is installed. If the receiving end voltage decreases, the voltage on the line from the transmitting end to the receiving end also decreases, and the voltage at the installation terminal of the voltage i + q regulator other than SvC installed on the line decreases. do. If the state is continued long enough to activate the voltage control of the voltage regulator other than SvC, the voltage control of the voltage regulator other than SVC will be activated and the SvC will be connected as shown in the diagram below. The voltage characteristics of the circuit are VS
Changes to (OLD > ip Vs (NEW),
The operating point of the SVC changes to reduce the output of the SvC. Condition Yr! When the width of the dead zone is returned to the same as in state a with AC, SV
The output current of C decreases compared to state a.

Therefore, by reducing the SvC current, the control capacity of the SvC is secured so that voltage fluctuations can be suppressed when the load fluctuates suddenly.

As another embodiment, FIG. 3 adds a reactive current detection circuit 15 for detecting the reactive current of the load 105 to the control block of the first embodiment shown in FIG.
Q(10^D) is added to the SvC output current Is. In this embodiment, the dead zone and S
As shown by the state of vC, this is applied to encourage the use of voltage regulators other than SvC while compensating for the power factor of the load at its own end of the SvC output.

[Effects of the Invention] As explained above, according to the present invention, the SvC Vref
By providing a dead band in the deviation signal of AC system voltage Vs and AC system voltage Vs, SVC
control means that reduces the output of the SvC with the width of the dead zone widened for a sufficient period of time to operate the voltage control of a voltage regulator other than the above, and then returns the width of the dead zone to the width during constant operation; Therefore, it is possible to provide an SvC device that can secure the control capacity of the SVC so that voltage fluctuations can be suppressed during sudden load changes.

[Brief explanation of drawings]

FIG. 1 is a control block diagram of an SvC device according to an embodiment of the present invention, FIG. 2 is a diagram showing a dead zone of the SVC device and the state of SvC, and FIG. 3 is a control block diagram of an SvC device according to a second embodiment of the present invention. The control block diagram of the device, FIG. 4 is the Sv according to the second embodiment.
A diagram showing the dead zone of the C device and the state of SVC, Figure 5 is an east line connection diagram of a well-known power system with a voltage regulator installed on the line and a functional explanatory diagram of the voltage regulator, and Figure 6 is a diagram showing the well-known SvC A schematic configuration diagram and a control block diagram of a well-known SvC device, FIG. 7 is a diagram of the interelectrode voltage of the thyristor device, the order of the thyristor device, and each waveform diagram of positive and negative currents flowing through the reverse direction thyristor. FIG. 8 is a diagram of the SvC device Figure 9 is a single-line diagram of a power system in which a large-capacity load with sudden load fluctuations is connected to the line, and voltage fluctuations due to the influence of the load are suppressed by SvC. . 1...Transformer 2...Reactor 3...
・Thyristor 4... Filter 5... Instrument transformer 6... Current transformer 7... SVC bus
8...AC system 9...SvC switch 1
0...Filter switch 11...Coefficient unit 12...Compensated reactive power determination circuit 13...Reactive power/firing angle conversion circuit 14...Variable dead band circuit

Claims (1)

[Claims] In a static var compensator connected on the same line as a voltage regulator installed on the line to control the terminal voltage at the load end within a specified range, the control objective of the static var compensator is A variable dead band circuit provided for inputting a deviation signal between the voltage and the AC system voltage, and the dead band width of the variable dead band circuit are widened by the time necessary to operate the voltage regulator other than the static reactive power compensator. 1. A static reactive power compensator comprising: a control circuit that reduces the output of the static reactive power compensator and then controls the output to return to a constant operating level.