JP7196528B2 - Reactive power compensation system - Google Patents

Description

The present invention provides a system for compensating the reactive power of an electric power system and controlling the voltage to a predetermined value by, for example, a static reactive power compensator (hereinafter also referred to as SVC: Static Var Compensator). The present invention relates to a reactive power compensation system capable of determining the direction of a place.

FIG. 6 is a configuration diagram showing an example of a conventional SVC, which is described in Patent Document 1. In FIG.
6, 100 is a distribution line or transmission line, 101 and 102 are current transformers, 103 is a voltage transformer, 104 is power flow direction detection means, 105 is calculation means, 106 is target value setting means, and 107 is control means, and 108 is an SVC main circuit comprising semiconductor switching elements, capacitors, reactors, and the like.

In this prior art, the power flow direction detection means 104 detects the power flow direction of the line 100 from the polarity of the active power, the phase difference between the phase voltage and the current, etc. based on the outputs of the current transformer 101 and the potential transformer 103. . The calculation means 105 inputs the output of the current transformer 101 or the sum of the inverted output of the current transformer 101 and the output of the current transformer 102 to the control means 107 according to the detected power flow direction. The control means 107 obtains the power factor or reactive power for each power flow direction based on the output of the calculation means 105 and the output of the voltage transformer 103, and adjusts the value to the target value set by the target value setting means 106. The main circuit 108 is operated to perform constant power factor control or constant reactive power control.

On the other hand, Non-Patent Document 1 discloses an SVR control method that controls the system voltage to a predetermined value by an automatic voltage regulator (hereinafter also referred to as SVR: Step Voltage Regulator) in a power system in which distributed power sources are interconnected. ing.
FIG. 7(a) shows a system model in which substations a and b, wire circuit breakers FCB _a and FCB _b , and loads LD _a and LD _b are connected to the primary and secondary sides of an SVR, respectively. Grid connection (forward transmission with substation a as the power source, reverse transmission with substation b as the power source) and power flow as the direction of power passing through the SVR (forward FIG. 7B is a diagram showing four combinations of system connection and power flow as operation modes I to IV.

When determining the system connection (forward or reverse) only from the power flow, in the state where the distributed power sources are not interconnected, as in operation modes I and II in FIG. When the power flow is reversed, it can be determined that the current is reversed, and the SVR can adjust the voltage based on these determination results.
However, for example, when a distributed power source such as a photovoltaic power generation device or a wind power generation device is connected between the SVR and the circuit breaker FCB _b during forward transmission (substation a is the power source), the generated power is transferred to the SVR. Since it flows as a reverse power flow, it should be in operation mode III, but the SVR judges that it is reverse transmission (substation b is the power source) based on the reverse power flow, and misidentifies it as operation mode II.

For this reason, in Non-Patent Document 1, the system connection (forward or reverse) is determined based on the impedance ratio or the like, which is the ratio between the primary side impedance and the secondary side impedance of the SVR, and the secondary side or primary side of the SVR is determined. The voltage is adjusted by switching the side taps.

JP-A-9-135535 (paragraphs [0012] to [0015], FIG. 1, etc.)

Hiroshi Kajita, Akira Kanbe, Kenji Fukawa, Shinya Kadokura, "Development of SVR Control System for Distributed Power Sources", pp. 10-16, Aichi Electric Technical Report, No. 26, 2005

According to the conventional technology described in Patent Document 1, it is possible to continuously control the SVC even when the power flow direction of the power system is switched. There is a risk of
FIG. 8 is a configuration diagram of a distribution system to which SVCs are connected as in Patent Document 1. In FIG. 8, 11 and 12 are distribution substations (hereinafter simply referred to as substations) installed at both ends of the distribution system 20, 50 is the SVC, and 31 and 32 are between the SVC 50 and the substations 11 and 12. 51 is a current transformer, 52 is a potential transformer, 60 is a load, and 70 is a distributed power source.

Now, as a normal operation, when power from the substation 11 is supplied to the load 60 via the switch 31 in the ON state, the SVC 50 detects forward power flow and the substation 11 is the power source (forward). Then, the reactive power compensation operation is performed. However, when the distributed power sources 70 start generating power, the power generated by the distributed power sources 70 flows through the distribution system 20 as a reverse power flow, as illustrated. As a result, the SVC 50 erroneously recognizes that the other substation 12 is the power source (reverse feed) even though the switch 32 is OFF.

Since the system impedance from the SVC 50 to each substation differs, and the optimum control gain of the SVC 50 differs according to the system impedance, it becomes difficult for the SVC 50 to perform an appropriate control operation if the system connection is misidentified. Further, the SVC described in Patent Document 1 performs constant power factor control or constant reactive power control, and does not mention at all how to determine grid connection when performing constant voltage control.
Furthermore, according to the technique described in Non-Patent Document 1, it is possible to prevent erroneous determination of system connection in the power system to which the SVR is connected. Can not.

Therefore, the problem to be solved by the present invention is to reliably determine the direction of the substation that is the power supply, that is, the system connection (forward or reverse) even when a distributed power source is interconnected to the power system to which the SVC is connected. The object of the present invention is to provide a reactive power compensation system that enables appropriate reactive power compensation and voltage compensation.

In order to solve the above problems, the invention according to claim 1 is a reactive power compensation system for injecting reactive power into a power system using a reactive power compensator to compensate for system voltage fluctuations, wherein the reactive power in the power system A first switch is connected between a connection point of the compensator and a first substation installed at one end of the power system, and a second substation installed at the other end of the power system; In a reactive power compensation system in which a second switch is connected between the connection point,
Determination signal injection means for injecting a substation direction determination signal of a predetermined frequency for determining which of the first substation and the second substation is the power supply from the reactive power compensator into the power system. When,
fluctuation component detection means for detecting a fluctuation component of power or current between the connection point and the first substation or between the connection point and the second substation;
comparison means for determining that the substation on which the fluctuation component is detected is a power supply when the frequency of the fluctuation component detected by the fluctuation component detection means is equal to the predetermined frequency of the substation direction determination signal; ,
characterized by comprising

The invention according to claim 2 is a reactive power compensation system for injecting reactive power into a power system by a reactive power compensator to compensate for system voltage fluctuations, wherein a connection point of a substation in the power system and the reactive power compensation A reactive power compensation system in which a first line having a first switch and a second line having a second switch are connected in parallel between a device,
A substation direction determination signal of a predetermined frequency for determining which of the first line and the second line is connected to the substation as a power supply is transmitted from the reactive power compensator to the first line. determination signal injection means for injecting into the line or the second line;
Fluctuation component detection means for detecting a fluctuation component of electric power or current from the first line or the second line;
When the frequency of the fluctuation component detected by the fluctuation component detection means is equal to the predetermined frequency of the substation direction determination signal, it is determined that the line on which the fluctuation component is detected is connected to the substation. a comparison means to
characterized by comprising

The invention according to claim 3 is the reactive power compensation system according to claim 1 or 2, further comprising means for switching a preset control method or control parameter according to the determination result of the comparison means. do.

The invention according to claim 4 is the reactive power compensation system according to claim 1 or 2, further comprising means for requesting an external system to update control parameters according to the determination result of the comparison means. do.

The invention according to claim 5 is the reactive power compensation system according to claim 3 or 4 , wherein the reactive power compensator is controlled by a voltage control method with slope characteristics, and the control parameter is at least slope reactance or It is characterized by including a control gain corresponding to its reciprocal.

The invention according to claim 6 is the reactive power compensation system according to any one of claims 1 to 5, wherein the comparison means compares the fluctuation component when the magnitude of the fluctuation component exceeds a predetermined threshold. It is characterized by judging that it is effective and using it for comparison with the substation direction judgment signal.

The invention according to claim 7 is the reactive power compensation system according to any one of claims 1 to 6, wherein the reactive power command value to be given to the reactive power compensator is set to the reactive power target value. It is characterized in that it is generated by superimposing signals.

The invention according to claim 8 is the reactive power compensation system according to any one of claims 1 to 7, wherein the substation direction determination signal is a reactive power fluctuation component or a reactive current fluctuation component. .

According to the present invention, even when a distributed power source is interconnected to a power system such as a distribution system to which an SVC is connected, and a power flow from the distributed power source flows through the power system, forward or reverse power is accurately detected and the power supply is detected. substation can be reliably determined. This makes it possible to perform reactive power compensation and voltage compensation of the system using an appropriate control method and control parameters.

1 is a schematic configuration diagram of a reactive power compensation system according to a first embodiment of the present invention; FIG. 1 is a schematic configuration diagram of a reactive power compensation system according to a first embodiment of the present invention; FIG. 1 is a configuration diagram of an SVC control circuit in each embodiment of the present invention; FIG. FIG. 4 is a diagram showing control characteristics of a voltage-controlled SVC with slope characteristics; FIG. 5 is a schematic configuration diagram of a reactive power compensation system according to a second embodiment of the present invention; 1 is a configuration diagram of a conventional technology described in Patent Document 1; FIG. 7A and 7B are diagrams illustrating the classification of system connection and power flow (FIG. 7(a)) and operation modes (FIG. 7(b)) described in Non-Patent Document 1. FIG. FIG. 2 is a configuration diagram when distributed power sources are interconnected with a distribution system to which an SVC is connected;

An embodiment of the present invention will be described below with reference to the drawings.
1 and 2 are schematic configuration diagrams of a reactive power compensation system according to a first embodiment of the present invention. In these figures, the same parts as those in FIG. 8 are denoted by the same reference numerals, and the explanation thereof is omitted.

In this first embodiment, the SVC 50 has a function of generating a substation direction determination signal ΔS′ of a predetermined frequency for determining the direction of the substation, which is the power source, and injecting it into the distribution system 20 . The type of the substation direction determination signal ΔS′ is not particularly limited, but since the distribution system 20 includes active power and reactive power due to loads, distributed power sources, etc., for example, a reactive power fluctuation component ΔQ′ ( Alternatively, the reactive current fluctuation component) may be used as the substation direction determination signal ΔS′.
In the following description, substation direction determination signal ΔS′=reactive power fluctuation component ΔQ′ is assumed to continue.

First, as shown in FIGS. 1 and 2, the first and second distribution substations 11 and 12 are installed at both ends, and the first and second distribution substations 11 and 12 are installed between the connection point of the SVC 50 and the substations 11 and 12. Assume a distribution system 20 provided with switches 31 and 32 of . Here, the case where the first switch 31 is ON, the second switch 32 is OFF, and the first distribution substation 11 is the power source (FIG. 1) is taken as forward, and the first The case where the switch 31 is OFF, the second switch 32 is ON, and the second distribution substation 12 is the power source (FIG. 2) is defined as reverse feed.
It is assumed that one of the switches 31 and 32 is turned on and the other is turned off.

When the switch 31 on the substation 11 side is turned on and the switch 32 on the substation 12 side is turned off as shown in FIG. detected and not detected on the substation 12 side. When the switch 32 on the substation 12 side is turned on and the switch 31 on the substation 11 side is turned off as shown in FIG. detected in the distribution system 20 on the side.
Therefore, instead of focusing on the power flow direction, the substation as the power source is determined based on which substation side the reactive power fluctuation component ΔQ' is detected with reference to the connection point of the SVC 50 in the distribution system 20. can do.

As a result, for example, a distributed power supply (not shown) is interconnected between the switches 31 and 32 in FIG. ) is detected by the SVC 50, when the reactive power fluctuation component ΔQ′ is detected from the distribution system 20 on the substation 11 side, it can be determined that the substation 11 is the power source (forward transmission), and the other substation There is no risk of misidentifying that the point 12 is the power source (reverse feed).
Similarly, assuming that a distributed power source is interconnected between the switches 31 and 32 in FIG. Also, when the reactive power fluctuation component ΔQ′ is detected from the distribution system 20 on the side of the substation 12, it can be determined that the substation 12 is the power source (reverse feed), and the other substation 11 is the power source ( forward delivery).

FIG. 3 is a configuration diagram of a control circuit for detecting the reactive power fluctuation component ΔQ′ and determining the substation direction.
Reactive power fluctuation component ΔQ' is input to adding means 56, added to reactive power target value Q', and given to SVC 50 as reactive power command value Q ^* . The SVC 50 controls the semiconductor switching elements according to the reactive power command value Q ^* to inject reactive power into the distribution system 20 and control the system voltage to a predetermined value.

On the other hand, the current transformer 51 and the voltage transformer 52 are installed on the substation 11 side from the connection point of the SVC 50 on the distribution system 20, as in FIG. V is input to the reactive power detection means 53 . The reactive power detection means 53 obtains the reactive power Q from the current detection value I and the voltage detection value V, and this reactive power Q is input to the filter 54 to extract the fluctuation component ΔQ. The filter 54 has a characteristic of passing the same frequency component as the reactive power fluctuation component ΔQ' described above.

The fluctuation component ΔQ output from the filter 54 is input as a signal A to one input terminal of the comparison means 55 . Further, the reactive power fluctuation component ΔQ′ is adjusted by the delay adjustment means 57 for the time delay until it is actually detected in the power distribution system 20 , and is input as the signal B to the other input terminal of the comparison means 55 .

The comparison means 55 compares the signals A and B, and if A=B, determines that the substation 11 on the switch 31 side is the power supply (forward). That is, when the detected reactive power Q contains the fluctuation component ΔQ of the same frequency as the reactive power fluctuation component ΔQ′, the switch 31 is in the ON state and the substation 11 on the switch 31 side is the power source. Determine that there is, and output the result.
Further, when A≠B, since the fluctuation component ΔQ having the same frequency as the reactive power fluctuation component ΔQ′ was not detected from the reactive power Q, the switch 31 on the substation 11 side is in the OFF state, in other words, the other switch 32 is in the ON state and the substation 12 on the switch 32 side is the power source (reverse feed), and the result is output.

It should be noted that loads and distributed power sources are connected to the distribution system 20, and the fluctuation component ΔQ may flow to the substation side, which is not the power source, depending on the connection positions of these. That is, even if the system state is forward transmission, the magnitude of the detected fluctuation component ΔQ does not reach a predetermined value, resulting in A≠B, and as a result, it may be misidentified as reverse transmission.
In order to prevent such a situation, for example, when the fluctuation component ΔQ exceeds a predetermined threshold, the comparison means 55 may determine that the signal A based on the fluctuation component ΔQ is valid and use it for comparison with the signal B. .

In this first embodiment, the fluctuation component ΔQ (signal A) is extracted from the reactive power Q detected by the current transformer 51 and the instrument transformer 52 on the substation 11 side, A=B is forwarded, A≠B is determined to be reverse feed, but the reactive power Q is detected by the current transformer and instrument transformer provided on the other substation 12 side, the fluctuation component ΔQ (signal A) is extracted, and A = B is It is also possible to determine reverse sending and A≠B as forward sending.

As described above, the system impedance from the SVC 50 to each of the substations 11 and 12 differs, and the optimum value of the control gain, which is the control parameter of the SVC 50, differs depending on the system impedance corresponding to its reciprocal.
For example, in FIG. 1, when the length of the transmission between the substation 11 and the SVC 50 during forward transmission is short, the system impedance is small, so it is desirable that the control gain of the SVC 50 is large. In addition, in FIG. 2, when the length of transmission between the substation 12 and the SVC 50 during reverse transmission is long, the system impedance is large, so it is desirable that the control gain of the SVC 50 is small.
According to this first embodiment, when the switches 31 and 32 are operated to switch the system connection (forward or reverse), the SVC 50 determines this and obtains the optimum control gain corresponding to forward or reverse. can be switched to That is, these optimum control gains may be stored in advance in the memory of the control circuit, and predetermined control gains may be automatically or manually read out from the memory and set in the SVC 50 when the system connection is switched.

Next, switching of the control gain will be specifically described.
In so-called voltage control with a slope characteristic, a slope (slope reactance) is provided in the slope characteristic between the reactive power Q compensated by SVC and the system voltage V to prevent destabilization of the control.

FIG. 4 is a diagram showing control characteristics of a voltage-controlled SVC with slope characteristics.
As is clear from FIG. 4, when the slope reactance _Xs is large, the amount of change in reactive power with respect to the voltage deviation is small, so the control is relatively stable. It is difficult to approach the target value.
On the other hand, when the slope reactance _Xs is small, the amount of change in reactive power with respect to the voltage deviation is large, so the control becomes somewhat unstable and the control operations by multiple SVCs are likely to interfere. There is an advantage that it is easy to approach the value.

Therefore, as described above, when the SVC determines forward feeding and the system impedance is small, control is performed so that the slope reactance _Xs becomes small (the control gain becomes large), and the system voltage approaches the voltage target value. When the SVC determines reverse transmission and the system impedance is large, reactive power compensation can be stably performed by controlling the slope reactance X _s to increase (control gain to decrease). .

In the first embodiment, when the SVC 50 can communicate with an external system such as a power distribution automation system, the external system is instructed to update the control parameters set in the SVC 50 according to the determination result of the comparison means 55. Means for requesting may be provided in the control circuitry of the SVC 50 so that the external system updates the control parameters according to this request.

Next, FIG. 5 is a schematic configuration diagram of a reactive power compensation system according to a second embodiment of the present invention.
In FIG. 5, lines 21 and 22 are connected in a loop on both sides of a connection point between a distribution substation 10 and a distribution system (bus) 20, and an SVC 50 is connected to the connection point between the lines 21 and 22. there is That is, lines 21 and 22 are connected in parallel between the connection point of the distribution substation 10 and the SVC 50 in the distribution system 20 . The lines 21 and 22 are provided with switches 31 and 32, respectively, and these switches 31 and 32 are controlled so that when one is ON, the other is OFF, as in FIGS. be done.

In the system configuration shown in FIG. 5, when the lengths of the lines 21 and 22 are different, the system impedances are also different, so the optimum value of the control gain, which is the control parameter of the SVC 50, is also different.
Therefore, in order to set the optimum control parameters for the SVC 50, the switch 31 is turned ON and the distribution substation 10 is connected to the SVC 50 via the line 21 (for convenience, this is referred to as a sequential transmission). It is necessary to determine whether the switch 32 is turned ON and the distribution substation 10 is connected to the SVC 50 via the line 22 (similarly reverse transmission).

Therefore, the SVC 50 determines which of the switches 31 and 32 is ON. In order to discriminate whether the substation is reverse feed or not, a substation direction determination signal ΔS′ having a predetermined frequency, for example, a reactive power fluctuation component ΔQ′ is generated and injected into the line 21 or line 22 as in the first embodiment. It has functionality.
Then, when the reactive power Q detected from the line 21 or the line 22 contains the fluctuation component ΔQ of the same frequency as the reactive power fluctuation component ΔQ′ by the comparing means 55 of the control circuit shown in FIG. is turned on and an electric circuit is formed to the distribution substation 10 (the line side is the power source).

As a result, for example, a distributed power supply (not shown) is interconnected between the switches 31 and 32, and even if the SVC 50 detects the power flow due to the generated power, the line side where the reactive power fluctuation component ΔQ' is detected is the power supply. By judging that it is, there is no risk of misidentifying forward or reverse.
In addition, depending on the load and the connection position of the distributed power supply, the fluctuation component ΔQ may flow into a part of the line on the non-power supply side. It is also possible to misidentify reverse transmission. In order to prevent this, as described above, when the fluctuation component ΔQ exceeds the predetermined threshold, the comparison means 55 determines that the signal A based on the fluctuation component ΔQ is valid and uses it for comparison with the signal B. can be
Furthermore, when the SVC 50 can communicate with an external system such as a power distribution automation system, means may be provided for updating the control parameters set in the SVC 50 through communication with the external system according to the determination result by the comparison means 55. good.

The present invention can also be applied to a separately-excited SVC composed of a shunt reactor and a phase-modifying capacitor described in Patent Document 1, and can also be applied to a self-excited SVC called a STATCOM (Static Synchronous Compensator). can do. Furthermore, it can also be applied to self-commutated power converters other than self-commutated SVC. For example, distributed power supply power conditioners (PCS) and BTB (Back To Back) devices have the ability to supply reactive power in addition to limiting the normal active power output, and the SVC function can be incorporated into the control. Because we can.

10, 11, 12: Distribution substation 20: Distribution system 21, 22: Lines 31, 32: Switch 50: Static var compensator (SVC)
51: current transformer 52: instrument transformer 53: reactive power detection means 54: filter 55: comparison means 56: addition means 57: delay adjustment means 60: load 70: distributed power supply

Claims (8)

A reactive power compensation system for injecting reactive power into an electric power system using a reactive power compensator to compensate for system voltage fluctuations, wherein the reactive power compensator is installed at a connection point of the reactive power compensator in the electric power system and at one end of the electric power system. A first switch is connected between the first substation and a second switch is connected between the connection point and a second substation installed at the other end of the electric power system. In a reactive power compensation system,
Determination signal injection means for injecting a substation direction determination signal of a predetermined frequency for determining which of the first substation and the second substation is the power supply from the reactive power compensator into the power system. When,
fluctuation component detection means for detecting a fluctuation component of power or current between the connection point and the first substation or between the connection point and the second substation;
comparison means for determining that the substation on which the fluctuation component is detected is a power supply when the frequency of the fluctuation component detected by the fluctuation component detection means is equal to the predetermined frequency of the substation direction determination signal; ,
A reactive power compensation system comprising: A reactive power compensation system for injecting reactive power into a power system using a reactive power compensator to compensate for variations in system voltage, wherein a first In a reactive power compensation system in which a first line with a switch and a second line with a second switch are connected in parallel,
A substation direction determination signal of a predetermined frequency for determining which of the first line and the second line is connected to the substation as a power supply is transmitted from the reactive power compensator to the first line. determination signal injection means for injecting into the line or the second line;
Fluctuation component detection means for detecting a fluctuation component of electric power or current from the first line or the second line;
When the frequency of the fluctuation component detected by the fluctuation component detection means is equal to the predetermined frequency of the substation direction determination signal, it is determined that the line on which the fluctuation component is detected is connected to the substation. a comparison means to
A reactive power compensation system comprising: In the reactive power compensation system according to claim 1 or 2,
A reactive power compensation system, comprising means for switching a preset control method or control parameter in accordance with the determination result of the comparison means. In the reactive power compensation system according to claim 1 or 2,
A reactive power compensation system, comprising means for requesting an external system to update control parameters in accordance with the result of determination by said comparison means. In the reactive power compensation system according to claim 3 or 4 ,
A reactive power compensation system, wherein said reactive power compensator is controlled by a voltage control method with slope characteristics, and said control parameters include at least a control gain corresponding to a slope reactance or its inverse. In the reactive power compensation system according to any one of claims 1 to 5,
A reactive power compensation system according to claim 1, wherein said comparison means determines that said fluctuation component is valid when the magnitude of said fluctuation component exceeds a predetermined threshold value, and uses said fluctuation component for comparison with said substation direction determination signal. In the reactive power compensation system according to any one of claims 1 to 6,
A reactive power compensation system, wherein a reactive power command value to be given to the reactive power compensator is generated by superimposing the substation direction determination signal on a reactive power target value. In the reactive power compensation system according to any one of claims 1 to 7,
A reactive power compensation system, wherein the substation direction determination signal is a reactive power fluctuation component or a reactive current fluctuation component.

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