JP3962318B2 - Distributed power system voltage control system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a distributed power supply system voltage control system.
[0002]
[Prior art]
Recently, there is a tendency that distributed power sources such as solar power generation and wind power generation are introduced on the power consumer side. However, when a distributed power source such as photovoltaic power generation is connected to the grid, the voltage at the connection point between the pole transformer and the power consumer may deviate from the control value due to reverse power flow.
[0003]
In such a case, voltage adjustment by reactive power control is generally an effective means, but in the connection to the low-voltage system, the resistance occupying the impedance viewed from the power consumer side to the system side is relatively Large, suppression of voltage change by reactive power control may not function sufficiently.
[0004]
For this reason, solar power generation systems linked to the low-pressure side often employ a method of suppressing output, and there may be dissatisfaction from the installer, such as insufficient power generation despite sufficient solar radiation. .
[Patent Literature]
Patent Publication 2000-333373 “Distributed Power Supply System”
[0005]
[Problems to be solved by the invention]
By the way, according to the grid interconnection guidelines of the Ministry of Economy, Trade and Industry, phase advance operation of up to 80% is possible so that the voltage rise due to the operation of the distributed power source can be suppressed. If the phase advance operation is performed so that the ratio of the resistance / reactance and the ratio of the reactive power / active power of the distributed power supply output is substantially the same, it is possible to take measures against the voltage rise due to the operation of the distributed power supply.
[0006]
For example, when ΔV is a voltage fluctuation, P is an active power, Q is a reactive power, R is a resistance when looking at the power supply side, and X is a reactance when looking at the power supply side, the voltage fluctuation ΔV is ΔV≈R · P + X · Q. Thus, if Q = −R / X · P, then ΔV≈0.
[0007]
However, the resistance-to-reactance ratio (resistance R / reactance X) when the power supply side on the pole transformer side is viewed from the distributed power supply side, which is generally the low-voltage circuit side, may be 1 or more. In such a case, there is a problem that the effect is not produced unless reactive power larger than the value recognized in the above-mentioned grid interconnection guidelines is passed.
[0008]
The present invention has been made paying attention to such problems, and it is an object of the present invention to provide a distributed power system interconnection voltage control system capable of effectively performing voltage adjustment with little reactive power adjustment. It is.
[0009]
[Means for Solving the Problems]
In order to solve such a problem, the voltage control system of the distributed power system interconnection of the present application, when the received voltage of the consumer deviates from a predetermined value, the impedance adjusting means and the signal from the detector of the received voltage By controlling either the reactive power supply device or the distributed power source in the consumer, the voltage is effectively reduced by inserting the reactance so that the ratio of the impedance resistance to the reactor is reduced when the power source side is viewed from the consumer. It is characterized by adjusting.
[0010]
That is, in a circuit in which power is supplied to the customer circuit from the low voltage side of the pole transformer via the lead-in line, between the low-voltage circuit and the lead line of the pole transformer or between the lead line and the customer circuit , Insert an impedance regulator that connects the reactor and switch in parallel and install a reactive power regulator (such as SVG) on the customer circuit side of the impedance regulator, or a distributed power source installed on the consumer Using the reactive power adjustment function, the received voltage of the consumer detected by either the voltage detector installed in the customer circuit or the voltage detector built in the reactive power regulator or the distributed power supply installed in the consumer is When the voltage rises to a predetermined value V1 or higher, a signal from the voltage detector causes a delayed reactive power consumption operation by the reactive power regulator or a phased operation of a distributed power source installed at a consumer. In addition, the voltage detector is opened when the switch of the impedance adjuster is opened to suppress an increase in received voltage, and the received voltage of the consumer detected by the detector falls below a predetermined value V2 lower than the predetermined value V1. The reactive power regulator is stopped by the signal from or the reactive power supply operation of the distributed power supply installed at the customer is stopped, and the switch of the impedance regulator is turned on to reduce the power loss, the voltage detector When the received voltage detected by the power source decreases to a predetermined value V3 or lower that is lower than the predetermined value V2, a delayed reactive power supply operation by the reactive power regulator or a distributed type installed by a consumer by a signal from the voltage detector The power supply is operated in a slow phase, and the voltage drop is suppressed by opening the switch of the impedance adjuster, and the received voltage of the consumer detected by the detector is a predetermined value V When the voltage rises higher than the predetermined value V4 higher than the predetermined value V1, the reactive power regulator is stopped by the signal from the voltage detector or the reactive power supply operation of the distributed power source installed at the consumer is stopped. In order to reduce power loss, an impedance adjuster switch is inserted.
[0011]
The voltage control system according to claim 3 of the present invention controls the impedance adjuster based on the voltage detected by the voltage detector built in the impedance adjuster and looks at the power supply side from the customer circuit. By adjusting the ratio of the resistance component of the impedance and the reactor component, the reactive power flowing to the customer circuit side can be utilized to effectively adjust the voltage.
[0012]
That is, in a circuit in which power is supplied to the customer circuit from the low voltage side of the pole transformer via the lead-in line, the reactor and the switching between the pole transformer and the lead-in line or between the lead-in line and the customer circuit The voltage detected by the voltage detector built in the impedance regulator that detects the voltage on the customer circuit side of the impedance regulator or the pole transformer side of the impedance regulator is inserted in series with an impedance regulator connected in parallel. When the value becomes equal to or greater than the predetermined value V1, the reactive power detected by the reactive power detector built in the impedance adjuster that detects the reactive power on the consumer circuit side of the impedance adjuster flows toward the consumer side. When it is electric power, the switch of the impedance adjuster is opened to suppress the voltage rise, and the voltage detected by the voltage detector is more than the predetermined value V1. If the reactive power detected by the reactive power detector is a phase reactive power flowing toward the consumer even when the voltage drops below the predetermined value V2 or the voltage is V2 or higher, the impedance regulator switch is turned on, When the voltage on the customer circuit side of the impedance adjuster detected by the voltage detector is less than the predetermined value V3 or lower than the predetermined value V2, the reactive power is reduced. When the reactive power on the customer circuit side of the impedance adjuster detected by the detector is the phase reactive power flowing toward the customer side, the switch built in the impedance adjuster is opened, and the voltage drop is suppressed. Reactive power detected by the reactive power detector when the voltage detected by the voltage detector rises above a predetermined value V4 higher than a predetermined value V3 and lower than a predetermined value V1 or when the voltage is V4 or lower. When it becomes a slow power flowing toward the customer was charged with switchgear impedance adjuster, reduced and useless voltage suppression of reduction in power loss.
[0013]
Further, in the case where the reliability of the voltage control may be lowered, the reactive power detector 11 is omitted, and a circuit in which power is supplied to the customer circuit from the low voltage side of the pole transformer via the lead-in line Insert an impedance regulator with a reactor and a switch connected in parallel between the pole transformer and the lead-in line or between the lead-in line and the customer circuit. When the voltage detected by the voltage detector built in the impedance adjuster that detects the voltage on the pole transformer side of the adjuster exceeds the predetermined value V1, the switch of the impedance adjuster is opened to suppress the voltage rise. If the effect of suppressing voltage rise does not appear, insert a switch with a built-in impedance adjuster to prevent unnecessary voltage rise and reduce power loss. When the detected voltage falls below the predetermined value V2 lower than the predetermined value V1, the impedance adjuster switch is turned on to reduce the power loss and the customer side of the impedance adjuster detected by the voltage detector When the voltage of the voltage becomes equal to or lower than the predetermined value V3 lower than the predetermined value V2, the built-in impedance adjuster is opened to suppress the voltage drop, and when the voltage drop suppression effect does not appear, the impedance adjuster is built in. When the voltage detected by the voltage detector rises above the predetermined value V4 higher than the predetermined value V3 and lower than the predetermined value V1 An impedance adjuster switch may be inserted to control power loss.
[0014]
DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1
Hereinafter, a distributed power system interconnection voltage control system according to a first embodiment of the present invention will be described with reference to the drawings.
[0015]
FIG. 3 is a conceptual diagram of this distributed power system interconnection voltage control system. An impedance adjuster 3 is provided on the low voltage side of the pole transformer 2 provided on the utility pole 1, and the power is supplied from the impedance adjuster 3. A lead-in wire 5 (lead-in wire) extends to the customer's building 4, and a reactive power regulator 6 (SVG (Static Var Generator: static reactive power) is provided on the lead-in wire 5 side of the impedance regulator 3 of the pole transformer 2. Compensator) or shunt reactor etc. is connected. A distributed power source 7 made of, for example, a solar power generator is connected near the building 4 of the lead-in line 5. The impedance adjuster 3 is connected to a lead-in line to other power users.
[0016]
In FIG. 4, the lead-in wire 5 extends from the low-voltage terminal of the pole transformer 2 provided on the power pole 1 to the building 4 of the power consumer, and the impedance adjuster 3 is provided on the building 4 side of the lead-in wire 5. Yes. A distributed power source 7 is connected in the vicinity of the impedance adjuster 3.
[0017]
That is, in FIG. 4, the impedance adjuster 3 is provided at the lead-in portion on the building 4 side of the lead-in wire 5 extending from the pole transformer 2 to the distributed power source side.
[0018]
FIG. 1 shows an impedance adjuster 3 and peripheral circuits. As shown in FIG. 1, the impedance adjuster 3 has a configuration in which a reactor 9 and a switch 8 are connected in parallel. The impedance adjuster 3 includes a voltage detector 10 and a control circuit 12 as control means. A distributed power source or reactive power regulator 6 is connected to the customer side circuit of the impedance regulator 3.
[0019]
The impedance adjuster 3 looks at the received voltage of the customer side circuit which becomes the interconnection voltage by the voltage detector 10 (voltage detection means).
[0020]
The control circuit 12 responds to the detected value of the received voltage on the customer side detected by the voltage detector 10, and controls the reactive power supply control for transmitting the reactive power control signal to the reactive power regulator 6 and the opening / closing of the switch 8. Control.
[0021]
Here, switching control and reactive power control of the switch 8 may be performed based on the voltage detected by the distributed power supply or SVG instead of the voltage detection of the voltage detection circuit 10.
[0022]
The voltage detector 10 may be provided separately from the impedance adjuster 3, and the interconnected voltage may be the distributed power supply 7 or the interconnected voltage of the reactive power adjuster 6. good.
[0023]
The control circuit 12 controls the reactive power regulator 6 and the switch 8 as follows based on the power reception voltage of the interconnection system detected by the voltage detector 10. The control circuit 12 includes comparison means for comparing the received voltage detected by the voltage detector 10, and the reference voltage for comparison by the comparison means includes a voltage V1 that is a management value on the power supply side, and a voltage V1. A lower voltage V2, a voltage V3 lower than the voltage V2, and a voltage V4 that can ensure stable operation are defined. Further, the comparison means outputs a signal for switching control to the switch 8 according to the comparison result, and outputs a signal for controlling the reactive power supply and stop to the reactive power regulator 6.
[0024]
First, when the received voltage is going to rise to a predetermined value V1 or more, the reactive power regulator 6 consumes delayed reactive power, and the switch 8 is opened to reduce the R / X ratio viewed from the system side. The reactor 9 is inserted so as to suppress the increase in the received voltage. Next, the reactive power regulator 6 is stopped and the switch 8 is turned on when the power reception voltage of the consumer drops below the voltage V2 lower than the predetermined voltage V1.
[0025]
Furthermore, when the power reception voltage of the consumer drops below the voltage V3 lower than the voltage V2, the delayed reactive power is supplied from the reactive power regulator 6 and the voltage drop is suppressed by opening the switch 8. To do.
[0026]
In addition, when the power reception voltage of the consumer rises above the voltage V4 at which the operation is stabilized so that hunting is eliminated at a voltage lower than the voltage V1 and higher than the voltage V3, the reactive power regulator 6 is turned on. While stopping, the switch 8 is turned on to control power loss.
[0027]
In this way, the control circuit 12 controls the received voltage so as not to deviate from the management value on the power supply side by adjusting a small amount of reactive power, and shorts the inserted reactor 9 when the received voltage problem does not occur, Reduce power loss.
[0028]
In other words, as shown in FIG. 2, reactive power of “Q = −R / (X1 + X2) · P = −R / X · P” is supplied to the inverter of the distributed power source 7 of this embodiment. . In the case of the reactive power adjuster 6, the reactive power is supplied so that the Q / P ratio of the power flow flowing to the consumer side terminal of the impedance adjuster 3 has the same value.
[0029]
As described above, in the control system according to the first embodiment, the reactor and the switch are connected in parallel to one of the circuits from the low voltage side of the pole transformer to the customer circuit of the customer. Impedance regulator 6 provided with a parallel circuit is connected in series to detect the received voltage of the customer circuit, and when the received voltage is detected to rise above a predetermined voltage V1, phase advance operation of reactive power is started. At the same time, it is characterized in that the switch 8 is opened.
[0030]
As a specific example, the first control method is a method in which the impedance adjuster 3 and the reactive power adjuster 6 individually detect the received voltage and operate individually. In the first control method, the voltage detector built in the reactive power adjuster 6 detects an increase in the received voltage of the voltage V1 or more and starts the operation to consume the delayed reactive power by itself, while the impedance adjuster 3 The built-in voltage detector 10 detects the voltage and opens the switch 8.
[0031]
The second control method is a method in which the reactive power regulator 6 detects an increase in the received voltage of V1 or more and transmits a signal to the impedance regulator 3. In the second control method, the voltage detector built in the reactive power regulator 6 detects the received voltage and starts the operation of consuming the delayed reactive power by itself, and a signal is sent from the voltage detector to the switch 8. The feed switch 8 is opened.
[0032]
In the third control method, the impedance adjuster 3 detects an increase in the received voltage over a predetermined value and transmits a signal to the reactive power adjuster 6. In the third control method, the voltage is detected by the voltage detector 10 built in the impedance adjuster 3, the switch 8 is opened, and a signal is sent from the voltage detector 10 to the reactive power adjuster 6 to adjust the reactive power. The device 6 operates to consume the slow phase reactive power.
[0033]
The fourth control method is a method of detecting on the power consumer side and transmitting a signal to the reactive power adjuster 6 and the impedance adjuster 3. In the fourth control method, the voltage is detected by the voltage detector of the distributed power source 7, a signal is sent to the reactive power adjuster 6 and the impedance adjuster 3, and the switch 8 of the impedance adjuster 3 is opened and disabled. The power regulator 6 performs an operation that consumes the slow phase reactive power.
[0034]
Moreover, as a case where the control circuit 12 is used, a parallel circuit in which the reactor and the switch 8 are connected in parallel is provided in any of the circuits from the low voltage side of the pole transformer to the customer circuit of the customer. The impedance adjuster 3 is connected in series, the reactive power adjuster 6 is provided on the customer circuit side from the impedance adjuster 3, the voltage detector 10 for detecting the received voltage of the consumer in the impedance adjuster 3, and the voltage detection Corresponding to the detected value of the received voltage detected by the means 10, a control circuit 12 (control means) that performs reactive power supply control of the reactive power regulator 6 and switching control of the switch 8 is provided.
[0035]
When the received voltage of the consumer rises to a predetermined value V1 or more, the control circuit 12 consumes delayed reactive power by the reactive power regulator 6 and opens the switch 8 to suppress the increase of the received voltage. When the power reception voltage of the consumer drops below the voltage V2 lower than the predetermined voltage V1, the reactive power regulator 6 is stopped and the switch 8 is turned on to reduce the power loss. However, when the voltage falls below the voltage V3 lower than the voltage V2, the reactive power regulator 6 supplies delayed reactive power, and the switch 8 is opened to suppress the voltage drop. The reactive power regulator 6 is stopped and the switch 8 is turned on when the voltage rises to a voltage V4 or higher that stabilizes the operation so that hunting is eliminated at a voltage lower than the voltage V1 and higher than the voltage V3. Power loss It shall have a control function of controlling to reduce.
[0036]
In addition, although the voltage detector 10 of FIG. 1 detects the voltage on the customer side of the impedance adjuster 3, the voltage on the pole transformer side of the impedance adjuster 3 may be detected.
[0037]
In FIG. 4, instead of using the reactive power regulator 6, instead of using the reactive power regulator 6, instead of using the reactive power regulator 7 as shown in FIG. May be used to adjust reactive power.
[0038]
Second Embodiment of the Invention
Next, a distributed power system interconnection voltage control system according to a second embodiment of the present invention will be described with reference to FIG.
[0039]
In the voltage control system shown in FIG. 5, the impedance adjuster 3 ′ including the voltage detector 10, the reactive power detector 11, and the control circuit 12 shown in FIG. 5 is used.
[0040]
When the control circuit 12 built in the impedance adjuster 3 ′ rises above the voltage predetermined value V1 detected by the built-in voltage detector 10, the delayed reactive power detected by the reactive power detector 11 is consumed by the customer. When the lagging reactive power detected by the reactive power detector 11 starts to flow from the consumer side, the switch 8 is turned on to open the voltage. When the rise is suppressed and the voltage detected by the voltage detector 10 falls below V2 lower than the predetermined value V1, the switch 8 is turned on to reduce the power loss, and the voltage detected by the voltage detector 10 becomes the predetermined voltage. When the slow reactive power detected by the reactive power detector 11 flows from the customer side when the voltage falls below the predetermined value V3 lower than the value V2, the switch 8 is opened to suppress the voltage drop. Detected by reactive power detector 11 When lagging reactive power flows to the customer side, the switch 8 is turned on to suppress the voltage drop, and when the voltage detected by the voltage detector 10 rises to V4 higher than the predetermined value V3, By switching on the switch 8 and reducing the power loss, the reactive power generated on the customer side is effectively used to adjust the voltage.
[0041]
5 detects the voltage on the customer side of the impedance adjuster 3 ′, but may detect the voltage on the pole transformer side of the impedance adjuster 3 ′.
[0042]
The voltage control system according to the second embodiment includes a parallel circuit in which a reactor and a switch 8 are connected in parallel to one of the circuits from the low voltage side of the pole transformer to the customer circuit of the customer. The impedance adjuster 3 'is connected in series, and the impedance adjuster 3' receives the received voltage on the customer circuit side or the voltage on the pole transformer side of the impedance adjuster 3 '. A voltage detector 10 to detect, a reactive power detector 11, and a control circuit 12 that performs switching control of the switch 8 are provided.
[0043]
The control circuit 12 is a slow phase reactive power in which the received voltage detected by the voltage detector 10 is equal to or higher than the predetermined voltage V1 and the reactive power detected by the reactive power detector 11 flows toward the customer circuit side. In some cases, the switch 8 is opened to suppress an increase in the received voltage, and when the received voltage detected by the voltage detector 10 falls below the voltage V2 lower than the voltage V1, the switch 8 is turned on. The power loss is reduced, and when the received voltage detected by the voltage detector 10 drops below the voltage V3 lower than the voltage V2, the invalidity on the customer circuit side of the impedance adjuster 3 detected by the reactive power detector 11 When the power is phase reactive power that flows toward the customer side, the switch 8 is opened to suppress the voltage drop, and the received voltage detected by the voltage detector 10 is lower than the voltage V1 and is the voltage V3. At higher voltage Nchingu in operation than the voltage V4 to stabilize such is eliminated, when coming to rise, and a control function by introducing a switch 8 is controlled so as to achieve a reduction in power loss.
[0044]
When the certainty of the voltage control may be lowered, the reactive power detector 11 may be omitted and the control may be performed based on the voltage detected by the voltage detector 10.
[0045]
That is, when the received voltage detected by the voltage detector 10 is equal to or higher than the predetermined voltage V1, the control circuit 12 opens the switch 8 to suppress the increase in the received voltage, and there is no effect of suppressing the voltage increase. When the switch 8 with the built-in impedance adjuster is turned on to prevent unnecessary voltage rise and reduce power loss, the received voltage detected by the voltage detector 10 falls below the voltage V2 lower than the voltage V1. In addition, the switch 8 is turned on to reduce the power loss. When the received voltage detected by the voltage detector 10 falls below the voltage V3 lower than the voltage V2, the switch 8 is opened to reduce the voltage drop. If the effect of suppressing voltage drop is not achieved, switch 8 with built-in impedance adjuster is inserted to prevent unnecessary voltage drop and reduce power loss, and the received voltage detected by voltage detector 10 But the voltage Control for controlling the power loss by turning on the switch 8 when the voltage rises above the voltage V4 at which the operation is stabilized so that hunting is eliminated at a voltage lower than 1 and higher than the voltage V3. You may make it provide a function.
[0046]
【The invention's effect】
According to the distributed power system interconnection voltage control system according to claims 1 to 3 of the present application, the voltage adjustment capability by reactive power can be increased, and a large voltage adjustment is possible with small reactive power. As described above, it is not necessary to suppress the output of solar power generation or the like when the voltage rises, and the customer-side distributed power source can be used effectively.
[0047]
In addition, since the reactive power control effect is increased, the capacity of the reactive power regulator or the distributed power source can be reduced, and the loss during reactive power control can be reduced. By using the reactor only when necessary, it is possible to prevent power loss and voltage fluctuation due to load fluctuation.
[0048]
According to the third aspect of the present invention, it is possible to easily and effectively perform voltage adjustment using reactive power generated on the consumer side without exchanging signals.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram of a distributed power system interconnection voltage control system according to an embodiment of the present invention.
FIG. 2 is a vector diagram showing a concept of reactive power control by turning on an impedance adjuster.
FIG. 3 is a conceptual diagram when a switch, an impedance adjuster, and a reactive power adjuster are provided on the pole transformer side.
FIG. 4 is a conceptual diagram when a switch, an impedance adjuster, and a reactive power adjuster are provided on the building side.
FIG. 5 is a conceptual diagram of a voltage control system according to a second embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Telephone pole 2 Transformer on pole 3 Impedance regulator 3 'Voltage detector, reactive power detector, impedance regulator 4 incorporating control circuit 4 Building for power users 5 Lead-in line 6 Reactive power regulator (SVG, etc.)
7 Distributed Power Supply 8 Switch 9 Reactor 10 Voltage Detector 11 Reactive Power Detector 12 Control Circuit

Claims (3)

Impedance adjusting means having a parallel circuit in which a reactor and a switch are connected in parallel is connected in series to any of the circuits from the low voltage side of the pole transformer to the customer circuit of the customer, and the consumer A distributed power supply characterized in that, while detecting the power reception voltage of the circuit, when the power reception voltage is detected to rise above a predetermined voltage, the operation of consuming the lagging reactive power is started and the switch is opened. Grid-connected voltage control system. Impedance adjustment is performed by connecting in series an impedance adjusting means including a parallel circuit in which a reactor and a switch are connected in parallel to any of the circuits from the low voltage side of the pole transformer to the customer circuit of the customer. Reactive power adjustment means is provided on the consumer circuit side from the means, voltage detection means for detecting the power reception voltage of the consumer in the impedance adjustment means, and a detected value of the received voltage detected by the voltage detection means Correspondingly, there is provided control means for performing reactive power supply control of the reactive power adjusting means and switching control of the switch,
The control means includes
When the power reception voltage of the consumer rises to a predetermined value V1 or more, the reactive power adjustment means consumes delayed reactive power, and the switch is opened to suppress an increase in the power reception voltage. When the power reception voltage of the house falls below the voltage V2 lower than the predetermined voltage V1, the reactive power adjusting means is stopped and the switch is turned on to reduce power loss. When the voltage drops below the voltage V3 lower than the voltage V2, the reactive power adjusting means supplies delayed reactive power, and the voltage is suppressed by opening the switch so that the received voltage of the consumer is The reactive power adjustment means is stopped when the voltage rises to a voltage V4 or higher that stabilizes the operation so that hunting is eliminated at a voltage lower than the voltage V1 and higher than the voltage V3. It said switch by introducing a distributed power system interconnection voltage control system which can be characterized that has a control function of controlling to achieve a reduction in power loss. Impedance adjusting means having a parallel circuit in which a reactor and a switch are connected in parallel is connected in series to any of the circuits from the low voltage side of the pole transformer to the customer circuit of the customer, and the impedance adjusting means Comprises voltage detecting means for detecting the voltage on the pole transformer side of the impedance adjusting means or the received voltage on the customer circuit side, reactive power detecting means, and control means for performing opening / closing control of the switch,
The control means includes
When the received voltage detected by the voltage detector is equal to or higher than a predetermined voltage V1, and the reactive power detected by the reactive power detector is slow phase reactive power flowing toward the consumer circuit side, The switch is opened to suppress an increase in the received voltage, and when the received voltage detected by the voltage detector falls below the voltage V2 lower than the voltage V1, the switch is turned on to reduce power loss. The reactive power on the consumer circuit side of the impedance adjusting means detected by the reactive power detector is reduced when the received voltage detected by the voltage detector drops below the voltage V3 lower than the voltage V2. When the phase-advancing reactive power flows toward the consumer side, the switch is opened to suppress the voltage drop, and the received voltage detected by the voltage detector is lower than the voltage V1 and the voltage V3. It has a control function to control to reduce the power loss by turning on the switch when the voltage rises to a voltage V4 or higher that stabilizes the operation so that hunting is eliminated at a higher voltage. The voltage control system of the distributed power system connection characterized by this.

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