Voltage control device, voltage control method, voltage control program, and voltage control system

Abstract

To provide a voltage control device, a voltage control method, a voltage control program, and a voltage control system capable of maintaining a distribution line voltage at a proper value while suppressing a power generation opportunity loss.SOLUTION: An inverter 101 receives a DC power supplied from a distributed power supply, converts the DC power into an AC power, and supplies the AC power to a power distribution system. An active power / reactive power controller 104, in a case where an interconnection point voltage at an interconnection point to the power distribution system is larger than a lower limit value, increases a delay-phase reactive power outputted from the inverter 101 to raise the interconnection point voltage.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a voltage control device, a voltage control method, a voltage control program, and a voltage control system. [Background technology]

[0002] In recent years, expectations for renewable energy sources that place less of a burden on the environment have been rising, and their introduction has been promoted. In particular, the introduction of photovoltaic (PV) power generation has expanded significantly. In addition, the Feed-in Tariff (FIT) system has further accelerated the spread of PV introduction in both residential and non-residential areas.

[0003] As PV becomes more widespread, voltage rises in distribution systems due to reverse power flow are becoming an issue. Distribution systems have traditionally been equipped with voltage regulating devices such as load control transformers (LRTs) and step voltage regulators (SVRs). Compensation control for voltage fluctuations due to fluctuations in power demand is carried out based on the tap changing control of these voltage regulating devices. However, voltage fluctuations due to reverse power flow from PV are steep because they are influenced by factors such as the weather, and there are cases where LRTs, SVRs, and other devices are unable to keep up with the fluctuations.

[0004] Meanwhile, the power conditioner (Power Conditioning Sub System: PCS) connected to the PV is equipped with an automatic voltage regulator with a voltage rise suppression function. The voltage rise suppression function performs leading-phase reactive power control or output suppression to prevent the voltage at the interconnection point to the distribution system from deviating from the upper limit of the appropriate voltage range. This makes it possible to prevent the distribution line voltage from exceeding the upper limit in a system that is interconnected to a PCS equipped with a voltage rise suppression function.

[0005] However, PCS does not have sufficient functions to deal with voltage drops. For this reason, there is a need for power generation companies to take measures against the voltage drop phenomenon caused by the reverse power flow of distributed power sources mentioned above.

[0006] On the other hand, considering the expiration of the purchase period and the decline in purchase prices under the surplus electricity purchase scheme and feed-in tariff scheme, which have supported the sale of PV electricity, it is possible that the purchase price will fall to below the supplied electricity rate in the future. In that case, it is expected that consumers will reduce their utility bills by reducing the amount of electricity and gas supplied through self-consumption using electric vehicles and storage batteries.

[0007] The emergence of aggregators that adjust supply and demand among consumer groups is also predicted. In that case, unlike the load movement so far, a large amount of load will be locally added, and voltage drops may occur due to smooth flow caused by line impedance. If this voltage drop becomes serious, there is a risk of events such as deviation from the 95V appropriate lower limit stipulated by the Electricity Business Act or disconnection of the PCS.

[0008] Here, there are the following technologies as grid voltage control technologies. For example, there is a conventional technology that controls the voltage rise suppression function power by using a correction value obtained by correcting the output voltage of the PCS AC output terminal with a voltage drop amount calculated based on the wiring impedance and AC output current from the measured voltage of the AC output terminal of the inverter device inside the PCS. There is also a conventional technology that suppresses the rise of the commercial grid voltage by sharing lagging power or supplying leading power and reducing active power according to the effective value of the commercial grid voltage. There is also a conventional technology that starts voltage suppression control of the PCS when the minimum value of the output voltages of multiple PCSs is equal to or greater than a threshold value. There is also a conventional technology that estimates the voltage distribution taking into account the phase difference by performing voltage estimation using a passing current that takes into account the phase difference between the current and voltage at each node, and controls the voltage using the estimation result. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] JP 2015-211589 A [Patent Document 2] JP 2016-185018 A [Patent Document 3] JP 2015-211480 A [Patent Document 4] JP 2020-089008 A Summary of the Invention [Problem to be solved by the invention]

[0010] However, in the conventional technology that controls the voltage rise suppression function by correcting the output voltage with the voltage drop calculated based on the impedance of the distribution line and the AC output current, it is possible to respond to voltage rises, but it is difficult to respond to voltage drops. In addition, in the conventional technology that controls the commercial grid voltage by supplying lagging-phase power or leading-phase power according to the effective value of the commercial grid voltage, voltage drops due to large-scale interconnection of distributed power sources are not assumed, and it is difficult to respond to voltage drops due to reverse power flow caused by PV and storage batteries. In addition, in the conventional technology that performs voltage suppression control based on the minimum value of the output voltages of multiple PCSs, the main focus is on voltage rise control of multiple PCSs, and it is difficult to adjust the grid voltage to the steep voltage fluctuations of each PCS. Furthermore, in the conventional technology that controls voltage by estimating the voltage distribution considering the phase difference, it is targeted at system equipment, and it is difficult to respond to voltage drops by controlling the PCS.

[0011] The disclosed technology has been made in consideration of the above, and aims to provide a voltage control device, a voltage control method, a voltage control program, and a voltage control system that maintain a distribution line voltage at an appropriate value while suppressing loss of power generation opportunities. [Means for solving the problem]

[0012] In one aspect of the voltage control device, voltage control method, voltage control program, and voltage control system disclosed in the present application, the converter receives DC power from a distributed power source, converts it into AC power, and supplies the AC power to a power distribution system. The output control unit performs constant power factor control to adjust the power factor of the output of the converter to a predetermined value. The reactive power adjustment unit is In a state where the power factor is adjusted to the predetermined value by the output control unit,When a voltage at a connection point to the distribution system exceeds a lower limit, the lagging reactive power output by the converter is increased to raise the voltage at the connection point. Effect of the Invention

[0013] According to one aspect, the present invention can maintain the distribution line voltage at an appropriate value while suppressing loss of power generation opportunities. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a diagram illustrating an example of a power distribution system model. [Diagram 2] FIG. 2 is a block diagram of the PCS. [Diagram 3] FIG. 3 is a diagram illustrating an output plane of active power and reactive power during control to keep the power factor constant at 1 according to the first embodiment. [Figure 4] FIG. 4 is a flowchart of automatic voltage adjustment control by the PCS. [Diagram 5] FIG. 5 is a flowchart of the voltage drop suppression control by the PCS according to the first embodiment. [Figure 6] FIG. 6 is a diagram illustrating an output plane of active power and reactive power during control to keep the power factor constant at 1 according to the second embodiment. [Figure 7] FIG. 7 is a flowchart of voltage drop suppression control by the PCS according to the second embodiment. [Figure 8] FIG. 8 is a diagram showing a power distribution system model used for verifying the operation of the automatic voltage regulation control. [Figure 9] FIG. 9 is a diagram showing the conditions of the PV output and the load used in the operation verification of the automatic voltage regulation control. [Figure 10] FIG. 10 is a diagram showing the verification results under the load condition at no load. [Figure 11] FIG. 11 is a diagram showing the verification results under a heavy load condition. [Figure 12] FIG. 12 is a diagram showing the voltage deviation amount and the output suppression amount in the operational verification of the automatic voltage regulation control. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, embodiments of the voltage control device, the voltage control method, the voltage control program, and the voltage control system disclosed in the present application will be described in detail with reference to the drawings. Note that the voltage control device, the voltage control method, the voltage control program, and the voltage control system disclosed in the present application are not limited to the following embodiments. EXAMPLES

[0016] 1 is a diagram showing an example of a power distribution system model 10. The power distribution system model 10 includes a power distribution substation 1, an SVR 2, a main line 3, a transformer 4, a customer's house 5, and a PCS 100.

[0017] The distribution substation 1 is connected to a main line 3. The distribution substation 1 reduces the voltage of the electric power sent from the power plant and sends it to the main line 3 to supply it to each customer's house 5.

[0018] The SVR 2 is disposed on the main line 3. The SVR 2 acquires a line voltage drop value at a predetermined point and adjusts the voltage at the predetermined point to fall within a predetermined voltage range by switching the tap according to the acquired value. An operation time limit for adjusting the system voltage is set in the SVR 2. This operation time limit is set, for example, between 45 and 120 seconds.

[0019] Hereinafter, the operation time limit of SVR2 will be referred to as the "SVR operation time limit." For example, when SVR2 detects a voltage deviation from a predetermined voltage range at a specific point, it adjusts the voltage at the specific point so that it falls within the predetermined voltage range after the SVR operation time limit has elapsed since the detection. This SVR operation time limit is an example of a "standby period."

[0020] The transformer 4 is disposed on a low-voltage distribution line 31 that branches off from the main line 3 and extends to a customer's residence 5. The transformer 4 adjusts the voltage to that used at the customer's residence 5, and supplies the electricity with the adjusted voltage to the customer's residence 5.

[0021] The consumer's house 5 has a PV 51, which is a distributed power source, and a residential load 52. The PV 51 transmits electric power generated by using sunlight to the main line 3 via the PCS 100 and the low-voltage distribution line 31. The residential load 52 is, for example, a home appliance, and uses electric power supplied via the transformer 4.

[0022] The PCS 100 is disposed on a path connecting the transformer 4 and the PV 51. The PCS 100 converts DC power supplied from the PV 51 into AC power and transmits it to the trunk line 3 via the low-voltage distribution line 31 and the transformer 4.

[0023] Fig. 2 is a block diagram of the PCS. Next, the details of the PCS 100 will be described with reference to Fig. 2. Hereinafter, the connection point of the PCS 100 to the low-voltage distribution line 31 extending from the transformer 4 is referred to as the "interconnection point" to the power distribution system. Also, the voltage at the interconnection point may be referred to as the "interconnection point voltage."

[0024] As shown in FIG. 2 , the PCS 100 has an inverter 101, an inverter control unit 102, an active power and reactive power calculation circuit 103, an active power and reactive power control unit 104, an active power adjustment unit 105, an active power target value providing unit 106, a reactive power adjustment unit 107, and a reactive power target value providing unit 108.

[0025] The inverter 101 receives DC power from the PV 51. Furthermore, the inverter 101 receives a control signal input from an inverter control unit 102 for outputting a determined amount of active power and reactive power. The inverter 101 then converts the supplied DC power into AC power so as to output the amount of active power and reactive power specified by the control signal. The inverter 101 then outputs the power converted into AC power and sends it to the main line 3 via the transformer 4. This inverter 101 is an example of a "converter."

[0026] The active power / reactive power calculation circuit 103 measures the voltage and current at the interconnection point of the inverter 101. Then, the active power / reactive power calculation circuit 103 calculates the output amounts of active power and reactive power to the interconnection point of the inverter 101 from the measured voltage and current. In the following description, the output amounts of active power and reactive power are called active power output and reactive power output. Reactive power output includes a leading-phase reactive power output for lowering the interconnection point voltage and a lagging-phase reactive power output for raising the interconnection point voltage. The leading-phase reactive power output and the lagging-phase reactive power output are called leading-phase reactive power output and lagging-phase reactive power output.

[0027] After calculating the active power output and reactive power output of the inverter 101 to the interconnection point, the active power and reactive power calculation circuit 103 outputs information on the calculated active power output to the active power and reactive power control unit 104 and the active power adjustment unit 105. In addition, the active power and reactive power calculation circuit 103 outputs information on the calculated reactive power output to the active power and reactive power control unit 104 and the reactive power adjustment unit 107. In addition, the active power and reactive power calculation circuit 103 outputs information on the interconnection point voltage to the active power and reactive power control unit 104.

[0028] The active and reactive power control unit 104 has information on the upper limit and lower limit of the appropriate voltage range of the active power in advance. The active and reactive power control unit 104 also has information on the minimum power factor in advance. This minimum power factor is an example of a "predetermined value."

[0029] Furthermore, the active power and reactive power control unit 104 has information on the operation time limit of output suppression in advance. This operation time limit is set longer than the SVR operation time limit. For example, this operation time limit is set to 200 seconds. This operation time limit of output suppression in the active power and reactive power control unit 104 is hereinafter referred to as the "output suppression operation time limit." This output suppression operation time limit is an example of a "predetermined period."

[0030] The active power and reactive power control unit 104 also has information on the rated capacity of the inverter 101 in advance. The active power and reactive power control unit 104 also has a timer that measures elapsed time. The active power and reactive power control unit 104 also stores in advance a value of an increase pullback voltage that serves as a threshold for voltage increase suppression recovery processing and a value of a decrease pullback voltage that serves as a threshold for voltage decrease suppression recovery processing.

[0031] The active power and reactive power control unit 104 performs constant power factor control to control the operating power factor of the power output from the inverter 101 to be constant during normal operation. For example, the active power and reactive power control unit 104 performs constant power factor control to make the operating power factor 1. Hereinafter, the constant power factor control to make the operating power factor 1 is referred to as "constant power factor 1 control." In this case, the active power and reactive power control unit 104 does not cause the inverter 101 to output reactive power during normal operation. That is, the active power and reactive power control unit 104 instructs the active power target value providing unit 106 to provide a target value of the active power output during normal operation. Furthermore, the active power and reactive power control unit 104 instructs the reactive power target value providing unit 108 to set the target value of the reactive power output to 0.

[0032] Also, for example, the active power / reactive power control unit 104 performs constant power factor control so that the operating power factor becomes 0.95. Hereinafter, the constant power factor control that makes the operating power factor 0.95 is referred to as "constant power factor 0.95 control." In this case, the active power / reactive power control unit 104 causes the inverter 101 to output reactive power so that the operating power factor becomes 0.95 during normal operation. That is, the active power / reactive power control unit 104 instructs the active power target value providing unit 106 to provide a target value of the active power output during normal operation. Furthermore, the active power / reactive power control unit 104 instructs the reactive power target value providing unit 108 to provide a target value of the reactive power output that makes the operating power factor 0.95 according to the target value of the active power output during normal operation.

[0033] The active power and reactive power control unit 104 measures the interconnection point voltage in the inverter 101. The active power and reactive power control unit 104 also receives input of information on the active power output and reactive power output at the interconnection point from the active power and reactive power calculation circuit 103. Next, the active power and reactive power control unit 104 determines whether or not the interconnection point voltage has exceeded the upper limit value of the appropriate voltage range from the active power output and reactive power output.

[0034] When the interconnection point voltage exceeds the upper limit of the appropriate voltage range, the active power and reactive power control unit 104 calculates the operating power factor of the inverter 101 using the active power output and reactive power output at the interconnection point of the inverter 101. Then, the active power and reactive power control unit 104 judges whether the operating power factor of the inverter 101 exceeds a predetermined minimum power factor. In this embodiment, a case where the minimum power factor is 0.85 will be described. If the operating power factor exceeds 0.85, the active power and reactive power control unit 104 repeats the adjustment of the leading-phase reactive power output of the interconnection point voltage and the adjustment of the active power output according to the judgment result of the output of the inverter 101 exceeding the rated capacity, which will be described below.

[0035] Here, we will explain how the active power and reactive power control unit 104 adjusts the leading phase reactive power output of the interconnection point voltage when the interconnection point voltage exceeds the upper limit value of the appropriate voltage range, and how it adjusts the active power output in response to the determination result that the output of the inverter 101 exceeds the rated capacity.

[0036] When the interconnection point voltage exceeds the upper limit of the appropriate voltage range and the operating power factor exceeds the minimum power factor, the active power / reactive power control unit 104 instructs the reactive power target value providing unit 108 to increase the leading-phase reactive power output. This increases the leading-phase reactive power output from the inverter 101, suppressing an increase in the interconnection point voltage. When the interconnection point voltage continues to exceed the upper limit of the appropriate voltage range, the active power / reactive power control unit 104 repeatedly instructs the reactive power target value providing unit 108 to increase the leading-phase reactive power output. Thereafter, when the interconnection point voltage falls below the upper limit of the appropriate voltage range, the active power / reactive power control unit 104 instructs the reactive power target value providing unit 108 to maintain the leading-phase reactive power output at that time.

[0037] Moreover, the active power / reactive power control unit 104 determines whether the output of the inverter 101 has exceeded the rated capacity while suppressing an increase in the interconnection point voltage by increasing the leading-phase reactive power output. If the output of the inverter 101 has exceeded the rated capacity, the active power / reactive power control unit 104 instructs the active power target value providing unit 106 to suppress the active power output. As a result, the active power / reactive power control unit 104 reduces the active power output of the inverter 101 and corrects the active power output so that the output of the inverter 101 falls within the rated capacity.

[0038] On the other hand, when the operating power factor reaches the minimum power factor, the active power and reactive power control unit 104 starts its own timer at that timing. Then, the active power and reactive power control unit 104 uses the timer to measure the elapsed time from when the operating power factor reaches 0.85 to when the output suppression operation time limit has elapsed.

[0039] Until the output suppression operation time limit is reached, the active power and reactive power control unit 104 repeatedly determines whether the voltage exceeds the upper limit of the appropriate voltage range. If the interconnection point voltage continues to exceed the upper limit of the appropriate voltage range, the active power and reactive power control unit 104 repeatedly adjusts the active power output according to the determination results of the leading-phase reactive power output and the inverter 101 output exceeding the rated capacity.

[0040] If the state in which the interconnection point voltage exceeds the upper limit of the appropriate voltage range continues until the output suppression operation time limit is reached, after the output suppression operation time limit is reached, the active power and reactive power control unit 104 instructs the reactive power target value providing unit 108 to reduce the leading-phase reactive power output. Furthermore, the active power and reactive power control unit 104 instructs the reactive power target value providing unit 108 to reduce the active power output. Then, the active power and reactive power control unit 104 adjusts the active power output and the leading-phase reactive power output so that the operating power factor becomes equal to or greater than the minimum power factor.

[0041] On the other hand, if the interconnection point voltage becomes equal to or lower than the upper limit of the voltage appropriate range before the output suppression operation time limit is reached, the active power and reactive power control unit 104 stops the instruction to increase the leading-phase reactive power output. Next, the active power and reactive power control unit 104 judges whether the interconnection point voltage is lower than the rising pullback voltage. If the interconnection point voltage is equal to or higher than the rising pullback voltage, the active power and reactive power control unit 104 decides to maintain the active power output and leading-phase reactive power output at that time. In this case, the active power and reactive power control unit 104 instructs the active power target value providing unit 106 to maintain the active power output. Also, the active power and reactive power control unit 104 instructs the reactive power target value providing unit 108 to maintain the leading-phase reactive power output.

[0042] On the other hand, when the interconnection point voltage falls below the rising pullback voltage, the active power / reactive power control unit 104 executes a voltage rise suppression control release process. Specifically, when active power output suppression is being performed, the active power / reactive power control unit 104 instructs the active power target value providing unit 106 to increase the active power output. Also, when leading-phase reactive power is being output, the active power / reactive power control unit 104 instructs the reactive power target value providing unit 108 to decrease the leading-phase reactive power output.

[0043] Furthermore, if the interconnection point voltage does not exceed the upper limit of the voltage appropriate range, the active power / reactive power control unit 104 judges whether the interconnection point voltage has fallen below the lower limit of the voltage appropriate range from the active power output and the reactive power output. If the interconnection point voltage has fallen below the lower limit of the voltage appropriate range, the active power / reactive power control unit 104 calculates the operating power factor of the inverter 101 using the active power output and the reactive power output at the interconnection point of the inverter 101. Then, the active power / reactive power control unit 104 judges whether the operating power factor of the inverter 101 is above a predetermined minimum power factor. If the operating power factor is above 0.85, the active power / reactive power control unit 104 repeats the adjustment of the lagging reactive power output described below and the adjustment of the active power output according to the judgment result of the inverter 101 output exceeding the rated capacity.

[0044] Here, we will explain the adjustment of the lagging reactive power output by the active power and reactive power control unit 104 when the interconnection point voltage falls below the lower limit of the appropriate voltage range, and the adjustment of the active power output in response to the determination result that the output of the inverter 101 exceeds the rated capacity.

[0045] When the interconnection point voltage falls below the lower limit of the appropriate voltage range and the operating power factor exceeds the minimum power factor, the active power / reactive power control unit 104 instructs the reactive power target value providing unit 108 to increase the lagging-phase reactive power output. This increases the lagging-phase reactive power output from the inverter 101, suppressing a drop in the interconnection point voltage. When the state in which the voltage remains below the lower limit of the appropriate voltage range continues, the active power / reactive power control unit 104 repeatedly instructs the reactive power target value providing unit 108 to increase the lagging-phase reactive power output. After that, when the voltage becomes equal to or greater than the lower limit of the appropriate voltage range, the active power / reactive power control unit 104 instructs the reactive power target value providing unit 108 to maintain the leading-phase reactive power output at that time.

[0046] Moreover, the active power and reactive power control unit 104 determines whether the output of the inverter 101 exceeds the rated capacity while suppressing a decrease in the interconnection point voltage by increasing the lagging reactive power output. If the output of the inverter 101 exceeds the rated capacity, the active power and reactive power control unit 104 instructs the active power target value providing unit 106 to suppress the active power output. As a result, the active power and reactive power control unit 104 reduces the active power output of the inverter 101 and corrects the active power output so that the output of the inverter 101 falls within the rated capacity.

[0047] On the other hand, when the operating power factor reaches the minimum power factor, the active power / reactive power control unit 104 stops issuing an instruction to increase the lagging reactive power output. Next, the active power / reactive power control unit 104 judges whether the interconnection point voltage has become equal to or higher than the pull-back voltage. If the interconnection point voltage is less than the pull-back voltage, the active power / reactive power control unit 104 decides to maintain the active power output and the lagging reactive power output at that time. In this case, the active power / reactive power control unit 104 instructs the active power target value providing unit 106 to maintain the active power output. Also, the active power / reactive power control unit 104 instructs the reactive power target value providing unit 108 to maintain the lagging reactive power output.

[0048] On the other hand, when the voltage falls below the lowering pullback voltage, the active power and reactive power control unit 104 executes a voltage suppression return process if the output of active power is being suppressed. Specifically, the active power and reactive power control unit 104 instructs the active power target value providing unit 106 to increase the active power output. Also, when lagging reactive power is being output, the active power and reactive power control unit 104 instructs the reactive power target value providing unit 108 to decrease the lagging reactive power output. This active power and reactive power control unit 104 is an example of an "output control unit".

[0049] Here, in both cases where the interconnection point voltage exceeds the upper limit of the appropriate voltage range and where it falls below the lower limit of the appropriate voltage range, it is possible that the SVR2 also detects the deviation of the voltage at the specified monitored point from the predetermined voltage range. In this case, the SVR2 adjusts the grid voltage when the SVR operation time has elapsed since the point of detection of the deviation of the interconnection point voltage from the predetermined voltage range. This SVR2 processing also reduces the interconnection point voltage of the PCS100 if the interconnection point voltage exceeds the upper limit of the appropriate voltage range, and increases it if it falls below the lower limit of the appropriate voltage range. In other words, the SVR2 promotes the return of the grid voltage to a state where it is within the appropriate voltage range, making it possible to transition to a stable state more quickly.

[0050] After activation, the active power target value providing unit 106 outputs a predetermined target value of the active power output to the active power adjusting unit 105. Thereafter, when the active power target value providing unit 106 receives an instruction to maintain the active power output from the active power and reactive power control unit 104, it maintains the target value of the active power output at that time.

[0051] On the other hand, when an instruction to suppress the active power output is received from the active power and reactive power control unit 104, the active power target value providing unit 106 outputs a value obtained by decreasing the target value of the active power output at that time by a predetermined amount as the target value of the active power output to the active power adjustment unit 105. Also, when an instruction to increase the active power output is received from the active power and reactive power control unit 104, the active power target value providing unit 106 outputs a value obtained by increasing the target value of the active power output at that time by a predetermined amount as the target value of the active power output to the active power adjustment unit 105.

[0052] The active power adjusting unit 105 receives an input of information on the active power output at the interconnection point of the inverter 101 from the active power / reactive power calculation circuit 103. The active power adjusting unit 105 also receives an input of a target value of the active power output from the active power target value providing unit 106. Then, the active power adjusting unit 105 calculates the difference between the actual active power output at the interconnection point of the inverter 101 and the target value of the active power output. Then, the active power adjusting unit 105 calculates an active power output that corrects the calculated difference, and notifies the inverter control unit 102 of information on the calculated active power output.

[0053] When the reactive power target value providing unit 108 receives an instruction to increase the leading-phase reactive power output from the active power and reactive power control unit 104, it outputs a value obtained by increasing the leading-phase reactive power output by a predetermined amount from the target value of the reactive power output at that time as the target value of the reactive power output to the reactive power adjusting unit 107. Also, when the reactive power target value providing unit 108 receives an instruction to suppress the leading-phase reactive power output from the active power and reactive power control unit 104, it outputs a value obtained by decreasing the leading-phase reactive power output by a predetermined amount from the target value of the reactive power output at that time as the target value of the reactive power output to the reactive power adjusting unit 107.

[0054] On the other hand, when receiving an instruction to increase the lagging reactive power output from the active power and reactive power control unit 104, the reactive power target value providing unit 108 outputs a value obtained by increasing the lagging reactive power output by a predetermined amount from the target value of the reactive power output at that time as the target value of the reactive power output to the reactive power adjustment unit 107. Also, when receiving an instruction to suppress the lagging reactive power output from the active power and reactive power control unit 104, the reactive power target value providing unit 108 outputs a value obtained by decreasing the lagging reactive power output by a predetermined amount from the target value of the reactive power output at that time as the target value of the reactive power output to the reactive power adjustment unit 107.

[0055] Furthermore, when an instruction to maintain the reactive power output is received from the active and reactive power control unit 104, the reactive power target value providing unit 108 maintains the target value of the reactive power output at that time.

[0056] The reactive power adjusting unit 107 receives an input of information on the reactive power output at the interconnection point of the inverter 101 from the active power / reactive power calculation circuit 103. The reactive power adjusting unit 107 also receives an input of a target value of the reactive power output from the reactive power target value providing unit 108. Then, the reactive power adjusting unit 107 calculates the difference between the actual reactive power output at the interconnection point of the inverter 101 and the target value of the reactive power output. Then, the reactive power adjusting unit 107 calculates a reactive power output that corrects the calculated difference, and notifies the inverter control unit 102 of the calculated reactive power output.

[0057] For example, if the result obtained as the difference between the target values ​​is that the leading-phase reactive power is less by a predetermined amount, the reactive power adjusting unit 107 obtains a reactive power output that increases the leading-phase reactive power by a predetermined amount and notifies the inverter control unit 102. On the other hand, if the result obtained as the difference between the target values ​​is that the lagging reactive power is less by a predetermined amount, the reactive power adjusting unit 107 obtains a reactive power output that increases the lagging reactive power by a predetermined amount and notifies the inverter control unit 102.

[0058] The inverter control unit 102 receives a notification of the output amount of active power to be output from the inverter 101 from the active power adjustment unit 105. The inverter control unit 102 also receives a notification of the output amount of reactive power to be output from the inverter 101 from the reactive power adjustment unit 107. Then, the inverter control unit 102 outputs a control signal to the inverter 101 for outputting the specified output amounts of active power and reactive power.

[0059] Next, referring to Fig. 3, changes in the active power output and the reactive power output when the voltage increase control function or the voltage decrease control function of the PCS100 according to this embodiment operates in the case of performing the power factor constant 1 control will be described. Fig. 3 is a diagram showing an output plane of the active power and the reactive power during the power factor constant 1 control according to the first embodiment. The horizontal axis of Fig. 3 represents the active power output, and the vertical axis represents the reactive power output. A curve 301 in Fig. 3 represents the rated capacity of the PCS100. In this case, the PCS100 executes the power factor constant control with the operating power factor set to 1.

[0060] During normal operation, the PCS 100 outputs active power indicated by vector 311. Furthermore, since the operating power factor is 1, the PCS 100 does not output reactive power. In this case, the PCS 100 outputs active power at output amount 321.

[0061] When the interconnection point voltage exceeds the upper limit of the appropriate voltage range, the PCS 100 starts outputting leading-phase reactive power. If the state in which the interconnection point voltage exceeds the upper limit of the appropriate voltage range continues, the PCS 100 gradually increases the leading-phase reactive power output as shown by vector 312.

[0062] Also, although not shown in FIG. 3, if the output exceeds the rated capacity represented by curve 301, PCS 100 reduces the active power output and corrects the active power output so that the output falls within the rated capacity.

[0063] Here, by increasing the leading-phase reactive power output, the active power output and the leading-phase reactive power output reach point 322 where the operating power factor reaches minimum power factor 302. When the operating power factor reaches point 322 where the operating power factor reaches minimum power factor 302 and the interconnection point voltage exceeds the upper limit value of the appropriate voltage range, PCS 100 waits for the output suppression operation time limit while maintaining the output of active power and leading-phase reactive power.

[0064] Thereafter, if the operating power factor falls below the minimum power factor 302 and the interconnection point voltage exceeds the upper limit of the voltage appropriate range even after the output suppression operation time limit has elapsed, the PCS 100 starts output suppression. As a result, the PCS 100 reduces both the active power output and the reactive power output while maintaining the operating power factor at the minimum power factor 302 as shown in vector 313. Then, at point 323, the interconnection point voltage falls below the upper limit of the voltage appropriate range. Therefore, the PCS 100 stops increasing the suppression amount of output suppression to maintain the active power output and reactive power output at point 323.

[0065] On the other hand, when the interconnection point voltage falls below the lower limit of the appropriate voltage range, the PCS 100 starts outputting lagging reactive power. If the interconnection point voltage continues to exceed the upper limit of the appropriate voltage range, the PCS 100 gradually increases the lagging reactive power output as shown by vector 314.

[0066] Also, although not shown in FIG. 3, if the output exceeds the rated capacity represented by curve 301, PCS 100 reduces the active power output and corrects the active power output so that the output falls within the rated capacity.

[0067] Here, by increasing the lagging reactive power output, the active power output and the leading reactive power output reach point 322 where the operating power factor reaches minimum power factor 302. When the operating power factor reaches point 324 where the operating power factor reaches minimum power factor 303, PCS 100 stops issuing instructions to increase the lagging reactive power output and maintains the outputs of active power and leading reactive power.

[0068] Next, the flow of automatic voltage regulation control by the PCS 100 according to this embodiment will be described with reference to Fig. 4. Fig. 4 is a flowchart of automatic voltage regulation control by the PCS.

[0069] The active power / reactive power calculation circuit 103 and the active power / reactive power control unit 104 detect the interconnection point voltage of the interconnection point of the PCS 100 with the power distribution system (step S1). The active power / reactive power calculation circuit 103 calculates an active power output and a reactive power output from the detected interconnection point voltage. Then, the active power / reactive power calculation circuit 103 notifies the active power / reactive power control unit 104 and the active power adjustment unit 105 of the calculated active power output. In addition, the active power / reactive power calculation circuit 103 notifies the active power / reactive power control unit 104 and the reactive power adjustment unit 107 of the calculated reactive power output.

[0070] The active and reactive power control unit 104 determines whether or not the interconnection point voltage exceeds the upper limit of the appropriate voltage range (step S2).

[0071] When the interconnection point voltage exceeds the upper limit of the voltage appropriate range (step S2: Yes), the active power / reactive power control unit 104 executes voltage rise suppression control (step S3). The active power target value providing unit 106 generates a target value of the active power output in response to an instruction from the active power / reactive power control unit 104, and outputs the target value to the active power adjustment unit 105. The active power adjustment unit 105 calculates the difference between the acquired target value of the active power output and the actual value of the active power output, and notifies the inverter control unit 102 of the active power output that corrects the calculated difference. In addition, the reactive power target value providing unit 108 generates a target value of the reactive power that increases the leading-phase reactive power output in response to an instruction from the active power / reactive power control unit 104, and outputs the target value to the reactive power adjustment unit 107. The reactive power adjustment unit 107 calculates the difference between the acquired target value of the reactive power output and the actual value of the reactive power output, and notifies the inverter control unit 102 of the reactive power output that corrects the calculated difference. The inverter control unit 102 receives a notification from the active power adjusting unit 105 and controls the inverter 101 to increase the active power output. Also, the inverter control unit 102 receives a notification from the reactive power adjusting unit 107 and controls the inverter 101 to increase the leading-phase reactive power output.

[0072] On the other hand, if the interconnection point voltage is equal to or lower than the upper limit value of the appropriate voltage range (step S2: No), the active and reactive power control unit 104 determines whether the interconnection point voltage has fallen below the lower limit value of the appropriate voltage range (step S4).

[0073] When the interconnection point voltage falls below the lower limit of the voltage appropriate range (step S4: Yes), the active power / reactive power control unit 104 executes voltage drop suppression control (step S5). The active power target value providing unit 106 generates a target value of the active power output in response to an instruction from the active power / reactive power control unit 104, and outputs the target value to the active power adjustment unit 105. The active power adjustment unit 105 calculates the difference between the acquired target value of the active power output and the actual value of the active power output, and notifies the inverter control unit 102 of the active power output that corrects the calculated difference. In addition, the reactive power target value providing unit 108 generates a target value of the reactive power that increases the lagging-phase reactive power output in response to an instruction from the active power / reactive power control unit 104, and outputs the target value to the reactive power adjustment unit 107. The reactive power adjustment unit 107 calculates the difference between the acquired target value of the reactive power output and the actual value of the reactive power output, and notifies the inverter control unit 102 of the reactive power output that corrects the calculated difference. The inverter control unit 102 receives a notification from the active power adjusting unit 105 and controls the inverter 101 to increase the active power output. Also, the inverter control unit 102 receives a notification from the reactive power adjusting unit 107 and controls the inverter 101 to increase the lagging reactive power output.

[0074] On the other hand, if the interconnection point voltage is equal to or higher than the lower limit of the appropriate voltage range (step S4: No), the active power and reactive power control unit 104 judges whether or not a voltage rise suppression control amount exists (step S6). The existence of a voltage rise suppression control amount means that leading-phase reactive power output or active power output suppression is being performed to suppress a voltage rise at the interconnection point voltage.

[0075] If a voltage rise suppression control amount exists (step S6: Yes), the active power and reactive power control unit 104 judges whether the interconnection point voltage is less than the upward pull-back voltage (step S7). If the interconnection point voltage is equal to or greater than the upward pull-back voltage (step S7: No), the active power and reactive power control unit 104 maintains the active power output and reactive power output at that time and ends the current automatic voltage adjustment control.

[0076] On the other hand, if the interconnection point voltage is less than the rising pullback voltage (step S7: Yes), the active power and reactive power control unit 104 performs a process of canceling the voltage rise suppression control (step S8). That is, the active power and reactive power control unit 104 decreases the active power output if it has been increased, and decreases the leading-phase reactive power output if it has been increased.

[0077] On the other hand, if there is no voltage rise suppression control amount (step S6: No), the active power and reactive power control unit 104 judges whether there is a voltage drop suppression control amount (step S9). The voltage drop suppression control amount exists when a lagging reactive power output or active power output suppression is being performed to suppress a voltage drop in the interconnection point voltage.

[0078] If a voltage drop suppression control amount exists (step S9: Yes), the active power and reactive power control unit 104 judges whether the interconnection point voltage is equal to or higher than the upward pullback voltage (step S10). If the interconnection point voltage is less than the downward pullback voltage (step S10: No), the active power and reactive power control unit 104 maintains the active power output and reactive power output at that time and ends the current automatic voltage adjustment control.

[0079] On the other hand, if the interconnection point voltage is less than the drop pullback voltage (step S10: Yes), the active power and reactive power control unit 104 performs a process of canceling the voltage drop suppression control (step S11). That is, the active power and reactive power control unit 104 decreases the active power output if it has been increased, and decreases the leading-phase reactive power output if it has been increased.

[0080] On the other hand, if there is no voltage drop suppression control amount (step S9: No), the active and reactive power control unit 104 causes constant power factor control to be performed (step S12).

[0081] 4 is a flowchart of one automatic voltage adjustment control process executed by the PCS 100. The PCS 100 repeats the automatic voltage adjustment control process shown in the flowchart of FIG.

[0082] Next, a flow of voltage drop suppression control by the PCS 100 according to the present embodiment will be described with reference to Fig. 5. Fig. 5 is a flowchart of the voltage drop suppression control by the PCS according to the first embodiment. Each process shown in the flowchart of Fig. 5 corresponds to an example of the process executed in step S5 in Fig. 4.

[0083] When the interconnection point voltage falls below the lower limit of the appropriate voltage range, the active power and reactive power control unit 104 calculates the operating power factor of the inverter 101. Then, the active power and reactive power control unit 104 determines whether the operating power factor of the inverter 101 is above 0.85, which is a predetermined minimum power factor (step S101). If the operating power factor is 0.85 or less (step S101: No), the active power and reactive power control unit 104 maintains the current active power output and lagging reactive power output, and ends the current voltage drop suppression control.

[0084] On the other hand, if the operating power factor exceeds 0.85 (step S101: Yes), the active power and reactive power control unit 104 instructs the reactive power target value providing unit 108 to increase the lagging reactive power output, thereby increasing the lagging reactive power output (step S102).

[0085] Next, the active and reactive power control unit 104 determines whether the output of the inverter 101 is within the rated capacity or not (step S103).

[0086] If the output of the inverter 101 exceeds the rated capacity (step S103: No), the active power / reactive power control unit 104 instructs the active power target value providing unit 106 to suppress the active power output (step S104).

[0087] On the other hand, if the output of the inverter 101 is within the rated capacity (step S103: Yes), the active power and reactive power control unit 104 maintains the current active power output and lagging reactive power output, and ends the current voltage drop suppression control.

[0088] As described above, the voltage control device according to the present embodiment suppresses the voltage by starting the output of leading-phase reactive power when the interconnection point voltage of the PCS exceeds the upper limit of the voltage appropriate range. Also, when the interconnection point voltage of the PCS exceeds the lower limit of the voltage appropriate range, the voltage control device immediately starts the output of lagging-phase reactive power to suppress the voltage drop. This makes it possible to suppress the voltage rise and voltage drop of the interconnection point voltage of the PCS. That is, in both cases of a voltage drop caused by the reverse power flow of a distributed power source such as a PV, and a power drop during a heavy load due to the spread of electric vehicles and storage batteries and the emergence of aggregators, the interconnection point voltage of the PCS can be kept within the appropriate range. Also, the voltage control device according to the present embodiment can avoid the promotion of a voltage drop due to the possibility of an increase in the apparent load during a heavy load by not suppressing the output of active power, and can more reliably suppress the power drop during a heavy load.

[0089] In the above description, the power supply source has been described by taking a PV as an example, but it may be any power source that supplies power to a power distribution system, such as a storage battery. EXAMPLES

[0090] Next, a second embodiment will be described. The PCS according to this embodiment is also shown in the block diagram of Fig. 2. The PCS according to this embodiment differs from the first embodiment in that it suppresses the lagging reactive current output and the active power output when the state in which the interconnection point voltage exceeds the lower limit value of the appropriate voltage range continues until the output suppression operation time limit is reached. In the following explanation, the explanation of the operation of each part similar to that of the first embodiment will be omitted.

[0091] When the interconnection point voltage does not exceed the upper limit value of the appropriate voltage range, the active power / reactive power control unit 104 determines whether the operating power factor of the inverter 101 exceeds a predetermined minimum power factor.

[0092] When the interconnection point voltage falls below the lower limit of the appropriate voltage range and the operating power factor exceeds the minimum power factor, the active and reactive power control unit 104 instructs the reactive power target value providing unit 108 to increase the lagging reactive power output.

[0093] Furthermore, the active power / reactive power control unit 104 determines whether the output of the inverter 101 exceeds the rated capacity while suppressing a decrease in the interconnection point voltage by increasing the lagging reactive power output. If the output of the inverter 101 exceeds the rated capacity, the active power / reactive power control unit 104 instructs the active power target value providing unit 106 to suppress the active power output.

[0094] On the other hand, when the operating power factor reaches the minimum power factor, the active power and reactive power control unit 104 starts its own timer at that timing. Then, the active power and reactive power control unit 104 uses the timer to measure the elapsed time from when the operating power factor reaches the minimum power factor to when the output suppression operation time limit has elapsed.

[0095] Until the output suppression operation time limit is reached, the active power and reactive power control unit 104 repeatedly determines whether the voltage is below the lower limit of the appropriate voltage range. If the voltage continues to be below the lower limit of the appropriate voltage range, the active power and reactive power control unit 104 determines whether the interconnection point voltage exceeds the lower limit of the appropriate voltage range and whether the output of the inverter 101 exceeds the rated capacity, and repeats adjustment of the leading-phase reactive power output and the active power output according to the determination results.

[0096] If the state in which the interconnection point voltage exceeds the lower limit of the appropriate voltage range continues until the output suppression operation time limit is reached, the active power and reactive power control unit 104 instructs the reactive power target value providing unit 108 to suppress the active power output. Also, the active power and reactive power control unit 104 instructs the reactive power target value providing unit 108 to suppress the lagging-phase reactive power output. As a result, the active power and reactive power control unit 104 suppresses the active power output and the lagging-phase reactive power output so that the operating power factor becomes equal to or greater than the minimum power factor.

[0097] On the other hand, if the interconnection point voltage becomes equal to or exceeds the lower limit of the voltage appropriate range before the output suppression operation time limit is reached, the active power and reactive power control unit 104 stops the instruction to increase the lagging reactive power output. Next, the active power and reactive power control unit 104 determines whether the interconnection point voltage has exceeded the pull-back voltage. If the interconnection point voltage is less than the pull-back voltage, the active power and reactive power control unit 104 determines to maintain the active power output and lagging reactive power output at that time.

[0098] On the other hand, when the interconnection point voltage falls to or above the reduced pullback voltage, the active power / reactive power control unit 104 executes voltage suppression recovery processing. Specifically, if active power output suppression is being performed, the active power / reactive power control unit 104 instructs the active power target value providing unit 106 to increase the active power output. Also, if lagging reactive power is being output, the active power / reactive power control unit 104 instructs the reactive power target value providing unit 108 to decrease the lagging reactive power output.

[0099] Next, referring to Fig. 3, changes in the active power output and the reactive power output when the voltage increase control function or the voltage decrease control function of the PCS100 according to this embodiment operates in the case of performing constant power factor 1 control will be described. Fig. 6 is a diagram showing an output plane of active power and reactive power during constant power factor 1 control according to the second embodiment. The horizontal axis of Fig. 6 represents active power output, and the vertical axis represents reactive power output. Curve 301 in Fig. 6 represents the rated capacity of the PCS100. In this case, the PCS100 executes constant power factor control with an operating power factor of 1.

[0100] During normal operation, the PCS 100 outputs active power indicated by vector 311. Furthermore, since the operating power factor is 1, the PCS 100 does not output reactive power. In this case, the PCS 100 outputs active power at output amount 321.

[0101] When the interconnection point voltage exceeds the upper limit value of the appropriate voltage range, the PCS 100 outputs leading-phase reactive power and executes voltage rise suppression control in the same manner as described with reference to FIG. 3 in the first embodiment.

[0102] On the other hand, when the interconnection point voltage falls below the lower limit of the appropriate voltage range, the PCS 100 starts outputting lagging reactive power. If the interconnection point voltage continues to exceed the upper limit of the appropriate voltage range, the PCS 100 gradually increases the lagging reactive power output as shown by vector 331.

[0103] Although not shown in FIG. 6, when the output exceeds the rated capacity, the PCS 100 reduces the active power output and corrects the active power output so that the output falls within the rated capacity.

[0104] Here, by increasing the lagging reactive power output, the active power output and the lagging reactive power output reach point 332 where the operating power factor reaches the minimum power factor of 0.85. When the operating power factor reaches point 332 where it falls below the minimum power factor and the interconnection point voltage exceeds the lower limit of the voltage appropriate range, the PCS 100 waits for the output suppression operation time limit while maintaining the outputs of active power and lagging reactive power.

[0105] Thereafter, if the operating power factor falls below the minimum power factor and the interconnection point voltage exceeds the lower limit of the voltage appropriate range even after the output suppression operation time limit has elapsed, the PCS100 starts output suppression. As a result, the PCS100 reduces both the active power output and the reactive power output while maintaining the operating power factor at the minimum power factor as shown in vector 333. Then, at point 334, the interconnection point voltage falls below the upper limit of the voltage appropriate range. Therefore, the PCS100 stops increasing the suppression amount of output suppression to maintain the active power output and reactive power output at point 334.

[0106] Next, a flow of the voltage drop suppression control by the PCS 100 according to the present embodiment will be described with reference to Fig. 7. Fig. 7 is a flowchart of the voltage drop suppression control by the PCS according to the second embodiment.

[0107] When the interconnection point voltage falls below the lower limit of the appropriate voltage range, the active power and reactive power control unit 104 calculates the operating power factor of the inverter 101. Then, the active power and reactive power control unit 104 determines whether the operating power factor of the inverter 101 is above 0.85, which is a predetermined minimum power factor (step S201).

[0108] If the operating power factor exceeds 0.85 (step S201: Yes), the active power and reactive power control unit 104 instructs the reactive power target value providing unit 108 to increase the lagging reactive power output, thereby increasing the lagging reactive power output (step S202).

[0109] Next, the active and reactive power control unit 104 determines whether the output of the inverter 101 is within the rated capacity or not (step S203).

[0110] If the output of the inverter 101 exceeds the rated capacity (step S203: No), the active power / reactive power control unit 104 instructs the active power target value providing unit 106 to suppress the active power output (step S204).

[0111] On the other hand, if the output of the inverter 101 is within the rated capacity (step S203: Yes), the active power and reactive power control unit 104 maintains the current active power output and lagging reactive power output, and ends the current voltage drop suppression control.

[0112] If the operating power factor is 0.85 or less (step S201: No), the active power and reactive power control unit 104 determines whether the standby time after the operating power factor became 0.85 or less exceeds the output suppression operation time limit (step S205).

[0113] If the output suppression operation time limit has not been reached (step S205: No), the active and reactive power control unit 104 maintains the current active power output and lagging reactive power output, and ends the current voltage drop suppression control.

[0114] On the other hand, if the standby time exceeds the output suppression operation time limit (step S205: Yes), the active power and reactive power control unit 104 instructs the reactive power target value providing unit 108 to suppress the active power output, and reduces the active power output (step S206).

[0115] Next, the active power and reactive power control unit 104 instructs the reactive power target value providing unit 108 to suppress the lagging reactive power output, thereby reducing the lagging reactive power output (step S207).

[0116] As described above, the power control device according to the present embodiment waits for the output suppression operation time limit to elapse when the output of the inverter exceeds the rated capacity while outputting leading-phase reactive power to suppress power reduction, thereby making it possible to suppress the output of the inverter to the rated capacity and to improve the safety of the power distribution system.

[0117] Here, a description will be given of the results of the operational verification of the automatic voltage regulation control by the PCS 100 of the first and second embodiments. Fig. 8 is a diagram showing a power distribution system model used in the operational verification of the automatic voltage regulation control. Fig. 9 is a diagram showing the PV output and load conditions used in the operational verification of the automatic voltage regulation control.

[0118] Here, a power distribution system model 400 was used for verification, assuming a rural area in which PV is centrally connected to the terminal and a load is connected, as shown in Fig. 8. In this case, the sending voltage from the substation was fixed.

[0119] In Fig. 9, the vertical axis represents the magnitude of the load or PV output, and the horizontal axis represents time. Graph 401 represents the PV output. In order to verify the control characteristics of Tei Jong-il's PCS100, which does not fluctuate, the PV output was set to a ramp fluctuation of 100 W per second, as shown in graph 401. Graph 402 represents the load conditions in the case of no load. Graph 403 represents the load conditions in the case of a heavy load, assuming charging of an electric vehicle or storage battery, and operation of a heat pump.

[0120] Furthermore, in addition to the above conditions, the upper limit value of the appropriate voltage range was set to 107 V and the lower limit value of the appropriate voltage range was set to 95 V, and the effects of the voltage rise suppression function and voltage drop suppression function of the PCS 100 in each embodiment were verified by simulation using the power distribution system model 400.

[0121] Fig. 10 is a diagram showing the verification results under a load condition when there is no load. The vertical axis of Fig. 10 represents the interconnection point voltage, and the horizontal axis represents the PV output. Graph 411 in Fig. 10 represents the interconnection point voltage. In this case, in both the configurations of Example 1 and Example 2, the PV output is represented by graph 412.

[0122] When the interconnection point voltage exceeds the appropriate voltage increase value at timing 413, output of leading-phase reactive power is started as shown in graph 412. This suppresses the increase in the interconnection point voltage as shown in graph 411. Thereafter, when the interconnection point voltage falls below the increase pullback threshold at timing 414, the output of leading-phase reactive power is reduced as shown in graph 412. Furthermore, when the interconnection point voltage falls below the appropriate voltage lower limit at timing 415, output of lagging-phase reactive power is started as shown in graph 412. This suppresses the decrease in the interconnection point voltage as shown in graph 411.

[0123] In this way, in either configuration of Example 1 or Example 2, when the interconnection point voltage exceeds the upper limit value of the appropriate voltage range, the leading-phase reactive power output is increased to suppress a voltage rise, and when the interconnection point voltage falls below the lower limit value of the appropriate voltage range, the lagging-phase reactive power output is increased to suppress a voltage drop, making it possible to maintain the distribution line voltage at an appropriate value.

[0124] Fig. 11 shows the verification results under heavy load conditions. The vertical axis of Fig. 11 indicates the interconnection point voltage on the left side of the page, and the active power output or reactive power output on the right side. The horizontal axis indicates the PV output.

[0125] Graph 421 represents the change in interconnection point voltage when automatic voltage regulation control is performed using the PCS100 having the configuration of the first embodiment. Graph 431 represents the change in interconnection point voltage when automatic voltage regulation control is performed using the PCS100 having the configuration of the second embodiment. Graph 422 represents the change in the suppression amount of active power output when automatic voltage regulation control is performed using the PCS100 having the configuration of the first embodiment. Graph 432 represents the change in the suppression amount of active power output when automatic voltage regulation control is performed using the PCS100 having the configuration of the second embodiment. Graph 423 represents the change in reactive power output when automatic voltage regulation control is performed using the PCS100 having the configuration of the first embodiment. Graph 433 represents the change in reactive power output when automatic voltage regulation control is performed using the PCS100 having the configuration of the second embodiment.

[0126] As shown in graph 432, the active power output is suppressed in the configuration of Example 2, but in the case of the configuration of Example 1, the active power output is not suppressed as shown in graph 422. In the configuration of Example 2, the apparent load is reduced by suppressing the active power, and as shown in graph 423, the increase in the lagging reactive power output is more gradual than that of the configuration of Example 1 (graph 433). Therefore, as shown in graph 431, the suppression of the voltage drop of the interconnection point voltage is also gradual. In contrast, as shown in graph 433, in the case of the configuration of Example 1, the apparent load does not decrease, so more lagging reactive power is output. As a result, in the configuration of Example 1, the voltage drop is more improved than that of the configuration of Example 2 as shown in graph 421. In this way, there are cases where the use of the PCS100 having the configuration of Example 1 can sufficiently suppress the voltage drop compared to the use of the PCS100 having the configuration of Example 2.

[0127] FIG. 12 is a diagram showing the voltage deviation amount and the output suppression amount in the operational verification of the automatic voltage regulation control. Graph 501 shows a voltage deviation index. In graph 501, the vertical axis shows the voltage deviation index, and the horizontal axis shows the verification conditions. The voltage deviation index is a converted value of the number of voltage deviations, with the case where automatic voltage regulation control is not performed being set to 1. Graph 502 shows an output suppression index. In graph 502, the vertical axis shows the output suppression index, and the horizontal axis shows the verification conditions. The output suppression index is the suppression amount of active power output under each condition, with the suppression amount of active power output in automatic voltage regulation control by PCS100 having the configuration of Example 2 being set to 1.

[0128] As shown in graph 501, the number of voltage deviations is reduced compared to when automatic voltage adjustment control is not performed in both the configuration of Example 1 and the configuration of Example 2. However, the PCS 100 having the configuration of Example 1 is better able to maintain the voltage of the power distribution line within an appropriate range than the PCS 100 having the configuration of Example 2.

[0129] Furthermore, as shown in graph 502, the PCS 100 having the configuration of the first embodiment can suppress the occurrence of power generation opportunity loss, compared to the PCS 100 having the configuration of the second embodiment.

[0130] In this way, in both the configurations of Example 1 and Example 2, the power control device can maintain the voltage of the distribution line at an appropriate value compared to the case where the automatic voltage adjustment control is not performed. However, in the case of the configuration of Example 2, even if a power drop occurs, the active power output may be suppressed, which may cause a loss of power generation opportunities and may result in insufficient suppression of the voltage drop due to a drop in the apparent load.

[0131] When performing constant lagging power factor control while reverse power flow is occurring, if the line impedance is, for example, 1+j1Ω, 1+j2Ω, and 1+j3Ω, the occurrence of voltage drops is sufficiently suppressed by the PCS 100 having the configuration of each embodiment 1. In other words, it can be said that the voltage drop caused by reverse power flow can be suppressed by performing lagging reactive power output without suppressing active power output.

[0132] In addition, when considering the power factor distribution of the PCS100 for making the sending voltage and the interconnection point voltage equal when a predetermined amount of reverse power flow is generated, it is desirable to suppress the active power output in the region where the power factor of the PCS100 is less than the minimum power factor while lagging reactive power is being output, but this region is very small and is the region immediately before voltage collapse occurs. The region where voltage collapse occurs means that it is difficult to interconnect a predetermined amount of reverse power with the target line impedance. Therefore, the region where the power factor of the PCS100 is less than the minimum power factor while lagging reactive power is being output can be ignored, and even the PCS100 having the configuration of the first embodiment, which does not suppress the active power output, can sufficiently optimize the voltage of the distribution line. [Explanation of symbols]

[0133] 1 Distribution substation 2 SVR 3 main line 4. Transformers 5 Consumer housing 10 Power distribution system model 51 PV 52 Residential load 100PCS 101 Inverter 102 Inverter control unit 103 Active power and reactive power calculation circuit 104 Active power and reactive power control section 105 Active power adjustment section 106 Active power target value provider 107 Reactive power adjustment section 108 Reactive power target value provider

Claims

1. a converter that receives DC power from the distributed power source, converts it into AC power, and supplies the AC power to a power distribution system; an output control unit that performs power factor constant control to adjust the power factor of the output of the converter to a predetermined value; a reactive power adjustment unit that increases a lagging reactive power output by the converter to raise a voltage at a connection point of the connection point to the power distribution system when the power factor is adjusted to the predetermined value by the output control unit and a voltage at the connection point of the connection point to the power distribution system exceeds a lower limit value; A voltage control device comprising:

2. 2. The voltage control device according to claim 1, further comprising an output control unit that reduces an output amount of active power and lagging reactive power output from the converter when the interconnection point voltage exceeds the lower limit value after a predetermined period of time has elapsed since the power factor of the converter output reaches a predetermined value while the lagging reactive power output from the converter is increased by the reactive power adjustment unit.

3. a reactive power adjusting unit that, when a voltage at a connection point of a connection point to the power distribution system exceeds an upper limit value, increases a leading-phase reactive power output by the converter to reduce the voltage at the connection point; The output control unit reduces the output amounts of active power and reactive power output from the converter when the interconnection point voltage exceeds the upper limit value after a predetermined period of time has elapsed since the power factor of the output of the converter reaches a predetermined value in a state in which the leading-phase reactive power output by the converter is increased by the reactive power adjustment unit.

3. The voltage control device according to claim 2 .

4. A converter receives DC power from a distributed power source, converts the DC power into AC power, and supplies the AC power to a power distribution system; performing constant power factor control for adjusting the power factor of the converter output to a predetermined value; Measure a voltage and a current at a connection point to a distribution system while adjusting the power factor to the predetermined value; When the interconnection point voltage exceeds a lower limit value, the lagging reactive power output by the converter is increased to raise the interconnection point voltage. A voltage control method comprising:

5. A converter receives DC power from a distributed power source, converts the DC power into AC power, and supplies the AC power to a power distribution system; performing constant power factor control for adjusting the power factor of the converter output to a predetermined value; Measure a voltage and a current at a connection point to a distribution system while adjusting the power factor to the predetermined value; When the interconnection point voltage exceeds a lower limit value, the lagging reactive power output by the converter is increased to raise the interconnection point voltage. A voltage control program that causes a computer to execute a process.

6. A power adjustment system having a distributed power source, a power distribution system, a voltage control device, and a voltage adjustment device disposed in the power distribution system, The voltage control device includes: a converter that receives DC power from the distributed power source, converts it into AC power, and supplies the AC power to a power distribution system; an output control unit that performs power factor constant control to adjust the power factor of the output of the converter to a predetermined value; a reactive power adjustment unit that increases a lagging reactive power output by the converter to raise a voltage at a connection point of the connection point to the power distribution system when the power factor is adjusted to the predetermined value by the output control unit and a voltage at the connection point of the connection point to the power distribution system exceeds a lower limit value; The voltage regulator starts operating after a predetermined waiting period has elapsed since the power factor reached a predetermined value, and increases the voltage of the power distribution system. A voltage control system comprising:

Images