Power supply system and control method for power supply system

Abstract

To interrupt a load from a power system at high speed and suppress overcurrent of a power converter, without changing a hardware side of equipment constituting a power supply system.SOLUTION: A power supply system includes: a switch 3 that is provided on a power line P for supplying power from a power system 10 to a load 20 and opens / closes the power line; a switch control unit for controlling the opening / closing of the switch; a current value acquisition unit for acquiring a current value that is a current value flowing through the switch; a power converter 7 that converts DC power of a power storage unit to AC power and supplies the power to the power line; an opening command output unit for outputting, to the switch control unit, an opening command to open the switch if an abnormality of the power system is detected; and a power converter control unit that controls voltage of the power converter such that the absolute value of voltage output by the power converter increases in response to the output of the opening command and that controls voltage of the power converter such that, when the acquired current value reaches a predetermined threshold, the absolute value of voltage output by the power converter decreases.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a power supply system and a method for controlling a power supply system. [Background technology]

[0002] 2. Description of the Related Art Conventionally, there is a power supply system that, when an abnormality occurs in the power system, cuts off the power supply from the power system to a load by opening a circuit breaker provided in a power line for supplying power from the power system to the load.

[0003] As shown in Patent Document 1, for example, this type of power supply system further includes a commutation circuit connected in parallel with the circuit breaker. When an abnormality in the power system is detected, this type of power supply system controls the circuit breaker to open, and also closes the commutation circuit to superimpose a harmonic current on the fault current flowing from the commutation circuit to the circuit breaker, thereby forming a zero current point of the fault current. As a result, the current flowing in the circuit breaker becomes zero, completing the opening of the circuit breaker and disconnecting the load from the power system. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2003-264932 A Summary of the Invention [Problem to be solved by the invention]

[0005] Here, in the above power supply system, the shorter the time from when control to open the circuit breaker is started to when the circuit breaker is completely opened, the shorter the time for the load voltage to drop, and therefore the smaller the impact on the load caused by the circuit breaker opening. Therefore, it is desirable for the above power supply system to converge the current flowing through the circuit breaker to zero almost at the same time as starting control to open the circuit breaker.

[0006] However, since the above power supply system only passes harmonic current from the commutation circuit to the circuit breaker, it may not be possible to converge the current flowing through the circuit breaker to zero almost immediately after starting control to open the circuit breaker. As a result, there is a risk that the impact on the load caused by the opening of the circuit breaker, such as an increase in voltage drop at the load, will become greater.

[0007] Therefore, it is conceivable to control the voltage of the power converter by fixing the voltage output by the power converter to an upper or lower limit value at approximately the same time as starting the control to open the circuit breaker. In this case, an oscillating current that is a current proportional to the voltage output by the power converter is superimposed on the current flowing from the power converter, and the rated current of the power converter is exceeded by the amount of the superimposed oscillating current. As a result, an overcurrent flows from the power converter, and the power converter may trip. Furthermore, in order to prevent an overcurrent from flowing from the power converter, the hardware aspects of the power converter must be modified, such as by increasing the rated current of the power converter, which increases costs.

[0008] In order to reduce the superimposed oscillating current, it is possible to change the upper or lower limit of the voltage output by the power converter to a smaller value, so that when an abnormality occurs in the power system, the voltage of the power converter is controlled to the changed upper and lower limit values. However, in this case, the voltage output by the power converter becomes smaller, so that the current flowing through the circuit breaker does not converge to 0 by the time the load voltage drops when the circuit breaker is opened and the load voltage should be compensated, and there is a risk that the disconnection from the power system to the load will fail.

[0009] Therefore, the present invention has been made in consideration of the above problems, and has as its main object to quickly disconnect a load from a power system and suppress overcurrents in power converters without modifying the hardware of the equipment that constitutes the power supply system. [Means for solving the problem]

[0010] That is, the power supply system of the present invention is a power supply system provided between a power system and a load and supplies power to the load, the power system comprising: a switch provided on a power line for supplying power from the power system to the load, which opens and closes the power line; a switch control unit which controls the opening and closing of the switch; a current value acquisition unit which acquires a current value flowing through the switch; a power converter connected to the power line and which converts DC power of a power storage unit into AC power and supplies the AC power to the power line; an opening command output unit which, when an abnormality in the power system is detected, outputs an opening command to the switch control unit to open the switch; and a power converter control unit which, in response to the output of the opening command, controls the voltage of the power converter so that the absolute value of the voltage output by the power converter becomes large, and, when the acquired current value reaches a predetermined threshold value, controls the voltage of the power converter so that the absolute value of the voltage output by the power converter becomes small.

[0011] In such a power supply system, the absolute value of the voltage output by the power converter becomes large at the timing when an opening command is output, so the current flowing through the switch can be quickly reduced to zero, and the load can be quickly disconnected from the power system. When the current value reaches a predetermined threshold value, the absolute value of the voltage output by the power converter becomes small, so overcurrent in the power converter can be suppressed. Therefore, without changing the hardware aspects of the devices that make up the power supply system, it is possible to quickly disconnect the load from the power system and suppress overcurrent in the power converter simply by changing the control of the power converter.

[0012] A specific aspect of the power converter control unit includes a limiter that limits the voltage output by the power converter within a predetermined range, and the power converter control unit controls the voltage of the power converter so that the voltage output by the power converter becomes the upper limit value or the lower limit value upon output of the open command, and reduces the absolute value of the upper limit value or the lower limit value after the acquired current value becomes a predetermined threshold value.

[0013] It is preferable that, when the measured current value is zero, the power converter control unit sets the voltage output by the power converter to zero.

[0014] With this configuration, when the measured current value is zero, the voltage output by the power converter is zero, so the current flowing through the switch is maintained at zero, making it possible to open the switch more reliably.

[0015] Here, since a switch that cannot self-extinguish cannot arbitrarily set the open and closed states of the switch, it is necessary to quickly converge the current flowing through the switch to 0 when a system abnormality occurs. Therefore, it is preferable that the switch cannot self-extinguish, and specifically, the switch is preferably a thyristor switch or a mechanical switch.

[0016] The switch is preferably a mechanical switch having a contact opening time of less than one quarter cycle.

[0017] With this configuration, the contact opening time of the mechanical switch is less than one-quarter of a cycle, which enables uninterrupted switching, thereby reducing the impact on the load of a voltage drop at the load when an abnormality occurs in the power grid.

[0018] A control method for a power supply system including a switch provided on a power line for supplying power from a power system to a load, the switch opening and closing the power line, and a power converter connected to the power line and converting DC power from a power storage unit into AC power to supply the power line, the control method comprising the steps of: acquiring a current value flowing through the switch; when an abnormality in the power system is detected, outputting an opening command to the switch control unit to open the switch; controlling the voltage of the power converter so that the absolute value of the voltage output by the power converter becomes larger in response to the output of the opening command; and controlling the voltage of the power converter so that the absolute value of the voltage output by the power converter becomes smaller when the acquired current value reaches a predetermined threshold value.

[0019] With this configuration, it is possible to obtain the same effects as the power supply system described above. Effect of the Invention

[0020] According to the present invention configured in this manner, it is possible to quickly disconnect the load from the power system and suppress overcurrent in the power converter without making any changes to the hardware of the devices that make up the power supply system. [Brief description of the drawings]

[0021] [Figure 1] 1 is a schematic diagram showing a configuration of a power supply system according to an embodiment of the present invention; [Diagram 2] FIG. 2 is a diagram showing functional blocks of a power converter control unit in the present embodiment. [Diagram 3] FIG. 2 is a schematic diagram showing a control block in the embodiment. [Figure 4] 3 is a schematic diagram of a voltage output by the power converter in the embodiment. FIG. [Diagram 5] 4 is a simulation result showing current cutoff control and voltage compensation control in the embodiment. [Figure 6] 13 is a simulation result showing current interruption control and voltage compensation control in a comparative example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] An embodiment of a power supply system according to the present invention will be described below with reference to the drawings. Note that in any of the drawings shown below, some parts may be omitted or exaggerated and illustrated in a schematic manner for ease of understanding. Identical components are given the same reference numerals and descriptions thereof will be omitted as appropriate.

[0023] <Device configuration> The power supply system 100 in this embodiment is provided between the power system 10 and the load 20, and when an abnormality occurs in the power system 10 due to a short circuit or the like in the power system 10, the power supply from the power system 10 to the load 20 is cut off, and then the voltage of the load 20 is compensated for. Note that although the power supply system 100 in this embodiment is a three-phase circuit, it may be a single-phase circuit, and the number of phases is not limited.

[0024] Specifically, as shown in FIG. 1 , power supply system 100 is provided on power line P for supplying power from power system 10 to load 20, and includes a switch 3 that opens and closes power line P, a voltage measurement unit 4 that measures the voltage of power system 10, a switch current measurement unit 5 that measures a current value that is the value of the current flowing through switch 3, a power converter 7 connected to power line P and converts DC power of a power storage unit 6 into AC power and supplies it to power line P, and a control device 8 that controls switch 3 and power converter 7.

[0025] The switch 3 is a switch that does not have a self-extinguishing capability, and is a thyristor switch in this embodiment. In this embodiment, the opening time of the switch 3, which is the time from when the control device 8 starts control to open the switch 3 to when the opening of the switch 3 is completed, is configured to be longer than the opening time of a switch that has a self-extinguishing capability, for example, a semiconductor switch.

[0026] Voltage measurement unit 4 is connected to power line P via system transformer 41, and measures the voltage of power system 10. The voltage measured by voltage measurement unit 4 is output to control device 8. Specifically, voltage measurement unit 4 measures the voltage on the power system 10 side rather than switch 3 so that control device 8 can detect an abnormality in power system 10 early.

[0027] The switch current measuring unit 5 is provided on the power line P and measures a current value. The current value measured by the switch current measuring unit 5 is output to the control device 8. In this embodiment, the current value measured by the switch current measuring unit 5 is defined as positive when the current flowing through the switch 3 flows from the power system 10 toward the load 20.

[0028] The power storage unit 6 is, for example, a power storage device such as a secondary battery (storage battery). The power storage unit 6 stores DC power, and when an abnormality in the power system 10 is detected, the DC power stored in the power storage unit 6 is supplied to the power converter 7.

[0029] The power converter 7 is connected to the power line P via the injection transformer T, and converts the DC power of the power storage unit 6 into AC power and supplies the AC power to the power line P. Specifically, the power converter 7 is provided in a parallel circuit connected in parallel with the switch 3.

[0030] The control device 8 is a dedicated or general-purpose computer equipped with a CPU, an internal memory, an input / output interface, an A / D converter, etc., and detects a voltage abnormality in the power system 10 using the voltage measured by the voltage measurement unit 4, and controls the switch 3 and the power converter 7. Specifically, the control device 8 includes an opening command output unit 81 that outputs an opening command to open the switch 3 when an abnormality in the power system 10 is detected, a closing command output unit 82 that outputs a closing command to close the switch 3 when the abnormality in the power system 10 is recovered from, a parameter acquisition unit 83 that acquires a current value measured by the switch current measurement unit 5, a switch control unit 84 that controls the opening and closing of the switch 3 based on the opening command or the closing command, and a power converter control unit 85 that controls the power converter 7.

[0031] The open command output unit 81 determines whether or not an abnormality has occurred in the power system 10 based on the voltage measured by the voltage measurement unit 4, and when it is determined that an abnormality has occurred in the power system 10, it outputs an open command to the switch control unit 84. Specifically, when the voltage measured by the voltage measurement unit 4 falls below a predetermined value, the open command output unit 81 determines that an abnormality has occurred in the power system 10, and outputs an open command to the switch control unit 84. Note that the predetermined value referred to here is a voltage value for detecting a momentary sag.

[0032] The closing command output unit 82 judges whether the abnormality in the power system 10 has been restored based on the voltage measured by the voltage measurement unit 4, and when it is judged that the abnormality in the power system 10 has been restored, outputs a closing command to the switch control unit 84. Specifically, when the voltage measured by the voltage measurement unit 4 becomes equal to or higher than a predetermined value over multiple cycles after the opening command is output, the opening command output unit 81 judges that the abnormality in the power system 10 has been restored, and outputs a closing command to the switch control unit 84.

[0033] The parameter acquiring unit 83 acquires various parameters measured in the power supply system 100. In this embodiment, the parameter acquiring unit 83 performs a function as a current value acquiring unit that acquires a current value measured by the switch current measuring unit 5, and a function as a voltage value acquiring unit that acquires a voltage value of the system voltage measured by the voltage measuring unit 4, but it is sufficient that the parameter acquiring unit 83 has at least the function as a current value acquiring unit during current interruption control.

[0034] The switch control unit 84 uses a drive circuit (not shown) to control the opening and closing of the switch 3. Specifically, the switch control unit 84 starts control to open the switch 3 upon receiving an opening command, and when the current flowing through the switch 3 becomes zero, the switch control unit 84 drives the drive circuit to open the switch 3. Then, when the opening of the switch 3 is completed, the switch control unit 84 outputs an opening completion signal which is a signal indicating that the opening of the switch 3 is completed.

[0035] Furthermore, upon receiving a closing command, the switch control unit 84 performs control to close the switch 3. Then, when the closing of the switch 3 is completed, the switch control unit 84 outputs a closing completion signal indicating that the closing of the switch 3 is completed.

[0036] The power converter control unit 85 has a current interruption control unit 851 that performs current interruption control, which is control to interrupt the load 20 from the power system 10, based on the current value acquired by the parameter acquisition unit 83 when an opening command is output, and a voltage compensation control unit 852 that performs voltage compensation control, which is control to compensate for the voltage of the load 20 after the current interruption control by the current interruption control unit 851 is completed. The case where the current interruption control is completed here refers to the case where the switch control unit 84 outputs an opening completion signal.

[0037] The current interruption control unit 851 controls the voltage of the power converter 7 so that the absolute value of the voltage output by the power converter 7 increases when an opening command is output, and controls the voltage of the power converter 7 so that the absolute value of the voltage output by the power converter 7 decreases when the acquired current value reaches a predetermined threshold value.

[0038] 3, the current cutoff control unit 851 includes a first limiter 851a and a second limiter 851b that limit the voltage output by the power converter 7 to a predetermined range. When the current value is a positive value, the current cutoff control unit 851 controls the voltage of the power converter 7 using the lower limit value of the first limiter 851a or the lower limit value of the second limiter 851b, and when the current value is a negative value, the current cutoff control unit 851 controls the voltage of the power converter 7 using the upper limit value of the first limiter 851a or the upper limit value of the second limiter 851b. That is, the voltage output by the power converter 7 is either the upper limit value and lower limit value of the first limiter 851a or the upper limit value and lower limit value of the second limiter 851b.

[0039] When an opening command is output, the current interruption control unit 851 uses the upper limit and lower limit values ​​of the first limiter 851a to control the voltage of the power converter 7. The absolute values ​​of the upper limit and lower limit values ​​of the first limiter 851a are expressed by the following Equation 1. In this embodiment, the absolute values ​​of the upper limit and lower limit values ​​of the first limiter 851a are equal, but may be different values.

[0040]

number

[0041] Then, as shown in FIG. 4, when the acquired current value reaches a predetermined threshold value, the current cutoff control unit 851 controls the voltage of the power converter 7 using the upper limit value and the lower limit value of the second limiter 851b. The absolute values ​​of the upper limit value and the lower limit value of the second limiter 851b are smaller than the absolute values ​​of the upper limit value and the lower limit value of the first limiter 851a. In this embodiment, the predetermined threshold value of the current value is the current value at which the power converter 7 trips. Specifically, it is the current value at which an oscillating current proportional to the voltage output by the power converter 7 is superimposed on the current output by the power converter 7 and exceeds the rated current of the power converter 7, causing an overcurrent in the power converter 7 and causing the power converter 7 to trip.

[0042] Furthermore, when the acquired current value becomes zero, the current cutoff control unit 851 sets the voltage output by the power converter 7 to zero.

[0043] In this embodiment, before outputting the upper limit value or the lower limit value, the current cutoff control unit 851 calculates a proportional gain Kp based on the difference between the acquired current value and a command value for making the current flowing through the switch 3 zero. The proportional gain Kp is set to a value that is sufficiently larger than the value obtained by dividing the square of the rated voltage by the rated capacity of the power converter 7. Calculation of the proportional gain Kp is not an essential configuration.

[0044] The voltage compensation control unit 852 controls the voltage of the power converter 7 based on a voltage command value that is a command value for a voltage to be output by the power converter 7, in order to compensate for the voltage of the load 20 so that the voltage of the load 20 becomes equal to, for example, a rated voltage. Specifically, as shown in Fig. 3, the voltage compensation control unit 852 compensates for the voltage of the load 20 based on the difference between the voltage measured by the voltage measurement unit 4 and the voltage command value.

[0045] <Power supply system control operation> Next, the control operation of the power supply system 100 will be described.

[0046] (1) Power grid 10 in normal operation The voltage measurement unit 4 measures the voltage of the power system 10, and outputs the measured voltage to the opening command output unit 81. The opening command output unit 81 compares the voltage of the power system 10 measured by the voltage measurement unit 4 with a predetermined value.

[0047] When the power system 10 is normal, the voltage measured by the voltage measuring unit 4 is equal to or higher than a predetermined value, and the switch 3 is closed. Therefore, AC power is supplied from the power system 10 to the load 20.

[0048] (2) Abnormality in power grid 10 If the voltage measured by the voltage measuring unit 4 is less than a predetermined value, the opening command output unit 81 determines that an abnormality has occurred in the power system 10, and outputs an opening command to the switch control unit .

[0049] When the opening command is output, the switch control unit 84 performs control to open the switch 3 using the drive circuit.

[0050] In addition, when an open command is output, the current cut-off control unit 851 controls the voltage output by the power converter 7 so that the voltage output by the power converter 7 becomes the upper limit value or the lower limit value of the first limiter 851a depending on whether the current value of the switch 3 is positive or negative.

[0051] Then, when the current value of switch 3 becomes a predetermined threshold value, the current cut-off control unit 851 controls the voltage output by the power converter 7 so that the voltage output by the power converter 7 becomes the upper limit value or the lower limit value of the second limiter 851b, depending on whether the current value of switch 3 is positive or negative.

[0052] Then, when the current value becomes 0, the current cutoff control unit 851 sets the voltage output by the power converter 7 to 0. As a result, the state in which the current flowing through the switch 3 is kept at 0, and the switch control unit 84 uses the drive circuit to open the switch 3. When the opening of the switch 3 is completed, the switch control unit 84 outputs a switch completion signal.

[0053] When the switch completion signal is output, the current cutoff control section 851 completes the current cutoff control, and the voltage compensation control section 852 starts the voltage compensation control.

[0054] When the voltage of the load 20 is compensated by the voltage compensation control by the voltage compensation control unit 852 and the closing command output unit 82 determines that the abnormality in the power system 10 has been restored, the closing command output unit 82 outputs a closing command. In response to the output of the closing command, the switch control unit 84 closes the switch 3.

[0055] When the closing of the switch 3 is completed, the switch control unit 84 outputs a closing completion signal. In response to the output of the closing completion signal, the voltage compensation control unit 852 completes the voltage compensation control.

[0056] <Simulation results> Next, the change over time in the value of the current flowing through the switch 3 in various power supply systems will be shown by simulation.

[0057] 5 shows a simulation result showing the time change of the current output from the power converter 7 when the voltage of the power converter 7 is controlled so that the absolute value of the voltage output from the power converter 7 increases when an opening command is output, and when the current value reaches a predetermined threshold, the voltage of the power converter 7 is controlled so that the absolute value of the voltage output from the power converter 7 decreases. As can be seen from FIG. 5, it was confirmed that the load 20 can be quickly disconnected from the power system 10 and the overcurrent of the power converter 7 can be suppressed.

[0058] In contrast, Fig. 6 shows the results of a simulation showing the time change in the current output from the power converter 7 in the case where the upper or lower limit value output by the power converter 7 when an opening command is output is equal to the upper or lower limit value output by the power converter 7 when the current value reaches a predetermined threshold value. As can be seen from Fig. 6, with this control, even when the current value reaches the predetermined threshold value, the absolute value of the voltage output by the power converter 7 is constant, so it was confirmed that there is a possibility of an overcurrent occurring in the power converter 7.

[0059] <Effects of this embodiment> According to the power supply system 100 of this embodiment, in response to an opening command, the voltage of the power converter 7 is controlled so that the absolute value of the current that is opposite in polarity to the current flowing through the switch 3 becomes maximum, so that the current value of the switch 3 can be made zero earlier than in the past. Therefore, since the current value of the switch 3 becomes zero almost simultaneously with the opening of the switch 3, the time from the completion of disconnection of the power system 10 and the load 20 to the voltage compensation of the load 20 can be shortened, and the effect on the load 20 can be reduced.

[0060] Moreover, since the upper limit value and the lower limit value are calculated using the opening time dt of the switch 3, which is a parameter determined according to the type of the switch 3, the current interruption control is completed according to the opening time of the switch 3. As a result, the load 20 can be reliably interrupted from the power system 10, and the voltage fluctuation to the load 20 can be reduced. In particular, since switch 3 does not have a self-extinguishing capability and has a slow opening time, the absolute values ​​of the upper limit value and the lower limit value calculated by equation 1 become small. Therefore, the voltage output by power converter 7 can be reduced, and the power supplied from power storage unit 6 can be reduced. As a result, the power consumption of power storage unit 6 due to opening of switch 3 can be suppressed, and power can be stably supplied from power storage unit 6 even when system abnormalities occur frequently.

[0061] Furthermore, since the voltage output by power converter 7 becomes 0 when the current value is 0, the state in which the current flowing through switch 3 is maintained at 0 can be maintained, and switch 3 can be opened more reliably. As a result, it is possible to transition to voltage compensation control after the current interruption control has been reliably completed.

[0062] <Other embodiments> The present invention is not limited to the above-described embodiment.

[0063] In this embodiment, the switch 3 is a thyristor switch, but the switch 3 is not limited to a thyristor switch as long as the switch does not have a self-extinguishing capability. For example, the switch 3 may be a mechanical switch such as a gas insulated switchgear (GIS) or a vacuum circuit breaker (VCB).

[0064] When the switch 3 is a mechanical switch, it may be configured so that the contact opening time is equal to or shorter than a quarter of a cycle. This makes it possible to suppress the effect on the load 20 of a voltage drop at the load 20 when an abnormality occurs in the power system 10, since the contact opening time of the switch 3 is equal to or shorter than a quarter of a cycle at which uninterrupted switching is possible.

[0065] In the above embodiment, the current cutoff control unit 851 has two limiters, but the limiters may have upper and lower limit values ​​with different absolute values, and the number of limiters is not particularly limited. For example, when the number of limiters is one, the limiter may be configured so that the upper and lower limit values ​​of the limiter are changed according to the acquired current value. Specifically, when an opening command is output, the current cutoff control unit 851 may increase the absolute values ​​of the upper and lower limit values ​​of the limiter to control the voltage of the power converter 7, and when the current value reaches a predetermined threshold value, may decrease the absolute values ​​of the upper and lower limit values ​​of the limiter to control the voltage of the power converter 7. Alternatively, when the number of limiters is three or more, the current cutoff control unit 851 may change to a limiter with different upper and lower limit values ​​according to the acquired current value to control the voltage of the power converter 7.

[0066] In the above embodiment, the absolute values ​​of the upper and lower limits of the first limiter 851a are calculated by Equation 1. However, the upper and lower limits are not limited to those calculated by Equation 1, as long as they are upper or lower limits that maximize the current in the opposite direction to the current flowing through the switch 3.

[0067] In the above embodiment, the power supply system 100 is configured to include the voltage measurement unit 4 and the switch current measurement unit 5. However, the voltage measurement unit 4 and the switch current measurement unit 5 may be provided separately from the power supply system 100.

[0068] Furthermore, the present invention is not limited to the above-described embodiment, and it goes without saying that various modifications are possible without departing from the spirit and scope of the present invention. [Explanation of symbols]

[0069] 100 Power System 10...Electric power system 20 Load 3. Switch 4. Voltage measurement section 5 Switch current measurement section 6. Storage unit 7 Power Converter 8. Control device 81...Open command output section 82 ... Closing command output section 83 Current value acquisition section 84 Switch control section 85 Power converter control section 851 Current interruption control unit 851a···First limiter 851b...Second limiter 852 Voltage compensation control section P...Power line

Claims

1. A power supply system provided between an electric power system and a load to supply electric power to the load, a switch provided on a power line for supplying power from the power system to the load, the switch opening and closing the power line; A switch control unit that controls opening and closing of the switch; a current value acquiring unit that acquires a current value that is a value of a current flowing through the switch; a power converter connected to the power line and configured to convert DC power from a power storage unit into AC power and supply the AC power to the power line; an opening command output unit that outputs an opening command to the switch control unit when an abnormality in the power system is detected; a power converter control unit that controls the voltage of the power converter so that the absolute value of the voltage output by the power converter becomes larger in response to the output of the open command, and controls the voltage of the power converter so that the absolute value of the voltage output by the power converter becomes smaller when the acquired current value reaches a predetermined threshold value.

2. the power converter control unit includes a limiter that limits a voltage output by the power converter to within a predetermined range; 2. The power supply system according to claim 1, wherein the power converter control unit controls a voltage of the power converter such that a voltage output by the power converter becomes the upper limit value or the lower limit value in response to output of the opening command, and reduces an absolute value of the upper limit value or the lower limit value after the acquired current value becomes a predetermined threshold value.

3. The power supply system according to claim 1 , wherein the power converter control unit sets a voltage output by the power converter to 0 when the current value is 0.

4. 4. The power supply system according to claim 1, wherein the switch is a mechanical switch having a contact opening time of less than or equal to a quarter cycle.

5. A control method for a power supply system including a switch provided on a power line for supplying power from a power system to a load, the switch opening and closing the power line, and a power converter connected to the power line, the power converter converting DC power of a power storage unit into AC power and supplying the AC power to the power line, the control method comprising the steps of: A current value flowing through the switch is acquired; When an abnormality in the power system is detected, an opening command to open the switch is output to the switch control unit; A control method comprising: controlling a voltage of the power converter so that an absolute value of the voltage output by the power converter increases in response to output of the open command; and controlling the voltage of the power converter so that an absolute value of the voltage output by the power converter decreases when the acquired current value reaches a predetermined threshold value.

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