Power supply system and method for controlling the power supply system

Abstract

A power supply system and a control method thereof are provided that prevent excessive voltage from being compensated for in voltage compensation control that compensates for the voltage of a load after a switch has been completely opened. [Solution] A power supply system that supplies power from a power system S to a load L when the power system is normal, and cuts off the power supply from the power system to the load when the power system is abnormal, and supplies power to the load from a DC power source. The power supply system includes a switch 2 provided on a power line P for supplying power from the power system to the load and opened when the power system is abnormal, a power converter 4 connected to the power line and converts DC power from the DC power source into AC power, and a power converter control unit 85 that controls the voltage output by the power converter when the power system is abnormal. The power converter control unit includes a voltage compensation control unit 852 that performs voltage compensation control, which is control that compensates for the load voltage based on the deviation between a target value and a measured value of the load voltage, after the switch has been opened when the power system is abnormal.

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] A conventional power supply system, as shown in Patent Document 1, for example, includes a circuit breaker provided on a power line for supplying power from a power system to a load, and a power converter connected to the load side of the circuit breaker and converting energy from an energy storage unit into AC power.

[0003] In this power supply system, when the power system is normal, the circuit breaker is closed, power is supplied from the power system to the load via the transformer, and the power converter is stopped. On the other hand, when the power system is abnormal, the circuit breaker is opened to cut off the power supply from the power system to the load. Since the load voltage drops when the circuit breaker is opened, after the circuit breaker is opened, the power converter converts the DC power from the energy storage unit into AC power and supplies the AC power to the load. In this way, the above power supply system performs voltage compensation control to compensate for the load voltage when the power system is abnormal.

[0004] Here, in the voltage compensation control, the power supply system compensates the load for a drop in the system voltage from the power converter based on the deviation between a measured system voltage, which is the voltage of the power system, and a target value of a load voltage, which is the voltage of the load.

[0005] However, conventional power supply systems perform voltage compensation control using the measured value of the system voltage, not the measured value of the load voltage, and therefore may compensate the load with an excessive voltage, which may result in an overcurrent flowing from the power converter or an increase in power consumption of the DC power supply. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 6677916 Summary of the Invention [Problem to be solved by the invention]

[0007] Therefore, the present invention has been made in consideration of the above problems, and its main objective is to prevent excessive voltage from being compensated for to the load in voltage compensation control that compensates for the voltage of the load after the switch has been completely opened. [Means for solving the problem]

[0008] That is, the power supply system of the present invention is a power supply system that supplies power from the power system to a load when the power system is normal, cuts off the power supply from the power system to the load when the power system is abnormal, and supplies power to the load from a DC power source, and is characterized in that it comprises: a switch that is provided on a power line for supplying power from the power system to the load and is opened when the power system is abnormal; a power converter that is connected to the power line and converts DC power from the DC power source into AC power; and a power converter control unit that controls the voltage output by the power converter when the power system is abnormal, and the power converter control unit comprises a voltage compensation control unit that performs voltage compensation control, which is control to compensate for the load voltage, by causing the power converter to output a compensation voltage calculated based on the deviation between a target value of a load voltage, which is the voltage of the load, and a measured value of the load voltage, after the switch has been opened when the power system is abnormal.

[0009] In such a power supply system, when performing voltage compensation control, the voltage compensation control unit causes the power converter to output a compensation voltage calculated based on the deviation between the target value of the load voltage and the measured value of the load voltage, so that excessive voltage is not compensated for to the load. As a result, it is possible to prevent an overcurrent from flowing from the power converter and to reduce the power consumption of the DC power supply more than with conventional voltage compensation control.

[0010] It is preferable that the power system further includes a power restoration determination unit which determines whether a system voltage, which is the voltage of the power system, has recovered when an abnormality occurs in the power system, and before the power restoration determination unit determines that the system voltage has recovered, the voltage compensation control unit sets the target value of the load voltage to a rated voltage, and after the power restoration determination unit determines that the system voltage has recovered, the switch is turned on and the voltage compensation control unit changes the target value of the load voltage to the measured value of the system voltage.

[0011] With this configuration, after the system voltage is restored, the measured system voltage is changed to the target load voltage, so that the load voltage and system voltage become equal. As a result, even if the system voltage fluctuates when the power is restored and the switch is turned on, the potential difference between the terminals of the switch is zero, so that it is possible to prevent a short circuit current from occurring between the power converter and the switch. In addition, before the system voltage recovers, the load voltage is feedback-controlled with the rated voltage set as the target value of the load voltage, so that the load voltage can be maintained at the rated voltage before the system voltage recovers. As a result, when the system voltage recovers to the rated voltage, both the system voltage and the load voltage are the rated voltage, so that it is possible to prevent a potential difference from occurring in the voltage between the terminals of the switch when the switch is turned on.

[0012] It is preferable that the voltage compensation control unit controls the power converter so that the target value of the load voltage becomes the lower limit value of an allowable range of the load voltage.

[0013] With this configuration, the power converter control unit controls the power converter so that the target value of the load voltage is the lower limit of the allowable range of the load voltage, thereby making it possible to reduce power consumption of the DC power supply during voltage compensation control and to achieve energy savings in the DC power supply. In particular, when the power converter is connected to a power line, for example, via an injection transformer or an interconnection reactor, the target value of the load voltage is set to the lower limit of the allowable range of the load voltage, so that only the necessary voltage can be compensated to the load regardless of the circuit conditions.

[0014] A specific embodiment of the lower limit of the permissible range of the load voltage is preferably 90% of the rated voltage of the load.

[0015] A control method for a power supply system that supplies power from a power system to a load when the power system is normal, cuts off the power supply from the power system to the load when the power system is abnormal, and supplies power to the load from a DC power source, the power supply system including a switch provided on a power line for supplying power from the power system to the load and opened when the power system is abnormal, and a power converter connected to the power line and converting DC power from the DC power supply into AC power, the control method for the power supply system including, after the switch has been opened when the power system is abnormal, performing voltage compensation control that compensates for the load voltage by causing the power converter to output a compensation voltage calculated based on the deviation between a target value of a load voltage, which is the voltage of the load, and a measured value of the load voltage.

[0016] With this configuration, it is possible to obtain the same effects as the power supply system described above. Effect of the Invention

[0017] According to the present invention configured in this manner, in voltage compensation control for compensating for the voltage of the load after the switch has been completely opened, it is possible to prevent excessive voltage from being compensated for in the load. [Brief description of the drawings]

[0018] [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 control device according to the present embodiment. [Diagram 3] FIG. 2 is a schematic diagram showing functional blocks of a power converter control unit in the present embodiment. [Figure 4] 13 shows a simulation result in this embodiment. [Diagram 5] 13 shows a simulation result in a conventional example. [Figure 6]13 shows a simulation result in this embodiment. [Figure 7] 13 shows a simulation result in a conventional example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] 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.

[0020] <Device configuration> The power supply system 100 in this embodiment is provided between an electric power system S and a load L, and when an abnormality occurs in the electric power system S, such as a short circuit accident in the electric power system S, the power supply from the electric power system S to the load L is cut off, and then the voltage of the load L is compensated for. Note that in this embodiment, the power supply system 100 is a three-phase circuit, but the number of phases is not particularly limited.

[0021] Specifically, as shown in FIG. 1 , the power supply system 100 includes a switch 2 that cuts off the power supply from a power system S to a load L, a DC power supply 3 that outputs DC power, a power converter 4 that converts the DC power of the DC power supply 3 into AC power and supplies it to a power line P, a system voltage measuring unit 5 that measures the system voltage that is the voltage of the power system S, a load voltage measuring unit 6 that measures the load voltage that is the voltage of the load L, a switch current measuring unit 7 that measures the switch current that is the current flowing through the switch 2, and a control device 8 that controls the switch 2 and the power converter 4.

[0022] The switch 2 is provided on a power line P for supplying power from a power system S to a load L, and opens and closes the power line P. Specifically, when the switch 2 is opened, the supply of AC power from the power system S to the load L is cut off, and when the switch 2 is closed, AC power is supplied from the power system S to the load L. Note that the switch 2 in this embodiment may be a semiconductor switch or a mechanical switch.

[0023] The DC power supply 3 is a battery such as a lead storage battery or a capacitor that stores DC power when the power system S is normal. When the power system S is abnormal, the DC power supply 3 discharges and outputs DC power.

[0024] The power converter 4 is connected in series to the power line P, and converts DC power from the DC power source 3 into AC power to supply the power to the load L. In this embodiment, as shown in Figs. 1 and 3, the AC power output from the power converter 4 is supplied to the power line P via an interconnection reactor and an injection transformer T. Note that although the power converter 4 is a single-phase inverter in this embodiment, it may be a three-phase inverter.

[0025] The system voltage measuring unit 5 is connected to the power lines P of each phase via a system transformer (not shown) and measures the system voltage. The measured system voltage measured by the system voltage measuring unit 5 is output to a parameter acquiring unit 81, which will be described later. In this embodiment, the system voltage measuring unit 5 measures the voltage on the power system S side rather than the switch 2 so that an opening command output unit 82, which will be described later, can detect an abnormality in the power system S early.

[0026] The load voltage measuring unit 6 is provided on the low-voltage side of the switch 2. The measured load voltage measured by the load voltage measuring unit 6 is output to a parameter acquiring unit 81, which will be described later.

[0027] The switch current measuring unit 7 is provided in the power line P of each phase and measures the switch current. The switch current measured by the switch current measuring unit 7 is output to a parameter acquiring unit 81, which will be described later.

[0028] 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 controls the switch 2 and the power converter 4 when an abnormality occurs in the power system S. Specifically, as shown in Fig. 2, the control device 8 includes a parameter acquisition unit 81 that acquires various parameters, an opening command output unit 82 that outputs an opening command to open the switch 2 when an abnormality in the power system S is detected, a power restoration determination unit 83 that determines whether the system voltage, which is the voltage of the power system S, has recovered, a switch control unit 84 that controls the opening and closing of the switch 2, and a power converter control unit 85 that controls the power converter 4.

[0029] The parameter acquiring unit 81 acquires various parameters measured by each measuring unit. In this embodiment, the parameter acquiring unit 81 acquires at least one of the measured system voltage measured by the system voltage measuring unit 5, the measured load voltage measured by the load voltage measuring unit 6, and the switch current measured by the switch current measuring unit 7. During voltage compensation of the load L, it is sufficient for the parameter acquiring unit 81 to acquire at least the measured load voltage.

[0030] The opening command output unit 82 judges whether an abnormality has occurred in the power system S based on the system voltage, and when it is judged that an abnormality has occurred in the power system S, it outputs an opening command to the switch control unit 84. Specifically, when the measured system voltage falls below a predetermined value, the opening command output unit 82 judges that an abnormality has occurred in the power system S, and outputs an opening command to the switch control unit 84. Note that the predetermined value referred to here is a voltage value for detecting a momentary sag.

[0031] When it is determined that the power system S has recovered from the abnormality, the power restoration determination unit 83 outputs an abnormality recovery signal indicating that the power system S has recovered from the abnormality to the switch control unit 84 and a voltage compensation control unit 852 described later. Specifically, when the system voltage becomes equal to or higher than a predetermined value (e.g., a rated voltage) over a plurality of cycles after the opening of the switch 2 is completed, the power restoration determination unit 83 determines that the power system S has recovered from the abnormality and outputs the abnormality recovery signal.

[0032] The switch control unit 84 uses a drive circuit (not shown) to control the opening and closing of the switch 2. Specifically, the switch control unit 84 receives an opening command and performs control to open the switch 2. Then, when the opening of the switch 2 is completed, the switch control unit 84 outputs an opening completion signal which is a signal indicating that the opening of the switch 2 is completed.

[0033] Furthermore, upon receiving the abnormality recovery signal, the switch control unit 84 performs control to close the switch 2. Then, when the closing of the switch 2 is completed, the switch control unit 84 outputs a closing completion signal indicating that the closing of the switch 2 is completed.

[0034] 3, 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 L from the power system S when an opening command is output, a voltage compensation control unit 852 that performs voltage compensation control, which is control to cause the power converter 4 to output a compensation voltage that is a voltage that compensates for the voltage of the load L that has dropped due to the current interruption control, after the opening of the switch 2 is completed, and a control switching unit 853 that switches between the current interruption control and the voltage compensation control. Note that the case where the opening of the switch 2 is completed here refers to the case where the switch control unit 84 outputs an opening completion signal.

[0035] The current cut-off control unit 851 performs feedback control of the current output from the power converter 4 in response to the output of the opening command so as to make the current flowing through the switch 2 zero. Specifically, the current cut-off control unit 851 subtracts the switch current acquired by the parameter acquisition unit 81 from a switch current command value for making the current flowing through the switch 2 zero. Then, the current cut-off control unit 851 multiplies the difference by a proportional gain Kp and causes the power converter 4 to output a voltage calculated by the multiplication.

[0036] The voltage compensation control unit 852 calculates a compensation voltage based on the difference between a voltage command value to be output by the power converter 4 in order to make the load voltage a predetermined voltage and the load voltage measured by the load voltage measurement unit 6, thereby performing feedback control of the voltage output by the power converter 4. Specifically, the voltage compensation control unit 852 performs dq / uvw conversion on the load voltage measured by the load voltage measurement unit 6, and calculates the deviation between the converted load voltage and the voltage command value. Then, the voltage compensation control unit 852 performs PI control and dq / uvw conversion on the calculated deviation to calculate the output voltage which is the voltage to be output by the power converter 4.

[0037] Here, voltage compensation control unit 852 sets the target value of the measured load voltage to the rated voltage from the start of voltage compensation control until power restoration determination unit 83 outputs an abnormality recovery signal. Therefore, voltage compensation control unit 852 feedback controls the voltage output by power converter 4 so that the measured load voltage becomes the rated voltage from the start of voltage compensation control until power restoration determination unit 83 outputs an abnormality recovery signal.

[0038] On the other hand, after the power restoration determination unit 83 outputs the abnormality recovery signal, the voltage compensation control unit 852 changes the target value of the load voltage from the rated voltage to the measured system voltage of the system voltage measurement unit 5. Therefore, after the power restoration determination unit 83 outputs the abnormality recovery signal, the voltage compensation control unit 852 feedback controls the voltage output by the power converter 4 so that the measured load voltage and the measured system voltage become equal.

[0039] The control switching unit 853 switches from the current cutoff control to the voltage compensation control after the current cutoff control is completed. After the current cutoff control is completed here means that the opening of the switch 2 in the current cutoff control is completed.

[0040] <Power supply system control operation> Next, the control operation of the power supply system 100 will be described.

[0041] (1) Power system S in normal operation The measured system voltage measured by the system voltage measuring unit 5 is output to the opening command output unit 82. The opening command output unit 82 compares the measured system voltage with a predetermined value.

[0042] When the power system S is normal, the switch 2 is turned on. Therefore, AC power is supplied from the power system S to the load L.

[0043] (2) When an abnormality occurs in power system S For example, when a voltage sag occurs and the system voltage falls below a predetermined value, the opening command output unit 82 determines that an abnormality has occurred in the power system S, and outputs an opening command to the switch control unit 84.

[0044] When the opening command is output, the switch control unit 84 performs control to open the switch 2 using the drive circuit. In addition, the current cut-off control unit 851 controls the current output from the power converter 4 so as to make the current flowing through the switch 2 zero.

[0045] Then, when the opening of the switch 2 is completed, the switch control unit 84 outputs a switch completion signal. When the switch completion signal is output, the control switching unit 853 switches from current cut-off control to voltage compensation control. As a result, the current cut-off control unit 851 completes the current cut-off control, and the voltage compensation control unit 852 calculates a compensation voltage and starts voltage compensation control.

[0046] Until the power restoration determination unit 83 determines that the abnormality in the power system S has been recovered from, the voltage compensation control unit 852 sets the target value of the measured load voltage to the rated voltage and feedback controls the power converter 4 so that the measured load voltage becomes the rated voltage.

[0047] When the power restoration determination unit 83 determines that the power system S has recovered from the abnormality, the power restoration determination unit 83 outputs an abnormality recovery signal. In response to the output of the abnormality recovery signal, the switch control unit 84 performs control to close the switch 2. In addition, the voltage compensation control unit 852 changes the target value of the measured load voltage from the rated voltage to the measured system voltage, and feedback controls the power converter 4 so that the measured load voltage and the measured system voltage become equal.

[0048] When the closing of the switch 2 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.

[0049] <Simulation results> Next, voltage and current waveforms in various power supply systems are shown by simulation. The accident condition in the following simulation is a three-phase short circuit accident with a momentary sag in which the voltage of the power system S drops by 100%.

[0050] 4 shows the results of a simulation in which the voltage compensation control unit 852 sets the target value of the load voltage to the rated voltage before it is determined that power has been restored and performs feedback control of the power converter 4, and changes the target value of the load voltage to the system voltage after it is determined that power has been restored and performs feedback control of the power converter 4. In addition to a three-phase short-circuit accident, this simulation also covers an event in which the system voltage drops by several percent after the power restoration determination unit 83 determines that power has been restored and starts controlling the closing of the switch 2.

[0051] When it is determined that power has been restored, the voltage compensation control unit 852 controls the power converter 4 so that the load voltage and the system voltage become equal, and therefore the power converter 4 does not apply a potential difference between the terminals of the switch 2. As a result, as shown in Fig. 4, when it is determined that power has been restored and the closing control of the switch 2 is started and the system voltage drops by several percent, no overcurrent flows from the power converter 4.

[0052] Fig. 5 shows the results of a simulation in which the drop in the system voltage is compensated for by the power converter 4 to the load L based on the deviation between the system voltage and the target value (rated voltage) of the load voltage, as in the conventional case. As in Fig. 4, this simulation also covers, in addition to a three-phase short circuit fault, an event in which the system voltage drops by several percent after the power restoration determination unit 83 determines that power has been restored and starts controlling the closing of the switch 2.

[0053] If the grid voltage drops by several percent after it is determined that power has been restored, the power converter 4 applies a potential difference between the terminals of the switch 2 based on the deviation between the grid voltage and the target value of the load voltage. As a result, an overcurrent flows from the power converter 4, as shown in FIG.

[0054] <Effects of this embodiment> According to the power supply system 100 of this embodiment, when performing voltage compensation control, the voltage compensation control unit 852 causes the power converter to output a compensation voltage calculated based on the deviation between the target value of the load voltage and the measured load voltage, so that excessive voltage is not compensated for to the load L. As a result, it is possible to prevent an overcurrent from flowing from the power converter 4 and to suppress the power consumption of the DC power supply 3 more than in conventional voltage compensation control.

[0055] According to the power supply system 100 of this embodiment, after the system voltage is restored, the measured system voltage is changed to the target value of the load voltage, so that the measured load voltage and the measured system voltage become equal. As a result, even if the system voltage fluctuates when the power restoration is determined and the switch 2 is turned on, the potential difference between the terminals of the switch 2 is zero, so that it is possible to suppress the occurrence of a short circuit current between the power converter 4 and the switch 2. In addition, before the system voltage recovers, the rated voltage is set as the target value of the load voltage and the power converter 4 is feedback-controlled, so that when the system voltage recovers to the rated voltage, both the system voltage and the load voltage become the rated voltage. As a result, it is possible to prevent a potential difference from occurring in the voltage between the terminals of the switch 2 when the switch is turned on.

[0056] <Other embodiments> The present invention is not limited to the above-described embodiment.

[0057] In the above embodiment, the voltage compensation control unit 852 sets the target value of the load voltage to the rated voltage before it is determined that power has been restored, and sets the target value of the load voltage to the system voltage after it is determined that power has been restored, but this is not limited to this. For example, the voltage compensation control unit 852 may perform voltage compensation control so that the target value of the load voltage becomes the lower limit of the allowable range of the load voltage. The allowable range of the load voltage here refers to, for example, 90% to 110% of the rated voltage of the load voltage, but is not limited to this. Moreover, the lower limit of the allowable range of the load voltage refers to, but is not limited to, 90% of the rated voltage.

[0058] FIG. 6 shows the results of a simulation in which the voltage compensation control section 852 feedback controls the power converter 4 so that the load voltage becomes 90% of the rated voltage, which is the lower limit of the allowable range of the load voltage.

[0059] 6, the voltage compensation control unit 852 performs voltage compensation control based on the load voltage, thereby controlling the load voltage to be 90% of the rated voltage. As a result, the voltage output by the power converter 4 becomes smaller than when the load voltage is controlled to be the rated voltage, so that the energy consumption of the DC power supply 3 can be reduced. As a result, the resource saving of the DC power supply 3 can be achieved.

[0060] 7 shows a simulation result of a case where the voltage compensation control unit 852 outputs, as in the past, the voltage drop caused by the impedance of an interconnection unit composed of an injection transformer T and an interconnection reactor R provided between the power converter 4 and the switch 2, and the system voltage drop, to the power converter 4. Here, the voltage drop caused by the impedance of the interconnection unit is a fixed value.

[0061] 7, by adding up the voltage drop caused by the impedance of the grid-connected unit and the drop in the system voltage, an excessive voltage is output from the power converter 4. As a result, even though the load voltage is within the allowable range (for example, 90% to 110% of the rated voltage), the load voltage becomes excessive, and the energy consumption of the DC power supply 3 increases.

[0062] In the above embodiment, the power supply system 100 is configured to include a system voltage measuring unit 5, a load voltage measuring unit 6, and a switch current measuring unit 7, but the system voltage measuring unit 5, the load voltage measuring unit 6, and the switch current measuring unit 7 may be provided separately from the power supply system 100.

[0063] 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]

[0064] 100 Power System 2 Switch 3...DC power supply 4. Power Converter 5. System voltage measurement section 6 Load voltage measurement section 7 Switch current measurement section 8. Control device 81 Parameter acquisition section 82...Open command output section 83...Power restoration determination unit 84 Switch control section 85 Power converter control section 851 Current interruption control unit 852 Voltage compensation control section 853 Control switching unit S...Power system L...Load P...Power line

Claims

1. A power supply system that supplies power from a power system to a load when the power system is normal, and cuts off power supply from the power system to the load when an abnormality occurs in the power system, and supplies power from a DC power supply to the load, a switch that is provided on a power line for supplying power from the power system to the load and that is opened when an abnormality occurs in the power system; a power converter connected to the power line and converting DC power from the DC power supply into AC power; a power converter control unit that controls a voltage output by the power converter when an abnormality occurs in the power grid; a power recovery determination unit that determines whether a system voltage, which is a voltage of the power system, has recovered when an abnormality occurs in the power system; The power converter control unit a voltage compensation control unit that performs voltage compensation control, which is control to compensate for the load voltage, by causing the power converter to output a compensation voltage calculated based on a deviation between a target value of a load voltage, which is a voltage of the load, and a measured value of the load voltage, after the switch has been opened when an abnormality occurs in the power system; before the power restoration determination unit determines that the grid voltage has been restored, the voltage compensation control unit sets the target value of the load voltage to a rated voltage, and after the power restoration determination unit determines that the grid voltage has been restored, the switch is turned on and the voltage compensation control unit changes the target value of the load voltage to the measured value of the grid voltage.

2. 2 . The power supply system according to claim 1 , wherein the voltage compensation control unit performs the voltage compensation control so that the target value of the load voltage becomes a lower limit value of an allowable range of the load voltage.

3. 3. The power supply system according to claim 2, wherein a lower limit of the allowable range of the load voltage is 90% of a rated voltage.

4. A control method for a power supply system, which supplies power from a power system to a load when the power system is normal, and cuts off power supply from the power system to the load when an abnormality occurs in the power system, and supplies power from a DC power supply to the load, comprising: The power supply system includes: a switch that is provided on a power line for supplying power from the power system to the load and that is opened when an abnormality occurs in the power system; a power converter connected to the power line to convert DC power from the DC power supply into AC power; The method for controlling a power supply system includes: When an abnormality occurs in the power grid, it is determined whether a system voltage, which is a voltage of the power grid, has recovered; a voltage compensation control for compensating for the load voltage by causing the power converter to output a compensation voltage calculated based on a deviation between a target value of a load voltage, which is a voltage of the load, and a measured value of the load voltage after the switch has been opened when an abnormality occurs in the power system; a control method for a power supply system, in which, in the voltage compensation control, before it is determined that the system voltage has recovered, the target value of the load voltage is set to a rated voltage, and after it is determined that the system voltage has recovered, the switch is turned on and the target value of the load voltage is changed to the measured value of the system voltage.

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