Power supply system and control method for power supply system

Abstract

To shorten the time between a time point when the opening of a switch has completed and a time point when current flowing through the switch is converged to zero.SOLUTION: There is provided a power supply system in which a control block includes: a switch 3 that is provided on a power line P for supplying power from a power system to a load 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 flowing through the switch; a power converter 7 that is connected to the power line and that converts DC power of a power storage unit to AC power and supplies 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 for controlling the power converter based on the acquired current value when the opening command is output. If the current value is a positive value, the power converter control unit controls the voltage of the power converter by using a lower limit of voltage output by the power converter, while if the current value is a negative value, the power converter control unit controls the voltage of the power converter by using an upper limit of voltage output by the power converter.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 switch. When an abnormality in the power system is detected, this type of power supply system opens the switch and closes the commutation circuit to superimpose a harmonic current on the fault current flowing from the commutation circuit to the switch, forming a zero current point of the fault current. As a result, the current flowing through the switch becomes zero, and the load is disconnected 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] In the above power supply system, the shorter the time between when the switch is opened and when the current flowing through the switch becomes zero, the shorter the time for the load voltage to drop, and therefore the smaller the effect on the load caused by the switch opening.

[0006] However, because the above power supply system only passes harmonic current from the commutation circuit to the switch, the current flowing through the switch may converge to zero a certain time after the switch is opened. As a result, there is a risk that the impact on the load caused by the opening of the switch, such as an increase in the voltage drop of the load, may become greater.

[0007] Therefore, the present invention has been made in consideration of the above problems, and its main objective is to shorten the time between the point at which the switch is completely opened and the point at which the current flowing through the switch converges to zero. [Means for solving the problem]

[0008] That is, the power supply system according to the present invention is provided on a power line for supplying power from a power system to a load, and includes a switch for opening and closing the power line, a switch control unit for controlling the opening and closing of the switch, a current value acquisition unit for acquiring a value of a current flowing through the switch, a power converter connected to the power line and converting DC power of a power storage unit into AC power and supplying the AC power to the power line, an opening command output unit for outputting an opening command to the switch control unit to open the switch when an abnormality in the power system is detected, and a power converter control unit for controlling the power converter based on the acquired current value when the opening command is output, wherein, when the direction of the current flowing through the switch from the power system to the load is defined as positive, the power converter control unit controls the voltage of the power converter using a lower limit value of the voltage output by the power converter when the current value is a positive value, and controls the voltage of the power converter using an upper limit value of the voltage output by the power converter when the current value is a negative value.

[0009] In such a power supply system, in response to an opening command, the voltage of the power converter is controlled so that the absolute value of the current that is opposite in polarity to the current flowing through the switch is maximized, so the current flowing through the switch can be reduced to zero more quickly than before. Therefore, the time between the completion of the switch opening and the point in time when the current flowing through the switch becomes zero can be shortened, and the effect on the load caused by the opening of the switch can be reduced.

[0010] A specific aspect of the power converter control unit is one in which the power converter control unit is provided with a limiter that limits the voltage output by the power converter to within a predetermined range, and the upper limit value and the lower limit value are the upper limit value and the lower limit value within the predetermined range.

[0011] Depending on the type of switch, some switches have a fast contact opening time and some have a slow contact opening time, and even for the same type of switches, the contact opening time of each switch varies due to, for example, instrument error. In this case, if the power converter uniformly outputs a voltage between both ends of the switch regardless of the switch contact opening time, depending on the voltage output by the power converter, the current flowing through the switch may not be zero when the switch completes opening, and the load may not be completely disconnected from the power system. Therefore, it is desirable to calculate the absolute value of the voltage output by the power converter between both ends of the switch using the following equation 1.

[0012]

number

[0013] With this configuration, the power converter outputs a voltage across the switch so that the current flowing from the power converter becomes the rated current in the opposite direction to the current flowing through the power line during the switch opening time, so that the current flowing through the switch can be reduced to zero almost simultaneously with the point in time when the switch opening is completed. In particular, in the case of a switch that has a slow contact opening time, the voltage output by the power converter can be reduced by the above formula, and the power supplied from the power storage unit can be reduced. As a result, the power consumption of the power storage unit due to the opening of the switch can be reduced, so that even if grid abnormalities occur frequently, power can be stably supplied from the power storage unit.

[0014] 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.

[0015] 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, ensuring that the power system and the load are shut off.

[0016] Here, a switch that cannot self-extinguish has a smaller current loss than a switch that can self-extinguish, but since it cannot cut off the current until the current becomes zero even when the contacts are opened, it is necessary to quickly converge the current flowing through the switch to zero in the event of a system abnormality. Therefore, a suitable switch in the present invention is a switch that cannot self-extinguish, and specifically, it is preferable that the switch is a thyristor switch or a mechanical switch.

[0017] The switch is preferably a mechanical switch having a contact opening time of less than one quarter cycle.

[0018] 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.

[0019] 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 of a power storage unit into AC power to supply the power line, the control method comprising the steps of: acquiring a current measurement value that is a measurement value of a current 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; when a direction in which a current flowing through the switch is positive from the power system to the load, when the opening command is output and the current measurement value is a positive value, controlling a voltage of the power converter using a lower limit value of a voltage output by the power converter; and when the opening command is output and the current measurement value is a negative value, controlling the voltage of the power converter using an upper limit value of a voltage output by the power converter.

[0020] With this configuration, it is possible to obtain the same effects as the power supply system described above. Effect of the Invention

[0021] According to the present invention configured in this manner, it is possible to shorten the time between the point at which the switch has been opened and the point at which the current flowing through the switch is converged to zero. [Brief description of the drawings]

[0022] [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

[0023] 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.

[0024] <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 the power supply system 100 in this embodiment is a three-phase circuit, but may be a single-phase circuit, and the number of phases is not limited.

[0025] 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.

[0026] The switch 3 is a switch that cannot self-extinguish, and is a thyristor switch in this embodiment. In this embodiment, when the opening of the switch 3 is completed and the current flowing through the switch 3 becomes zero, the opening of the switch 3 is completed. Here, the opening time of the switch 3 refers to the time from when a command to turn off the gate signal is output to when the gate signal is actually turned off.

[0027] The voltage measurement unit 4 is connected to the power line P via a system transformer (not shown) and measures the voltage of the power system 10. The voltage measured by the voltage measurement unit 4 is output to the control device 8. Specifically, the voltage measurement unit 4 measures the voltage on the power system 10 side rather than the switch 3 so that the control device 8 can detect an abnormality in the power system 10 early.

[0028] 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.

[0029] 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.

[0030] The power converter 7 is connected to both ends of the switch 3 in the power line P, converts the DC power of the power storage unit 6 into AC power, and supplies the power to the power line P. Here, the power converter 7 being connected to both ends of the switch 3 in the power line P means that the power converter 7 is connected to both terminals, a first terminal 3a which is a terminal of the switch 3 on the power system 10 side, and a second terminal 3b which is a terminal of the switch 3 on the load 20 side. More specifically, the power converter 7 is branched from the first terminal 3a and the second terminal 3b in the power line P, and is provided in a parallel circuit provided in parallel to the switch 3. In this embodiment, the power converter 7 is connected to the power line P via an injection transformer T.

[0031] 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 various parameters, 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.

[0032] The opening command output unit 81 judges whether or not an abnormality has occurred in the power system 10 based on the voltage measured by the voltage measurement unit 4, and outputs an opening command to the switch control unit 84 when it is judged that an abnormality has occurred in the power system 10. Specifically, when the voltage measured by the voltage measurement unit 4 falls below a predetermined value, the opening command output unit 81 judges that an abnormality has occurred in the power system 10, and outputs an opening command to the switch control unit 84. Here, the opening command refers to a command to the switch 3 to turn off the gate signal. The predetermined value referred to here is a voltage value for detecting a momentary sag.

[0033] 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 after the opening command is output is equal to or higher than a predetermined value over multiple cycles, 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.

[0034] 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.

[0035] The switch control unit 84 uses a drive circuit (not shown) to control the opening and closing of the switch 3. Specifically, upon receiving an opening command, the switch control unit 84 turns off a gate signal for the switch 3 to open the switch 3. Then, when the opening of the switch 3 is completed and the current flowing through the switch 3 becomes zero, the switch control unit 84 outputs an opening completion signal which is a signal indicating that the opening of the switch 3 is completed.

[0036] 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.

[0037] 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.

[0038] The current interruption control unit 851 controls the voltage of the power converter 7 using a lower limit value of the voltage that the power converter 7 outputs between both ends of the switch 3 when the current value is a positive value in response to the output of an opening command, and controls the voltage of the power converter 7 using an upper limit value of the voltage that the power converter 7 outputs between both ends of the switch 3 when the current value is a negative value. Here, the voltage output by the power converter 7 refers to the voltage of the first terminal 3a relative to the second terminal 3b. Therefore, the upper limit value of the voltage that the power converter 7 outputs between both ends of the switch 3 refers to the maximum value (positive value with the maximum absolute value) of the voltage of the first terminal 3a relative to the second terminal 3b, and the lower limit value of the voltage that the power converter 7 outputs between both ends of the switch 3 refers to the minimum value (negative value with the maximum absolute value) of the voltage of the first terminal 3a relative to the second terminal 3b.

[0039] Specifically, the current cutoff control unit 851 includes a limiter 851a that limits the voltage output by the power converter 7 to within a predetermined range. In this embodiment, the upper and lower limit values ​​of the voltage output by the power converter 7 across the switch 3 correspond to the upper and lower limit values ​​of the limiter 851a, respectively. Then, as shown in FIG. 4, the current cutoff control unit 851 controls the voltage of the power converter 7 so that the voltage output by the power converter 7 across the switch 3 becomes the upper or lower limit value of the limiter 851a.

[0040] The absolute value of the upper limit value and the absolute value of the lower limit value of limiter 851a are expressed by the following Expression 2. That is, in this embodiment, the absolute value of the upper limit value and the absolute value of the lower limit value of limiter 851a are equal to the voltage that the power converter 7 outputs between both ends of switch 3.

[0041]

number

[0042] More specifically, in Equation 2, the opening time of switch 3 is the actual value of switch 3 measured at the manufacturing stage of switch 3. Here, a switch 3 is provided for each phase, and the opening time of each switch 3 varies from its own inherent value. Therefore, in reality, dt in Equation 2 is the maximum value among the actual values ​​of the opening time of each switch 3.

[0043] 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.

[0044] 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.

[0045] 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, the voltage compensation control unit 852 acquires the voltage measured by the voltage measurement unit 4 from the parameter acquisition unit 83, and compensates for the voltage of the load 20 based on the difference between the voltage and the voltage command value.

[0046] <Power supply system control operation> Next, the control operation of the power supply system 100 will be described.

[0047] (1) Power grid 10 in normal operation Voltage measurement unit 4 measures the voltage of power system 10, and outputs the measured voltage to opening command output unit 81. Opening command output unit 81 compares the voltage of power system 10 measured by voltage measurement unit 4 with a predetermined value.

[0048] 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 turned on. Therefore, AC power is supplied from the power system 10 to the load 20.

[0049] (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 .

[0050] When the open command is output, the switch control unit 84 turns off the gate signal for the switch 3, thereby opening the switch 3.

[0051] When an opening command is output, if the current value is a positive value, the current cutoff control unit 851 performs V OUT On the other hand, when an opening command is output and the current value is a negative value, the current interruption control unit 851 controls the voltage of the power converter 7 using the negative value of V OUT The voltage of the power converter 7 is controlled using the positive value (the maximum value in absolute value) of

[0052] The current cutoff control unit 851 is V OUT When the voltage of power converter 7 is controlled using the above, power converter 7 outputs a voltage across switch 3 so that a current flows in the opposite direction to the current flowing through power line P in a parallel circuit provided in parallel with switch 3. As a result, the current flowing through switch 3 converges to 0 at a slope of di / dt per unit time.

[0053] In equation 2, the power converter 7 applies V between both ends of the switch 3 so that the current flowing through the parallel circuit within the opening time dt of the switch 3 becomes the rated current.OUT Since the output terminal 12 outputs a voltage of magnitude equal to the magnitude of the load 20, the current flowing through the switch 3 becomes zero within the opening time dt of the switch 3. This makes it possible to make the current flowing through the switch 3 zero substantially simultaneously with the completion of the opening of the switch 3, so that the completion of the opening of the switch 3 and the disconnection of the power system 10 and the load 20 can be substantially simultaneous.

[0054] Then, when the current value becomes 0, the current interruption 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 maintained at 0, completing the interruption of the power system 10 and the load 20. Then, when the opening of the switch 3 is completed and the interruption of the power system 10 and the load 20 is completed, the switch control unit 84 outputs an opening completion signal.

[0055] When the opening 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.

[0056] 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.

[0057] 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.

[0058] <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.

[0059] 5 shows a simulation result showing a change over time in the current flowing through the switch 3 when the absolute value of the voltage output by the power converter 7 is controlled to be the value shown in Equation 1 in response to an opening command. That is, in this simulation, similar to the above embodiment, when the current value of the switch 3 is a positive value, the voltage output by the power converter 7 is set to the upper limit value of the limiter 851a, and when the current value of the switch 3 is a negative value, the voltage output by the power converter 7 is set to the lower limit value of the limiter 851a.

[0060] 5, at approximately the same time that an opening command is output and current interruption control is started, the time rate of change of the current value of switch 3 becomes a value obtained by dividing the upper or lower limit value of limiter 851a by the reactance of the circuit in which power converter 7 is provided, based on equation 1. As a result, it was confirmed that the current value of switch 3 converges to 0 according to the opening time of switch 3, and current interruption control can be completed.

[0061] In contrast, Fig. 6 shows the results of a simulation showing the change over time in the current flowing through the switch 3 when the power converter 7 is controlled so as to form a zero point of the current flowing through the switch 3 in response to an opening command. As can be seen from Fig. 6, this control does not take into account the opening time of the switch 3, so that the voltage compensation control starts before the current value of the switch 3 converges to zero, and it was confirmed that disconnection of the load 20 from the power system 10 fails.

[0062] <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.

[0063] Moreover, since the upper limit value and the lower limit value are calculated using the contact 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 contact 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 self-extinguishing capability and has a slow contact opening time, the absolute values ​​of the upper limit and lower limit calculated by equation 2 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.

[0064] 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.

[0065] <Other embodiments> The present invention is not limited to the above-described embodiment.

[0066] In this embodiment, the switch 3 is a thyristor switch, but the switch 3 is not limited to a thyristor switch. For example, the switch 3 may be a mechanical switch. When the switch 3 is a mechanical switch, the contact opening time of the switch 3 refers to the time from the point at which control for separating the physical contacts of the mechanical switch is started to the point at which the physical contacts of the mechanical switch are actually separated. Note that examples of the mechanical switch include a gas insulated switchgear (GIS) and a vacuum circuit breaker (VCB).

[0067] 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.

[0068] In the above embodiment, the absolute values ​​of the upper and lower limits of the limiter 851a are calculated by Equation 2. However, the upper and lower limits are not limited to those calculated by Equation 2, so long as they are upper or lower limits that maximize the current in the opposite direction to the current flowing through the switch 3.

[0069] 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.

[0070] 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]

[0071] 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 Opening 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···Limiter 852 Voltage compensation control section P...Power line

Claims

1. 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; A switch control unit that controls opening and closing of the switch; a current value acquiring unit for acquiring a value of a current flowing through the switch; a power converter connected to both ends of the switch in the power line, converting DC power from a power storage unit into AC power and supplying 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 power converter based on the acquired current value when the opening command is output, When a direction of a current flowing through the switch from the power grid to the load is defined as a positive direction, the power converter control unit: a power supply system that controls a voltage of the power converter using a lower limit value of a voltage that the power converter outputs across the switch when the current value is a positive value, and controls the voltage of the power converter using an upper limit value of a voltage that the power converter outputs across the switch when the current value is a negative value.

2. the power converter control unit includes a limiter that limits a voltage output by the power converter to within a predetermined range; The power supply system according to claim 1 , wherein the upper limit value and the lower limit value are upper limit value and lower limit value of the predetermined range.

3. 2. The power supply system of claim 1, wherein the absolute value of the voltage output by the power converter across the switch is calculated by the following formula: Here, V ｏｕｔ is the absolute value of the voltage that the power converter outputs across the switch, L is the reactance of the circuit in which the power converter is provided, di is the rated current, and dt is the opening time of the switch.

4. 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.

5. The power supply system according to claim 1 , wherein the switch is a thyristor switch or a mechanical switch.

6. 5. 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.

7. A control method for a power supply system including: a switch that is 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 that is connected to both ends of the switch on 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 is output to open the switch; When the current flowing through the switch is positive in the direction from the power system to the load, a control method for controlling a voltage of the power converter using a lower limit value of a voltage output by the power converter when the opening command is output and the current value is a positive value, and for controlling a voltage of the power converter using an upper limit value of a voltage output by the power converter when the opening command is output and the current value is a negative value.

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