Power supply system and method for controlling the power supply system

Abstract

To prevent application of excess voltage when opening a breaker after occurence of abnormality in a power system.SOLUTION: A power supply system 100 comprises: an opening / closing switch 3 that is provided on a power line L1 for supplying power from a power system 10 to a load 20 and opens / closes the power line L1; a power converter 7 that is connected to the power line L1 and converts DC power of a power storage unit 6 to AC power and supplies power to the power line L1; a switch control unit 82 for controlling the opening / closing switch 3; a power converter control unit 83 for controlling the power converter 7; and an abnormality detection unit 81 for detecting abnormality of the power system L1. When abnormality of the power system 10 is detected by the abnormality detection unit 81, the switch control unit 82 outputs an opening signal C for opening the opening / closing switch 3. When the abnormality of the power system 10 is detected by the abnormality detection unit 81, the power converter control unit 83 performs current interruption control for controlling the power converter 7 so as to make current flowing through the opening / closing switch 3 be 0.SELECTED DRAWING: Figure 1

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] In a conventional power supply system, when an abnormality occurs in the power system, a circuit breaker installed in a power line for supplying power from the power system to the load is opened to cut off the power supply from the power system to the load.Then, the voltage of the load is compensated by supplying power to the load from a power converter connected to an energy storage unit.

[0003] In this type of power supply system, when an abnormality in the power system is detected and the circuit breaker is opened, an arbitrary voltage is applied from the power converter to the circuit breaker, as shown in Patent Document 1. This allows the circuit breaker to be opened quickly, so that when an abnormality occurs in the power system, the power supply from the power system to the load can be quickly cut off. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-010212 Summary of the Invention [Problem to be solved by the invention]

[0005] In the above power supply system, when the circuit breaker is opened, a voltage is applied from the power converter to the circuit breaker, so that an excess voltage is applied between the completion of the circuit breaker opening and the start of voltage compensation. As a result, an overcurrent occurs due to the application of the excess voltage, so that it is necessary to provide the power converter with a certain tolerance, which increases the cost of the power converter.

[0006] Therefore, the present invention has been made in consideration of the above problems, and its main objective is to prevent excess voltage from being applied when an abnormality occurs in the power system and a circuit breaker is opened. [Means for solving the problem]

[0007] That is, the power supply system of the present invention is provided on a power line for supplying power from a power system to a load, and includes an open / close switch for opening and closing the power line, a power converter connected to the power line and converting DC power from a power storage unit into AC power and supplying the power to the power line, a switch control unit for controlling the open / close switch, a power converter control unit for controlling the power converter, and an abnormality detection unit for detecting an abnormality in the power system, wherein when an abnormality in the power system is detected by the abnormality detection unit, the switch control unit outputs an open signal to open the open / close switch, and when an abnormality in the power system is detected by the abnormality detection unit, the power converter control unit performs current interruption control for controlling the power converter to reduce the current flowing through the open / close switch to zero.

[0008] With this configuration, the current flowing through the switch is forcibly set to zero, so that the switch can be opened at that point, thereby preventing excessive voltage from being applied to the switch. Furthermore, since the occurrence of overcurrent due to the application of excessive voltage can be suppressed, it becomes unnecessary to provide the power converter with a tolerance, and it is possible to suppress an increase in the cost of the power converter.

[0009] The power converter control unit may perform, after the current interruption control, voltage compensation control for controlling the power converter so as to compensate for the voltage of the load. With this configuration, power is supplied from the power converter to the load after the open / close switch has been completely opened, so that the voltage of the load can be reliably compensated for.

[0010] The power converter is preferably a three-phase inverter. With this configuration, compared to a single-phase inverter, there is no need to control each phase individually, so the utilization rate of the power converter can be improved and the capacity of the power converter can be increased, thereby reducing the cost of the power converter.

[0011] Furthermore, a control method for a power supply system according to the present invention is a control method for a power supply system that supplies power from a power system to a load 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 power storage unit, the power supply system including a thyristor switch that is provided on a power line for supplying power from the power system to the load and opens and closes the power line, and a power converter that is connected to the power line and converts DC power from the power storage unit to AC power and supplies the AC power to the power line, and is characterized in that when an abnormality in the power system is detected, an extinguishing command for the thyristor switch is output, and in response to the output of the extinguishing command, current cut-off control is performed that feedback controls the power converter so as to set a current flowing through the thyristor switch to zero, and after the current cut-off control, voltage compensation control is performed that controls the power converter to compensate for a voltage of the load. Effect of the Invention

[0012] According to the present invention configured as above, when an abnormality occurs in the power system and the circuit breaker is opened, application of an excessive voltage can be eliminated. [Brief description of the drawings]

[0013] [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 schematic diagram showing a control block in the embodiment. [Diagram 3] 4 is a timing chart showing a case where current interruption control is performed in the embodiment. [Figure 4] 11 is a timing chart when a constant voltage is applied in a conventional example. [Diagram 5]2A is a schematic diagram showing a circuit configuration of a three-phase inverter in the embodiment, and FIG. 2B is a schematic diagram showing a circuit configuration of a single-phase inverter in the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] 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.

[0015] <1.Device configuration> 1, a power supply system 100 in this embodiment is provided between an electric power system 10 and a load 20, and constitutes a three-phase circuit. When the electric power system 10 is normal, the power supply system 100 supplies power from the electric power system 10 to the load 20, and when an abnormality occurs in the electric power system 10 due to a short circuit or the like, the power supply system 100 cuts off the power supply from the electric power system 10 to the load 20 and supplies power from the power storage unit 6 to the load 20.

[0016] Specifically, the power supply system 100 includes an open / close switch 3 that switches the power supply from the power system 10 to the load 20 by opening and closing, a voltage measurement unit 4 that measures the voltage of the power system 10, a switch current measurement unit 5 that measures the current flowing through the open / close switch 3, a power converter 7 that converts DC power from a power storage unit 6 into AC power and supplies it to a power line L1, and a control device 8 that controls the open / close switch 3 and the power converter 7.

[0017] The open / close switch 3 is provided on a power line L1 for supplying power from the power system 10 to the load 20, and is driven by a drive circuit (not shown) to switch between open and closed states of the power line L1. In order to more quickly cut off the power supply from the power system 10 to the load 20 when an abnormality occurs in the power system 10, the open / close switch 3 is preferably provided on the load 20 side rather than the power system 10, but is not limited thereto. In this embodiment, the open / close switch 3 is a thyristor switch.

[0018] The voltage measuring unit 4 measures the voltage of the power system 10 and outputs the measured voltage to the control device 8. Specifically, as shown in Fig. 1, the voltage measuring unit 4 is connected to the power line L1, and measures the voltage on the power system 10 side rather than the open / close switch 3 so that the voltage of the power system 10 can be measured earlier.

[0019] The switch current measuring unit 5 measures the current flowing through the open / close switch 3, and outputs the measured value I to the control device 8. Specifically, the switch current measuring unit 5 is provided in the power line L1 between the connection point between the power converter 7 and the power line L1, and is connected in series to the open / close switch 3 and in parallel to the power converter 7.

[0020] 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.

[0021] The power converter 7 converts the DC power of the power storage unit 6 into AC power and supplies the AC power to the power line L1 when an abnormality occurs in the power system 10. Specifically, the power converter 7 is connected to the power line L1 via an injection transformer T, and is connected in parallel with the open / close switch 3.

[0022] Specifically, the power converter 7 includes an inverter unit 71 that converts DC power from the power storage unit 6 into AC power, a reactor 72 that is connected in series to the output side of the inverter element 71 and stabilizes the AC current, and a capacitor element 73 that is connected to the reactor element 72 and stabilizes the voltage. In this embodiment, the inverter element 71 is configured as a three-phase inverter. The reactor element 72 and the capacitor element 73 may be connected to the input side of the inverter element 71 in order to rectify the DC power of the power storage unit 6.

[0023] The control device 8 detects an abnormality in the power system 10 and controls the open / close switch 3 and the power converter 7. The control device 8 includes an abnormality detection unit 81 that detects an abnormality in the power system 10, a switch control unit 82 that controls the open / close switch 3, and a power converter control unit 83 that controls the power converter 7.

[0024] The abnormality detection unit 81 detects an abnormality in the power system 10 based on the voltage measured by the voltage measurement unit 4. Specifically, the abnormality detection unit 81 determines that an abnormality has occurred in the power system 10 when the system voltage is below a set value over multiple cycles, and outputs an abnormality signal indicating the abnormality in the power system 10 to the switch control unit 82 and the power converter control unit 83. The set value in this embodiment is a voltage value for detecting a momentary sag or a power outage.

[0025] The switch control unit 82 controls switching the opening / closing switch 3 between on and off. In this embodiment, the switch control unit 82 acquires an abnormality signal from the abnormality detection unit 81, and outputs an opening signal C for opening the opening / closing switch 3 to a drive circuit (not shown). The drive circuit receives the opening signal and opens the opening / closing switch 3. When the opening of the opening / closing switch 3 is completed, the switch control unit 82 outputs an opening completion signal F indicating that the opening of the opening / closing switch 3 is completed to the power converter control unit 83.

[0026] The power converter control unit 83 includes a current interruption control unit 831 that performs current interruption control to control the power converter 7 so as to reduce the current flowing through the opening / closing switch 3 to zero when the abnormality detection unit 81 detects an abnormality in the power system 10, a voltage compensation control unit 832 that performs voltage compensation control to control the power converter 7 so as to compensate for the voltage of the load 20 after the current interruption control, and an output control unit 833 that controls the power converter 7 based on the output from the current interruption control unit 831 or the voltage compensation control unit 832.

[0027] Specifically, the current cutoff control unit 831 performs feedback control of the power converter 7 based on the switch current measured by the switch current measuring unit 5 in response to the opening signal C output by the switch control unit 82. More specifically, the current cutoff control unit 831 performs feedback control of the power converter 7 based on the measured value I measured by the switch current measuring unit 5 and the current command value I for making the current flowing through the open / close switch 3 zero. ref Then, based on the deviation ΔI, proportional control is performed using a proportional gain Kp, and the voltage target value V out In this embodiment, the proportional gain Kp and the voltage target value V out satisfy equations (1) and (2), respectively. Kp ≥ V 2 / S (V: rated voltage, S: rated capacity of power converter 7) (1) V out =Kp × ΔI (2)

[0028] The voltage compensation control unit 832 controls the power converter 7 so as to compensate for the voltage of the load 20 that has dropped due to the current interruption control. Specifically, as shown in FIG. 2, the voltage compensation control unit 832 calculates the voltage V measured by the voltage measurement unit 4 and the voltage command value V ref Based on the deviation from the calculated voltage, a voltage compensation value for compensating for the voltage of the load 20 is calculated, and the power converter 7 is feedback-controlled.

[0029] The output control unit 833 receives the output from the current cutoff control unit 831 or the voltage compensation control unit 832, and controls the power converter 7 so that a predetermined voltage is generated. Specifically, in the case of current cutoff control, the output control unit 833 controls the voltage target value V out In the case of voltage compensation control, the power converter 7 is controlled based on a voltage compensation value calculated by the voltage compensation control unit 832.

[0030] Furthermore, upon receiving the opening completion signal F, the output control section 833 outputs a switching signal for switching from current cutoff control to voltage compensation control to the current cutoff control section 831 and the voltage compensation control section 832 .

[0031] 2. Power supply system control operation Next, the control operation of the power supply system 100 will be described.

[0032] (1) Power grid 10 in normal operation Voltage measurement unit 4 constantly measures the voltage of power system 10, and inputs the measured voltage to abnormality detection unit 81. Abnormality detection unit 81 compares the voltage measured by voltage measurement unit 4 with a predetermined setting value.

[0033] When the power system 10 is normal, the voltage measured by the voltage measuring unit 4 is equal to or higher than the set value, and the open / close switch 3 is in a conducting state. This causes AC power to be supplied from the power system 10 to the load 20.

[0034] (2) Abnormality in power grid 10 When an abnormality occurs in the power system 10 , the voltage measured by the voltage measuring unit 4 is less than the set value, and the abnormality detecting unit 81 outputs an abnormality signal to the switch control unit 82 and the power converter control unit 83 .

[0035] When the abnormality signal is output, the switch control unit 82 outputs an open signal C to the drive circuit. In response to the output of the open signal C, the power converter control unit 83 performs current cut-off control on the power converter 7, and the power converter 7 converts the DC power from the power storage unit 6 to AC power and supplies it to the power line L1. This AC power is supplied so that the current flowing through the open / close switch 3 is set to zero, so that a zero current point is forcibly formed in the open / close switch 3. When the zero current point is formed, the drive circuit opens the open / close switch 3.

[0036] When the opening of the opening / closing switch 3 is completed and the switch control unit 82 outputs an opening completion signal F, the output control unit 833 outputs a switching signal to the current cut-off control unit 831 and the voltage compensation control unit 832 to switch from current cut-off control to voltage compensation control.

[0037] The current cutoff control unit 831 receives the switching signal from the output control unit 833 and ends the current cutoff control. Meanwhile, the voltage compensation control unit 832 controls the power converter 7 so as to compensate for the voltage of the load 20 that has dropped due to the current cutoff control. Then, after the voltage of the load 20 is compensated for, the voltage of the power system 10 recovers.

[0038] <3. Experimental Example> Below are experimental examples of the above-described power supply system 100. Note that the present invention is not limited to the following experimental examples, and may be modified within the scope of the above and below-described aims, and all such modifications are within the technical scope of the present invention.

[0039] (1) Comparison of current interruption control and conventional control Fig. 3 shows the results of an experimental example in which the power converter control unit 83 controls the power converter 7 to make the current flowing through the open / close switch 3 zero when an abnormality occurs in the power system 10 and the open / close switch 3 is opened. Fig. 3 shows the time variations of the system voltage, system current, load voltage, load current, switch current flowing through the open / close switch 3, inverter current flowing through the inverter, and pulse output in PWM control. As can be seen from Fig. 3, when the current flowing through the open / close switch 3 becomes zero, the current output by the power converter 7 decreases and the load voltage and load current do not diverge.

[0040] In contrast, Fig. 4 shows the results of an experiment in which the power converter control unit 83 controlled the power converter 7 to apply a constant voltage to the open / close switch 3. As can be seen from Fig. 4, when the current flowing through the open / close switch 3 becomes zero, the current output by the power converter 7 increases, resulting in increases in the load voltage and load current.

[0041] (2) Comparison of three-phase inverters and single-phase inverters As shown in FIG. 5, a comparison is made between the case where inverter element 71 is a three-phase inverter (see FIG. 5(a)) and the case where inverter element 71 is a single-phase inverter (see FIG. 5(b)). As shown in FIG. 5, when inverter element 71 is a three-phase inverter, one three-phase inverter has six switching elements S. Also, when inverter element 71 is a single-phase inverter, one single-phase inverter has four switching elements S. In this case, the three-phase AC power output by the three-phase inverter and the single-phase inverter are expressed by equations (3) and (4), respectively. P = √3VI × 2 (V: rated voltage, S: rated current) (3) P'=VI×3 (4)

[0042] In formulas (3) and (4), each inverter has the same rating. Furthermore, when outputting three-phase AC power using a single-phase inverter, each phase needs to be controlled individually, so at least three single-phase inverters are required. As a result, a single-phase inverter that outputs three-phase AC power needs 12 switching elements S. Therefore, in order to make the number of switching elements S in the single-phase inverter and the three-phase inverter the same and to facilitate comparison, formula (3) is based on the case where there are two three-phase inverters, and formula (4) is based on the case where there are three single-phase inverters, so that both cases have 12 switching elements S.

[0043] According to equations (3) and (4), the AC power output by the three-phase inverter is about 1.15 times that of the single-phase inverter. Therefore, it can be seen that the three-phase inverter outputs more power than the single-phase inverter.

[0044] <4. Effects of this embodiment> According to this embodiment, the current flowing through the open / close switch 3 is forcibly set to zero, so that the open / close switch 3 can be opened at that point, and as a result, it is possible to prevent excessive voltage from being applied to the open / close switch 3. Furthermore, since it is possible to prevent the occurrence of an overcurrent due to the application of excessive voltage, it becomes unnecessary to provide the power converter 7 with a tolerance, and it is possible to prevent an increase in the cost of the power converter 7.

[0045] Furthermore, according to this embodiment, the power converter control unit 83 controls the power converter 7 to supply power to the load 20 after the opening / closing switch 3 has been completely opened, so that the voltage of the load 20 can be reliably compensated.

[0046] Furthermore, according to this embodiment, the inverter element 71 is configured as a three-phase inverter, so that it is not necessary to control each phase individually, as compared to a single-phase inverter. As a result, the utilization rate of the power converter 7 can be improved, and the capacity of the power converter 7 can be increased, so that the cost of the power converter 7 can be reduced.

[0047] <5. Other embodiments> The present invention is not limited to the above-described embodiment.

[0048] 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 such as a gas insulated switchgear (VIS) or a vacuum circuit breaker (VCB). In this case, in order to prevent the voltage of the load 20 from decreasing due to a voltage drop caused by an abnormality in the power system 10, it is preferable that the opening time of the mechanical switch is equal to or shorter than ¼ cycle, which allows switching without interruption.

[0049] In this embodiment, the inverter element 71 is configured by a three-phase inverter, but the inverter element 71 may be configured by a single-phase inverter.

[0050] Although the abnormality detection unit 81 in the present embodiment detects an abnormality in the power system 10 based on a change in the system voltage, the detection of an abnormality is not limited to this. For example, the abnormality detection unit 81 may detect an abnormality in the power system 10 based on a change in the current or frequency in the power system 10. Accordingly, the setting value of the abnormality detection unit 81 is not limited to the voltage value of the power system 10, and may be the current value or frequency in the power system 10.

[0051] In this embodiment, the power converter control unit 83 performs current interruption control simultaneously with the open signal C, but the power converter control unit 83 may also perform current interruption control after receiving the output of an abnormality signal or the open signal C.

[0052] In the present embodiment, the output control unit 833 switches the control for the power converter 7 in response to the output of the opening completion signal F, but the timing of the switching does not have to be in response to the output of the opening completion signal F. For example, the output control unit 833 may switch from the current interruption control to the voltage compensation control after a predetermined time has elapsed from any one of the following starting points: the time when the opening signal C is output, the time when an abnormality in the power system 10 is detected, the time when the current interruption control unit 831 starts control, or the time when the measured value I of the current flowing through the open / close switch 3 becomes 0.

[0053] In the present embodiment, the power supplied from the power system 10 to the load 20 is AC power, but the power supplied from the power system 10 to the load 20 may be DC power.

[0054] In this embodiment, the power supply system 100 is a three-phase circuit, but the number of phases is not particularly limited.

[0055] 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]

[0056] 100 Power Supply System 10...Electric power system 20 Load 3 Open / Close Switch 4. Voltage measurement section 5 Switch current measurement section 6. Storage unit 7 Power Converter 8. Control device 81 Abnormality detection unit 82 Switch control section 83 Power converter control section L1...power line C...Open signal S...Opening completion signal

Claims

1. an open / close switch provided on a power line for supplying power from a power system to a load, the open / close switch opening and closing the power line; 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; A switch control unit that controls the open / close switch; a power converter control unit for controlling the power converter; an abnormality detection unit that detects an abnormality in the power system; a switch current measuring unit that measures a current flowing through the open / close switch and outputs the measured value to the power converter control unit; the switch control unit outputs an open signal to open the open / close switch when the abnormality detection unit detects an abnormality in the power system; the power converter control unit performs current interruption control to control the power converter so as to reduce a current flowing through the open / close switch to zero when an abnormality in the power system is detected by the abnormality detection unit; In the current interruption control, proportional control using a proportional gain is performed on the power converter based on a deviation between a command value for making the current flowing through the open / close switch zero and the measured value.

2. 2 . The power supply system according to claim 1 , wherein the power converter control unit performs, after the current interruption control, a voltage compensation control for controlling the power converter so as to compensate for a voltage of the load.

3. 3. The power supply system according to claim 1, wherein the power converter is formed of a three-phase inverter.

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 power storage unit to the load, comprising: The power supply system includes an open / close switch that is provided on a power line for supplying power from the power grid to the load and opens and closes the power line; 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; A switch current measuring unit that measures a current flowing through the open / close switch, When an abnormality in the power system is detected, the open / close switch is opened, and a current interruption control is performed to control the power converter so that a current flowing through the open / close switch is set to zero. a control method for a power supply system, wherein, in the current interruption control, proportional control using a proportional gain is performed on the power converter based on a deviation between a command value for making the current flowing through the open / close switch zero and a measured value measured by the switch current measuring unit.

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