Power System

Abstract

To prevent, in a power supply system that supplies power to a plurality of important loads connected in parallel, an influence of occurrence of a short-circuit accident on a load side from spreading to all the loads.SOLUTION: Provided is a power supply system 100 that is provided between a commercial power system 10 and a plurality of important loads 30 connected in parallel to each other and supplies power to the plurality of important loads, including: a distributed power supply 2 connected to a main power line L1 for supplying power from the commercial power system to the plurality of important loads; a plurality of open / close switches 9 provided respectively for a plurality of branch power lines L2 that are branched on the main power line at a place closer to the important loads than the distributed power supply, and are configured to supply power to the respective important loads; an impedance measurement unit 93 that measures impedance of each of the branch power lines; and a second control unit 94 that, in a case where impedance of any of the plurality of branch power lines falls below a predetermined setting value, opens the open / close switch provided for the relevant branch power line.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a power supply system. [Background technology]

[0002] Conventionally, a power supply system that satisfies the FRT requirements while simultaneously achieving both an uninterruptible power supply function and a load leveling function using a common distributed power source has been proposed, as shown in Patent Document 1.

[0003] The power supply system described in Patent Document 1 is configured with a changeover switch, such as a semiconductor switch, and an impedance element connected in parallel to the changeover switch between a commercial power system and a critical load, and a distributed power source is provided on the critical load side of the changeover switch. A parallel-off switch is also provided on the commercial power system side of the changeover switch. When a momentary voltage drop (hereinafter also referred to as a voltage sag) occurs in the commercial power system, this power supply system opens the changeover switch to connect the commercial power system and the distributed power source via the impedance element, and the distributed power source continues operation, including reverse power flow (FRT operation). On the other hand, when the commercial power system returns to a healthy state, once synchronization is established by comparing the commercial power system with the voltage on the load side, the changeover switch is turned on to resume normal operation. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 2019-047656 Summary of the Invention [Problem to be solved by the invention]

[0005] In the power supply system described above, multiple critical loads are connected in parallel, and each load may be provided with a circuit breaker or other device for short-circuit protection. In such a power supply system, as shown in Figure 6, if a short-circuit fault occurs on the critical load side during normal operation, a fault current immediately flows from the commercial electrode system and the distributed generator toward the short-circuit point. As a result, the voltage on the commercial power grid drops, and the distributed generator begins FRT operation by opening the selector switch. When the selector switch is opened and the commercial power grid is connected via an impedance element, the fault current from the commercial power grid is limited and the voltage on the commercial power grid is restored. Meanwhile, on the critical load side, the voltage drop and the supply of fault current from the distributed generator continue until the short-circuit point is interrupted.

[0006] As shown in Figure 7, it is desirable to detect a voltage drop on the commercial power grid and open the transfer switch instantaneously (e.g., within 2 ms), given the capacity of the critical load. On the other hand, load-side circuit breakers and overcurrent relays are often configured to trip short-circuit currents (more than 10 times the rated current) in approximately 20 ms. In this case, if the transfer switch were to open instantaneously (within 2 ms), an impedance element would be inserted before the short-circuit point was tripped, suppressing the fault current from the commercial power grid. As a result, the short-circuit current flowing toward the short-circuit point would be reduced to, for example, approximately 1.5 times the rated current. This would result in the circuit breaker and overcurrent relay having an inverse time characteristic that would extend the tripping time (approximately 1 to 30 minutes for a typical low-voltage circuit breaker at 1.3 to 1.5 times the rated current). As a result, voltage drops due to short-circuit accidents may be prolonged in healthy critical loads, the duration of overcurrent supply in distributed power sources may be prolonged, or the voltage drop may cause synchronization with the commercial power grid to be lost, leading to equipment protection and the failure of distributed power sources, causing the effects of the short-circuit accident to spread to all critical loads.

[0007] The present invention has been made to solve the above problems, and its main objective is to prevent the effects of a short-circuit accident on the load side from spreading to all of the important loads in a power supply system that supplies power to multiple important loads connected in parallel. [Means for solving the problem]

[0008] That is, the power supply system according to the present invention is a power supply system provided between a commercial power system and a plurality of important loads connected in parallel to one another, for supplying power to the plurality of important loads, the power supply system including: a distributed power source connected to a main power line for supplying power from the commercial power system to the plurality of important loads; a changeover switch provided on the main power line closer to the commercial power system than the distributed power source and for opening and closing the main power line; an impedance element connected in parallel to the changeover switch on the main power line; a system-side voltage detection unit for detecting a voltage on the commercial power system side than the changeover switch; The distributed power system includes a plurality of open / close switches provided on a plurality of branch power lines that branch off from the critical load side and supply power to the critical loads, an impedance measurement unit that measures the impedance of each of the branch power lines, a first control unit that opens the changeover switch when a detected voltage of the grid-side voltage detection unit becomes equal to or lower than a predetermined set value, and connects the distributed power system and the commercial power system via the impedance element, and a second control unit that opens the open / close switch provided on the corresponding branch power line when the impedance of any of the plurality of branch power lines becomes equal to or lower than a predetermined set value.

[0009] In such a power supply system, the impedance of each branch power line connected to the critical load is measured, and if the impedance of any branch power line falls below a set value, the corresponding branch power line is shut off. Therefore, even if a short circuit occurs on the critical load side during normal operation, the short-circuit point can be immediately shut off, thereby instantly restoring the voltage drop of healthy critical loads and preventing overcurrent supply from distributed power sources, thereby preventing the effects of a short circuit from spreading to all critical loads.

[0010] A specific configuration of the power supply system includes a load-side voltage detection unit that detects a voltage value applied to the branch power line, and a load-side current detection unit that detects a current value flowing through the branch power line, and the impedance measurement unit calculates the impedance of the branch power line based on the detected voltage value and current value.

[0011] Furthermore, in the power supply system, it is preferable that the second control unit opens the open / close switch provided on the corresponding branch power line when a current value of any of the plurality of branch power lines becomes equal to or greater than a predetermined set value or when an impedance of any of the plurality of branch power lines becomes equal to or less than a predetermined set value. In this way, if a large current flows toward the important load before the changeover switch is opened, the branch power line can be immediately cut off.

[0012] As a specific configuration of the power supply system, the open / close switch may be a semiconductor switch or a hybrid switch that combines a semiconductor switch and a mechanical switch, which allows high-speed switching. In this way, the effects of a short circuit accident can be more effectively prevented from spreading to all of the important loads. [Effects of the Invention]

[0013] According to the present invention configured in this manner, in a power supply system that supplies power to multiple important loads connected in parallel, when a short-circuit accident occurs on the load side, it is possible to prevent the impact from spreading to all of the loads. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a schematic diagram showing the configuration of a power supply system according to an embodiment of the present invention; [Figure 2] FIG. 2 is a schematic diagram showing a state of the power supply system of the embodiment during normal operation. [Figure 3]FIG. 2 is a schematic diagram showing a state of the power supply system of the embodiment during a momentary sag. [Figure 4] FIG. 2 is a schematic diagram showing a state of the power supply system of the embodiment when a load side is short-circuited. [Figure 5] 4A and 4B are diagrams showing simulation results of the operation of the power supply system of the embodiment when a short circuit occurs on the load side. [Figure 6] FIG. 1 is a schematic diagram showing a state when a load side short circuit occurs in a conventional power supply system. [Figure 7] FIG. 10 is a diagram showing the results of a simulation of the operation of a conventional power supply system when a short circuit occurs on the load side. DETAILED DESCRIPTION OF THE INVENTION

[0015] A power supply system according to an embodiment of the present invention will be described below with reference to the drawings.

[0016] As shown in FIG. 1, the power supply system 100 of this embodiment is provided between a commercial power system 10 and a plurality of (here, two) important loads 30 connected in parallel with each other, and functions as an uninterruptible power supply system (uninterruptible power supply function) that supplies power to each important load 30 in the event of an abnormality in the commercial power system 10, and also functions as a distributed power supply system (load leveling function) that levels the load by providing forward and reverse power flows to the commercial power system 10.

[0017] Specifically, the power supply system 100 includes a distributed power source 2 connected to a main power line L1 for supplying power from a commercial power system 10 to each important load 30, a changeover switch 3 that connects the commercial power system 10 to the distributed power source 2 and the important load 30, an impedance element 4 connected in parallel to the changeover switch 3, a system-side voltage detection unit 5 that detects the voltage on the commercial power system 10 side of the changeover switch 3, and a first control unit 6 that opens the changeover switch 3 when the detected voltage of the system-side voltage detection unit 5 becomes equal to or lower than a set value.

[0018] Here, the commercial power system 10 is a power supply network of an electric power company (electric utility), and includes a power plant, a power transmission system, and a power distribution system. Each important load 30 is a load that must be supplied with a stable supply of power even during a system abnormality such as a power outage or voltage drop. Each important load 30 is connected to a plurality of branch power lines L2 that branch off from the main power line L1 on the important load side 30 relative to the distributed power source 2.

[0019] The distributed power sources 2 are connected to the commercial power grid 10 and include, for example, a power source having a DC power generation facility 21a such as a solar power generation facility or a fuel cell and a power converter 22, a power storage facility (electricity storage device) 21b such as a secondary battery (storage battery) and a power converter 22, a power generation facility (not shown) that rectifies AC electrical energy output from a wind power generation facility or a micro gas turbine to DC and is then connected to the grid using a power converter, or an AC power generation facility 21c such as a synchronous generator or an induction generator. Note that the power supply system 100 includes at least the power storage facility 21b, and may also include any of the above-mentioned distributed power sources 2.

[0020] The changeover switch 3 is located on the main power line L1 closer to the commercial power grid 10 than the connection point of the distributed power source 2 and switches the main power line L1 on and off. A changeover switch capable of high-speed switching, such as a semiconductor switch or a hybrid switch that combines a semiconductor switch and a mechanical switch, can be used. For example, when a semiconductor switch is used, the switching time can be reduced to 2 ms or less, allowing for disconnection regardless of the zero point. Furthermore, when a hybrid switch is used, the switching time can be reduced to 2 ms or less, allowing for disconnection regardless of the zero point, and also eliminating current loss. The opening and closing of this changeover switch 3 is controlled by a first control unit 6.

[0021] The impedance element 4 is connected in parallel to the changeover switch 3 on the main power line L1, and is a current-limiting reactor in this embodiment.

[0022] The grid-side voltage detection unit 5 detects the voltage on the main power line L1 closer to the commercial power system 10 than the changeover switch 3 via a voltage transformer. Specifically, the grid-side voltage detection unit 5 is connected to the commercial power system 10 side of the parallel circuit made up of the changeover switch 3 and the impedance element 4 via a voltage transformer.

[0023] The first control unit 6 compares the detected voltage detected by the grid-side voltage detection unit 5 with a predetermined set value, and if the detected voltage is equal to or lower than the set value, outputs a control signal to the changeover switch 3 to open the changeover switch 3. Note that the set value in this embodiment is a voltage value for detecting a momentary sag. When the first control unit 6 opens the changeover switch 3 in this manner, the commercial power grid 10, the distributed generation 2, and the important load 30 are connected via the impedance element 4. In this state, the distributed generation continues operation, including reverse power flow.

[0024] This power supply system 100 also includes a disconnection switch 7 provided on the main power line L1 closer to the commercial power system 10 than the distributed power source 2, and a power supply side voltage detection unit 8 that detects the voltage on the distributed power source 2 side than the disconnection switch 7.

[0025] The parallel-off switch 7 is an open / close switch for disconnecting the commercial power grid 10 from the distributed power sources 2, and is, for example, a mechanical switch. In FIG. 1 , the parallel-off switch 7 is provided closer to the commercial power grid 10 than the changeover switch 3, but it may also be provided closer to the distributed power sources 2 than the changeover switch 3. The first control unit 6 controls the opening and closing of the parallel-off switch 7.

[0026] Specifically, the first control unit 6 opens the parallel-off switch 7 when the voltage detected by the grid-side voltage detection unit 5 satisfies a predetermined condition for parallel-off. Here, the predetermined condition for parallel-off is that the voltage drop in the grid voltage (the state in which the detected voltage is equal to or lower than the set value) continues for a predetermined value or more (a time longer than the duration of the momentary sag). With the parallel-off switch 7 open, the distributed power source 2 enters the isolated operation mode and supplies power to the important load 30. Note that, because the changeover switch 3 has already been opened, the reactor 4 suppresses the overcurrent caused by opening the parallel-off switch 7.

[0027] The first control unit 6 also turns on the parallel-off switch 7 when the voltage detected by the grid-side voltage detection unit 5 eliminates a predetermined parallel-off condition and the voltage detected by the grid-side voltage detection unit 5 and the voltage detected by the power supply-side voltage detection unit 8 satisfy a synchronization test condition.

[0028] Therefore, in order to prevent the effects of a short-circuit accident on the load side from spreading to the entire load, the power supply system 100 of this embodiment includes an open / close switch 9 provided on each of the multiple branch power lines L2, a load-side voltage detection unit 91 that detects the voltage value across each branch power line L2, a load-side current detection unit 92 that detects the voltage value flowing through each branch power line L2, an impedance measurement unit 93 that measures the impedance of each branch power line L2, and a second control unit 94 that opens the open / close switch 9 based on the measurement value of the impedance measurement unit 93.

[0029] The on-off switch 9 switches the branch power line L2 and is provided for each important load 30. Specifically, the on-off switch 9 may be a changeover switch (high-speed switch) capable of high-speed switching, such as a semiconductor switch or a hybrid switch that combines a semiconductor switch and a mechanical switch. For example, when a semiconductor switch is used, the switching time can be reduced to 2 ms or less, allowing for disconnection regardless of the zero point. Furthermore, when a hybrid switch is used, the switching time can be reduced to 2 ms or less, allowing for disconnection regardless of the zero point, and also reducing conduction loss to zero. The on-off switch 9 is controlled by a second control unit 94.

[0030] The load-side voltage detector 91 is connected to the branch power line L2 closer to the distributed power source 2 than the open / close switch 9, and detects the voltage applied to the branch power line L2 via a potential transformer. The voltage value detected by the load-side voltage detector 91 is preferably a three-phase instantaneous voltage effective value, and its frequency may be a fundamental wave or a harmonic. The voltage value detected by the load-side voltage detector 91 is input to an impedance measuring unit 94 and used to measure impedance.

[0031] The load-side current detection unit 92 is connected to the branch power line L2 closer to the distributed power source 2 than the ON / OFF switch 9, and detects the current flowing through the branch power line L2 via an instrument current transformer. The current value detected by the load-side current detection unit 92 is input to an impedance measurement unit 94 and used to measure impedance. The current value detected by the load-side current detection unit 92 is preferably a three-phase instantaneous current effective value, and its frequency may be a fundamental wave or a harmonic. This current value is also input to a second control unit 94 and used to control the ON / OFF switch 9.

[0032] The impedance measuring unit 93 measures the impedance of the branch power line L2 based on the voltage value detected by the load-side voltage detecting unit 91 and the current value detected by the load-side current detecting unit 92. The measured impedance is input to a second control unit 94 and used to control the open / close switch 9.

[0033] When the impedance of any of the plurality of branch power lines L2 falls below a predetermined set value (impedance set value), the second control unit 94 outputs a control signal to the open / close switch 9 provided on the corresponding branch power line L2 to open the open / close switch 9. This impedance set value is a value for detecting a short circuit (load-side short circuit) in the branch power line L2, and is set to, for example, about 30% of the steady-state impedance value. When the measured impedance falls below the impedance set value, the second control unit 94 opens the open / close switch 9 after a predetermined determination time (for example, about 20 ms) has elapsed.

[0034] In addition, when the current value of any of the plurality of branch power lines L2 becomes equal to or greater than a predetermined set value (current set value), the second control unit 94 outputs a control signal to the open / close switch 9 provided on the corresponding branch power line L2 to open the open / close switch 9.

[0035] Next, the operation of the power supply system 100 of this embodiment (during normal operation, during a momentary voltage sag, and during a load-side short circuit) will be described.

[0036] (1) Continuous operation In normal operation, as shown in Fig. 2, the power supply system 100 keeps the changeover switch 3, the parallel-off switch 8, and the open / close switch 9 closed, and the distributed power source 2 and each important load 30 are connected to the commercial power grid 10 via the changeover switch 3. Note that although the reactor 4 is connected in parallel to the changeover switch 3, the impedance of the changeover switch 3 is smaller than the impedance of the reactor 4, so power is exchanged between the commercial power grid 10 and the distributed power source 2 and each important load 30 on the side of the changeover switch 3. Peak cutting and peak shifting can be achieved by the reverse power flow from the distributed power source 2.

[0037] (2) When a power drop occurs and when it is restored When a short-circuit fault (e.g., a three-phase short circuit) occurs on the commercial power grid 10 side, the voltage on the commercial power grid 10 side drops. This voltage drop is detected by the grid-side voltage detection unit 5. The first control unit 6 opens the changeover switch 3 when the voltage detected by the grid-side voltage detection unit 5 is equal to or lower than a set value. As shown in FIG. 3 , when the changeover switch 3 is opened, the distributed power source 2 and each important load 30 are connected to the commercial power grid 10 via the reactor 4. In this state, the current flowing from the distributed power source 2 to the short-circuit fault point is limited by the reactor 4, thereby suppressing the fault current flowing to the short-circuit fault point and preventing a voltage drop at each important load 30. Furthermore, in this state, the distributed power source 2 continues operation, including reverse power flow, and continues to output power.

[0038] The grid-side voltage detection unit 5 detects the voltage on the commercial power grid 10 side regardless of whether the changeover switch 3 is open or closed, and the first control unit 6 closes the changeover switch 3 when the detected voltage of the grid-side voltage detection unit 5 becomes equal to or higher than a predetermined recovery voltage, for example, when the remaining voltage of the commercial power grid becomes equal to or higher than 80%.

[0039] (3) When the load side is short-circuited When a short-circuit fault occurs on the important load 30 side (specifically, on the branch power line L2), the voltage on the commercial power grid 10 side and the impedance of the branch power line L2 where the fault occurs drop. This voltage drop is detected by the grid-side voltage detection unit 5. The first control unit 6 opens the changeover switch 3 when the detected voltage detected by the grid-side voltage detection unit 5 is equal to or lower than a set value. As shown in FIG. 4 , when the changeover switch 3 is opened, the distributed power source 2 and each important load 30 are connected to the commercial power grid 10 via the reactor 4. Here, the impedance of the branch power line L2 where the short circuit occurred continues to drop. This drop in impedance of the branch power line L2 is detected by the impedance measurement unit 93. When the state in which the impedance measured by the impedance measurement unit 93 is equal to or lower than a set value (approximately 30% of the steady-state value) exceeds a predetermined determination time (approximately 20 ms), the second control unit 94 opens the open / close switch 9 of the branch power line L2 where the impedance has dropped. The open / close switch 9 on the healthy branch power line L2 where no short-circuit fault has occurred remains closed.

[0040] Next, FIG. 5 shows the results of a simulation of the operation of power supply system 100 configured as shown in FIG. 1 when a short circuit occurs on the load side.

[0041] The simulation results of this operation show the voltage and current waveforms on the commercial power grid side, as well as the impedance, voltage, and current waveforms on the load side, when a load-side short-circuit fault occurs, a voltage drop on the commercial power grid 10 side is detected and the changeover switch 3 is opened within 2 ms, and a drop in impedance on the load side is detected and the open / close switch 9 at the fault point is opened within 20 ms. Note that the commercial power grid side voltage / current waveforms represent the voltage and current detected on the commercial power grid side of the changeover switch 3 in the main power line, and the load side voltage / current waveforms represent the impedance, voltage, and current detected in the branch power line where the short circuit occurred.

[0042] From the simulation results of Figure 5, it was confirmed that when a short circuit occurs on the load side, a drop in impedance is detected and the voltage on the important load 30 side is restored by opening the open / close switch 9 of the branch power line L2 where the fault occurs, and recovery is possible without the effects of the short circuit accident spreading to the entire load side.

[0043] <Advantages of the power supply system 100 of this embodiment> According to the power supply system 100 of the present embodiment configured as described above, the impedance of each branch power line L2 connected to the important load 30 is measured, and if the impedance of any branch power line L2 falls below a set value, the corresponding branch power line L2 is shut off. Therefore, even if a short-circuit accident occurs on the important load 30 side during normal operation, the short-circuit point can be immediately shut off. This allows the voltage drop of healthy important loads 30 to be instantly restored, prevents the distributed power source 2 from supplying an overcurrent, and prevents the effects of a short-circuit accident from spreading to the entire important load 30.

[0044] <Other Modified Embodiments> The present invention is not limited to the above-described embodiment.

[0045] Furthermore, although the power supply system 100 of the above embodiment is configured to open the open / close switch 9 provided on the corresponding branch power line L2 when the current value of any of the plurality of branch power lines L2 becomes equal to or greater than a predetermined set value (current set value), this is not limiting. The power supply system 100 of other embodiments may be configured to open the open / close switch 9 provided on the corresponding branch power line L2 only when the impedance of any of the plurality of branch power lines L2 becomes equal to or less than a predetermined set value, without comparing the current value of the branch power line L2 with the current set value.

[0046] Furthermore, the impedance element 4 may be a capacitor, or may be a combination of a reactor, a resistor, or a capacitor.

[0047] Furthermore, the grid-side voltage detector 5 of the above embodiment may be included in the grid-connection protection device. Examples of grid-connection protection devices specified in the grid-connection regulations include an overvoltage relay (OVR), an undervoltage relay (UVR), a directional short-circuit relay (DSR), an earth fault overvoltage relay (OVGR), an overfrequency relay (OFR), an underfrequency relay (UFR), and a transfer circuit breaker. In this case, the first control unit 6 may open the parallel-out switch 7 when any one of the interconnection protection devices is activated. The first control unit 6 may also close the parallel-out switch 7 when all of the grid-connection protection devices are in an inoperative state and the detected voltages of the grid-side voltage detector 5 and the power-source voltage detector 8 satisfy the synchronization test condition. This configuration uses the voltage detector included in the interconnection protection device, eliminating the need for a separate grid-side voltage detector, simplifying the device configuration.

[0048] In the above embodiment, two important loads 30 are connected in parallel, but this is not limiting. In other embodiments, three or more important loads 30 may be connected in parallel, and each important load 30 may be provided with an open / close switch 9.

[0049] Furthermore, the power supply system 100 of another embodiment does not necessarily have to include the parallel-off switch 7.

[0050] Furthermore, the power supply side voltage detector 8 in the above embodiment is provided between the parallel-off switch 7 and the selector switch 3, but may be replaced by a function for measuring the voltage at the grid connection point of the distributed power source 2.

[0051] 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 of the present invention. [Explanation of symbols]

[0052] 100 Power Supply System 10...Commercial power system 30...Important load L1...Main power line L2: Branch power line 2...Distributed power supply 3. Selector switch 4. Impedance element 5. Grid voltage detection section 6 First control section 7. Parallel-off switch 8 Power supply voltage detection section 9. Open / close switch 91 Load side voltage detection section 92 Load side current detection section 93 Impedance measurement section 94 Second control section

Claims

1. A power supply system provided between a commercial power system and a plurality of important loads connected in parallel to each other, the power supply system supplying power to the plurality of important loads, a distributed power source connected to a main power line for supplying power from the commercial power system to the plurality of critical loads; a changeover switch that is provided on the main power line closer to the commercial power system than the distributed power source and that opens and closes the main power line; an impedance element connected in parallel to the changeover switch in the main power line; a system-side voltage detection unit that detects a voltage on the commercial power system side of the changeover switch; a plurality of open / close switches provided on a plurality of branch power lines that branch off from the main power line at a side closer to the important loads than the distributed power source and that supply power to the important loads; an impedance measuring unit that measures the impedance of each of the branch power lines; a first control unit that opens the changeover switch when a detected voltage of the grid-side voltage detection unit becomes equal to or lower than a predetermined set value, thereby connecting the distributed power source and the commercial power grid via the impedance element; a second control unit that, when an impedance of any of the plurality of branch power lines becomes equal to or less than a predetermined setting value, opens the open / close switch provided on the corresponding branch power line.

2. a load-side voltage detection unit that detects a voltage value applied to the branch power line; a load-side current detection unit that detects a current value flowing through the branch power line, The power supply system according to claim 1 , wherein the impedance measuring unit calculates the impedance of the branch power line based on the detected voltage value and current value.

3. The second control unit, The load-side voltage detection unit is configured to compare a voltage value detected by the load-side voltage detection unit with a predetermined set value, and to compare a current value detected by the load-side current detection unit with a predetermined set value, 3. The power supply system according to claim 2, wherein when a current value of any of the plurality of branch power lines becomes equal to or greater than a predetermined set value, or when an impedance of any of the plurality of branch power lines becomes equal to or less than a predetermined set value, the open / close switch provided on the corresponding branch power line is opened.

4. 2. The power supply system according to claim 1, wherein the open / close switch is capable of high-speed switching.