Power switching device, power supply device, and control method

Abstract

To improve reliability in a power switching device.SOLUTION: A power switching device comprises: an AC line installed between a power system and a load; a bistable relay provided in the AC line at a position closer to the power system than a first point where a power supply unit different from the power system is connected in parallel to the power system; and a control unit that switches between a first mode in which the AC power is supplied from the power system to the load by closing the bistable relay and connecting the power system and the load, and a second mode in which the AC power is supplied from the power system to the load by opening the bistable relay and disconnecting the power system and the load.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a power switching device, a power supply device, and a control method.

Background Art

[0002] There is known a power switching device that switches a power supply source for supplying AC power to a load between a power grid and a power source unit such as a storage battery. Patent Document 1 discloses a distribution board including a power line connecting the power grid and the load, a switch provided at a position closer to the power grid than a power supply point that is a power supply point of power supplied from a power supply device among the power lines, and a control unit that controls the switch. When detecting a power outage in the power grid, the control unit turns off the switch using the power supplied from the power supply device, thereby forming a circuit for supplying power from the power supply device to the load in the distribution board during a power outage.

[0003] Patent Document 2 discloses a disconnection relay that disconnects a power conversion device and a photovoltaic power generation device from the power grid when a power outage occurs in the power grid. Patent Document 3 discloses an open switch that cuts off an important load and a power source unit from the commercial power grid when a voltage drop occurs in the commercial power grid.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] In a power switching device, if the relay that disconnects the load and power supply from the power grid fails, it becomes impossible to supply power from the power grid to the load and power supply. Therefore, high reliability is required for this relay.

[0006] In light of these challenges, this disclosure aims to further improve the reliability of power switching devices. [Means for solving the problem]

[0007] The power switching device of the present disclosure comprises: an AC circuit provided between a power system and a load; a bistable relay provided in the AC circuit at a position closer to the power system than a first point where a power supply unit different from the power system is connected in parallel to the power system; and a control unit that switches between a first mode in which AC power is supplied from the power system to the load by closing the bistable relay and connecting the power system and the load, and a second mode in which AC power is supplied from the power supply unit to the load by opening the bistable relay and disconnecting the power system and the load.

[0008] The control method of the present disclosure is a control method for a power switching device that switches the power source for supplying AC power to a load from a power system to a power supply unit different from the power system, wherein the power switching device includes a bistable relay provided in an AC circuit between the power system and the load, at a position closer to the power system than a first point where the power supply unit is connected in parallel to the power system, and the control method comprises: a first step of supplying AC power from the power system to the load by closing the bistable relay to connect the power system and the load when AC power is supplied from the power system; and a second step of supplying AC power from the power supply unit to the load by opening the bistable relay to disconnect the power system and the load when the power system fails. [Effects of the Invention]

[0009] According to this disclosure, the reliability of power switching devices can be further improved. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a diagram illustrating the configuration of a power supply device according to an embodiment. [Figure 2] Figure 2 is a flowchart illustrating a control method according to an embodiment. [Figure 3] Figure 3 is a flowchart illustrating a control method according to an embodiment. [Figure 4] Figure 4 is a flowchart illustrating a control method according to an embodiment. [Figure 5] Figure 5 shows the configuration of a modified power supply device. [Figure 6] Figure 6 shows the configuration of a modified power supply device. [Modes for carrying out the invention]

[0011] [Description of Embodiments in this Disclosure] Embodiments of this disclosure include, in essence, at least the following:

[0012] (1) The power switching device of the present disclosure is a power switching device comprising: an AC circuit provided between a power system and a load; a bistable relay provided in the AC circuit at a position closer to the power system than a first point where a power supply unit different from the power system is connected in parallel to the power system; and a control unit that switches between a first mode in which AC power is supplied from the power system to the load by closing the bistable relay and connecting the power system and the load, and a second mode in which AC power is supplied from the power supply unit to the load by opening the bistable relay and disconnecting the power system and the load.

[0013] By using a bistable relay when switching the power source supplying AC power to a load, circuit degradation due to relay heat generation can be suppressed compared to using a monostable relay, for example, thus improving the reliability of the power switching device.

[0014] (2) In the power supply switching device of (1) above, the bistable relay may include a main contact that can open and close the AC circuit, a first coil that closes the main contact by an excitation input from the power grid, and a second coil that opens the main contact by an excitation input from the power supply unit.

[0015] With this configuration, during a power outage in the power grid, the first coil is not excited and the main contact can be maintained in the open state. Also, by opening the main contact by an excitation input from a power supply unit different from the power grid, the power grid can be disconnected from the power supply unit and the load during a power outage. Thereby, while suppressing reverse power flow to the power grid during a power outage, AC power can be supplied from the power supply unit to the load.

[0016] (3) The power supply switching device of (2) above may include a first input path that supplies a current for exciting the first coil from the power grid, a first rectifying unit provided in the first input path that rectifies the current supplied from the power grid, and a first contact that can open and close the first input path. In this case, the control unit may maintain the first contact in the open state from the detection of a power outage in the power grid until the detection of the restoration of power in the power grid.

[0017] For example, when the first contact is not provided in the first input path, when low-voltage AC power that does not reach the reference voltage is input to the AC circuit by the power grid, an excitation input to the first coil is made and the main contact closes, and there is a possibility that unstable AC power is supplied to the load. By configuring as in (3) above, the power grid can be connected to the load in a state where the power grid supplies a voltage within the reference range. Thereby, it is possible to suppress the supply of unstable AC power to the load.

[0018] (4) The power supply switching device of (3) above may include a first converter provided at a position closer to the power grid than the first rectifying unit and the first contact in the first input path, and that converts the AC power supplied from the power grid into DC power of a predetermined voltage.

[0019] By configuring it in this way, since the first coil is excited by the DC power of a predetermined voltage adjusted in the first converter, the first coil can be stably excited.

[0020] (5) In the power supply switching device of (4) above, the first contact may be provided at a position closer to the first coil than the first rectifying section in the first input path. In this case, the power supply section may include a DC power supply that supplies DC power and an inverter that converts the DC power from the DC power supply into AC power, and the power supply switching device has a first end connected between the DC power supply and the inverter, and a third input path having a second end opposite to the first end connected between the first rectifying section and the first contact, and a second converter provided in the third input path for converting the DC power from the DC power supply into DC power of the predetermined voltage.

[0021] By configuring it in this way, even when one of the first converter and the second converter fails, the other of the first converter and the second converter can continue to supply DC current to the first coil, so that the reliability of the power supply switching device can be further enhanced.

[0022] (6) The power supply switching device according to any one of (2) to (5) above may include a second input path for supplying a current for exciting the second coil from the power supply section, and a second contact capable of opening and closing the second input path. In this case, the control unit may at least temporarily close the second contact between detecting a power outage of the power system and detecting a power restoration of the power system.

[0023] By configuring it in this way, the time during which current is supplied to the second coil can be shortened. Thereby, by suppressing heat generation in the bistable relay, deterioration of the circuit can be suppressed.

[0024] (7) Any of the power switching devices described in (1) to (6) above may include a switch for opening and closing the circuit between the power supply unit and the first point. In this case, the control unit may keep the switch open from the time the power system is shut off until the bistable relay is put into the second state, and close the switch from the time the bistable relay is put into the second state until the power system is restored.

[0025] With this configuration, during a power outage in the power grid, at least one of the bistable relay and the switch remains open. Therefore, the power supply unit is isolated from the power grid by at least one of the bistable relay and the switch. This prevents reverse power flow from the power supply unit into the power grid.

[0026] (8) The power supply device of the present disclosure is a power supply device comprising any of the power switching devices described in (1) to (7) above, and the power supply unit.

[0027] (9) A control method of the present disclosure is a control method for a power switching device that switches the source of supplying AC power to a load from a power system to a power supply unit different from the power system, wherein the power switching device includes a bistable relay provided in an AC circuit between the power system and the load, at a position closer to the power system than a first point where the power supply unit is connected in parallel to the power system, and the control method includes: a first step of supplying AC power from the power system to the load by closing the bistable relay to connect the power system and the load when AC power is supplied from the power system; and a second step of supplying AC power from the power supply unit to the load by opening the bistable relay to disconnect the power system and the load when the power system fails.

[0028] By using a bistable relay when switching the power source supplying AC power to a load, circuit degradation due to relay heat generation can be suppressed compared to using a monostable relay, for example, thus improving the reliability of the power switching device.

[0029] [Details of the embodiments of this disclosure] Specific examples of the power switching device and power supply device disclosed herein will be described below with reference to the drawings.

[0030] [1. Power supply device] [1.1 Configuration of the power supply device] Figure 1 shows an example of the configuration of a power supply device 1 according to an embodiment. The power supply device 1 is a device that supplies AC power from the power system 60 or AC power from the power supply unit 40 to a load 70 installed at a consumer (for example, a general household or factory). The power supply device 1 comprises a power switching device 10 and a power supply unit 40.

[0031] The power system 60 is, for example, a single-phase commercial power system. However, the power system 60 may also be a three-phase power system or a non-commercial power system (for example, a power system within a factory).

[0032] The power supply unit 40 is an AC power source separate from the power system 60, and is installed, for example, at a customer's site. The power supply unit 40 is an auxiliary power source that supplies AC power to the load 70 when the power system 60 experiences a power outage. In addition, the power supply unit 40 may supply AC power to the load 70 together with the power system 60 during normal times when the power system 60 is not experiencing a power outage. The power supply unit 40 includes a DC power supply 41, a chopper 42, and an inverter 43.

[0033] The DC power supply 41 is a power source that supplies DC power, such as a storage battery. In this case, the DC power supply 41 may be a lithium-ion battery or another type of storage battery. The DC power supply 41 may also be a solar cell or a combination of a storage battery and a solar cell. If the DC power supply 41 includes a storage battery and a solar cell, the storage battery may be charged by the power generated by the solar cell.

[0034] The chopper 42 is a circuit that boosts or lowers the DC power from the DC power supply 41 to a voltage controllable by the inverter 43. The chopper 42 is installed, for example, between the DC power supply 41 and the inverter 43. If the DC power supplied from the DC power supply 41 is already adjusted to a voltage controllable by the inverter 43, the chopper 42 may be omitted.

[0035] The inverter 43 is a bidirectional inverter circuit that converts DC power and AC power in both directions. For example, when the DC power supply 41, which is a storage battery, is charging, the inverter 43 converts the AC power supplied from the power grid 60 into DC power and outputs it to the chopper 42. On the other hand, when the DC power supply 41, which is a storage battery (or solar cell), is discharging, the inverter 43 converts the DC power supplied from the DC power supply 41 through the chopper 42 into AC power and outputs it to the load 70.

[0036] [1.2 Configuration of the power switching device 10] The power switching device 10 is a device that switches the power source supplying AC power to the load 70 between the power system 60 and the power supply unit 40. The power switching device 10 is installed, for example, at a customer's site. The power switching device 10 comprises an AC circuit 11, a bistable relay 12, a control device 13, a first input circuit 14, a second input circuit 15, a first contact 16, a second contact 17, and a switch 18.

[0037] The AC circuit 11 is an electrical circuit installed between the power system 60 and the load 70. For example, if the power system 60 is single-phase, the AC circuit 11 includes two power lines: a grounded power line and an ungrounded power line. In Figure 1, the grounded power line is omitted for simplicity. Furthermore, if the power system 60 is three-phase, the AC circuit 11 includes three power lines.

[0038] The AC circuit 11 includes a first point P1 to which the power supply unit 40 is connected in parallel to the power system 60. In the example shown in Figure 1, the first point P1 is located inside the power switching device 10 within the AC circuit 11, but the first point P1 may also be located between the power switching device 10 and the load 70 (i.e., outside the power switching device 10 within the AC circuit 11).

[0039] The bistable relay 12 is an element for forming a circuit that, for example, in the event of a power outage in the power system 60, isolates the power system 60 from the power supply unit 40 and the load 70, and supplies AC power from the power supply unit 40 to the load 70. In the prior art described in Patent Document 1, a monostable relay was used as the relay for isolating the power system from the load. A monostable relay is a relay in which the contacts operate when an excitation input is applied to the coil and return to their original position when the excitation input is removed, and is also called a constantly excited relay.

[0040] A monostable relay requires a continuous supply of current to the coil to maintain, for example, a closed contact (or open contact). Therefore, monostable relays tend to generate heat due to this current supply, which can lead to circuit degradation.

[0041] In contrast, the power switching device 10 of this embodiment is equipped with a bistable relay 12. The bistable relay 12 is a relay in which the contacts operate or return when an excitation input is applied to the coil, and maintain that state even after the excitation input is removed. Therefore, with the bistable relay 12, it is sufficient to supply current to the coil when switching the contacts, and the closed state (or open state) of the contacts can be maintained without continuously supplying current to the coil. As a result, compared to a monostable relay, the reliability of the power switching device 10 can be improved compared to conventional devices by suppressing circuit deterioration due to heat generation of the relay. In addition, by reducing the time for which current is supplied compared to conventional devices, the power consumption required to operate the relay in the power switching device 10 can be reduced.

[0042] The bistable relay 12 is located in the AC circuit 11 at a position closer to the power system 60 than to the first point P1. The bistable relay 12 is, for example, a double-wound relay and includes a main contact 21, a first coil 22, a second coil 23, a first rectifier 24, and a second rectifier 25. The bistable relay 12 is also called a latching relay (or latching electromagnetic contactor).

[0043] The main contact 21 is a contact that can open and close the AC circuit 11. When the main contact 21 is closed (on), the power system 60 and the load 70 are electrically connected in the AC circuit 11. When the main contact 21 is open (off), the power system 60 and the load 70 are electrically disconnected in the AC circuit 11.

[0044] The first coil 22 is a coil that closes the main contact 21 by an excitation input from the power system 60. The first coil 22 is excited by the current supplied from the first input line 14. The first input line 14 is a power line drawn from the second point P2, which is located between the main contact 21 and the power system 60 in the AC circuit 11, to the first coil 22. The first input line 14 is provided with a first contact 16 and a first rectifier 24.

[0045] The first contact 16 is a contact capable of opening and closing the first input path 14. The first contact 16 is controlled to open and close by the control unit 31 included in the control device 13. In the example in Figure 1, the first contact 16 is a b-contact (break contact). However, the first contact 16 may also be an a-contact (make contact).

[0046] The first rectifier unit 24 rectifies the current supplied from the power system 60. The first rectifier unit 24 includes, for example, a diode with the anode closer to the second point P2. When the first contact 16 is closed, the current supplied from the power system 60 is rectified by the first rectifier unit 24, thereby supplying a DC current to the first coil 22.

[0047] In the example in Figure 1, the first rectifier 24 is built into the bistable relay 12. Alternatively, the first rectifier 24 may be located outside the bistable relay 12 within the first input path 14. In the example in Figure 1, the first rectifier 24 is located closer to the first coil 22 than the first contact 16 within the first input path 14. Alternatively, the first rectifier 24 may be located closer to the second point P2 than the first contact 16 within the first input path 14.

[0048] In the bistable relay 12, when an excitation input is applied to the first coil 22 while the main contact 21 is in the open state, the main contact 21 switches to the closed state. The main contact 21 then remains in the closed state even after the excitation input to the first coil 22 is removed.

[0049] The second coil 23 is a coil that opens the main contact 21 in response to an excitation input from the power supply unit 40. The second coil 23 is excited by the current supplied from the second input path 15. The second input path 15 is a power line drawn from a third point P3 located between the switch 18 and the power supply unit 40 to the second coil 23. The second input path 15 is provided with a second contact 17 and a second rectifier unit 25.

[0050] The second contact 17 is a contact capable of opening and closing the second input path 15. The second contact 17 is controlled to open and close by the control unit 31. In the example in Figure 1, the second contact 17 is an a-contact (make contact). However, the second contact 17 may also be a b-contact (break contact).

[0051] The second rectifier unit 25 rectifies the current supplied from the power supply unit 40. The second rectifier unit 25 includes, for example, a diode with the anode closer to the third point P3. When the second contact 17 is closed, the current supplied from the power supply unit 40 is rectified by the second rectifier unit 25, thereby supplying a DC current to the second coil 23.

[0052] In the example in Figure 1, the second rectifier 25 is built into the bistable relay 12. Alternatively, the second rectifier 25 may be located outside the bistable relay 12 within the second input path 15. In the example in Figure 1, the second rectifier 25 is located closer to the second coil 23 than the second contact 17 within the second input path 15. Alternatively, the second rectifier 25 may be located closer to the third point P3 than the second contact 17 within the second input path 15.

[0053] In the bistable relay 12, when the main contact 21 is in the closed state, applying an excitation input to the second coil 23 causes the main contact 21 to switch to the open state. The main contact 21 remains in the open state even after the excitation input to the second coil 23 is removed.

[0054] The control device 13 is a device that monitors and controls each part of the power switching device 10. The control device 13 includes a control unit 31, a storage unit 32, and a voltage sensor 33. A reading unit 34 may be attached to the control device 13. These parts 31, 32, 33, and 34 are electrically connected to each other by a bus.

[0055] The control device 13 is powered by either the power system 60 or the power supply unit 40. For example, under normal conditions (when the power system 60 is not experiencing a power outage), the control device 13 operates using AC power supplied by the power system 60. In the event of a power outage in the power system 60, the control device 13 operates using AC power supplied by the power supply unit 40. However, under normal conditions, the control device 13 may also operate using only power supplied by the power supply unit 40.

[0056] The control unit 31 includes, for example, a circuit configuration such as a processor. Specifically, the control unit 31 includes one or more CPUs (Central Processing Units). The processor included in the control unit 31 may be a GPU (Graphics Processing Unit). The control unit 31 reads the computer program stored in the memory unit 32 and performs various calculations and controls.

[0057] The control unit 31 may be a programmable logic device (PLD) whose internal circuit configuration can be rewritten. In this case, the control unit 31 may be a complex PLD (CPLD) or a field programmable gate array (FPGA). If the control unit 31 is a PLD, the control unit 31 performs various calculations and controls based on a program that has been pre-written to the control unit 31.

[0058] The storage unit 32 has volatile memory and non-volatile memory, and stores various types of data. The volatile memory includes, for example, RAM (Random Access Memory). The non-volatile memory includes, for example, flash memory, HDD (Hard Disk Drive), SSD (Solid State Drive), or ROM (Read Only Memory). The storage unit 32 stores computer programs and various parameters in the non-volatile memory, for example.

[0059] The voltage sensor 33 is a sensor that monitors the voltage of the power system 60. The voltage sensor 33 is installed in the AC circuit 11 between the bistable relay 12 and the power system 60. The voltage sensor 33 detects the voltage of the power system 60 in the AC circuit 11 and outputs the detected voltage to the control unit 31.

[0060] When a reading unit 34 is attached to the control device 13, the reading unit 34 reads information from a computer-readable recording medium 35. The recording medium 35 is, for example, an optical disc such as a CD or DVD, or a USB flash memory. The reading unit 34 is, for example, an optical drive or a USB terminal. The recording medium 35 contains a computer program and various parameters, and by having the reading unit 34 read the recording medium 35, the computer program and various parameters are stored in the non-volatile memory of the storage unit 32.

[0061] The control unit 31 determines the state of the power system 60 (specifically, whether or not there is a power outage) based on the detection result of the voltage sensor 33. Based on the determination result, the control unit 31 controls the first contact 16, the second contact 17, the switch 18, and the power supply unit 40. The control operation by the control unit 31 will be described later.

[0062] The switch 18 opens and closes the electrical circuit between the power supply unit 40 and the first point P1. The switch 18 is controlled to open and close by the control unit 31.

[0063] [1.3 Control method for power switching device 10] Next, the control method performed by the power switching device 10 will be described. In the power switching device 10, for example, the control unit 31 reads a computer program stored in the memory unit 32 and performs various calculations and processes, thereby performing the power switching.

[0064] Figures 2 to 4 are flowcharts illustrating a control method according to an embodiment. The order of the steps shown in Figures 2 to 4 may be rearranged as appropriate.

[0065] Refer to Figure 2. First, the control unit 31 controls the power supply device 1 to its initial state (step S11). For example, at the initial point when the power switching device 10 is installed in the customer's premises, the power system 60 is not connected to the power switching device 10, and the DC power supply 41 of the power supply unit 40 is in a state where it can supply DC power (in the case of a battery, it is fully charged). In this state, the worker installing the power switching device 10 in the customer's premises connects the power supply unit 40 to the power switching device 10. This starts the supply of power from the power supply unit 40 to the control device 13.

[0066] In this state, the control unit 31 opens the first contact 16 and closes the second contact 17. The control unit 31 also opens the switch 18. In this state, the control unit 31 controls the inverter 43. As a result, the inverter 43 converts the DC power from the DC power supply 41 into AC power and outputs it to the third point P3. The AC power output from the power supply unit 40 (inverter 43) is supplied to the second input path 15, rectified in the second rectifier unit 25, and then the second coil 23 is excited, which opens the main contact 21.

[0067] The control unit 31 opens the main contact 21 and then the second contact 17, thereby removing the excitation input to the second coil 23 while keeping the main contact 21 in the open (off) state. The control unit 31 then switches the control of the inverter 43 and then closes the switch 18. As a result, the power supply device 1 returns to its initial state. That is, the main contact 21, the first contact 16 and the second contact 17 are open, and the switch 18 is closed. In this state, the inverter 43 can convert the DC power of the DC power supply 41 into AC power and output it to the load 70.

[0068] Next, power supply from the power grid 60 is initiated (step S12). For example, a worker installing the power switching device 10 inside the customer's premises connects the wiring of the power grid 60 to the terminals of the power switching device 10, thereby initiating power supply from the power grid 60.

[0069] Next, the control unit 31 closes the first contact 16 based on the power supply from the power system 60 (step S13). Specifically, when the voltage detected by the voltage sensor 33 falls within a predetermined range due to the power supply from the power system 60 (for example, if the power system 60 is single-phase 100V, the detected voltage is between 95V and 107V), the control unit 31 determines that "there is power supply from the power system 60". After this determination, the control unit 31 closes the first contact 16.

[0070] When the first contact 16 is closed, AC current from the power system 60 is supplied to the first input path 14, and after being rectified in the first rectifier unit 24, the first coil 22 is excited, thereby closing the main contact 21 (step S14). After the main contact 21 is closed (on), the control unit 31 opens the first contact 16 (step S15). This removes the excitation input to the first coil 22 while maintaining the closed state of the main contact 21.

[0071] In step S14, the main contact 21 is closed (first state), thereby supplying AC power from the power system 60 to the power supply unit 40 and the load 70 (step S16). Here, the state in which the main contact 21 is closed and AC power is supplied from the power system 60 to the load 70 is referred to as the "first mode".

[0072] AC power is supplied to the power supply unit 40 via the first point P1, the switch 18, and the third point P3. The AC power is converted to DC power in the inverter 43, then stepped up or down in the chopper 42 and input to the DC power supply 41. This charges the DC power supply 41 (storage battery).

[0073] Furthermore, if the DC power supply 41 is a solar cell, the inverter 43 stops operating in step S16 to prevent DC power from being supplied to the DC power supply 41. Alternatively, if the DC power supply 41 is a solar cell, in step S13, the control unit 31 may close the first contact 16 and open the switch 18 to disconnect the power system 60 and the power supply unit 40 in the first mode.

[0074] Refer to Figure 3. When the power system 60 experiences a power outage (step S21), the control unit 31 detects the power outage based on the voltage detected by the voltage sensor 33 (step S22). Here, the power system 60 is described as having a "power outage" when the AC power supplied from the power system 60 falls below the standard power by a predetermined value. Specifically, the control unit 31 determines that the power system 60 has a power outage if the voltage detected by the voltage sensor 33 remains outside a predetermined range (for example, if the power system 60 is single-phase 100V, the detected voltage is less than 95V) for a predetermined period of time.

[0075] After detecting a power outage, the control unit 31 opens the switch 18 (step S23). This disconnects the power supply unit 40 from the power system 60 and the load 70, suppressing the flow of AC power from the power supply unit 40 into the power system 60 during the power outage (reverse power flow).

[0076] Next, the control unit 31 switches the control of the inverter 43 (step S24). As a result, the inverter 43 converts the DC power from the DC power supply 41 into AC power and outputs it to the third point P3.

[0077] Next, the control unit 31 closes the second contact 17 (step S25). As a result, the current output from the inverter 43 is supplied to the second input path 15, rectified in the second rectifier unit 25, and then the second coil 23 is excited, opening the main contact 21 (step S26). This disconnects the power system 60 from the power supply unit 40 and the load 70 in the AC circuit 11.

[0078] After the main contact 21 is in the open state (second state), the control unit 31 opens the second contact 17 (step S27). This removes the excitation input to the second coil 23 while maintaining the open state of the main contact 21.

[0079] Furthermore, after the main contact 21 opens, the control unit 31 closes the switch 18 (step S28). This electrically connects the power supply unit 40 and the load 70. At this time, the power system 60 and the power supply unit 40 are isolated, and the inverter 43 is in a state where it converts the DC power of the DC power supply 41 into AC power and outputs it to the load 70. Therefore, the power supply unit 40 supplies AC power to the load 70 while suppressing reverse power flow to the power system 60 (step S29). Here, the state in which the main contact 21 is in the second state and AC power is supplied from the power supply unit 40 to the load 70 is called the "second mode".

[0080] Refer to Figure 4. When power is restored to the power system 60 (step S31), the control unit 31 detects the restoration of power based on the voltage detected by the voltage sensor 33 (step S32). For example, when the voltage detected by the voltage sensor 33 falls within a predetermined range (for example, if the power system 60 is single-phase 100V, the detected voltage is between 95V and 107V), the control unit 31 determines that "power is being supplied from the power system 60 (i.e., the power system 60 has been restored)."

[0081] After the determination, the control unit 31 switches the control of the inverter 43 (step S33). Then, the control returns to step S13 in Figure 2, and the control from step S13 onward is repeated. In this way, a series of control methods in the power switching device 10 are executed.

[0082] [1.4 Effects of the Power Switching Device 10] The control unit 31 of the power switching device 10 switches between a first mode, which supplies AC power from the power system 60 to the load 70 by closing the bistable relay 12 and connecting the power system 60 and the load 70, and a second mode, which supplies AC power from the power supply unit 40 to the load 70 by opening the bistable relay 12 and disconnecting the power system 60 and the load 70.

[0083] By using a bistable relay 12 when switching the power source supplying AC power to the load 70, circuit degradation due to relay heat generation can be suppressed compared to using a monostable relay. Therefore, the reliability of the power switching device 10 can be further improved. In addition, by shortening the time for which current is supplied to the relay compared to when using a monostable relay, the power consumption required to operate the relay in the power switching device 10 can be reduced.

[0084] The bistable relay 12 includes a first coil 22 that closes the main contact 21 in response to an excitation input from the power system 60. With this configuration, when the power system 60 is experiencing a power outage, the first coil 22 is not energized, and the main contact 21 can be kept open. Furthermore, when power is restored to the power system 60, the main contact 21 can be closed by an excitation input from the power system 60, thereby connecting the power system 60 to the power supply unit 40 and the load 70.

[0085] The bistable relay 12 includes a second coil 23 that opens the main contact 21 in response to an excitation input from the power supply unit 40. By opening the main contact 21 in response to an excitation input from the power supply unit 40, which can operate without power supply from the power system 60, the power system 60 can be isolated from the power supply unit 40 and the load 70 during a power outage. This allows AC power to be supplied from the power supply unit 40 to the load 70 while suppressing reverse power flow to the power system 60 during a power outage.

[0086] The control unit 31 maintains the first contact 16 in an open state from the time it detects a power outage in the power system 60 until it detects the restoration of power to the power system 60. For example, if the first contact 16 is not provided in the first input path 14, even when the power system 60 inputs low-voltage AC power below the reference voltage to the AC circuit 11, excitation input is made to the first coil 22, causing the main contact 21 to close and potentially supplying unstable AC power to the load 70. In contrast, by providing the first contact 16 in the first input path 14 and maintaining the first contact 16 in an open state from the time it detects a power outage in the power system 60 until it detects the restoration of power to the power system 60, the power system 60 can be connected to the load 70 while the power system 60 is supplying a voltage within the reference range. This suppresses the supply of unstable AC power to the load 70.

[0087] Furthermore, the control unit 31 keeps the first contact 16 open until it detects the restoration of power to the power system 60 and switches the control of the inverter 43. If the main contact 21 is closed while the inverter 43 is outputting power from the DC power supply 41, there is a risk that reverse power flow from the power supply unit 40 will flow into the power system 60. In contrast, since the control unit 31 keeps the first contact 16 open until it switches the control of the inverter 43, no excitation input is made to the first coil 22 during this period, and the main contact 21 is not closed. Therefore, it is possible to suppress the flow of reverse power flow from the power supply unit 40 into the power system 60.

[0088] The control unit 31 closes the second contact 17 at least temporarily from the time it detects a power outage in the power system 60 until it detects the restoration of power in the power system 60. For example, if the second contact 17 is not provided in the second input path 15, the second coil 23 is continuously energized while the inverter 43 is converting the DC power of the DC power supply 41 to AC power and outputting it. In the example shown in Figures 2 to 4, the second coil 23 is continuously energized from step S24 to step S33, which may cause the bistable relay 12 to overheat and degrade the circuit included in the power switching device 10. In contrast, by providing the second contact 17 in the second input path 15 and configuring it to close the second contact 17 at least temporarily, the time during which current is supplied to the second coil 23 can be shortened. This suppresses heat generation in the bistable relay 12, thereby suppressing circuit degradation.

[0089] The control unit 31 maintains the switch 18 in the open state from the time the power system 60 is shut down until the bistable relay 12 is opened, and closes the switch 18 from the time the bistable relay 12 is opened until the power system 60 is restored to power. In other words, during a power outage in the power system 60, at least one of the bistable relay 12 and the switch 18 is in the open state. As a result, the power supply unit 40 is shut off from the power system 60 by at least one of the bistable relay 12 and the switch 18. This prevents reverse power flow from the power supply unit 40 into the power system 60.

[0090] [2. Variant] While embodiments of this disclosure have been described above, various modifications are possible to this disclosure in addition to the forms described above. Hereinafter, modifications of embodiments of this disclosure will be described. In the following modifications, components similar to those in the embodiments are denoted by the same reference numerals and their descriptions are omitted.

[0091] [2.1 Modification 1 of the first and second input paths] In the power switching device 10 according to this embodiment, a first contact 16 is provided in the first input path 14, and a second contact 17 is provided in the second input path 15. However, at least one of the first contact 16 and the second contact 17 may be omitted.

[0092] [2.2 Modifications of the First and Second Input Paths 2] Figure 5 shows the configuration of a modified power switching device 10a. The power switching device 10a differs from the power switching device 10 of the embodiment in that the power that energizes the first coil 22 is adjusted by the first converter 51 (or second converter 53), and the power that energizes the second coil 23 is adjusted by the third converter 55.

[0093] In the first input path 14 of the power switching device 10a, the first contact 16a (with the same internal configuration as the first contact 16) is located closer to the first coil 22 than the first rectifier 24. The power switching device 10a further comprises a first converter 51, a third input path 52, a second converter 53, a third rectifier 54, and a third converter 55.

[0094] The first converter 51 is located in the first input path 14, closer to the power system 60 than the first rectifier 24 and the first contact 16a. The first converter 51 is an AC-DC converter that converts AC power supplied from the power system 60 into DC power of a predetermined voltage V1. The predetermined voltage V1 is, for example, 12V.

[0095] The third input circuit 52 is an electrical circuit connecting the first terminal P4 and the second terminal P5. The first terminal P4 is located between the DC power supply 41 and the inverter 43. In the example in Figure 5, the first terminal P4 is located between the DC power supply 41 and the chopper 42, but the first terminal P4 may also be located between the chopper 42 and the inverter 43. The second terminal P5 is the terminal opposite to the first terminal P4. The second terminal P5 is located between the first rectifier 24 and the first contact 16a.

[0096] The second converter 53 is provided in the third input path 52. The second converter 53 is a DC-DC converter that converts DC power from the DC power supply 41 into DC power of a predetermined voltage V1. That is, the DC power output from the first converter 51 to the second terminal P5 and the DC power output from the second converter 53 to the second terminal P5 are both at the same predetermined voltage V1.

[0097] The third rectifier 54 is located in the third input path 52, closer to terminal P5 than the second converter 53. The third rectifier 54 rectifies the DC power output from the second converter 53.

[0098] The third converter 55 is located in the second input path 15, closer to the third point P3 than the second rectifier 25 and the second contact 17. The third converter 55 is an AC-DC converter that converts AC power supplied from the power supply unit 40 (i.e., AC power output from the inverter 43) into DC power of a predetermined voltage V2. The predetermined voltage V2 may be the same as or different from the predetermined voltage V1 output from the first converter 51 and the second converter 53, respectively.

[0099] In the power switching device 10a, the first coil 22 is excited by DC power of a predetermined voltage V1 adjusted in the first converter 51 or the second converter 53, so the first coil 22 can be stably excited. Also, the second coil 23 is excited by DC power of a predetermined voltage V2 adjusted in the third converter 55, so the second coil 23 can be stably excited.

[0100] Furthermore, in the power switching device 10a, a third input path 52, which supplies current from the DC power supply 41, is connected between the first rectifier 24 and the first contact 16a of the first input path 14, which supplies current from the power system 60. With this configuration, even if one of the first converter 51 and the second converter 53 fails, the other of the first converter 51 and the second converter 53 can continue to supply DC current to the first coil 22. By providing redundancy in the circuitry within the power switching device 10a in this way, the reliability of the power switching device 10a can be further enhanced.

[0101] In this case, if a current sensor is provided in the power switching device 10a to detect the current value supplied from the power system 60 to the load 70, it is preferable to place the current sensor between the second point P2 and the main contact 21 in the AC circuit 11. If the current sensor is placed closer to the power system 60 than the second point P2 in the AC circuit 11, it will detect both the current flowing to the load 70 and the current flowing to the first input circuit 14, making it impossible to accurately detect the current flowing to the load 70.

[0102] Furthermore, if the current supplied to the load 70 is large, or if high accuracy is not required for the detected current value, the current sensor may be installed in the AC circuit 11 at a position closer to the power system 60 than the second point P2.

[0103] [2.3 Modified versions of the second input path] Figure 6 shows the configuration of a modified power switching device 10b. The power switching device 10b differs from the power switching device 10 of the embodiment in that a second input path 15a is provided instead of the second input path 15, and the switch 18 is omitted.

[0104] The second input circuit 15a is an electrical circuit drawn from the first terminal P4 between the DC power supply 41 and the inverter 43 to the second coil 23. DC current is supplied to the second input circuit 15a from the DC power supply 41. The second input circuit 15a is provided with a second contact 17 and a second rectifier 25, similar to the second input circuit 15.

[0105] In the power switching device 10b, no switch 18 is provided between the inverter 43 and the first point P1. The control method performed by the control unit 31 in the power switching device 10b will be described below.

[0106] Refer to Figure 3. When the control unit 31 of the power switching device 10b detects a power outage in the power system 60, it omits the step S23 of opening the switch 18 and the step S24 of switching the control of the inverter 43 to a control that converts the DC power of the DC power supply 41 to AC power and outputs it, and instead performs control to stop the operation of the inverter 43. This makes it possible to suppress reverse power flow from the power supply unit 40 to the power system 60.

[0107] After stopping the operation of the inverter 43, the control unit 31 of the power switching device 10b closes the second contact 17 (step S25) and energizes the second coil 23 to open the main contact 21 (step S26). Subsequently, the control unit 31 opens the second contact 17 (step S27).

[0108] After opening the main contact 21, the control unit 31 omits step S28, which involves closing the switch 18, and instead switches the control of the inverter 43 to a control that converts the DC power of the DC power supply 41 into AC power for output. As a result, power is supplied from the power supply unit 40 to the load 70 (second mode: step S29).

[0109] As described above, when the second input path 15a is drawn from the first terminal P4, the switch 18 can be omitted. In this case, the control unit 31 can suppress reverse power flow to the power system 60 by stopping the operation of the inverter 43 from the time it detects a power outage in the power system 60 until the main contact 21 opens. Furthermore, after the main contact 21 opens, the control unit 31 can supply AC power from the power supply unit 40 to the load 70 while suppressing reverse power flow to the power system 60 by switching the control of the inverter 43 to a control that converts the DC power of the DC power supply 41 to AC power and outputs it.

[0110] [2.4 Variations of Bistable Relays] The bistable relay 12 in this embodiment is a double-wound relay, but a single-wound bistable relay may also be used. In this case, for example, the second coil 23 is omitted. The first coil 22 closes the main contact 21 with an excitation input from a current flowing in the first direction, and opens the main contact 21 with an excitation input from a current flowing in the second direction opposite to the first direction. The second input path 15 is drawn from the third point P3 and connected to a position in the first input path 14 that is closer to the first coil 22 than to the first rectifier 24, via the second contact 17 and the second rectifier 25.

[0111] Furthermore, a switching element is newly connected to the portion of the first input path 14 to which the second input path 17 is connected. The switching element is controlled by the control unit 31, and when supplying current in the first direction from the first input path 14 to the first coil 22, the switching element disconnects the second input path 17 from the first input path 14. On the other hand, when supplying current in the second direction from the second input path 15 to the first coil 22, the switching element disconnects the first input path 14 from the first coil 22. Even with this configuration, the reliability of the power switching device 10 can be improved compared to conventional designs by suppressing circuit degradation due to heat generation from the relay, compared to monostable relays.

[0112] [3. Supplementary Notes] Furthermore, at least some of the embodiments and various modifications described above may be combined in any way. Also, the embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of this disclosure is indicated by the claims, and all modifications within the meaning and scope of equivalence to the claims are intended. [Explanation of Symbols]

[0113] 1 Power supply device 10 Power Switching Device 10a Power Switching Device 10b Power Switching Device 11 AC line 12 Bistable Relays 13 Control device 14. First Input Path 15. Second input path 15a Second input path 16. First Contact Point 16a First contact 17. Second contact point 18 Switch 21 Main contacts 22. First coil 23. Second coil 24 1st rectifier 25 2nd rectifier 31 Control Unit 32 Storage section 33 Voltage Sensor 34 Reading Unit 35 Recording media 40 Power supply section 41 DC power supply 42 Chopper 43 Inverter 51 First Converter 52 Third Input Path 53 Second Converter 54 3rd rectifier 55 Third Converter 60 Power system 70 load P1 1st point P2 2nd point P3 3rd point P4 1st end P5 2nd end A1 connector A2 connector A3 Connector V1 Predetermined voltage V2 specified voltage

Claims

1. AC circuits installed between the power system and the load, A bistable relay is provided in the aforementioned AC circuit at a position closer to the power system than the first point where a power supply unit different from the power system is connected in parallel to the power system, A control unit that switches between a first mode in which AC power is supplied from the power system to the load by closing the bistable relay and connecting the power system and the load, and a second mode in which AC power is supplied from the power supply unit to the load by opening the bistable relay and disconnecting the power system and the load, Equipped with, The aforementioned bistable relay is The aforementioned AC circuit has a main contact that can open and close, A first coil that closes the main contacts in response to an excitation input from the power system, A second coil opens the main contacts in response to the excitation input from the power supply unit, Includes, A first input path that supplies current from the power system to excite the first coil, A first contact capable of opening and closing the first input path, Furthermore, The control unit maintains the first contact open from the time it detects a power outage in the power system until it detects the restoration of power to the power system. Power switching device.

2. A first rectifier unit provided in the first input path for rectifying the current supplied from the power system, A first converter is provided in the first input path at a position closer to the power system than the first rectifier and the first contact, and converts AC power supplied from the power system into DC power of a predetermined voltage. Furthermore, The power switching device according to claim 1.

3. The first contact is provided in the first input path at a position closer to the first coil than the first rectifier section. The aforementioned power supply unit is A DC power supply that provides DC power, An inverter that converts DC power from the aforementioned DC power source into AC power, Includes, The aforementioned power switching device is A third input path having a first end connected between the DC power supply and the inverter, and a second end opposite to the first end connected between the first rectifier and the first contact, A second converter is provided in the third input path and converts DC power from the DC power supply into DC power of a predetermined voltage, Furthermore, The power switching device according to claim 2.

4. A second input path supplies current from the power supply unit to excite the second coil, A second contact capable of opening and closing the second input path, Furthermore, The control unit, after detecting a power outage in the power system, closes the second contact at least temporarily until it detects the restoration of power to the power system. The power switching device according to claim 1.

5. The system includes a switch for opening and closing the electrical circuit between the power supply unit and the first point, The control unit, The switch is kept open from the time the power system experiences a power outage until the bistable relay is opened. Close the switch between the time the bistable relay is opened and the time the power system is restored. A power switching device according to any one of claims 1 to 4.

6. A power switching device according to any one of claims 1 to 4, The aforementioned power supply unit, Equipped with, Power supply device.

7. A control method for a power switching device that switches the power source supplying AC power to a load between a power grid and a power supply unit different from the said power grid, The power switching device includes a bistable relay provided in an AC circuit between the power system and the load, at a position closer to the power system than the first point where the power supply unit is connected in parallel to the power system. The aforementioned bistable relay is The aforementioned AC circuit has a main contact that can open and close, A first coil that closes the main contacts in response to an excitation input from the power system, A second coil opens the main contacts in response to the excitation input from the power supply unit, Includes, The aforementioned power switching device is A first input path that supplies current from the power system to excite the first coil, A first contact capable of opening and closing the first input path, Furthermore, The control method described above is When AC power is supplied from the power system, the first step is to close the first contact, thereby closing the bistable relay by supplying current through the first input path, connecting the power system and the load, and supplying AC power from the power system to the load; In the event of a power outage in the aforementioned power system, the second step is to open the bistable relay to disconnect the power system from the load, thereby supplying AC power from the power supply unit to the load. Equipped with, The second step includes keeping the first contact open from the time a power outage in the power system is detected until the power is restored to the power system. Control method.

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