Power supply equipment

Abstract

It supplies more power to the load than the power supply normally capable of providing. [Solution] The power generation unit 10 generates output power including DC power and charging power, and has a power output unit 1 that outputs DC power based on normal power generated by a normal power source, and a storage battery 2 provided in parallel with the power output unit 1 that stores charging power charged by DC power, and a power supply unit 4 that supplies output power to a load, a switching unit provided between the power generation unit 10 and the power supply unit 4 that switches between a state in which output power is supplied to the power supply unit 4 and a state in which output power is not supplied, and a control unit 9 that controls the state of the switching unit to switch between a first state in which the storage battery is charged by DC power without supplying output power to the load, and a second state in which the power supply unit 4 can supply output power to the load.

Description

[Technical Field]

[0001] The present invention relates to a power supply device that supplies power to a load. [Background technology]

[0002] Power supply devices such as uninterruptible power supplies supply power to the load from their onboard batteries when the normal power supply becomes unable to supply power to the load due to a power outage or the like (for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-54020 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] Sometimes, a load requires more power than the normal power supply can provide. The technology described in Patent Document 1 had the problem that it could not supply more power to the load than the normal power supply could provide.

[0005] Therefore, the present invention has been made in view of these points, and aims to provide a power supply device that can supply more power to a load than the power that can be supplied by a normal power supply. [Means for solving the problem]

[0006] A power supply device according to a first aspect of the present invention includes a power output unit that outputs DC power based on normal power generated by a normal power source, a storage battery provided in parallel with the power output unit and storing charging power charged by the DC power, a power generation unit that generates output power including the DC power and the charging power, a power supply unit that supplies the output power to a load, a switching unit provided between the power generation unit and the power supply unit and switching between a state in which the output power is supplied to the power supply unit and a state in which the output power is not supplied, and a control unit that controls the state of the switching unit to switch between a first state in which the storage battery is charged by the DC power without supplying the output power to the load, and a second state in which the power supply unit can supply the output power to the load.

[0007] The power supply device further includes a voltage detection unit for detecting the battery voltage of the storage battery, and the control unit may set the power supply device to the first state by switching the switching unit to a state in which the output power is not supplied to the power supply unit while the battery voltage is less than a first voltage, and switch the power supply device from the first state to the second state by switching the switching unit to a state in which the output power is supplied to the power supply unit in response to the battery voltage changing from less than a first voltage to a first voltage or higher.

[0008] The control unit may switch the power supply device from the second state to the first state by switching the switching unit to a state in which it does not supply the output power to the power supply unit when the battery voltage changes from a second voltage or higher (lower than the first voltage) to a voltage lower than the second voltage.

[0009] When the power supply device is in the second state, the power output unit changes the DC power output according to the load state as long as the DC power output is below a predetermined threshold, and when the DC power output reaches the threshold, it does not need to increase the DC power regardless of the load state.

[0010] When the power supply device is in the second state, the power output unit may increase the DC power output by increasing the duty cycle of pulse width modulation as the power consumption of the load increases, as long as the DC power output is less than the threshold.

[0011] The storage battery may output the charging power when the power that the power supply unit should supply to the load is greater than the threshold. The storage battery may output the charging power while the relationship between the input impedance of the power supply unit and the input impedance of the storage battery satisfies the condition that DC power is not supplied to the storage battery. The storage battery may output the charging power after the input impedance of the power supply unit becomes less than or equal to the input impedance of the storage battery.

[0012] The storage battery may be charged based on the DC power while the relationship between the input impedance of the power supply unit and the input impedance of the storage battery satisfies the condition that the DC power output by the power output unit is supplied to the storage battery.

[0013] The power supply unit may supply the output power to the load via the output terminal, and the control unit may control the power supply unit and the switching unit to store the supplied power in the storage battery when set to a mode in which power is supplied from the battery of an electric vehicle connected to the output terminal.

[0014] When the control unit is set to a mode for supplying power to an electric utility, it may control the power supply unit and the switching unit to return the power stored in the battery to the electric utility from the input terminal side. [Effects of the Invention]

[0015] According to the present invention, it is possible to supply a load with more power than that that can be supplied by the normal power supply. [Brief explanation of the drawing]

[0016] [Figure 1] It is a diagram showing an overview of the power supply device of the embodiment. [Figure 2] It is a diagram for explaining changes in the operating state of the power supply device. [Figure 3] It is a flowchart showing the processing procedure of power supply to a load by the power supply device. [Figure 4] It is a diagram showing the configuration of the power supply device of the modified example.

Mode for Carrying Out the Invention

[0017] [Overview of Power Supply Device 100] FIG. 1 is a diagram showing an overview of the power supply device 100 of the present embodiment. The power supply device 100 is supplied with normal power from a normal power source (not shown). The normal power source is, for example, a commercial AC power source. The normal power source is not limited to a commercial AC power source as long as it is a device that generates power, and may be an industrial power source, a solar power generation device, a power generation device using hydrogen fuel or fossil fuel, or a storage battery.

[0018] The power supply device 100 supplies power based on the normal power supplied from the normal power source to a load. The power supply device 100 operates as an uninterruptible power supply device. When the supply of normal power from the normal power source stops, the power supply device 100 supplies output power from the built-in storage battery 2 to the load. The storage battery 2 stores normal power and discharges the stored charging power when the supply of normal power stops. When the power supply device 100 is connected to a load that requires more power than the normal power that can be supplied by the normal power source, in addition to the power from the normal power source, the charging power stored in the built-in storage battery 2 is supplied to the load.

[0019] In this way, the power supply device 100 can supply more power to the load than the normal power that can be supplied from the normal power source. For example, the power supply device 100 can rapidly charge an EV (Electric Vehicle) or charge many smartphones simultaneously during a disaster. The power supply device 100 comprises a power output unit 1, a storage battery 2, a first relay 3, a power supply unit 4, a second relay 5, a relay control unit 6, a relay control unit 7, a voltage detection unit 8, and a control unit 9.

[0020] The power output unit 1 outputs DC power based on the normal power generated by the normal power supply. For example, the power output unit 1 is a DC / AC inverter that converts AC power supplied from the normal power supply via the input terminal 11 into DC power. If DC normal power is supplied from the normal power supply, the power output unit 1 may also be a DC / DC converter that converts the supplied DC normal power into power. The DC power P1 supplied by the power output unit 1 is shown by a thick arrow in Figure 1.

[0021] The power output unit 1 operates based on control data input from the control unit 9. When the power output unit 1 detects that the supply of normal power from the normal power source to the power output unit 1 has started, it may input information to the control unit 9 indicating that the supply of normal power has started. When the power output unit 1 detects that the supply of normal power from the normal power source to the power output unit 1 has stopped, it may input information to the control unit 9 indicating that the supply of normal power has stopped.

[0022] In the example shown in Figure 1, the power output unit 1 has a PWM (Pulse Width Modulation) control circuit that changes the duty cycle according to the load size, for example, using the PWM method. The power output unit 1 outputs DC power P1 corresponding to the DC voltage and DC current obtained by smoothing the voltage generated by the PWM control circuit. The power output unit 1 outputs the DC power P1 to the storage battery 2 or the power supply unit 4.

[0023] In the first state, when the generated DC power P1 is not supplied to the load via the power supply unit 4, the power output unit 1 charges the storage battery 2 with the DC power P1. In the second state, when the DC power P1 can be supplied to the load, the power output unit 1 changes the DC power P1 according to the load condition as long as the output DC power P1 is below a predetermined threshold. The threshold is, for example, a value smaller than the normal power supplied to the power output unit 1.

[0024] For example, the power output unit 1 increases the DC power P1 as the power consumption of the load connected to the power supply unit 4 increases. In this case, the power output unit 1 increases the DC power P1 by increasing the duty cycle of the PWM. The power output unit 1 has a limiter to prevent it from outputting power exceeding a preset threshold, and when the output DC power P1 reaches the threshold, it does not increase the DC power P1 regardless of the load condition. The threshold is determined, for example, based on the maximum value of DC power P1 that the power output unit 1 can output.

[0025] The first relay 3 is located between the power output unit 1 and the storage battery 2. Based on the control signal output by the relay control unit 6, the first relay 3 switches between a state in which the power output unit 1 and the storage battery 2 are connected and a state in which the power output unit 1 and the storage battery 2 are not connected. In other words, the first relay 3 switches between an ON state in which the DC power P1 output by the power output unit 1 is supplied to the storage battery 2 or the power supply unit 4, and an OFF state in which the DC power P1 output by the power output unit 1 is not supplied.

[0026] The storage battery 2 is, for example, a lithium-ion battery, a lithium titanate battery, or an all-solid-state battery. The storage battery 2 is installed in parallel with the power output unit 1. The storage battery 2 comprises, for example, multiple storage battery modules connected in series. The storage battery 2 stores charging power charged by DC power P1. The storage battery 2 supplies the stored charging power to the load via the power supply unit 4. The charging power P2 supplied by the storage battery 2 to the load is shown by a thick arrow in Figure 1.

[0027] As shown by the dashed rectangle in Figure 1, the power output unit 1, the battery 2, and the first relay 3 constitute the power generation unit 10. The power generation unit 10 generates output power P3, which includes the DC power P1 output by the power output unit 1 and the charging power P2 stored in the battery 2. The output power P3 is shown by a thick arrow in Figure 1.

[0028] The power supply unit 4 supplies the output power P3 generated by the power generation unit 10 to the load. The power supply unit 4 supplies the output power P3 to the load via the output terminal 12. For example, the power supply unit 4 is a DC / AC inverter that converts the output power generated by the power generation unit 10 into AC power. The power supply unit 4 may also be a DC / DC converter that converts the output power generated by the power generation unit 10 into DC power.

[0029] When both the first relay 3 and the second relay 5 are ON, the battery 2 charges based on the DC power P1 output by the power output unit 1, or outputs charging power P2 to the power supply unit 4. More specifically, the battery 2 charges based on the DC power P1 while the relationship between the input impedance of the power supply unit 4 and the input impedance of the battery 2 satisfies the conditions for the DC power P1 output by the power output unit 1 to be supplied to the battery 2. Specifically, the battery 2 charges based on the DC power P1 when the input impedance of the power supply unit 4 is greater than the input impedance of the battery 2, or while the second relay 5 is OFF.

[0030] Meanwhile, the battery 2 outputs charging power P2 while the relationship between the input impedance of the power supply unit 4 and the input impedance of the battery 2 satisfies the condition that the DC power P1 output by the power output unit 1 is not supplied to the battery 2. The condition that the DC power P1 is not supplied to the battery 2 is, for example, that the input impedance of the power supply unit 4 is less than or equal to the input impedance of the battery 2.

[0031] When the power to be supplied to the load increases while the battery 2 is not discharging its charged power P2, and the DC power P1 output by the power output unit 1 reaches a threshold, the output impedance of the power output unit 1 at the time the DC power P1 reaches the threshold becomes greater than the output impedance of the battery 2. As a result, the battery 2 starts outputting the charged power P2. In this way, the battery 2 can compensate for the shortage of DC power P1 with the charged power P2 when the power that the power supply unit 4 should supply to the load exceeds the maximum DC power P1 that the power output unit 1 can output.

[0032] The second relay 5 is located between the power generation unit 10 and the power supply unit 4. The second relay 5 operates as a switching unit to switch between an ON state, in which the output power P3 generated by the power generation unit 10 is supplied to the power supply unit 4, and an OFF state, in which this output power P3 is not supplied to the power supply unit 4. The second relay 5 switches between the ON state and the OFF state based on a control signal output by the relay control unit 7.

[0033] The relay control unit 6 controls the first relay 3. Based on the control information generated by the control unit 9, the relay control unit 6 switches the first relay 3 between the ON state and the OFF state. The relay control unit 7 controls the second relay 5. Based on the control information generated by the control unit 9, the relay control unit 7 switches the second relay 5 between the ON state and the OFF state. The relay control unit 6 and the relay control unit 7 may be included in the control unit 9.

[0034] The voltage detection unit 8 detects the voltage output by the storage battery 2 (hereinafter referred to as "battery voltage"). The voltage detection unit 8 inputs information indicating the detected battery voltage to the control unit 9.

[0035] The control unit 9 is, for example, a CPU (Central Processing Unit). The control unit 9 controls the operating states of the power output unit 1, the first relay 3, and the second relay 5. The control unit 9 also identifies the battery voltage based on information indicating the battery voltage input from the voltage detection unit 8. The control unit 9 controls the operating state of the power supply unit 4. If the load connected to the output terminal 12 is a robot that repeatedly charges and discharges according to a predetermined schedule, the control unit 9 can predict the power required by the load. In this way, if the control unit 9 can predict the power required by the load connected to the output terminal 12, it calculates the upper limit of the output power P3 as the output power P3 requested by the power supply unit 4 plus a predetermined margin when supplying the predicted power to the load. The control unit 9 may limit the output power P3 supplied to the power supply unit 4 so as not to exceed this upper limit. In this way, the control unit 9 can detect when the battery voltage of the storage battery 2 suddenly drops and the second voltage V th2 The output power P3 can be limited so that it does not become a value smaller than a certain value.

[0036] [Changes in the operating state of the power supply device 100] The power supply device 100 has multiple operating states that change according to the charge state of the storage battery 2 and the magnitude of the load. The control unit 9 changes the operating state by controlling the first relay 3 and the second relay 5 via the relay control unit 6 and the relay control unit 7.

[0037] The control unit 9 switches the on state and the off state of the first relay 3 via the relay control unit 6. The control unit 9 also switches the on state and the off state of the second relay 5 via the relay control unit 7. By controlling the state of the second relay 5, the control unit 9 switches between a first state in which the battery is charged with DC power P2 without supplying the output power P3 generated by the power generation unit 10 to the load, and a second state in which the power supply unit 4 can supply the output power P3 to the load.

[0038] In the examples herein, the control unit 9 switches between a first state and a second state based on the battery voltage of the storage battery 2 detected by the voltage detection unit 8. More specifically, the control unit 9 switches between a first state and a second state when the battery voltage of the storage battery 2 is the first voltage V th1 While the voltage is less than the first voltage V, the power supply device 100 is put into the first state by switching the second relay 5 (corresponding to the switching unit) to a state where the output power P3 generated by the power generation unit 10 is not supplied to the power supply unit 4. The control unit 9 checks when the battery voltage of the storage battery 2 is less than the first voltage V th1 From less than the first voltage V th1 In response to the above changes, the power supply device 100 is switched from the first state to the second state by switching the second relay 5 to a state in which the output power P3 generated by the power generation unit 10 is supplied to the power supply unit 4.

[0039] Figure 2 is a diagram illustrating the changes in the operating state of the power supply device 100. Figure 2(a) shows the change in output power P3 generated by the power generation unit 10. Figure 2(b) shows the change in charging power P2 output from the storage battery 2. In Figure 2(b), the region where a positive value is shown indicates that the storage battery 2 is outputting charging power P2, and the region where a negative value is shown indicates that the storage battery 2 is being charged.

[0040] Figure 2(c) shows the change in DC power P1 supplied by the power output unit 1. Figure 2(d) shows the change in battery voltage of the storage battery 2. Figure 2(e) shows the change in state of the first relay 3. Figure 2(f) shows the change in state of the second relay 5.

[0041] The vertical axis of the graphs in Figures 2(a) to 2(c) represents power, the vertical axis of the graph in Figure 2(d) represents voltage, and the vertical axis of the graphs in Figures 2(e) and 2(f) represents the on / off state of the first relay 3 or the second relay 5, respectively. The horizontal axis represents time.

[0042] In the stopped state, normal power is not supplied from the normal power source to the power output unit 1. In the stopped state, the first relay 3 and the second relay 5 are in the off state. In the stopped state, the power output unit 1 is not connected to either the battery 2 or the power supply unit 4, so it does not supply DC power P1 to either the battery 2 or the power supply unit 4, and as shown in the graph of the stopped state in Figure 2(c), P1 = 0W. Since the battery 2 is not connected to the power supply unit 4, it does not supply charging power P2 to the power supply unit 4, and as shown in Figure 2(b), P2 = 0W.

[0043] When the control unit 9 receives information from the power output unit 1 indicating that the supply of normal power from the normal power source to the power output unit 1 has started while the unit is stopped, it instructs the relay control unit 6 to switch the first relay 3 to the ON state. When the first relay 3 is switched to the ON state, the power supply device 100 enters the first state.

[0044] In the first state, as shown in Figure 2(e), the first relay 3 is ON, and as shown in Figure 2(f), the second relay 5 is OFF. In the first state, the DC power P1 output by the power output unit 1 is not supplied to the power supply unit 4 as output power P3, so P3 = 0W (Figure 2(a)). The control unit 9 charges the storage battery 2 with this DC power P1, so the charging power P2 shows a negative value, as shown in the graph of the first state in Figure 2(b). At this time, the battery voltage of the storage battery 2 gradually increases (Figure 2(d)).

[0045] The battery 2 outputs charging power P2 when the output power that the power supply unit 4 should supply to the load is greater than a threshold. In the first state, while the control unit 9 is charging the battery 2, the battery voltage of the battery 2 gradually increases. The control unit 9 determines when the battery voltage of the battery 2 is V th1 When this happens, the second relay 5 is switched from the off state to the on state. As the second relay 5 switches to the on state, the power supply device 100 transitions from the first state to the second state. In the second state, as shown in Figure 2(e), the first relay 3 remains in the on state.

[0046] The second state includes mode A in which the charging power P2 of the storage battery 2 is not supplied to the power supply unit 4, and mode B in which the charging power P2 of the storage battery 2 is supplied to the power supply unit 4. Fig. 2 shows an example in which the power supply device 100 makes a single transition from mode A to mode B in the second state, but the power supply device 100 may make a plurality of transitions between mode A and mode B in the second state.

[0047] When the output power P3 that the power supply unit 4 should supply to the load is less than or equal to the threshold value, the power supply device 100 operates in mode A. In mode A, as shown in Fig. 2(b), the charging power P2 output from the storage battery 2 becomes 0 W.

[0048] When the output power P3 that the power supply unit 4 should supply to the load is greater than the threshold value, the power supply device 100 operates in mode B. In mode B, the output impedance of the power output unit 1 becomes greater than the output impedance of the storage battery 2. Therefore, after the charging power P2 starts to be output from the storage battery 2, the charging power P2 is supplied to the power supply unit 4. At this time, the output power P3 supplied from the power generation unit 10 to the power supply unit 4 is the sum of the DC power P1 and the charging power P2 (P3 = P1 + P2).

[0049] In mode B, since the charging power P2 supplied from the storage battery 2 to the power supply unit 4 is supplied, the battery voltage of the storage battery 2 gradually decreases as shown in Fig. 2(d). The control unit 9 determines whether the battery voltage of the storage battery 2 detected by the voltage detection unit 8 is less than or equal to the second voltage V th2 The second voltage V th2 is a value lower than the first voltage V th1 The second voltage V th2 is determined according to, for example, the remaining battery level of the storage battery 2 required when the power supply device 100 operates during the emergency stop of the normal power supply.

[0050] The control unit 9 determines that the battery voltage of the storage battery 2 is from the second voltage V th2 or more to the second voltage V th2When the value changes to less than a certain level, the second relay 5 is switched to a state where output power P3 is not supplied to the power supply unit 4, thereby switching the power supply device 100 from the second state to the first state. In this first state, as described above, the storage battery 2 is charged by the DC power P1 output by the power output unit 1. Subsequently, the power supply device 100 switches to the second state, and when the power to be supplied to the load increases, it enters mode B, in which output power P3, including DC power P1 and charging power P2, is supplied to the load.

[0051] [Procedure for supplying power to the load by the power supply device 100] Figure 3 is a flowchart showing the processing procedure for supplying power to a load by the power supply device 100. For example, this processing procedure starts when the power output unit 1 detects that the supply of normal power from the normal power source to the power output unit 1 has started, and the power output unit 1 inputs information indicating that the supply of normal power has started to the control unit 9.

[0052] First, the control unit 9 instructs the relay control unit 6 to switch the first relay 3 from the off state to the on state (S101). The control unit 9 then checks when the battery voltage of the storage battery 2 is the first voltage V th1 The control unit 9 determines whether the battery voltage of the storage battery 2 is greater than or equal to the first voltage V th1 If it is determined that the above is true (YES in S102), the control unit 9 instructs the relay control unit 7 to switch the second relay 5 from the off state to the on state (S103). The control unit 9 determines that the battery voltage of the storage battery 2 is the second voltage V th2 Determine whether the following applies (S104).

[0053] The control unit 9 determines when the battery voltage of the storage battery 2 is the second voltage V th2If the following is determined (YES in S104), the control unit 9 instructs the relay control unit 7 to switch the second relay 5 from the ON state to the OFF state (S105). The control unit 9 determines whether or not the power output unit 1 has detected that the supply of normal power from the normal power source has been stopped (S106). If the power output unit 1 has detected that the supply of normal power has been stopped (YES in S106), the control unit 9 instructs the relay control unit 6 to switch the first relay 3 from the ON state to the OFF state (S107), and terminates the process.

[0054] In the determination in S102, the control unit 9 determines that the battery voltage of the storage battery 2 is the first voltage V th1 If it is determined that the value is less than (NO in S102), the determination in S102 is repeated. The control unit 9 determines in the determination in S104 that the battery voltage of the storage battery 2 is less than the second voltage V th2 If it is determined to be higher (NO in S104), the determination in S104 is repeated. If the power output unit 1 has not detected that the supply of normal power has been stopped in the determination in S106 (NO in S106), the control unit 9 returns to the process in S102.

[0055] [First variation] In this embodiment, an example was described in which the power supply device 100 includes a first relay 3 and a second relay 5. However, the present invention is not limited to an example in which the power supply device 100 includes two relays. For example, the power supply device 100 may include only one relay.

[0056] Figure 4 shows the configuration of the power supply device 100 of this modified example. In the example of Figure 4, the power supply device 100 differs from the power supply device 100 shown in Figure 1 in that it does not have either the first relay 3 or the relay control unit 6 corresponding to the first relay. In the power supply device 100 shown in Figure 4, the circuit elements other than the first relay and the relay control unit 6 are the same as in Figure 1.

[0057] [Second variation] The control unit 9 may be configured by the user to switch to a power acceptance mode in which it accepts power supplied from the EV battery connected to the output terminal 12. In this power acceptance mode, the control unit 9 accepts power supplied from the EV battery connected to the output terminal 12 by controlling the power output unit 1 and the power supply unit 4, for example, when the user purchases power from the EV.

[0058] In power reception mode, the control unit 9 controls the power supply unit 4 and the relay control unit 6 to store the received power in the battery 2. The control unit 9 may also transition to supply mode for the purpose of selling electricity to an electric utility. When set to supply mode, the control unit 9 may control the power supply unit 4 and the relay control unit 7 to return the power stored in the battery 2 from the input terminal 11 side. In this way, the power supply device 100 can exchange power bidirectionally.

[0059] [Effects of the power supply device 100] In the power supply device 100 of this embodiment, the power supply unit 4 supplies output power to the load, which includes DC power based on the normal power supplied from the normal power source and charging power from the storage battery 2. Therefore, the power supply unit 4 can supply power to the load that is greater than the normal power itself.

[0060] Although the present invention has been described above using embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments, and various modifications and changes are possible within the scope of its gist. For example, all or part of the apparatus can be configured by functionally or physically distributing and integrating in any unit. Furthermore, new embodiments resulting from any combination of multiple embodiments are also included in the embodiments of the present invention. The effects of the new embodiments resulting from the combinations are combined with the effects of the original embodiments. [Explanation of symbols]

[0061] 1 Power output section 2. Storage battery 3. First Relay 4 Power supply section 5. 2nd Relay 6 Relay Control Unit 7 Relay Control Unit 8 Voltage detection unit 9. Control Unit 10 Power generation unit 100 Power supply equipment

Claims

1. A power output unit that outputs DC power based on the normal power generated by a normal power supply, and a storage battery provided in parallel with the power output unit and storing the charging power charged by the DC power, and a power generation unit that generates output power including the DC power and the charging power, A power supply unit that supplies the output power to the load, A switching unit is provided between the power generation unit and the power supply unit, and switches between a state in which the output power is supplied to the power supply unit and a state in which the output power is not supplied. A control unit that controls the state of the switching unit to switch between a first state in which the storage battery is charged by the DC power without supplying the output power to the load, and a second state in which the power supply unit can supply the output power to the load, A power supply device equipped with the following features.

2. The system further includes a voltage detection unit for detecting the battery voltage of the aforementioned storage battery, The control unit sets the power supply device to the first state by switching the switching unit to a state in which it does not supply the output power to the power supply unit while the battery voltage is less than the first voltage, and switches the power supply device from the first state to the second state by switching the switching unit to a state in which it supplies the output power to the power supply unit in response to the battery voltage changing from less than the first voltage to the first voltage or higher. The power supply device according to claim 1.

3. The control unit switches the power supply device from the second state to the first state by switching the switching unit to a state in which it does not supply output power to the power supply unit when the battery voltage changes from a second voltage or higher (lower than the first voltage) to a voltage lower than the second voltage. The power supply device according to claim 2.

4. The power output unit, when the power supply device is in the second state, changes the DC power output according to the load state as long as the DC power output is below a predetermined threshold, and when the DC power output reaches the threshold, does not increase the DC power regardless of the load state. A power supply device according to any one of claims 1 to 3.

5. When the power supply device is in the second state, the power output unit increases the DC power output by increasing the duty cycle of pulse width modulation as the power consumption of the load increases, while the DC power output is below the threshold. The power supply device according to claim 4.

6. The storage battery outputs the charging power when the power to be supplied by the power supply unit to the load is greater than the threshold. The power supply device according to claim 4.

7. The storage battery outputs the charging power while the relationship between the input impedance of the power supply unit and the input impedance of the storage battery satisfies the condition that DC power is not supplied to the storage battery. The power supply device according to claim 6.

8. The storage battery outputs the charging power after the input impedance of the power supply unit becomes less than or equal to the input impedance of the storage battery. The power supply device according to claim 7.

9. The storage battery is charged based on the DC power while the relationship between the input impedance of the power supply unit and the input impedance of the storage battery satisfies the condition that the DC power output by the power output unit is supplied to the storage battery. A power supply device according to any one of claims 1 to 3.

10. The power supply unit supplies the output power to the load via the output terminal. When the control unit is set to a mode in which it receives power from the battery of an electric vehicle connected to the output terminal, it controls the power supply unit and the switching unit to store the received power in the storage battery. A power supply device according to any one of claims 1 to 3.

11. When the control unit is set to a mode for supplying power to the electric utility, it controls the power supply unit and the switching unit to return the power stored in the battery to the electric utility from the input terminal side. A power supply device according to any one of claims 1 to 3.

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