Power converter

Abstract

To provide a power conversion device that can reduce power loss. [Solution] The power converter A1 comprises a DC terminal section T1 to which a storage battery B1 is connected and to which a DC storage battery voltage is applied, an AC terminal section T2 to which an AC power supply B2 is connected and to which an AC power supply voltage is applied, a conversion circuit 1 connected between the DC terminal section T1 and the AC terminal section T2 and capable of converting between the storage battery voltage and the power supply voltage, and a changeover switch 3 that switches between a first connection state and a second connection state. When the changeover switch 3 is in the first connection state, the conversion circuit 1 is in a first circuit state that performs a first conversion between the storage battery voltage and the power supply voltage, and when the changeover switch 3 is in the second connection state, it is in a second circuit state that performs a second conversion between the storage battery voltage and a DC relay voltage and a third conversion between the relay voltage and the power supply voltage.

Description

Technical Field

[0001] The present disclosure relates to a power conversion device capable of bidirectionally converting direct current and alternating current.

Background Art

[0002] Conventionally, there is a power conversion device capable of bidirectionally converting direct current and alternating current. Such a power conversion device is used, for example, in a power storage device that charges and discharges a storage battery. Patent Document 1 discloses an example of a conventional power storage device. The power storage device described in Patent Document 1 includes a converter circuit and an inverter circuit. In this power storage device, for example, between the power system and the storage battery, the inverter circuit and the converter circuit appropriately perform power conversion to charge and discharge the storage battery. The converter circuit steps down or steps up the DC voltage supplied from the inverter circuit and outputs it to the storage battery, or steps up or steps down the DC discharge voltage of the storage battery and outputs it to the inverter circuit. The inverter circuit performs an AC / DC conversion operation of converting the input AC voltage into a DC voltage and outputting it, and a DC / AC conversion operation of converting the input DC voltage into an AC voltage and outputting it.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Some rechargeable batteries require periodic initial charging (e.g., redox flow batteries) or complete discharge. Initial charging means charging the battery from 0V, while complete discharge means discharging it to near 0V. During such initial charging and complete discharge, the difference between the battery voltage and the voltage in the power system becomes large, requiring a boost / buck converter circuit. On the other hand, for battery charge and discharge control other than initial charging and complete discharge, an inverter circuit alone may suffice without the boost / buck converter circuit. For example, this is the case when the difference between the battery voltage and the voltage in the power system is small. However, in the charging device described in Patent Document 1, even in such cases, a converter circuit is required, which can result in power loss in the converter. Consequently, this leads to a deterioration in the conversion efficiency of the power converter.

[0005] This disclosure was conceived in view of the above circumstances, and its purpose is to provide a power conversion device that can reduce power loss. [Means for solving the problem]

[0006] The power converter provided by this disclosure comprises a DC terminal section to which a battery is connected and to which a DC battery voltage is applied, an AC terminal section to which an AC power supply is connected and to which an AC power supply voltage is applied, a conversion circuit connected between the DC terminal section and the AC terminal section and capable of converting between the battery voltage and the power supply voltage, and a changeover switch that switches between a first connection state and a second connection state, wherein when the changeover switch is in the first connection state, the conversion circuit is in a first circuit state that performs a first conversion between the battery voltage and the power supply voltage, and when the changeover switch is in the second connection state, it is in a second circuit state that performs a second conversion between the battery voltage and a DC relay voltage and a third conversion between the relay voltage and the power supply voltage.

[0007] In a preferred embodiment of the power converter, the conversion circuit performs the first conversion as a three-phase full-bridge inverter in the first circuit state, and performs the third conversion as a single-phase full-bridge inverter while performing the second conversion as a DC / DC converter in the second circuit state.

[0008] In a preferred embodiment of the power conversion device, the conversion circuit includes an inductor connected to the changeover switch, a first series circuit in which a first high-side switching element and a first low-side switching element are connected in series via a first connection point, a second series circuit in which a second high-side switching element and a second low-side switching element are connected in series, and a third series circuit in which a third high-side switching element and a third low-side switching element are connected in series. The DC terminal section includes a high-potential terminal connected to the high-potential side of the battery and a low-potential terminal connected to the low-potential side of the battery. The inductor is electrically connected between the first connection point and the AC terminal section when the changeover switch is in the first connection state, and electrically connected between the high-potential terminal of the DC terminal section and the first connection point when the changeover switch is in the second connection state.

[0009] In a preferred embodiment of the power converter, the changeover switch includes a first terminal connected to the high-potential terminal of the DC terminal section, a second terminal connected to each of the first high-side switching element, the second high-side switching element, and the third high-side switching element, a third terminal connected to the AC terminal section, and a fourth terminal connected to the inductor. In the first connection state, the first terminal and the second terminal are conductive, and the third terminal and the fourth terminal are conductive. In the second connection state, the first terminal and the fourth terminal are conductive, and the second terminal and the third terminal are open.

[0010] In a preferred embodiment of the power conversion device, a control circuit for controlling the changeover switch is further provided, and the control circuit sets the changeover switch to the second connected state when performing initial charging of the storage battery or complete discharge of the storage battery. [Effects of the Invention]

[0011] In the power conversion device of this disclosure, the conversion circuit switches between a first circuit state and a second circuit state by switching the changeover switch between a first connection state and a second connection state. In the first circuit state, the battery voltage of the storage battery and the power supply voltage of the AC power source are directly converted. In the second circuit state, the battery voltage and the power supply voltage of the AC power source are converted via a DC relay voltage. Here, the conversion between the battery voltage and the relay voltage is a DC voltage-to-DC voltage conversion, and the conversion between the relay voltage and the power supply voltage is a DC voltage-to-AC voltage conversion. With this configuration, by setting the changeover switch to the second connection state, the conversion circuit can be set to the second circuit state, which is suitable for initial charging and complete discharge. Also, by setting the changeover switch to the first connection state, the conversion circuit can be set to the first circuit state, which directly converts the battery voltage of the storage battery and the power supply voltage of the AC power source. Therefore, in battery charge and discharge control, excluding initial charging and complete discharge, it is possible to directly convert the battery voltage and the power supply voltage without going through a relay voltage, thereby reducing power loss that occurs when converting to a relay voltage. In other words, the power conversion device of this disclosure can reduce power loss.

[0012] Other features and advantages of this disclosure will become more apparent from the detailed description below, based on the accompanying drawings. [Brief explanation of the drawing]

[0013] [Figure 1] This figure shows an example configuration of a power conversion device according to one embodiment. [Figure 2] This diagram illustrates the conversion circuit (first circuit state) when the changeover switch is in the first connection state in the power conversion device shown in Figure 1. [Figure 3]This diagram illustrates the conversion circuit (second circuit state) when the changeover switch is in the second connection state in the power conversion device shown in Figure 1. [Figure 4] This figure shows an example of the configuration of a power conversion device according to the first modified example. [Figure 5] This figure shows an example of the configuration of a power conversion device according to the second modified example. [Modes for carrying out the invention]

[0014] Preferred embodiments of the power converter of this disclosure will be described below with reference to the drawings. Hereafter, identical or similar components will be denoted by the same reference numerals, and redundant descriptions will be omitted. The terms "first," "second," "third," etc., in this disclosure are used merely as labels and are not necessarily intended to assign a sequence to the objects.

[0015] Figure 1 shows a power converter A1 according to one embodiment of the present disclosure. As shown in the figure, the power converter A1 comprises a DC terminal section T1, an AC terminal section T2, a conversion circuit 1, a changeover switch 3, and a control circuit 6. The control circuit 6 includes a switch control section 61 and a drive control section 62.

[0016] Power converter A1 is connected between the battery B1 and the AC power source B2. Power converter A1 converts the DC power input from the battery B1 into AC power and outputs it to the AC power source B2. This causes power converter A1 to discharge the battery B1. It also converts the AC power input from the AC power source B2 into DC power and outputs it to the battery B1. This causes power converter A1 to charge the battery B1. The AC power source B2 is, for example, a grid power source (power grid). In this example, power converter A1 is, for example, a grid-connected inverter device (power conditioner for the battery). Note that the battery B1 may be installed in a building or mounted in an electric vehicle. The AC power source B2 is not limited to a grid power source; for example, it may be an inverter device capable of converting DC power to AC power. In addition, other distributed power sources and / or loads such as a solar power conditioner (including solar cells) may be connected to the AC power source B2.

[0017] The DC terminal section T1 is an external terminal in the power converter A1. A battery B1 is connected to the DC terminal section T1, and the DC battery voltage (voltage of battery B1) is applied to it. The DC terminal section T1 includes a high-potential terminal T11 connected to the high-potential terminal of battery B1, and a low-potential terminal T12 connected to the low-potential terminal of battery B1. The AC terminal section T2 is an external terminal in the power converter A1. An AC power supply B2 is connected to the AC terminal section T2, and the AC power supply voltage (voltage of AC power supply B2) is applied to it. In this embodiment, the AC power supply B2 is a three-phase AC power supply, and the power supply voltage is a three-phase AC voltage. The AC terminal section T2 includes three connection terminals T21, T22, and T23 corresponding to each of the three phases.

[0018] The conversion circuit 1 is connected between the DC terminal T1 and the AC terminal T2. The conversion circuit 1 converts between the battery voltage applied to the DC terminal T1 and the power supply voltage applied to the AC terminal T2. As shown in Figure 1, the conversion circuit 1 includes a first series circuit 11, a second series circuit 12, a third series circuit 13, multiple inductors L1 to L3, multiple capacitors C1 to C3, a capacitor C4, two power lines 81 and 82, and three power lines 91 to 93.

[0019] The first series circuit 11, the second series circuit 12, and the third series circuit 13 are respectively connected between two power lines 81 and 82. The first series circuit 11, the second series circuit 12, and the third series circuit 13 are connected in parallel with each other.

[0020] The first series circuit 11 includes a first high-side switching element SW1 and a first low-side switching element SW2. The first high-side switching element SW1 and the first low-side switching element SW2 are connected in series via a first connection point 111. The first high-side switching element SW1 is connected between the power line 81 and the first connection point 111, and the first low-side switching element SW2 is connected between the power line 82 and the first connection point 111. In the present embodiment, a diode D1 is connected in anti-parallel to the first high-side switching element SW1, and a diode D2 is connected in anti-parallel to the first low-side switching element SW2.

[0021] The second series circuit 12 includes a second high-side switching element SW3 and a second low-side switching element SW4. The second high-side switching element SW3 and the second low-side switching element SW4 are connected in series via a second connection point 121. The second high-side switching element SW3 is connected between the power line 81 and the second connection point 121, and the second low-side switching element SW4 is connected between the power line 82 and the second connection point 121. In the present embodiment, a diode D3 is connected in anti-parallel to the second high-side switching element SW3, and a diode D4 is connected in anti-parallel to the second low-side switching element SW4.

[0022] The third series circuit 13 includes a third high-side switching element SW5 and a third low-side switching element SW6. The third high-side switching element SW5 and the third low-side switching element SW6 are connected in series via a third connection point 131. The third high-side switching element SW5 is connected between the power line 81 and the third connection point 131, and the third low-side switching element SW6 is connected between the power line 82 and the third connection point 131. In this embodiment, a diode D5 is connected in antiparallel to the third high-side switching element SW5, and a diode D6 is connected in antiparallel to the third low-side switching element SW6.

[0023] The first to third high-side switching elements SW1, SW3, SW5 and the first to third low-side switching elements SW2, SW4, SW6 are each switched on and off in response to a drive signal input from the control circuit 6 (drive control unit 62, described later). In the illustrated example, the first to third high-side switching elements SW1, SW3, SW5 and the first to third low-side switching elements SW2, SW4, SW6 are each IGBTs (Insulated-Gate Bipolar Transistors), but other transistors such as MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors) and bipolar transistors may also be used. Note that if each of the first to third high-side switching elements SW1, SW3, SW5 and the first to third low-side switching elements SW2, SW4, SW6 is an element that includes a reverse-conducting diode (for example, an RC (Reverse Conductive)-IGBT), then the diodes D1 to D6 do not need to be connected.

[0024] Power line 81 electrically connects the changeover switch 3 (second terminal 32 described later) to the high-potential side of each of the first to third series circuits 11 to 13. Power line 82 connects the low-potential terminal T12 of the DC terminal section T1 to the low-potential side of each of the first to third series circuits 11 to 13. Power line 91 electrically connects the changeover switch 3 (third terminal 33 described later) to the connection terminal T21 of the AC terminal section T2. ​​Power line 92 electrically connects the second series circuit 12 (second connection point 121) to the connection terminal T22 of the AC terminal section T2. ​​Power line 93 electrically connects the third series circuit 13 (third connection point 131) to the connection terminal T23 of the AC terminal section T2.

[0025] One end of inductor L1 is connected to the first connection point 111 of the first series circuit 11, and the other end of inductor L1 is connected to the changeover switch 3 (the fourth terminal 34 described later). Inductor L2 is connected to the power line 92. One end of inductor L2 is connected to the second connection point 121 of the second series circuit 12, and the other end of inductor L2 is connected to the connection terminal T22 of the AC terminal section T2. ​​Inductor L3 is connected to the power line 93. One end of inductor L3 is connected to the third connection point 131 of the third series circuit 13, and the other end of inductor L3 is connected to the connection terminal T23 of the AC terminal section T2. ​​The inductance values ​​of the three inductors L1 to L3 are, for example, the same. However, it is preferable that the magnetic saturation characteristics of inductor L1 are better than the magnetic saturation characteristics of each inductor L2 and L3. Magnetic saturation characteristics refer to the characteristic that when a DC current is passed through an inductor, magnetic saturation occurs at a certain current value, and the inductance value decreases. The current value at this time is called the magnetic saturation allowable current (DC superimposed allowable current), and good magnetic saturation characteristics mean that the magnetic saturation allowable current (DC superimposed allowable current) is higher. For example, if each inductor L1 to L3 has an iron core, the magnetic saturation characteristics can be improved by making the iron core of inductor L1 thicker than the iron cores of inductors L2 and L3.

[0026] The three capacitors C1, C2, and C3 are connected in a star (Y) configuration to the three power lines 91, 92, and 93. Specifically, capacitor C1 is connected between the neutral point Y and power line 91, capacitor C2 is connected between the neutral point Y and power line 92, and capacitor C3 is connected between the neutral point Y and power line 93. Alternatively, the three capacitors C1, C2, and C3 may be connected in a delta configuration. Capacitor C4 is connected between the two power lines 81 and 82.

[0027] The changeover switch 3 is switched between a first connection state and a second connection state by the control circuit 6 (the switch control unit 61 described later). This switches the electrical interconnection relationships (wiring) of each component of the conversion circuit 1. In Figure 1, the changeover switch 3 is shown with a solid line when it is in the first connection state and with a dashed line when it is in the second connection state. When the changeover switch 3 is in the first connection state, the conversion circuit 1 is in the first circuit state, performing a first conversion (DC / AC conversion) between the battery voltage applied to the DC terminal T1 and the power supply voltage applied to the AC terminal T2. On the other hand, when the changeover switch 3 is in the second connection state, the conversion circuit 1 is in the second circuit state, performing a second conversion (DC / DC conversion) between the battery voltage applied to the DC terminal T1 and the DC relay voltage, while also performing a third conversion (DC / AC conversion) between the relay voltage and the power supply voltage applied to the AC terminal T2. Details of the first and second circuit states will be described later.

[0028] As shown in Figure 1, the changeover switch 3 includes a first terminal 31, a second terminal 32, a third terminal 33, and a fourth terminal 34. The first terminal 31 is connected to the high-potential terminal T11 of the DC terminal section T1. The power line 81 is connected to the second terminal 32. The second terminal 32 is connected to the high-potential side (first to third high-side switching elements SW1, SW3, SW5) of the first series circuit 11, the second series circuit 12, and the third series circuit 13, respectively. The third terminal 33 is connected to the connection terminal T21 of the AC terminal section T2. ​​The fourth terminal 34 is connected to the inductor L1.

[0029] When the changeover switch 3 is in the first connection state (see the solid line in Figure 1), the first terminal 31 and the second terminal 32 conduct, while the third terminal 33 and the fourth terminal 34 conduct. As a result, the high-potential terminal T11 of the DC terminal section T1 conducts with the power line 81 to which the high-potential sides of the first series circuit 11, the second series circuit 12, and the third series circuit 13 are connected, while the connection terminal T21 of the AC terminal section T2 conducts with the inductor L1. Therefore, the first connection point 111 is connected to the connection terminal T21 of the AC terminal section T2 via the inductor L1.

[0030] On the other hand, when the changeover switch 3 is in the second connection state (see the dashed line in Figure 1), the first terminal 31 and the fourth terminal 34 conduct, while the second terminal 32 and the fourth terminal 34 are open. As a result, the high-potential terminal T11 of the DC terminal section T1 conducts to the inductor L1. Therefore, the high-potential terminal T11 of the DC terminal section T1 conducts to the first connection point 111 via the inductor L1. In addition, the connection terminal T21 of the AC terminal section T2 is open, and the high-potential sides of the first to third series circuits 11 to 13 (first to third high-side switching elements SW1, SW3, SW5) are disconnected from the high-potential terminal T11 of the DC terminal section T1.

[0031] The control circuit 6 performs various controls in the power converter A1. The control circuit 6 is implemented by, for example, a microcomputer, but may also be implemented by one or more analog circuits, one or more digital circuits, or both. As mentioned above, the control circuit 6 includes a switch control unit 61 and a drive control unit 62. The switch control unit 61 and the drive control unit 62 may be implemented on a common microcomputer, or they may be implemented on different microcomputers.

[0032] The switch control unit 61 switches between the first and second connection states of the changeover switch 3. For example, if the user of the power converter A1 instructs the control circuit 6 to perform initial charging and complete discharging, the switch control unit 61 sets the changeover switch 3 to the second connection state. Otherwise, the switch control unit 61 sets the changeover switch 3 to the first connection state. The control circuit 6 may be configured to not include the switch control unit 61. In this example, the user of the power converter A1 may be configured to manually switch between the first and second connection states of the changeover switch 3.

[0033] The drive control unit 62 generates drive signals (e.g., PWM signals) to control the driving (switching operation) of each of the first to third high-side switching elements SW1, SW3, SW5 and the first to third low-side switching elements SW2, SW4, SW6 of the conversion circuit 1. These signals are then output to each of the first to third high-side switching elements SW1, SW3, SW5 and the first to third low-side switching elements SW2, SW4, SW6. When the changeover switch 3 is in the first connection state, the drive control unit 62 generates each drive signal so that the conversion circuit 1 functions in the first circuit state described later, and when the changeover switch 3 is in the second connection state, the drive control unit 62 generates each drive signal so that the conversion circuit 1 functions in the second circuit state. The drive control unit 62 may, for example, determine the connection state of the changeover switch 3 (whether it is in the first connection state or the second connection state) based on the switching signal from the switch control unit 61, or it may configure the drive control unit 62 to receive a contact signal from the changeover switch 3 and determine the connection state of the changeover switch 3 (whether it is in the first connection state or the second connection state) based on that contact signal.

[0034] In the control circuit 6, when the switch control unit 61 switches between the first and second connection states of the changeover switch 3, the drive control unit 62 stops outputting drive signals to each of the first to third high-side switching elements SW1, SW3, SW5 and the first to third low-side switching elements SW2, SW4, SW6 (or outputs a drive signal to turn them off). In other words, it turns off the first to third high-side switching elements SW1, SW3, SW5 and the first to third low-side switching elements SW2, SW4, SW6.

[0035] Next, the first and second circuit states of the conversion circuit 1 will be explained with reference to Figures 2 and 3. Figure 2 is a circuit diagram of the conversion circuit 1 in the first circuit state, showing the connection status of each component. Figure 3 is a circuit diagram of the conversion circuit 1 in the second circuit state, showing the connection status of each component. For ease of understanding, in Figures 2 and 3, only the first to fourth terminals 31 to 34 and the conductive contacts of the changeover switch 3 are shown, and the control circuit 6 is omitted from the diagram.

[0036] When the changeover switch 3 is in the first connection state, the conversion circuit 1 is in the first circuit state shown in Figure 2. In this first circuit state, the high-potential terminal T11 of the DC terminal section T1 is conductive to the high-potential side of the first to third series circuits 11 to 13 (each of the first to third high-side switching elements SW1, SW3, and SW5) via the power line 81. The low-potential terminal T12 of the DC terminal section T1 is conductive to the low-potential side of the first to third series circuits 11 to 13 (each of the first to third low-side switching elements SW2, SW4, and SW6) via the power line 82. In addition, the first connection point 111 of the first series circuit 11 is conductive to the connection terminal T21 of the AC terminal section T2 via the inductor L1 and the power line 91. The second connection point 121 of the second series circuit 12 is conductive to the connection terminal T22 of the AC terminal section T2 via the inductor L2 and the power line 92. The third connection point 131 of the third series circuit 13 is conductive to the connection terminal T23 of the AC terminal section T2 via the inductor L3 and the power line 93. In the first connection state shown in Figure 2, the first to third series circuits 11 to 13 are electrically connected as a three-phase full-bridge inverter.

[0037] Therefore, when the changeover switch 3 is in the first connected state, the drive control unit 62 of the control circuit 6 generates and outputs drive signals to the first to third high-side switching elements SW1, SW3, SW5 and the first to third low-side switching elements SW2, SW4, SW6 so that they operate as a three-phase full-bridge inverter. The three inductors L1 to L3 and the three capacitors C1 to C3 function as smoothing filters.

[0038] Therefore, when the changeover switch 3 is in the first connection state, that is, when the conversion circuit 1 is in the first circuit state, the conversion circuit 1 functions as a three-phase full-bridge inverter. During the discharge of battery B1, the battery voltage of battery B1 is converted to an AC voltage by the three-phase full-bridge inverter and output to the AC power supply B2. On the other hand, during the charging of battery B1, the power supply voltage of AC power supply B2 is converted to a DC voltage (rectified) by the three-phase full-bridge inverter and output to battery B1.

[0039] When the changeover switch 3 is in the second connection state, the conversion circuit 1 enters the second circuit state shown in Figure 3. In this second circuit state, the high-potential terminal T11 of the DC terminal section T1 is connected to one end of the inductor L1, and the other end of the inductor L1 is connected to the first connection point 111 of the first series circuit 11. Since the second terminal 32 of the changeover switch 3 is open, the high-potential sides of the first to third series circuits 11 to 13 (each of the first to third high-side switching elements SW1, SW3, and SW5) are conductive to each other via the power line 81. The low-potential sides of the first to third series circuits 11 to 13 (each of the first to third low-side switching elements SW2, SW4, and SW6) are conductive to each other via the power line 82. In addition, the second connection point 121 of the second series circuit 12 is conductive to the connection terminal T22 of the AC terminal section T2 via the inductor L2 and the power line 92. The third connection point 131 of the third series circuit 13 is conductive to the connection terminal T23 of the AC terminal section T2 via the inductor L3 and the power line 93. The connection terminal T21 of the AC terminal section T2 is connected to the third terminal 33 of the changeover switch 3, but the third terminal 33 is open. In the second circuit state shown in Figure 3, the inductor L1, the first series circuit 11, and the capacitor C4 are electrically connected as a DC / DC converter, and the second series circuit 12 and the third series circuit 13 are electrically connected as a single-phase full-bridge inverter.

[0040] Therefore, when the changeover switch 3 is in the second connection state, the drive control unit 62 of the control circuit 6 generates and outputs drive signals to the first high-side switching element SW1 and the first low-side switching element SW2 so that they operate as a DC / DC converter, while simultaneously generating and outputting drive signals to the second and third high-side switching elements SW3, SW5 and the second and third low-side switching elements SW4, SW6 so that they operate as a single-phase full-bridge inverter. Here, with respect to the DC / DC converter including the inductor L1, the first series circuit 11 and the capacitor C4, the drive control unit 62 turns off the first high-side switching element SW1 (while current flows through the diode D1 as appropriate) and switches the first low-side switching element SW2 (alternating between on and off) to boost the battery voltage and convert it into an intermediate voltage. In this boosting operation, the boost ratio is adjusted by changing the duty cycle of the drive signal (PWM signal) to the first low-side switching element SW2 that is switched. Furthermore, the drive control unit 62 converts the relay voltage to the battery voltage by switching the first high-side switching element SW1 (alternating between on and off) while turning off the first low-side switching element SW2 (while allowing an appropriate current to flow through diode D2). In this step-down operation, the step-down ratio is adjusted by changing the duty cycle of the drive signal (PWM signal) to the first high-side switching element SW1 that is being switched. The two inductors L2 and L3 and the two capacitors C2 and C3 function as smoothing filters.

[0041] Therefore, when the changeover switch 3 is in the second connection state, that is, when the conversion circuit 1 is in the second circuit state, the conversion circuit 1 functions as a DC / DC converter and a single-phase full-bridge inverter. During the discharge of battery B1, the battery voltage of battery B1 is boosted by the DC / DC converter, then converted to an AC voltage by the single-phase full-bridge inverter and output to the AC power supply B2. On the other hand, during the charging of battery B1, the power supply voltage of AC power supply B2 is converted to a DC voltage (rectified) by the single-phase full-bridge inverter, then stepped down by the DC / DC converter and output to battery B1.

[0042] In power converter A1, when the changeover switch 3 is in the first connection state, the conversion circuit 1 enters a first circuit state that performs a first conversion between the battery voltage of battery B1 and the power supply voltage of AC power supply B2. When the changeover switch 3 is in the second connection state, it enters a second circuit state that performs a second conversion between the battery voltage of battery B1 and a DC relay voltage, and a third conversion between the aforementioned relay voltage and the power supply voltage of AC power supply B2. With this configuration, when performing initial charging or complete discharge of battery B1, the battery voltage and power supply voltage can be converted via the relay voltage by setting the changeover switch 3 to the second connection state. Therefore, initial charging and complete discharge of battery B1 can be performed appropriately. On the other hand, in charge / discharge control of battery B1 other than initial charging and complete discharge, the battery voltage and power supply voltage can be converted directly without going through the relay voltage by setting the changeover switch 3 to the first connection state. Therefore, power loss that occurs when converting to the relay voltage can be reduced. In other words, power converter A1 can reduce power loss.

[0043] In power converter A1, the conversion circuit 1 performs the first conversion (conversion between battery voltage and power supply voltage) as a three-phase full-bridge inverter in the first circuit state, and in the second circuit state, it performs the second conversion (conversion between battery voltage and relay voltage) as a DC / DC converter while simultaneously performing the third conversion (conversion between relay voltage and power supply voltage) as a single-phase full-bridge inverter. With this configuration, when the conversion circuit 1 is in the first circuit state, it functions as a three-phase full-bridge inverter, so it can directly convert between battery voltage and power supply voltage. Also, when the conversion circuit 1 is in the second circuit state, it functions as a DC / DC converter and a single-phase full-bridge inverter, so it can convert between battery voltage and power supply voltage via relay voltage. Therefore, power converter A1 can reduce power loss in the first circuit state and perform initial charging and complete discharge of battery B1 in the second circuit state.

[0044] In power converter A1, when the changeover switch 3 is in the first connection state, inductor L1 is electrically connected between the first connection point 111 of the first series circuit 11 and the AC terminal section T2 (connection terminal T21). When the changeover switch 3 is in the second connection state, inductor L1 is electrically connected between the high-potential terminal T11 of the DC terminal section T1 and the first connection point 111 of the first series circuit 11. With this configuration, when the changeover switch 3 is in the first connection state, inductor L1 is used as part of a smoothing filter between the three-phase full-bridge inverter and the AC terminal section T2, and when the changeover switch 3 is in the second connection state, it is used as part of a DC / DC converter (chopper circuit). Therefore, power converter A1 makes it possible to configure the conversion circuit 1 with common components for both the first and second circuit states.

[0045] In power converter A1, when the changeover switch 3 is in the first connection state, the first terminal 31 and the second terminal 32 conduct, while the third terminal 33 and the fourth terminal 34 conduct. When the changeover switch 3 is in the second connection state, the first terminal 31 and the fourth terminal 34 conduct, while the second terminal 32 and the third terminal 33 are open. With this configuration, the conversion circuit 1 can be switched between the first circuit state (three-phase full-bridge inverter) and the second circuit state (DC / DC converter and single-phase full-bridge inverter) by switching the changeover switch 3. Therefore, power converter A1 can switch between the first circuit state and the second circuit state by changing the wiring to add the changeover switch 3 to, for example, a three-phase full-bridge inverter. In other words, power converter A1 does not need to add a DC / DC converter which is necessary when initially charging or completely discharging the battery B1, so it can be made smaller, lighter, and cost-effective.

[0046] In power converter A1, the control circuit 6 (switch control unit 61) sets the changeover switch 3 to the second connection state when performing initial charging or complete discharge of the battery B1. With this configuration, the conversion circuit 1 switches to the second circuit state through the switching control of the changeover switch 3 by the control circuit 6 (switch control unit 61). Therefore, even if the conversion circuit 1 is composed of components equivalent to a simple inverter circuit (a three-phase full-bridge inverter in this embodiment), power converter A1 can handle initial charging and complete discharge of the battery B1 by adding the changeover switch 3 (including wiring to the changeover switch 3) and updating the software of the control circuit 6. Furthermore, since the control circuit 6 controls the switching of the changeover switch 3, it can determine the timing of the switch between the first connection state and the second connection state of the changeover switch 3. Therefore, when the changeover switch 3 is switched, it is possible to stop the output of the drive signals to the first to third high-side switching elements SW1, SW3, SW5 and the first to third low-side switching elements SW2, SW4, SW6.

[0047] Figure 4 shows a power converter A2 according to the first modified example. Power converter A2 differs from power converter A1 in the following respect: the second series circuit 12 includes two capacitors C11 and C12, respectively, instead of the second high-side switching element SW3 and the second low-side switching element SW4.

[0048] The second series circuit 12 of power converter A2 divides the battery voltage using two capacitors C11 and C12. In this embodiment, the capacitances of the two capacitors C11 and C12 are the same, so the battery voltage is divided equally. Therefore, the connection point of the two capacitors C11 and C12 (second connection point 121) becomes the neutral point potential of the battery voltage. The second series circuit 12 then outputs this neutral point potential of the battery voltage to the AC power supply B2.

[0049] In power converter A2, when the changeover switch 3 is in the first connection state, the conversion circuit 1 functions as a three-phase half-bridge inverter, and when the changeover switch 3 is in the second connection state, the conversion circuit 1 functions as a DC / DC converter and a single-phase half-bridge inverter.

[0050] In power converter A2, as in power converter A1, power loss can be reduced. Furthermore, power converter A2 has a configuration common to power converter A1 and therefore achieves the same effects as power converter A1. Also, as can be seen from power converter A2, by providing a changeover switch 3 to the three-phase half-bridge inverter, it is possible to make it function as a three-phase half-bridge inverter in the first circuit state, and as a single-phase half-bridge inverter and DC-DC inverter (chopper circuit) in the second circuit state.

[0051] Figure 5 shows a power converter A3 according to the second modified example. Power converter A3 differs from power converter A1 in that it includes an inverter circuit 71. In addition, power converter A3 includes a capacitor C5 and a filter circuit 72. Note that the control circuit 6 is omitted in Figure 5.

[0052] In power converter A3, the inverter circuit 71 is connected in parallel to the conversion circuit 1. The input / output terminals of the inverter circuit 71 on the battery B1 side are connected to the DC terminal section T1 (high-potential terminal T11 and low-potential terminal T12), and the input / output terminals of the inverter circuit 71 on the AC power supply B2 side are connected to the AC terminal section T2 (three connection terminals T21, T22, T23) via the filter circuit 72. The inverter circuit 71 converts DC power to AC power between the input / output terminals on the battery B1 side and the input / output terminals on the AC power supply B2 side. The inverter circuit 71 is, for example, a PWM controlled inverter. In the illustrated example, the inverter circuit 71 is composed of a three-phase full-bridge inverter with six switching elements, but the configuration of the inverter circuit 71 is not limited to this. The switching elements of the inverter circuit 71 are switched on and off by a drive signal from a control circuit 6 (drive control unit 62) (not shown).

[0053] The filter circuit 72 is connected between the input / output terminals on the AC power supply B2 side of the inverter circuit 71 and the AC terminal section T2 (three connection terminals T21, T22, T23). The filter circuit 72 is, for example, a three-phase LC filter circuit. In the illustrated example, the filter circuit 72 is connected in the same way as the three inductors L1 to L3 and the three capacitors C1 to C3 when the conversion circuit 1 is in the first circuit state.

[0054] Capacitor C5 is connected between the input / output terminal on the battery B1 side of the inverter circuit 71 and the DC terminal section T1 (high-potential terminal T11 and low-potential terminal T12).

[0055] The inverter circuit 71 is connected in parallel to the first to third series circuits 11 to 13 when the conversion circuit 1 is in the first circuit state, that is, when the first to third series circuits 11 to 13 constitute a three-phase full-bridge inverter.

[0056] In power converter A3, when conversion circuit 1 is in the first circuit state, the control circuit 6 (drive control unit 62) outputs drive signals to each of the first to third high-side switching elements SW1, SW3, SW5 and the first to third low-side switching elements SW2, SW4, SW6, while also outputting drive signals to each switching element of the inverter circuit 71, so that the battery voltage and power supply voltage are converted by conversion circuit 1 (three-phase full-bridge inverter) and inverter circuit 71. On the other hand, when conversion circuit 1 is in the second circuit state, the control circuit 6 (drive control unit 62) outputs drive signals to each of the first to third high-side switching elements SW1, SW3, SW5 and the first to third low-side switching elements SW2, SW4, SW6, so that the battery voltage and power supply voltage are converted by conversion circuit 1 (DC / DC converter and single-phase full-bridge inverter) alone. At this time, no drive signals are output to each switching element of the inverter circuit 71, and the inverter circuit 71 is stopped. In other words, when the conversion circuit 1 is in the second circuit state, the control circuit 6 stops the inverter circuit 71 and allows only the conversion circuit 1 to perform the second conversion (DC / DC conversion) between the battery voltage and the relay voltage and the third conversion (DC / AC conversion) between the battery B1 and the AC power supply B2.

[0057] In power converter A3, as in power converter A1, power loss can be reduced. Furthermore, power converter A3 has a configuration common to the other power converters A1 and A2, and therefore achieves the same effects as those power converters A1 and A2.

[0058] In the second modified example (power converter A3) described above, an example was shown in which one inverter circuit 71 is connected in parallel to the conversion circuit 1. However, the number of inverter circuits 71 may be two or more. In other words, the power converter of this disclosure may have two or more inverter circuits 71 connected in parallel to the conversion circuit 1.

[0059] The power conversion device relating to this disclosure is not limited to the embodiments described above. The specific configuration of each part of the power conversion device relating to this disclosure can be modified in various ways. [Explanation of symbols]

[0060] A1, A2, A3: Power converter, B1: Battery, B2: AC power supply, T1: DC terminal section, T11: High potential terminal, T12: Low potential terminal, T2: AC terminal section, T21, T22, T23: Connection terminals, SW1: First high-side switching element, SW2: First low-side switching element, SW3: Second high-side switching element, SW4: Second low-side switching element, SW5: Third high-side switching element, SW6: Third low-side switching element, L1: Inductor, 1: Conversion circuit, 11: First series circuit, 12: Second series circuit, 13: Third series circuit, 111: First connection point, 121: Second connection point, 131: Third connection point, 3: Changeover switch, 31: First terminal, 32: Second terminal, 33: Third terminal, 34: Fourth terminal, 6: Control circuit, 61: Switch control section, 62: Drive control section

Claims

1. A DC terminal section to which a battery is connected and to which a DC battery voltage is applied, An AC terminal section to which an AC power supply is connected and an AC power supply voltage is applied, A conversion circuit is connected between the DC terminal section and the AC terminal section and is capable of converting between the battery voltage and the power supply voltage. A toggle switch that switches between the first connection state and the second connection state, Equipped with, The conversion circuit is in a first circuit state that performs a first conversion between the battery voltage and the power supply voltage when the changeover switch is in the first connection state, and in a second circuit state that performs a second conversion between the battery voltage and a DC relay voltage and a third conversion between the relay voltage and the power supply voltage when the changeover switch is in the second connection state.

2. The power conversion device according to claim 1, wherein the conversion circuit performs the first conversion as a three-phase full-bridge inverter in the first circuit state, and performs the second conversion as a DC / DC converter while performing the third conversion as a single-phase full-bridge inverter in the second circuit state.

3. The conversion circuit includes an inductor connected to the changeover switch, a first series circuit in which a first high-side switching element and a first low-side switching element are connected in series via a first connection point, a second series circuit in which a second high-side switching element and a second low-side switching element are connected in series, and a third series circuit in which a third high-side switching element and a third low-side switching element are connected in series. The DC terminal section includes a high-potential terminal connected to the high-potential side of the battery and a low-potential terminal connected to the low-potential side of the battery. The power conversion device according to claim 2, wherein the inductor is electrically connected between the first connection point and the AC terminal when the changeover switch is in the first connection state, and is electrically connected between the high-potential terminal of the DC terminal and the first connection point when the changeover switch is in the second connection state.

4. The changeover switch includes a first terminal connected to the high-potential terminal of the DC terminal section, a second terminal connected to each of the first high-side switching element, the second high-side switching element, and the third high-side switching element, a third terminal connected to the AC terminal section, and a fourth terminal connected to the inductor. The power conversion device according to claim 3, wherein in the first connection state, the first terminal and the second terminal are conductive, and the third terminal and the fourth terminal are conductive, and in the second connection state, the first terminal and the fourth terminal are conductive, and the second terminal and the third terminal are open.

5. The system further includes a control circuit for controlling the aforementioned changeover switch, The power conversion device according to any one of claims 1 to 4, wherein the control circuit sets the changeover switch to the second connected state when performing initial charging of the storage battery or complete discharge of the storage battery.

Images