Power conversion device

Abstract

To provide a power conversion device capable of performing both of DC / AC conversion and DC / DC conversion with a simple configuration.SOLUTION: A power conversion device 10 comprises: a first connection unit 201 to which a DC power supply is connected; a second connection unit 202 to which an AC power supply or a power consuming device is connected; a conversion unit 200 that performs power conversion between the first connection unit 201 and the second connection unit 202; and a control unit 130 that controls operation of the conversion unit 200. The control unit 130 performs both of AC control that controls the operation of the conversion unit 200 so that an input or an output of AC power is performed in the second connection unit 202 and DC control that controls the operation of the conversion unit 200 so that an output of DC power is performed in the second connection unit 202.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a power conversion device.

Background Art

[0002] As described in Patent Document 1 below, an electric vehicle is provided with, for example, a power conversion device for performing power conversion between an external power source and a storage battery. The power conversion device can convert AC power supplied from an external power source into DC power and supply it to the storage battery, convert DC power supplied from the storage battery into AC power and output it to the outside, and the like.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a power conversion device configured to perform DC / AC conversion as described in Patent Document 1 above, for example, a first connection portion to which a DC power source such as a storage battery is connected, and a second connection portion to which, for example, an AC power consuming device or an AC power source is connected are provided. In such a conventional configuration, it is possible to output AC power from the second connection portion, etc., but it is not possible to output DC power from the second connection portion. For this reason, for example, in an electric vehicle, in order to supply DC power to a heater for an electric heating catalyst (ECH), it is necessary to separately provide a power conversion device configured to perform DC / DC conversion, which increases the cost. Although it is also possible to supply AC power to the heater, in that case, in addition to a decrease in energy efficiency, noise increases with the output of AC power.

[0005] An object of the present invention is to provide a power conversion device capable of performing both DC / AC conversion and DC / DC conversion with a simple configuration.

Means for Solving the Problems

[0006] The power conversion device according to the present invention includes a first connection portion to which a DC power supply is connected, a second connection portion to which an AC power supply or an electric power consuming device is connected, a conversion portion that performs power conversion between the first connection portion and the second connection portion, and a control portion that controls the operation of the conversion portion. The control portion performs both an AC control that controls the operation of the conversion portion so that AC power is input or output at the second connection portion, and a DC control that controls the operation of the conversion portion so that DC power is output at the second connection portion.

[0007] In the power conversion device having such a configuration, by simply changing the control mode performed by the control portion on the conversion portion, it is possible to switch between control in which AC power is input or output at the second connection portion (i.e., DC / AC conversion) and control in which DC power is output at the second connection portion (i.e., DC / DC conversion).

Effects of the Invention

[0008] According to the present invention, there is provided a power conversion device capable of performing both DC / AC conversion and DC / DC conversion with a simple configuration.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

[0010] Hereinafter, this embodiment will be described with reference to the accompanying drawings. For ease of understanding of the description, the same reference numerals are given to the same components in each drawing as much as possible, and duplicate descriptions are omitted.

[0011] The first embodiment will be described. The power conversion device 10 according to this embodiment is a device mounted on an electric vehicle (not shown). The electric vehicle includes a storage battery 12 and a rotating electric machine (not shown), and generates a driving force necessary for traveling by supplying the power stored in the storage battery 12 to the rotating electric machine. The power conversion device 10 converts the DC power supplied from the storage battery 12 into AC power and supplies the AC power to the rotating electric machine.

[0012] As shown in FIG. 1, the power conversion device 10 includes a control device 100 and a conversion unit 200. The control device 100 is a device that controls the operation of the power conversion device 10 including the conversion unit 200. The conversion unit 200 is a circuit configured to perform power conversion such as DC / AC conversion.

[0013] First, the configuration of the conversion unit 200 will be described. The conversion unit 200 includes connectors CN11, CN12, CN2, a first conversion unit 210, and a second conversion unit 220.

[0014] The connector CN11 is a connector configured as a part for receiving AC power from the outside. For example, a wiring connected to the AC inlet of the electric vehicle is connected to the connector CN11. When AC power is supplied from the AC inlet to the electric vehicle, the power is converted into DC power by the power conversion device 10 and stored in the storage battery 12.

[0015] The connector CN12 is a connector configured as a part for outputting DC power. A wiring connected to the power-consuming device mounted on the electric vehicle is connected to the connector CN12. The power-consuming device is a device that operates by receiving the operation of DC power from the power conversion device 10. In this embodiment, an example in which a heater 13 for heating an electric machine heated catalyst (EHC) is connected as the power-consuming device will be described.

[0016] As shown in FIG. 1, a pair of wirings 271 and 272 extend from the first conversion unit 210 of the power conversion device 10, and each wiring branches in the middle. A set of branched wirings is connected to the connector CN11, and another set of wirings is connected to the connector CN12. A relay RL1 is provided in the middle of the wiring connected to the connector CN11. Similarly, a relay RL2 is provided in the middle of the wiring connected to the connector CN12. The operations of the relays RL1 and RL2 are controlled by the control device 100.

[0017] As will be described later, the conversion unit 200 is capable of performing each of an operation of receiving AC power from the wirings 271 and 272 and an operation of outputting DC power from the same wirings 271 and 272. When the conversion unit 200 operates to receive AC power, the relay RL1 is in a closed state, the relay RL2 is in an open state, and AC power is supplied from the connector CN11 via the wirings 271 and 272. When the conversion unit 200 operates to output DC power, the relay RL1 is in an open state, the relay RL2 is in a closed state, and DC power is output from the wirings 271 and 272 via the connector CN12.

[0018] Note that the conversion unit 200 may be configured to be capable of performing an operation of outputting AC power from the wirings 271 and 272. In this case, when the conversion unit 200 operates to output AC power, the relay RL1 is in a closed state, the relay RL2 is in an open state, and AC power is output from the wirings 271 and 272 via the connector CN11.

[0019] In the first conversion unit 210, the portion where the wirings 271 and 272 are connected from the outside is a portion to which an AC power source at the tip of the AC inlet or an electric power consuming device such as the heater 13 is electrically connected. This portion is also referred to as the "second connection portion 202". The second connection portion 202 may be configured as a removable connector. Also, only either an AC power source or an electric power consuming device may be connected to the second connection portion 202.

[0020] Connector CN2 is a connector configured as a part to which a storage battery 12, which is a DC power source, is connected. The conversion unit 200 of the present embodiment is configured to be able to perform both an operation of receiving DC power from the storage battery 12 from the connector CN2 and an operation of outputting DC power from the connector CN2 to charge the storage battery 12, but it may also be configured to be able to perform only one of them. Further, the DC power source connected to the connector CN2 may be a storage battery 12 capable of charging and discharging as in the present embodiment, or may be a power source capable of discharging only. The connector CN2, which is the part to which the DC power source is connected, is hereinafter also referred to as the "first connection part 201". The conversion unit 200 can be said to be a part that performs power conversion between the first connection part 201 and the second connection part 202.

[0021] The first conversion unit 210 is a full-bridge inverter circuit configured to perform DC / AC conversion or the like between the second connection part 202 and a second conversion unit 220 described later. The first conversion unit 210 has four switching elements including a first switching element 211, a second switching element 212, a third switching element 213, and a fourth switching element 214 between a wiring 261 and a wiring 262. All of these are N-channel type MOSFETs, and a diode is connected in parallel between their drain and source.

[0022] The first switching element 211 and the second switching element 212 are connected in series with each other between the wiring 261 and the wiring 262. Similarly, the third switching element 213 and the fourth switching element 214 are also connected in series with each other between the wiring 261 and the wiring 262.

[0023] The first switching element 211 and the third switching element 213 are arranged on the wiring 261 side and constitute the "upper arm" of the full-bridge inverter circuit. The second switching element 212 and the fourth switching element 214 are arranged on the wiring 262 side and constitute the "lower arm" of the full-bridge inverter circuit.

[0024] One end of a wiring 271 is connected between the first switching element 211 and the third switching element 213. A reactor 245 for smoothing is arranged in the middle of the wiring 271. One end of a wiring 272 is connected between the second switching element 212 and the fourth switching element 214. A reactor 246 for smoothing is arranged in the middle of the wiring 272.

[0025] The opening and closing operations of each of the first switching element 211, the second switching element 212, the third switching element 213, and the fourth switching element 214 are controlled by a control device 100 described later. The control device 100 can cause the first conversion unit 210 to perform DC / AC conversion by controlling the operations of the first switching element 211 and the like. Since a known method can be used for such control, the specific content thereof will be omitted.

[0026] Also, the control device 100 can also cause the first conversion unit 210 to output DC power toward the connector CN2 by controlling the operations of the first switching element 211 and the like. The specific content of the control will be described later.

[0027] The second conversion unit 220 is a circuit configured to perform DC / DC conversion between the first connection unit 201 (connector CN2) and the first conversion unit 210. In the second conversion unit 220, two full-bridge inverter circuits are connected to each other via a transformer 241.

[0028] One of the full-bridge inverter circuits has four switching elements 221, 222, 223, 224. These switching elements 221, 222, 223, 224 are arranged between a pair of wirings 261, 262 extending from the first conversion unit 210.

[0029] Switching elements 221 and 222 are connected in series with each other between wiring 261 and wiring 262. Similarly, switching elements 223 and 224 are also connected in series with each other between wiring 261 and wiring 262.

[0030] Switching elements 221 and 223 are arranged on the wiring 261 side and constitute the "upper arm" of the full-bridge inverter circuit. Switching elements 222 and 224 are arranged on the wiring 262 side and constitute the "lower arm" of the full-bridge inverter circuit.

[0031] One of the wirings connected to the primary side of transformer 241 is connected between switching element 221 and switching element 223, and the other of the wirings connected to the primary side of transformer 241 is connected between switching element 222 and switching element 224. Note that the above "primary side" refers to the "primary side" when the conversion unit 200 performs the charging operation on the storage battery 12.

[0032] The other full-bridge inverter circuit included in the second conversion unit 220 has four switching elements 231, 232, 233, and 234. These switching elements 231, 232, 233, and 234 are arranged between a pair of wirings 251 and 252 connected to the connector CN2.

[0033] Switching elements 231 and 232 are connected in series with each other between wiring 251 and wiring 252. Similarly, switching elements 233 and 234 are also connected in series with each other between wiring 251 and wiring 252.

[0034] Switching elements 231 and 233 are arranged on the wiring 251 side and constitute the "upper arm" of the full-bridge inverter circuit. Switching elements 232 and 234 are arranged on the wiring 252 side and constitute the "lower arm" of the full-bridge inverter circuit.

[0035] One of the wirings connected to the secondary side of the transformer 241 is connected between the switching element 231 and the switching element 233, and the other of the wirings connected to the secondary side of the transformer 241 is connected between the switching element 232 and the switching element 234. The above-mentioned "secondary side" refers to the "secondary side" when the conversion unit 200 performs the charging operation on the storage battery 12.

[0036] The opening and closing operations of each of the switching elements 221, 222, 223, 224, 231, 232, 233, and 234 are controlled by the control device 100. By controlling the operations of the switching elements 221 and the like, the control device 100 can cause the second conversion unit 220 to perform DC / DC conversion. Since a known method can be used for such control, the specific content thereof will be omitted.

[0037] Other configurations of the conversion unit 200 will be described. Between the first conversion unit 210 and the second conversion unit 220, a smoothing capacitor 243 is disposed in the middle of the wiring connecting between the wiring 261 and the wiring 262. Similarly, in the vicinity of the connector CN2, a smoothing capacitor 242 is disposed in the middle of the wiring connecting between the wiring 251 and the wiring 252.

[0038] The second connection portion 202 is provided with a leakage detector 280. The leakage detector 280 is a sensor for detecting leakage occurring somewhere in the power path including the wirings 271 and 272. In this embodiment, a zero-phase current transformer (ZCT) is used as the leakage detector 280. Therefore, the detection of leakage by the leakage detector 280 is possible only when the potential difference between the wiring 271 and the wiring 272 varies periodically. The leakage detector 280 transmits a signal indicating the detection result of the leakage to the control device 100. The control device 100 can grasp the presence or absence and the magnitude of the leakage based on the signal.

[0039] The first conversion unit 210 is provided with four temperature sensors 291, 292, 293, and 294. These are sensors for detecting the temperatures of the first switching element 211, the second switching element 212, the third switching element 213, and the fourth switching element 214 respectively. Specifically, they are thermistors arranged in the vicinity of each of the first switching element 211 and the like. The temperature sensors 291, 292, 293, and 294 transmit signals indicating the measured temperatures to the control device 100. Based on the signals, the control device 100 can individually grasp the temperatures of the first switching element 211 and the like. The temperature sensors 291, 292, 293, and 294 correspond to the "temperature detection unit" that detects the temperature of the conversion unit 200. The positions where the temperature sensors 291 and the like are provided may be the same as those of the first switching element 211 and the like, or may be positions separated from the first switching element 211 and the like.

[0040] Continuing to refer to FIG. 1, the configuration of the control device 100 will be described. The control device 100 is configured as a computer system having a CPU, a ROM, a RAM, and the like. The control device 100 controls the operation of the power conversion device 10 in response to a request from the upper ECU 11 mounted on the electric vehicle. The control device 100 includes a communication unit 110, a determination unit 120, and a control unit 130 as elements representing its functions.

[0041] The communication unit 110 is a part that serves as an interface for performing two-way communication with other devices mounted on the electric vehicle. The control device 100 communicates with the upper ECU 11 via the communication unit 110 and performs processes such as receiving a control signal from the upper ECU 11.

[0042] The determination unit 120 is a part that performs a process of determining the presence or absence of leakage based on the signal output from the leakage detector 280.

[0043] The control unit 130 is a part that performs a process of controlling the operation of the conversion unit 200. The control unit 130 controls the opening and closing operations of each switching element (such as the first switching element 211) provided in the conversion unit 200 individually, thereby causing the conversion unit 200 to perform power conversion. As described above, in addition to performing DC / AC conversion in the conversion unit 200 and inputting and outputting AC power from the second connection unit 202, the power conversion device 10 of the present embodiment can also perform DC / DC conversion in the conversion unit 200 and output DC power from the second connection unit 202. The control that the control unit 130 performs on the conversion unit 200 so that AC power is input or output at the second connection unit 202 is hereinafter also referred to as "AC control". The control that the control unit 130 performs on the conversion unit 200 so that DC power is output at the second connection unit 202 is hereinafter also referred to as "DC control". The control unit 130 can perform both AC control and DC power.

[0044] For example, when AC power is supplied from the AC inlet to the electric vehicle, charging of the storage battery 12 is performed by AC control. At this time, the control unit 130 causes the first switching element 211 of the first conversion unit 210 to perform a switching operation, thereby outputting DC power from the first conversion unit 210 to the second conversion unit 220. The control unit 130 further causes the switching element 221 of the second conversion unit 220 to perform a switching operation, thereby outputting DC power from the second conversion unit 220 to the storage battery 12. As a specific control method of each switching element in AC control, a known method can be adopted, so detailed description is omitted.

[0045] A specific method of DC control will be described. In DC control, the control unit 130 controls the operation of the switching element 221 included in the second conversion unit 220, thereby causing the second conversion unit 220 to perform DC / DC conversion. As a result, a DC voltage is applied between the wiring 261 and the wiring 262.

[0046] The control unit 130 causes the second conversion unit 220 to perform DC / DC conversion as described above, and switches the states of the first switching element 211 and the like included in the first conversion unit 210 as shown in FIG. 2. Specifically, the control unit 130 closes the first switching element 211 and the fourth switching element 214, and opens the second switching element 212 and the third switching element 213. As a result, current flows through the path indicated by the arrow in FIG. 2, and DC power is supplied from the second connection part 202 to the heater 13.

[0047] In DC control, the control unit 130 may switch the states of the first switching element 211 and the like included in the first conversion unit 210 as shown in FIG. 3 instead of FIG. 2. In the example of FIG. 3, the control unit 130 closes the second switching element 212 and the third switching element 213, and opens the first switching element 211 and the fourth switching element 214. In this case, as indicated by the arrow in FIG. 3, current flows through a path opposite to that in the example of FIG. 2, and DC power is supplied from the second connection part 202 to the heater 13.

[0048] As described above, the DC control performed by the control unit 130 of the present embodiment includes two types: control in the state of FIG. 2 and control in the state of FIG. 3. The DC control in the state of FIG. 2 is also hereinafter referred to as "first DC control". The DC control in the state of FIG. 3 is also hereinafter referred to as "second DC control".

[0049] The specific processing flow performed by the control device 100 in DC control will be described with reference to FIG. 4. In the first step S01 of the processing, the control device 100 determines whether there is a leakage detection request. The "leakage detection request" is a request signal transmitted from the upper ECU 11 to the control device 100 so that the power conversion device 10 performs a process of detecting leakage. In the present embodiment, the upper ECU 11 is configured to cause the power conversion device 10 to perform leakage detection prior to DC control. Instead of such an aspect, when an instruction to execute DC control is received from the upper ECU 11, the control device 100 may be configured to perform leakage detection in advance (at its own discretion).

[0050] When the leakage detection request from the upper ECU 11 has not yet arrived, the control device 100 repeatedly executes the process of step S01 and waits until the leakage detection request arrives. When the leakage detection request arrives, it proceeds to step S02. In step S02, the control unit 130 starts detection control. "Detection control" is the control to control the operation of the conversion unit 200 so that the potential difference between a pair of wirings 271 and 272, which is the path through which power is input and output at the second connection part 202, changes in a rectangular wave shape.

[0051] For example, when the first switching element 211 and the third switching element 213 are in the open state and the second switching element 212 and the fourth switching element 214 are in the closed state, the potential difference between the wirings 271 and 272 becomes 0. In the detection control, the control unit 130 controls the operations of the first switching element 211, etc. so that the above state and the state of FIG. 2 alternate. As a result, the potential difference between the wirings 271 and 272 changes in a rectangular wave shape, alternating between a predetermined voltage V1 and 0V as shown in FIG. 5. The time t0 shown in FIG. 5 is the time when the detection control is started.

[0052] At this time, since the potential difference between the wiring 271 and the wiring 272 fluctuates periodically, it is in a state where the leakage detector 280 can detect leakage. During the execution of the detection control, the leakage detector 280 transmits a signal indicating the presence or absence of leakage and the magnitude of the leakage current in the power path to the control device 100. The determination unit 120 determines the presence or absence of leakage based on the signal transmitted from the leakage detector 280 during the execution of the detection control. By executing the detection control, it is possible to detect leakage while using a relatively inexpensive zero-phase current transformer (ZCT) as the leakage detector 280.

[0053] In addition, in the detection control, the control unit 130 may control the operations of the first switching element 211, etc. so that the state of FIG. 2 and the state of FIG. 3 alternate.

[0054] Returning to FIG. 4, the description will be continued. In step S03 following step S02, it is determined whether the magnitude of the leakage current detected by the leakage current detector 280 is equal to or less than a preset threshold value.

[0055] If the leakage current exceeds the threshold value, the process proceeds to step S11. In step S11, the determination unit 120 determines that an abnormality, that is, a leakage, has occurred. In step S12 following step S11, the control unit 130 performs a process of stopping the power supply to the heater 13. Thereafter, the series of processes shown in FIG. 4 is terminated. By performing the above processes, a situation where the power supply to the heater 13 continues while a leakage has occurred is prevented.

[0056] In step S03, if the leakage current is equal to or less than the threshold value, the process proceeds to step S04. In step S04, the determination unit 120 determines that it is normal, that is, no leakage has occurred. Thereafter, the process proceeds to step S05.

[0057] In step S05, the control device 100 determines whether there is a warm-up request. The "warm-up request" is a request signal transmitted from the upper ECU 11 to the control device 100 so as to supply DC power to the heater 13 and start heating the electric heating catalyst.

[0058] If the warm-up request from the upper ECU 11 has not yet been received, the control device 100 repeatedly executes the process of step S05 and waits until the warm-up request is received. When the warm-up request is received, the process proceeds to step S06. In step S06, DC control is started by the control unit 130. Thereafter, DC power is supplied from the second connection part 202 of the power conversion device 10 to the heater 13, and the electric heating catalyst is heated. At this time, the potential difference between the wirings 271 and 272 is maintained at a constant voltage V2 as shown in FIG. 6. The time t1 shown in FIG. 6 is the time when the DC control is started. The voltage V2 during the DC control may be the same as or different from the voltage V1 during the detection control.

[0059] In step S07 following step S06, it is determined whether or not the amount of power supplied to the heater 13 after step S06 has reached a predetermined target value. The "target value" mentioned here is a value preset as the amount of power required to raise the temperature of the electro-heated catalyst to the activation temperature. The target value may be a fixed value, or may be a value set each time according to the situation such as the outside air temperature.

[0060] If the amount of power supplied to the heater 13 has not yet reached the target value, the control device 100 repeatedly executes the process of step S07 and continues the DC control.

[0061] When the amount of power supplied to the heater 13 becomes equal to or greater than the target value, the process proceeds to step S08. In step S08, the DC control by the control unit 130 is stopped. Then, the process shown in FIG. 4 is terminated.

[0062] As described above, in the present embodiment, since DC power is supplied to the heater 13 by DC control, the heater 13 can be operated with high efficiency. Also, generation of noise associated with the switching operation of the first conversion unit 210 or the like can be suppressed. Note that noise is generated in the detection control executed prior to the DC control, but since the detection control is executed only for the minimum period necessary for detecting leakage, the noise hardly becomes a problem.

[0063] The DC control started in step S06 may be the first DC control (FIG. 2) described above, or may be the second DC control (FIG. 3). As described below, in the present embodiment, switching is performed between the first DC control and the second DC control according to the situation during the execution of the DC control.

[0064] The flowchart shown in FIG. 7 shows a more specific flow of the process executed after step S06 in FIG. 6.

[0065] When DC control is started, first, the first DC control is started in step S21. When the first DC control is being performed, as indicated by the arrows in FIG. 2, current flows through the path passing through the first switching element 211 and the fourth switching element 214, so the temperatures of these two switching elements gradually increase. On the other hand, for the second switching element 212 and the third switching element 213, since no current flows through them, the temperatures of these two switching elements hardly increase.

[0066] In step S22 following step S21, it is determined whether or not the amount of electric power supplied to the heater 13 after step S21 has reached a predetermined target value. This determination is the same as that performed in step S07 of FIG. 4. When the amount of electric power has reached the target value, the process proceeds to step S28, and the DC control by the control unit 130 is stopped.

[0067] In step S22, if the amount of electric power supplied to the heater 13 has not yet reached the target value, the process proceeds to step S23. In step S23, it is determined whether the DC control being performed at that time is the first DC control. If the first DC control is being executed, the process proceeds to step S24.

[0068] In step S24, it is determined whether the temperature of either the first switching element 211 (through which current is flowing) or the fourth switching element 214 has exceeded a predetermined upper limit temperature. The "upper limit temperature" is a temperature preset as the upper limit of an appropriate temperature range so that the load such as the first switching element 211 does not become too large. If the temperatures of both the first switching element 211 and the fourth switching element 214 are within the upper limit temperature, the processes after step S22 are executed again while continuing the first DC control. If the temperature of the first switching element 211 or the fourth switching element 214 exceeds the upper limit temperature, the process proceeds to step S25.

[0069] In step S25, the control unit 130 performs a process of switching from the first DC control to the second DC control. Thereafter, while continuing the second DC control, the processes after step S22 are executed again. After switching to the second DC control in step S25, no current flows through the first switching element 211 and the fourth switching element 214, so their temperatures gradually decrease.

[0070] When the second DC control is being performed in step S23, the process proceeds to step S26. In step S26, it is determined whether the temperature of either the second switching element 212 or the third switching element 213 (through which current is flowing) exceeds the upper limit temperature. The upper limit temperature used for this determination may be the same as or different from the upper limit temperature used for the determination in step S24. If the temperatures of both the second switching element 212 and the third switching element 213 are within the upper limit temperature, the processes after step S22 are executed again while continuing the second DC control. If the temperature of either the second switching element 212 or the third switching element 213 exceeds the upper limit temperature, the process proceeds to step S27.

[0071] In step S27, the control unit 130 performs a process of switching from the second DC control to the first DC control. Thereafter, while continuing the first DC control, the processes after step S22 are executed again. After switching to the first DC control in step S27, no current flows through the second switching element 212 and the third switching element 213, so their temperatures gradually decrease.

[0072] FIG. 8 shows an example of the temperature change of the first switching element 211 and the like when DC control is performed as described above. "Element temperature 1" in FIG. 8 refers to the temperatures of the first switching element 211 and the fourth switching element 214. "Element temperature 2" refers to the temperatures of the second switching element 212 and the third switching element 213. All of these are measured by the temperature sensors 291, 292, 293, and 294 and are used for the determination in steps S24 and S26 of FIG. 7.

[0073] When a warm-up request is transmitted from the upper ECU 11 at time t10, the first DC control is started, and the temperature (element temperature 1) of the first switching element 211 and the like gradually rises. Then, when the temperature (element temperature 1) of the first switching element 211 and the like reaches the upper limit temperature at time t11, the control is switched to the second DC control. After time t11, while the temperature (element temperature 1) of the first switching element 211 and the like gradually decreases, the temperature (element temperature 2) of the second switching element 212 and the like gradually rises. Then, when the temperature (element temperature 2) of the second switching element 212 and the like reaches the upper limit temperature at time t12, the control is switched to the first DC control. Thereafter, similarly, every time the temperature of the switching element reaches the upper limit temperature at times t13 and t14, the control is alternately switched between the first DC control and the second DC control.

[0074] As described above, the control unit 130 of the control device 100 according to the present embodiment performs a process of switching between the first DC control and the second DC control based on the temperature detected by the temperature sensor 291 and the like. Thereby, the temperature of the conversion unit 200 (in this example, the temperatures of all the switching elements included in the first conversion unit 210) can be maintained within an appropriate temperature range below the upper limit temperature. Since the required heat resistance performance for each switching element is lowered, a switching element with low heat resistance (that is, low cost) can be used as the first switching element 211 and the like.

[0075] Of the four switching elements included in the first conversion unit 210, only two are in the closed state during the execution of DC control, and the remaining two are in the open state so that no current flows. Since the cooling and heating cycles applied to the individual switching elements are halved, an advantage is obtained in that the heat resistance performance required for the switching elements is further reduced.

[0076] Note that the example in FIG. 7 is an example in which the first DC control is performed first in DC control, but the second DC control may be performed first.

[0077] Also, the process of switching between the first DC control and the second DC control is performed based on the temperatures measured by each of the four temperature sensors 291, 292, 293, and 294 in the present embodiment, but it may be performed based on only some of these temperatures.

[0078] The second embodiment will be described. In this embodiment, it is different from the first embodiment in the content of the process executed in DC control. Hereinafter, the points different from the first embodiment will be mainly described, and the description of the points common to the first embodiment will be omitted as appropriate.

[0079] The series of processes shown in FIG. 9 are executed by the control device 100 of the present embodiment instead of the series of processes shown in FIG. 7. The processes performed in step S31, step S32, and step S37 in FIG. 9 are the same as the processes performed in step S21, step S22, and step S28 in FIG. 7, respectively.

[0080] In step S32, if the amount of power supplied to the heater 13 has not yet reached the target value, in this embodiment, the process proceeds to step S33. In step S33, it is determined whether or not a predetermined period has elapsed since the start of the current DC control. The "current DC control" here refers to the DC control that is currently being executed among the first DC control or the second DC control. For example, when the process of step S33 is performed for the first time, the first DC control started in step S31 is the "current DC control".

[0081] The above-mentioned "predetermined period" refers to a period of a preset fixed length. In this embodiment, the above-mentioned predetermined period is set as the period during which the first DC control and the second DC control can be continuously executed.

[0082] In step S33, if it is determined that the predetermined period has not elapsed, the processes after step S32 are executed again while continuing the current DC control. If it is determined that the predetermined period has elapsed since the start of the current DC control, the process proceeds to step S34. In step S34, it is determined whether the DC control being performed at that time is the first DC control. If the first DC control is being executed, the process proceeds to step S35.

[0083] In step S35, the control unit 130 performs a process of switching from the first DC control to the second DC control. Then, the processes after step S32 are executed again while continuing the second DC control.

[0084] When the second DC control is being performed in step S33, the process proceeds to step S36. In step S36, the control unit 130 performs a process of switching from the second DC control to the first DC control. Then, the processes after step S32 are executed again while continuing the first DC control.

[0085] As a result of performing the above-described processing, in the present embodiment, the control unit 130 executes processing for alternately switching between the first DC control and the second DC control as time elapses. Specifically, the control unit 130 switches between the first DC control and the second DC control every time a "predetermined period" of a certain length elapses. If the "predetermined period" is set in advance as a period of such a length that the temperature of the first switching element 211 or the like does not exceed the upper limit temperature, the same effects as those described in the first embodiment can be achieved.

[0086] Note that in the example of FIG. 9, the first DC control is performed first in the DC control. However, the second DC control may be performed first.

[0087] The third embodiment will be described. In the present embodiment, the content of the processing executed in the DC control is different from that in the first embodiment. Hereinafter, the differences from the first embodiment will be mainly described, and the description of the points common to the first embodiment will be omitted as appropriate.

[0088] The series of processes shown in FIG. 10 is executed by the control device 100 of the present embodiment instead of the series of processes shown in FIG. 7. In the first step S41, it is determined whether the DC control executed when the process of FIG. 10 was performed last time was the first DC control. In order to realize such processing, the type of the DC control executed last time may be stored in the non-volatile storage device of the control device 100.

[0089] If the first DC control was executed last time, the process proceeds to step S42. In step S42, the second DC control is started as the DC control. That is, the DC control of the other side than the previous time is executed. Then, the process proceeds to step S44 described later.

[0090] In step S41, if the second DC control was executed last time, the process proceeds to step S43. In step S44, the first DC control is started as the DC control. That is, the DC control of the other side than the previous time is executed.

[0091] After the process of step S42 or step S43 is executed, the process proceeds to step S44 while continuing the DC control. In step S44, similar to step S22 in FIG. 7, a process of waiting until the amount of power supplied to the heater 13 reaches the target value is performed. When the amount of power reaches the target value, the process proceeds to step S45, and the DC control by the control unit 130 is stopped.

[0092] Also in this embodiment, similar to the second embodiment in FIG. 9, a process of alternately switching between the first DC control and the second DC control as time elapses is executed by the control unit 130. In this embodiment, each time the process in FIG. 10 is executed, the control executed as the DC control is switched between the first DC control and the second DC control. When the processes shown in FIGS. 4 and 10 are configured to start at the start of the control device 100 (for example, when the ignition switch of the electric vehicle is turned ON), the control unit 130 alternately switches between the first DC control and the second DC control each time it is started.

[0093] The present embodiment has been described above with reference to specific examples. However, the present disclosure is not limited to these specific examples. As long as those skilled in the art appropriately make design changes to these specific examples and have the features of the present disclosure, they are included in the scope of the present disclosure. Each element included in the above-described specific examples and its arrangement, conditions, shape, etc. are not limited to those illustrated and can be changed as appropriate. Each element included in the above-described specific examples can be combined as appropriate as long as no technical contradiction occurs.

Description of Reference Numerals

[0094] 10: Power conversion device 200: Conversion unit 201: First connection part 202: Second connection part 130: Control unit

Claims

1. A first connection part to which a DC power supply is connected, A second connection part to which an AC power supply or an electric power consuming device is connected, A conversion part that performs power conversion between the first connection part and the second connection part, A control part that controls the operation of the conversion part, A pair of wirings that are paths through which power is input and output in the second connection part, and a leakage current detector provided in the wirings, The control part, AC control for controlling the operation of the conversion part so that AC power is input or output in the second connection part, Both DC control for controlling the operation of the conversion part so that DC power is output in the second connection part, and Prior to performing the DC control, A power conversion device that performs detection control for controlling the operation of the conversion part so that the potential difference between the wirings changes in a rectangular wave shape.

2. The power conversion device according to claim 1, further comprising a determination part that determines the presence or absence of leakage current based on a signal output from the leakage current detector when the detection control is performed.

3. A first connection part to which a DC power supply is connected, A second connection part to which an AC power supply or an electric power consuming device is connected, A conversion part that performs power conversion between the first connection part and the second connection part, A control part that controls the operation of the conversion part, A temperature detection part that detects the temperature of the conversion part, The conversion part, Is a circuit having a first switching element and a second switching element connected in series, and a third switching element and a fourth switching element connected in series, Including a full-bridge circuit in which each of the first switching element and the third switching element constitutes an upper arm, and each of the second switching element and the fourth switching element constitutes a lower arm, The control part, AC control for controlling the operation of the conversion part so that AC power is input or output in the second connection part, Both DC control for controlling the operation of the conversion part so that DC power is output in the second connection part, and The DC control performed by the control part includes A first DC control in which the first switching element and the fourth switching element are in a closed state, and the second switching element and the third switching element are in an open state, and Both a second DC control in which the second switching element and the third switching element are in a closed state, and the first switching element and the fourth switching element are in an open state. A power conversion device in which the control unit switches between the first DC control and the second DC control based on the temperature detected by the temperature detection unit.

4. The temperature detection unit detects the temperature of at least a part of the first switching element, the second switching element, the third switching element, and the fourth switching element, The control unit, When the first DC control is being performed, if the temperature of the first switching element or the fourth switching element exceeds a predetermined upper limit temperature, switch from the first DC control to the second DC control, The power conversion device according to claim 3, wherein when the second DC control is being performed and the temperature of the second switching element or the third switching element exceeds a predetermined upper limit temperature, switch from the second DC control to the first DC control.

5. A first connection part to which a DC power supply is connected, A second connection part to which an AC power supply or an electric power consuming device is connected, A conversion part that performs power conversion between the first connection part and the second connection part, A control unit that controls the operation of the conversion unit, The conversion unit, A circuit having a first switching element and a second switching element connected in series, and a third switching element and a fourth switching element connected in series, Including a full-bridge circuit in which each of the first switching element and the third switching element constitutes an upper arm, and each of the second switching element and the fourth switching element constitutes a lower arm, The control unit, AC control for controlling the operation of the conversion unit so that AC power is input or output at the second connection part, Performing both DC control for controlling the operation of the conversion unit so that DC power is output at the second connection part, In the DC control performed by the control unit, A first DC control in which the first switching element and the fourth switching element are in a closed state and the second switching element and the third switching element are in an open state, Both include a second DC control in which the second switching element and the third switching element are in a closed state and the first switching element and the fourth switching element are in an open state, The control unit, A power conversion device that switches between the first DC control and the second DC control as time passes.

6. The control unit, The power conversion device according to claim 5, which switches between the first DC control and the second DC control every time a predetermined period elapses.

7. The control unit The power conversion device according to claim 5, which switches between the first DC control and the second DC control every time it is started.

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