Power conversion apparatus and method for cooling power conversion apparatus

Abstract

A power conversion apparatus and a method for cooling the power conversion apparatus according to an embodiment of the present invention comprise: a semiconductor module including a semiconductor switching element and a diode connected to the semiconductor switching element; a control device that outputs a control signal indicating the duty of the semiconductor switching element; and a heat sink that is connected to the semiconductor module, has a flow path allowing a refrigerant to flow therethrough, and absorbs heat generated by the semiconductor module. The control device changes, in accordance with the duty, the flow rate of the refrigerant flowing through the heat sink.

Description

Power conversion device and cooling method for power conversion device

[0001] FIELD Embodiments of the present invention relate to a power conversion device and a cooling method for a power conversion device.

[0002] Conventionally, power conversion devices equipped with semiconductor modules such as insulated gate bipolar transistor (IGBT) modules have been known. However, in chopper circuits and double chopper circuits using semiconductor modules, heat distribution can be uneven within the module. That is, depending on the duty cycle during module control, excessive heat generation can occur in the IGBT chips or diode chips.

[0003] Patent No. 7218480 JP 2021-44866 A

[0004] An object of the present invention is to provide a power converter and a cooling method for the power converter that can reduce uneven distribution of heat within a semiconductor module.

[0005] According to an embodiment, a power conversion device and a cooling method for a power conversion device include a semiconductor module including a semiconductor switching element and a diode connected to the semiconductor switching element, a control device that outputs a control signal representing a duty of the semiconductor switching element, and a heat sink connected to the semiconductor module, having a flow path for a coolant to flow, and absorbing heat generated by the semiconductor module. The control device changes the flow rate of the coolant flowing through the heat sink in accordance with the duty.

[0006] 6 is a circuit diagram showing an example of a chopper circuit according to an embodiment. FIG. 7 is a circuit diagram showing an example of a double chopper circuit according to an embodiment. FIG. 8 is an explanatory diagram showing an example of uneven heat generation in the semiconductor switching elements and diodes of the chopper circuit shown in FIG. 1 when the power supply is being discharged. FIG. 9 is an explanatory diagram showing an example of a cooling path for the semiconductor switching elements and diodes in the state of FIG. 3. FIG. 10 is a graph showing a time change in an on / off signal for a semiconductor switching element that is turned on when the power supply is being discharged. FIG. 11 is an explanatory diagram showing an example of uneven heat generation in the semiconductor switching elements and diodes of the chopper circuit shown in FIG. 1 when the power supply is being charged. FIG. 12 is an explanatory diagram showing an example of a cooling path for the semiconductor switching elements and diodes in the state of FIG. 6. FIG. 13 is a graph showing a time change in an on / off signal for a semiconductor switching element that is turned on when the power supply is being charged. FIG. 14 is an explanatory diagram showing a current flow when the chopper circuit of FIG. 1 is discharging a power supply. FIG. 15 is an explanatory diagram showing a current flow when the chopper circuit of FIG. 1 is charging a power supply. FIG. 16 is an explanatory diagram showing a first example of a current flow when the double chopper circuit shown in FIG. 2 is discharging a power supply. FIG. 17 is an explanatory diagram showing a second example of a current flow when the double chopper circuit shown in FIG. 2 is discharging a power supply. FIG. 18 is an explanatory diagram showing a first example of a current flow when the double chopper circuit shown in FIG. 2 is charging a power supply. 16 is an explanatory diagram showing a second example of current flow when the double chopper circuit shown in Fig. 2 is charging a power source. 17 is an explanatory diagram showing an example of uneven heat generation in the semiconductor switching elements and diodes when the double chopper circuit shown in Fig. 2 is discharging a power source. 18 is an explanatory diagram showing an example of cooling paths for the semiconductor switching elements and diodes in the state of Fig. 15. 19 is an explanatory diagram showing an example of uneven heat generation in the semiconductor switching elements and diodes when the double chopper circuit shown in Fig. 2 is charging a power source. 19 is an explanatory diagram showing an example of cooling paths for the semiconductor switching elements and diodes in the state of Fig. 2

[0007] A power conversion apparatus and a cooling method for a power conversion apparatus according to an embodiment will now be described with reference to the drawings. FIG. 1 is a circuit diagram illustrating an example of a chopper circuit C1 according to an embodiment. As shown in FIG. 1 , the chopper circuit C1 in the DC-DC converter (power conversion apparatus) according to the embodiment has positive and negative semiconductor modules Q1, Q2 connected between a positive terminal (high-potential DC terminal) and a negative terminal (low-potential DC terminal) of a DC power source B1, such as a capacitor or a secondary battery. The DC power source B1 is connected to a load M1, such as an electric motor, via the two semiconductor modules Q1, Q2. Hereinafter, the period when the load M1 is driven by power from the DC power source B1 will be referred to as a power source discharging period, and the period when the DC power source B1 is charged by energy input to the load M1 will be referred to as a power source charging period.

[0008] Each semiconductor module Q1, Q2 includes, for example, an insulated gate bipolar transistor (IGBT) T1, T2 to which a diode D1, D2 is connected in anti-parallel. Hereinafter, the IGBT of the first semiconductor module Q1 will be referred to as a first semiconductor switching element T1, and the diode D1 connected to the first semiconductor switching element T1 will be referred to as a first diode D1. The IGBT of the second semiconductor module Q2 will be referred to as a second semiconductor switching element T2, and the diode D2 connected to the second semiconductor switching element T2 will be referred to as a second diode D2. For example, although the semiconductor switching elements T1, T2 in the embodiment are IGBTs, they may also be metal-oxide-semiconductor field-effect transistors (MOSFETs).

[0009] Each of the semiconductor modules Q1 and Q2 may be configured to switch at a frequency of 100 Hz or higher. Each of the semiconductor modules Q1 and Q2 may use a combination of multiple semiconductor switching elements connected in parallel depending on the current capacity. The driving of each of the semiconductor modules Q1 and Q2 may be controlled by a driving signal from a driving device E2.

[0010] FIG. 2 is a circuit diagram showing an example of a double chopper circuit C2 according to an embodiment. As shown in FIG. 2 , the double chopper circuit C2 in the DC-DC converter (power conversion device) according to the embodiment has positive and negative semiconductor modules Q1, Q2 connected between the positive terminal (high-potential DC terminal) and negative terminal (low-potential DC terminal) of a first DC power source B1, such as a capacitor or a secondary battery. The double chopper circuit C2 also has positive and negative semiconductor modules Q3, Q4 connected between the positive terminal (high-potential DC terminal) and negative terminal (low-potential DC terminal) of a second DC power source B2, such as a capacitor or a secondary battery. Each of the DC power sources B1, B2 is connected to a load M1, such as an electric motor, via four semiconductor modules Q1 to Q4.

[0011] Each of the semiconductor modules Q1 to Q4 uses, for example, an IGBT with diodes D1 to D4 connected in anti-parallel. Hereinafter, the IGBT of the third semiconductor module Q3 will be referred to as the third semiconductor switching element T3, and the diode D3 connected to the third semiconductor switching element T3 will be referred to as the third diode D3. Furthermore, the IGBT of the fourth semiconductor module Q4 will be referred to as the fourth semiconductor switching element T4, and the diode D4 connected to the fourth semiconductor switching element T4 will be referred to as the fourth diode D4.

[0012] Each of the semiconductor modules Q1 to Q4 may be configured to switch at a frequency of 100 Hz or higher. Each of the semiconductor modules Q1 to Q4 may use a combination of multiple semiconductor switching elements connected in parallel depending on the current capacity. The driving of each of the semiconductor modules Q1 to Q4 may be controlled by a drive signal from a drive device E2.

[0013] Fig. 3 is an explanatory diagram showing an example of the uneven heat generation of the semiconductor modules Q1 and Q2 when the chopper circuit C1 shown in Fig. 1 is discharging its power supply, Fig. 4 is an explanatory diagram showing an example of the cooling paths of the semiconductor modules Q1 and Q2 in the state shown in Fig. 3, and Fig. 5 is a graph showing the time change in the on / off signal of the first semiconductor module Q1 that is turned on when the power supply is discharging. Note that the chip arrangements shown in Figs. 3 and 4 and Figs. 6, 7, and 15 to 18 described below are examples.

[0014] As shown in Fig. 3, when the power supply of the chopper circuit C1 is discharged, current flows through the first semiconductor switching element T1, but no current flows through the second semiconductor switching element T2. Therefore, the amount of heat generated by the first semiconductor switching element T1 is relatively large compared to the entire circuit (shown by the dark shading in the figure, and the same applies to other figures). At this time, current also flows through the diode D2 of the second semiconductor module Q2, but the amount of heat generated therefrom is relatively small compared to the entire circuit (shown by the light shading in the figure, and the same applies to other figures). In response to this imbalance in the amount of heat generated, the coolant flow rate corresponding to the first semiconductor module Q1 is controlled to be relatively large, as shown in Fig. 4.

[0015] This control is achieved, for example, by switching between large flow paths F1, F2' and small flow paths F2, F1' (see FIG. 4 and FIG. 7 described later) having different flow path cross-sectional areas using control valves V1, V2 connected to the integrated heat sink H1. That is, referring to FIG. 4, when the chopper circuit C1 is discharging power, the flow path in the heat sink H1 at the location R1 where the first semiconductor module Q1 is located switches to the large flow path F1 with a large cross-sectional area (large flow rate), and the flow path in the heat sink H1 at the location R2 where the second semiconductor module Q2 is located switches to the small flow path F2 with a small cross-sectional area (small flow rate). This flow path switching is achieved, for example, by operating the control valves V1, V2 provided upstream of the heat sink H1.

[0016] As shown in FIG. 5, during the power supply discharge, the on-duty ratio D (on period Ton / (on period Ton+off period Toff)) of the first semiconductor module Q1 is larger than during the power supply charge. At this time, the flow path of the portion of the heat sink H1 where the first semiconductor module Q1 is mounted (arrangement portion R1) is switched to the large flow path F1 under the control of a control device E1, which is an ECU (Electronic Control Unit). Based on a control signal from the control device E1, a drive device E2 outputs a drive signal to drive the semiconductor switching elements T1 to T4. As a result, the refrigerant flow rate of the portion of the heat sink H1 corresponding to the first semiconductor module Q1 (arrangement portion R1) becomes relatively large, thereby improving the cooling performance of the first semiconductor module Q1.

[0017] On the other hand, the flow path in the portion of the heat sink H1 where the second semiconductor module Q2 is mounted (the placement portion R2) is switched to the small flow path F2 under the control of the control device E1, so that the refrigerant flow rate in the portion of the heat sink H1 corresponding to the second semiconductor module Q2 (the placement portion R2) becomes relatively small, thereby suppressing changes in the refrigerant flow rate throughout the entire heat sink H1.

[0018] 6 is an explanatory diagram showing an example of the uneven heat generation of each semiconductor module Q1, Q2 when the chopper circuit C1 shown in FIG. 1 is charging with a power source, FIG. 7 is an explanatory diagram showing an example of the cooling path of each semiconductor module Q1, Q2 in the state shown in FIG. 6, and FIG. 8 is a graph showing the time change in on / off of the second semiconductor module Q2 that is turned on when the above-mentioned power source is charging.

[0019] As shown in Figure 6, when the chopper circuit C1 is charging, current flows through the second semiconductor switching element T2, but not through the first semiconductor switching element T1. Therefore, the amount of heat generated by the second semiconductor module Q2 is relatively large compared to the entire circuit. At this time, current also flows through the diode D1 of the first semiconductor module Q1, but the amount of heat generated by the diode D1 is relatively small compared to the entire circuit. In response to this imbalance in the amount of heat generated, the refrigerant flow rate of the second semiconductor module Q2 is controlled to be relatively large, as shown in Figure 7.

[0020] This control is achieved, for example, by switching between large flow paths F1, F2' and small flow paths F2, F1' (see FIGS. 4 and 7) with different flow path cross-sectional areas using control valves V1, V2 (not shown) connected to the integrated heat sink H1. That is, referring to FIG. 7, when the chopper circuit C1 is being charged, the flow path in the heat sink H1 at the location R2 where the second semiconductor module Q2 is located switches to the large flow path F2' with a large cross-sectional area (large flow rate), and the flow path in the heat sink H1 at the location R1 where the first semiconductor module Q1 is located switches to the small flow path F1' with a small cross-sectional area (small flow rate). This flow path switching is achieved, for example, by controlling the control valves V1, V2 provided upstream of the heat sink H1.

[0021] As shown in FIG. 7, during charging, the on-duty ratio D (on period Ton / (on period Ton+off period Toff)) of the second semiconductor module Q2 is larger than during discharging. At this time, the flow path of the portion of the heat sink H1 where the second semiconductor module Q2 is mounted (arrangement portion R2) is switched to the large flow path F2' by control of the control device E1. As a result, the refrigerant flow rate of the portion of the heat sink H1 corresponding to the second semiconductor module Q2 (arrangement portion R2) becomes relatively large, and the cooling performance of the second semiconductor module Q2 is improved.

[0022] On the other hand, the flow path in the portion of the heat sink H1 where the first semiconductor module Q1 is mounted (the placement portion R1) is switched to the small flow path F1' under the control of the control device E1, so that the refrigerant flow rate in the portion of the heat sink H1 corresponding to the first semiconductor module Q1 (the placement portion R1) becomes relatively small, thereby suppressing changes in the refrigerant flow rate throughout the entire heat sink H1.

[0023] Each semiconductor module Q1, Q2 is mounted on one side of a heat sink H1. The heat sink H1 is, for example, water-cooled, and circulates a refrigerant through multiple flow paths formed within the body. A circulation device that circulates the refrigerant through each flow path and a heat exchanger that dissipates heat absorbed by each flow path are connected to the heat sink H1 (neither is shown). A cooling device CL including the heat sink H1, the circulation device, and the heat exchanger absorbs heat generated by each semiconductor module Q1, Q2 mounted on one side of the heat sink H1 and dissipates this heat to the atmosphere outside the power conversion device. The heat sink H1 is not limited to a water-cooled type, and may be one that uses a refrigerant other than cooling water (including gas).

[0024] The heat sink H1 has, for example, large flow paths F1, F2' with a relatively high refrigerant flow rate and small flow paths F2, F1' with a relatively low refrigerant flow rate, arranged in parallel, for each of the semiconductor modules Q1, Q2. The cooling device CL has, for example, control valves V1, V2 that selectively circulate the refrigerant through the large flow paths F1, F2' and the small flow paths F2, F1' within the heat sink H1. The operation of the control valves V1, V2 (switching between the large flow paths F1, F2' and the small flow paths F2, F1') is controlled, for example, by a control device E1.

[0025] 5 , when the on-duty ratio D of the first semiconductor module Q1 becomes equal to or greater than a specified value (e.g., equal to or greater than 50%) during power discharge of the chopper circuit C1, the control device E1 operates the control valves V1 and V2 as follows: That is, by operating the control valves V1 and V2, the flow path of the placement portion R1 of the heat sink H1 for the first semiconductor module Q1 is switched to the large flow path F1, and the flow path of the placement portion R2 for the second semiconductor module Q2 is switched to the small flow path F2.

[0026] 8, when the on-duty ratio D of the second semiconductor module Q2 becomes equal to or greater than a specified value (e.g., equal to or greater than 50%) during power charging of the chopper circuit C1, the control device E1 operates the control valves V1 and V2 as follows: That is, by operating the control valves V1 and V2, the flow path of the arrangement portion R2 of the heat sink H1 for the second semiconductor module Q2 is switched to the large flow path F2′, and the flow path of the arrangement portion R1 for the first semiconductor module Q1 is switched to the small flow path F1′.

[0027] Fig. 9 is an explanatory diagram showing the current flow in the chopper circuit C1 of Fig. 1 when the power supply is being discharged. Fig. 10 is an explanatory diagram showing the current flow in the chopper circuit C1 of Fig. 1 when the power supply is being charged. Referring to Fig. 9, in the chopper circuit C1 when the power supply is being discharged, a current I1 flows when the first semiconductor switching element T1 is in the ON state, and this current I1 is supplied to the load M1. Furthermore, the second semiconductor switching element T2 remains in the OFF state, and a current I2 flows through the second diode D2.

[0028] When the power source is discharged, heat generated by the first semiconductor module Q1 is absorbed by the heat sink H1. At this time, as shown in Fig. 4, in the portion of the heat sink H1 corresponding to the first semiconductor module Q1, the refrigerant flows through the large flow path F1, thereby improving the cooling performance of the first semiconductor module Q1. Furthermore, in the portion of the heat sink H1 corresponding to the second semiconductor module Q2, the refrigerant flows through the small flow path F2, thereby suppressing an increase in the capacity of the circulation device.

[0029] 10, in the chopper circuit C1 during charging of the power source, the first semiconductor switching element T1 remains in the off state, and the current I3 from the load M1 flows through the first diode D1 to the DC power source B1. The second semiconductor switching element T2 repeatedly turns on and off, causing a current I4 based on a portion of the energy of the load M1 to flow.

[0030] The heat generated by the second semiconductor module Q2 during charging is absorbed by the heat sink H1. At this time, as shown in Figure 7, in the portion of the heat sink H1 corresponding to the second semiconductor module Q2, the refrigerant flows through the large flow path F2', thereby improving the cooling performance of the second semiconductor module Q2. Furthermore, in the portion of the heat sink H1 corresponding to the first semiconductor module Q1, the refrigerant flows through the small flow path F1', thereby suppressing an increase in the capacity of the circulation device.

[0031] Fig. 11 is an explanatory diagram showing a first example of current flow when the double chopper circuit C2 shown in Fig. 2 is discharging the power supply. Fig. 12 is an explanatory diagram showing a second example of current flow when the double chopper circuit C2 shown in Fig. 2 is discharging the power supply. In the example of Fig. 11, when the double chopper circuit C2 is discharging the power supply, a current I1 flows when the first and fourth semiconductor switching elements T1 and T4 are on, and this current I1 is supplied to the load M1. Furthermore, the second and third semiconductor switching elements T2 and T3 remain off, and a current I2 flows through the second and third diodes D2 and D3.

[0032] During power discharge, heat generated by the first and fourth semiconductor modules Q1 and Q4 is absorbed by, for example, separate heat sinks H1 and H2. At this time, as shown in FIG. 16 (described later), in the portions of each heat sink H1 and H2 corresponding to the first and fourth semiconductor modules Q1 and Q4 (arrangement portions R1 and R4), the refrigerant flows through the large flow paths F1 and F4, respectively, thereby enhancing the cooling performance of the first and fourth semiconductor modules Q1 and Q4. Furthermore, in the portions of each heat sink H1 and H2 corresponding to the second and third semiconductor modules Q2 and Q3 (arrangement portions R2 and R3), the refrigerant flows through the small flow paths F2 and F3, respectively, thereby minimizing an increase in the capacity of the circulation device. An integrated heat sink may be provided instead of the heat sinks H1 and H2.

[0033] 12, in the double chopper circuit C2 during power supply discharge, when the first and fourth semiconductor switching elements T1 and T4 are on, currents I1a and I1b flow alternately, and these currents I1a and I1b are alternately supplied to the load M1. Also, the second and third semiconductor switching elements T2 and T3 remain off, and either the current I1a or I1b flows through the second and third diodes D2 and D3.

[0034] During power discharge, heat generated by the first and fourth semiconductor modules Q1, Q4 is absorbed by, for example, separate heat sinks H1, H2. At this time, as shown in FIG. 18 (described later), in the portions of each heat sink H1, H2 corresponding to the first and fourth semiconductor modules Q1, Q4 (arrangement portions R1, R4), the refrigerant flows through the large flow paths F1, F4, respectively, thereby enhancing the cooling performance of the first and fourth semiconductor modules Q1, Q4. Furthermore, in the portions of each heat sink H1, H2 corresponding to the second and third semiconductor modules Q2, Q3 (arrangement portions R2, R3), the refrigerant flows through the small flow paths F2, F3, respectively, thereby minimizing an increase in the capacity of the circulation device.

[0035] Fig. 13 is an explanatory diagram showing a first example of current flow in the double chopper circuit C2 shown in Fig. 2 when the power source is being charged. Fig. 14 is an explanatory diagram showing a second example of current flow in the double chopper circuit C2 shown in Fig. 2 when the power source is being charged. In the example of Fig. 13, in the double chopper circuit C2 when the power source is being charged, the first and fourth semiconductor switching elements T1 and T4 remain in the off state, and current I3 from the load M1 flows through the first and fourth diodes D1 and D4 to the DC power sources B1 and B2. The second and third semiconductor switching elements T2 and T3 repeatedly turn on and off, causing current I4 to flow using part of the energy of the load M1.

[0036] Heat generated by the second and third semiconductor modules Q2, Q3 during charging is absorbed by, for example, separate heat sinks H1, H2, respectively. At this time, in the portions of each heat sink H1, H2 corresponding to the second and third semiconductor modules Q2, Q3, the refrigerant flows through the large flow paths F2', F3', respectively, thereby enhancing the cooling performance of the second and third semiconductor modules Q2, Q3. In the portions of each heat sink H1, H2 corresponding to the first and fourth semiconductor modules Q1, Q4, the refrigerant flows through the small flow paths F1', F4', respectively, thereby suppressing an increase in the capacity of the circulation device.

[0037] 14, in the double chopper circuit C2 during charging of the power source, the first and fourth semiconductor switching elements T1 and T4 remain in the off state, and currents I3a and I3b input to and output from the load M1 flow through the first and fourth diodes D1 and D4 and are input to and output from the DC power sources B1 and B2. The second and third semiconductor switching elements T2 and T3 are repeatedly turned on and off, and currents I3a and I3b flow alternately.

[0038] Heat generated by the second and third semiconductor modules Q2, Q3 during charging is absorbed by the heat sinks H1, H2. At this time, in the portions of the heat sinks H1, H2 corresponding to the second and third semiconductor modules Q2, Q3, the refrigerant flows through the large flow paths F2', F3', thereby improving the cooling performance of the second and third semiconductor modules Q2, Q3. In the portions of the heat sinks H1, H2 corresponding to the second and third semiconductor modules Q2, Q3, the refrigerant flows through the small flow paths F1', F4', thereby suppressing an increase in the capacity of the circulation device.

[0039] FIG. 15 is an explanatory diagram showing an example of the uneven distribution of heat among the semiconductor modules Q1 to Q4 during power discharge in the double chopper circuit C2 shown in FIG. 2 . FIG. 16 is an explanatory diagram showing an example of the cooling paths for the semiconductor modules Q1 to Q4 in the state shown in FIG. 15 . As shown in FIGS. 15 and 16 , during power discharge, the heat generated by the first and fourth semiconductor modules Q1 and Q4 increases. At this time, the refrigerant flows through the large flow paths F1 and F4 in the portions of the heat sinks H1 and H2 corresponding to the first and fourth semiconductor modules Q1 and Q4. Furthermore, the refrigerant flows through the small flow paths F2 and F3 in the portions of the heat sinks H1 and H2 corresponding to the second and third semiconductor modules Q2 and Q3. This flow path switching is performed, for example, by controlling the control valves V1 to V4 provided upstream of the heat sinks H1 and H2.

[0040] FIG. 17 is an explanatory diagram showing an example of the uneven heat generation among the semiconductor modules Q1 to Q4 during power charging of the double chopper circuit C2 shown in FIG. 2 . FIG. 18 is an explanatory diagram showing an example of the cooling paths for the semiconductor modules Q1 to Q4 in the state shown in FIG. 17 . As shown in FIGS. 17 and 18 , during power charging, the second and third semiconductor modules Q2 and Q3 generate high heat. At this time, the refrigerant flows through the large flow paths F2′ and F3′ in the portions of each heat sink H1 and H2 corresponding to the second and third semiconductor modules Q2 and Q3. Furthermore, the refrigerant flows through the small flow paths F1′ and F4′ in the portions of each heat sink H1 and H2 corresponding to the first and fourth semiconductor modules Q1 and Q4. This flow path switching is performed, for example, by controlling the control valves V1 to V4 provided upstream of the heat sinks H1 and H2.

[0041] The power conversion device of the embodiment described above includes semiconductor modules Q1-Q4, each including semiconductor switching elements T1-T4 and diodes D1-D4 connected in anti-parallel to the semiconductor switching elements T1-T4, a control device E1 that outputs a control signal representing the duty of the semiconductor switching elements T1-T4, a drive device E2 that drives the semiconductor switching elements T1-T4 (outputs a drive signal) based on the control signal from the control device E1, and a cooling device CL that cools the semiconductor modules Q1-Q4. The cooling device CL is connected to the semiconductor modules Q1-Q4, has a flow path for a refrigerant, and includes heat sinks H1 and H2 that absorb heat generated by the semiconductor modules Q1-Q4. The control device E1 changes the flow rate of the refrigerant flowing through the heat sinks H1 and H2 depending on the duty during module control.

[0042] This configuration achieves the following effect by changing the coolant flow rate in the heat sinks H1 and H2 connected to the semiconductor modules Q1 to Q4 according to the duty. That is, even if the semiconductor switching elements T1 to T4 or the diodes D1 to D4 generate excessive heat depending on the operating state of the power conversion device, it is possible to take measures such as increasing the coolant flow rate in the locations where the components that generate the most heat are located. This reduces the uneven distribution of heat within the semiconductor modules Q1 to Q4.

[0043] In the power conversion device of the embodiment, the heat sinks H1 and H2 are provided with large flow paths F1, F2', F3', and F4 having large flow path cross-sectional areas and small flow paths F1', F2, F3, and F4' having small flow path cross-sectional areas, for each of the arrangement positions R1 to R4 of the semiconductor modules Q1 to Q4. The cooling device CL is provided with control valves V1 to V4 that guide the refrigerant to one of the large flow paths F1, F2', F3', and F4 or the small flow paths F1', F2, F3, and F4'.

[0044] With this configuration, by switching the control valves V1 to V4 to flow refrigerant through one of the large flow paths F1, F2', F3', and F4 and the small flow paths F1', F2, F3, and F4' of the heat sinks H1 and H2, the following effects are achieved. That is, even if one of the semiconductor switching elements T1 to T4 or the diodes D1 to D4 generates excessive heat depending on the operating state of the power conversion device, it is possible to take measures such as increasing the refrigerant flow rate to the location of the component that generates the most heat. This reduces heat distribution imbalance within the semiconductor modules Q1 to Q4.

[0045] The cooling method for a power conversion device of an embodiment is a cooling method for a power conversion device that includes semiconductor modules Q1 to Q4, each including semiconductor switching elements T1 to T4 and diodes D1 to D4 connected in anti-parallel to the semiconductor switching elements T1 to T4, a control device E1 that outputs a control signal representing the duty of the semiconductor switching elements T1 to T4, and heat sinks H1, H2 that are connected to the semiconductor modules Q1 to Q4, have flow paths for flowing a refrigerant, and absorb heat generated by the semiconductor modules Q1 to Q4, and changes the flow rate of the refrigerant flowing through the heat sinks H1, H2 according to the duty during module control.

[0046] This configuration achieves the following effect by changing the coolant flow rate in the heat sinks H1 and H2 connected to the semiconductor modules Q1 to Q4 according to the duty. That is, even if the semiconductor switching elements T1 to T4 or the diodes D1 to D4 generate excessive heat depending on the operating state of the power conversion device, it is possible to take measures such as increasing the coolant flow rate in the locations where the components that generate the most heat are located. This reduces the uneven distribution of heat within the semiconductor modules Q1 to Q4.

[0047] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are intended to be included within the scope and spirit of the invention, as well as within the scope of the invention and its equivalents as defined in the claims.

[0048] C1...chopper circuit, C2...double chopper circuit, CL...cooling device, D1 to D4...diodes, E1...control device, E2...driver, F1, F2', F3', F4...large flow path, F1', F2, F3, F4'...small flow path, H1, H2...heat sink, Q1 to Q4...semiconductor module, R1 to R4...arrangement portion, T1 to T4...semiconductor switching element, V1 to V4...control valve

Claims

1. A power conversion device comprising: a semiconductor module including a semiconductor switching element and a diode connected to the semiconductor switching element; a control device that outputs a control signal representing the duty of the semiconductor switching element; and a heat sink connected to the semiconductor module, having a flow path for flowing a coolant, and absorbing heat generated by the semiconductor module, wherein the control device changes the flow rate of the coolant flowing through the heat sink in accordance with the duty.

2. The power conversion device according to claim 1, wherein the heat sink comprises a large flow path with a large cross-sectional area and a small flow path with a small cross-sectional area for each location of the semiconductor module, and the cooling device including the heat sink comprises a control valve that directs refrigerant to one of the large flow path and the small flow path.

3. A cooling method for a power conversion device comprising: a semiconductor module including a semiconductor switching element and a diode connected to the semiconductor switching element; a control device that outputs a control signal representing the duty of the semiconductor switching element; and a heat sink connected to the semiconductor module, having a flow path for flowing a coolant, and absorbing heat generated by the semiconductor module, wherein the flow rate of the coolant flowing through the heat sinks H1 and H2 is changed according to the duty during module control.

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