JP6950556B2 - Inverter cooling control system - Google Patents

Description

The present invention relates to the technical field of an inverter cooling control system.

As a system of this type, a system that cools an inverter by using a refrigerant such as cooling water is known. For example, Patent Document 1 discloses a technique of improving cooling efficiency by locating the lower arm side having a small thermal resistance downstream of the refrigerant flow in an inverter having two arms.

Japanese Unexamined Patent Publication No. 2011-228638

Each of the plurality of switching elements included in the inverter has a different element heat generation amount. Specifically, the calorific value of each switching element becomes a different value due to deterioration of thermal resistance and loss variation peculiar to the element. Therefore, in order to cool the inverter efficiently, it is preferable to consider the difference in the amount of heat generated by each switching element. However, in the technique described in Patent Document 1 described above, cooling cannot be performed by utilizing the difference in the amount of heat generated in the switching element. That is, there is sufficient room for improvement in terms of efficiently cooling the inverter.

The present invention has been made in view of the above problems, for example, and an object of the present invention is to provide an inverter cooling control system capable of suitably cooling an inverter in consideration of element heat generation.

One aspect of the cooling control system for the inverter according to the present invention is the cooling control system for the inverter using the cooling water flowing from the first switching element group to the second switching element group, in the inflow portion to the inverter. A predetermined current is applied to the first acquisition means for acquiring the temperature of the cooling water as the first temperature and the first switching element group or the second switching element group, and the temperature is the highest in the second switching element group. Based on the second acquisition means for acquiring the temperature of the element having a high temperature as the second temperature and the first temperature and the second temperature, the heat generated by the first switching element group is generated by the second switching via the cooling water. Based on the first calculation means for calculating the rising temperature of the interference component given to the element or the rising temperature of the self-heating component in the second switching element, and the rising temperature of the interference component or the rising temperature of the self-heating component. The second switching element group includes a second calculation means for calculating an allowable heat generation temperature, and a control means for controlling the flow rate of the cooling water based on the heat generation allowable temperature.

It is a block diagram which shows the structure of the cooling control system of the inverter which concerns on 1st Embodiment. It is the schematic which shows the structure of the cooling device of the inverter which concerns on 1st Embodiment. It is a flowchart which shows the operation flow of the cooling control system of the inverter which concerns on 1st Embodiment. It is a conceptual diagram which shows the calculation method of the heat generation allowable temperature by the cooling control system of the inverter which concerns on 1st Embodiment. It is a map which shows the expansion effect of the drive current by the cooling control system of the inverter which concerns on 1st Embodiment. It is a map which shows the flow rate reduction effect of the cooling water by the cooling control system of the inverter which concerns on 1st Embodiment. It is a flowchart which shows the operation flow of the cooling control system of the inverter which concerns on 2nd Embodiment. It is a conceptual diagram which shows the calculation method of the heat generation allowable temperature by the cooling control system of the inverter which concerns on 2nd Embodiment. It is a map which shows the expansion effect of the drive current by the cooling control system of the inverter which concerns on 2nd Embodiment. It is a map which shows the flow rate reduction effect of the cooling water by the cooling control system of the inverter which concerns on 2nd Embodiment.

Hereinafter, embodiments of the inverter cooling control system will be described with reference to the drawings.

<First Embodiment>
The inverter cooling control system according to the first embodiment will be described with reference to FIGS. 1 to 6. In the first embodiment, the cooling control system of the inverter mounted on the vehicle will be described as an example.

<Overall configuration>
First, the configuration of the vehicle power supply system according to the first embodiment will be described with reference to FIG. FIG. 1 is a block diagram showing a configuration of an inverter cooling control system according to the first embodiment.

As shown in FIG. 1, the inverter cooling control system according to the present embodiment is configured as a system for cooling the inverter 30 configured as a part of the vehicle power supply system. The vehicle power supply system includes a battery 10, a system main relay 12, a smoothing capacitor C1, a converter 20, a smoothing capacitor C2, an inverter 30, a motor generator MG, and an ECU (Electronic Control Unit) 100. There is.

The battery 10 is a rechargeable power storage device. As an example of the battery 10, for example, a secondary battery (for example, a nickel hydrogen battery, a lithium ion battery, etc.) can be mentioned. The power supply from the battery 10 is configured to be cut off by the system main relay 12.

The smoothing capacitor C1 is a voltage smoothing capacitor connected between the positive electrode wire of the battery 10 and the negative electrode wire of the battery 10. The smoothing capacitor C1 is a capacitor for smoothing the fluctuation of the voltage VL between the terminals between the positive electrode line and the negative electrode line.

The converter 20 includes a reactor L1, a switching element Q1 to which the rectifier diode D1 is connected, and a switching element Q2 to which the rectifier diode D2 is connected. In the converter 20, the switching elements Q1 and Q2 are controlled to be turned on and off in a complementary and alternating manner within each switching cycle.

The converter 20 boosts the DC voltage VL supplied from the battery 10 to the DC voltage VH during the boosting operation. This boosting operation is performed by supplying the electromagnetic energy stored in the reactor L1 during the ON period of the switching element Q2 via the switching element Q1 and the rectifier diode D1.

Further, the converter 20 steps down the DC voltage VH to the DC voltage VL during the step-down operation. This step-down operation is performed by supplying the electromagnetic energy stored in the reactor L1 during the ON period of the switching element Q1 via the switching element Q2 and the rectifier diode D2.

The voltage conversion ratio (that is, the ratio of VH and VL) in these step-up operations and step-down operations is controlled by the on-period ratio (that is, duty ratio) of the switching elements Q1 and Q2 in the switching cycle. If the switching elements Q1 and Q2 are fixed on and off, respectively, VH = VL (voltage conversion ratio = 1.0) can be set.

The smoothing capacitor C2 is a voltage smoothing capacitor arranged between the converter 20 and the inverter 30. The smoothing capacitor C2 is a capacitor for smoothing fluctuations in the boosted voltage VH.

The inverter 30 converts the DC power (DC voltage) supplied from the converter 20 into AC power (specifically, three-phase AC voltage). In the inverter 30, in order to convert DC power into AC power, a U-phase arm including a p-side switching element Cup and an n-side switching element Qun, a V-phase arm including a p-side switching element Qvp and an n-side switching element Qvn, and a V-phase arm, and It includes a W-phase arm including a p-side switching element Qwp and an n-side switching element Qwn. Each arm included in the inverter 30 is connected in parallel between the positive electrode line and the negative electrode line. Rectifying diodes Dup, Dvp, and Dwp are connected to the p-side switching elements Up, Qvp, and Qwp, respectively. Similarly, for the n-side switching elements Qun, Qvn and Qwn, the rectifying diodes Dun, Dvn and Dwn are connected, respectively. Switching on / off of each of the switching elements Cup to Qwn of the inverter 30 is controlled by PWM (Pulse Width Modulation) control.

The intermediate points between the upper arm (that is, each p-side switching element) and the lower arm (that is, each n-side switching element) of each phase arm in the inverter 30 are connected to each phase coil of the motor generator MG, respectively. As a result, the AC power (three-phase AC voltage) generated as a result of the conversion operation by the inverter 30 is supplied to the motor generator MG. The upper arm is a specific example of the "first switching element group" in the appendix described later, and the lower arm is a specific example of the "second switching element group" in the appendix described later.

The motor generator MG is configured as a three-phase AC motor generator. The motor generator MG is driven to generate the torque required for the vehicle to travel. The torque generated by the motor generator MG is transmitted to the drive wheels via a drive shaft mechanically connected to the rotation shaft of the motor generator MG. The motor generator MG may regenerate electric power (power generation) when braking the vehicle or the like.

The ECU 100 is an electronic control unit for controlling the operation of each part in the power supply system of the vehicle. Further, the ECU 100 according to the present embodiment is particularly partially configured as a cooling control system for an inverter. The ECU 100 has a cooling water temperature acquisition unit 110, an element temperature acquisition unit 120, a rise temperature calculation unit 130, a heat generation allowable temperature calculation unit 140, and a control unit 150 as processing blocks for realizing the function of the inverter as a cooling control system. It has.

The cooling water temperature acquisition unit 110 is a specific example of the “first acquisition means” in the appendix described later, and acquires the temperature of the cooling water for cooling the inverter. The element temperature acquisition unit 120 is a specific example of the “second acquisition means” described later, and acquires the temperature of the lower arm (that is, each n-side switching element). The rising temperature calculation unit 130 is a specific example of the “first calculation means” in the appendix described later, and is the temperature of the cooling water acquired by the cooling water temperature acquisition unit 110 and the lower temperature acquired by the element temperature acquisition unit 120. Based on the temperature of the arm, the temperature rise due to the energization of the lower arm is calculated. The heat generation allowable temperature calculation unit 140 is a specific example of the “second calculation means” in the appendix described later, and calculates the heat generation allowable temperature of the lower arm based on the temperature rise calculated by the temperature rise calculation unit 130. The control unit 150 is a specific example of the “control means” in the appendix described later, and controls the inverter 30 or the cooling device of the inverter based on the heat generation allowable temperature calculated by the heat generation allowable temperature calculation unit 140. The operation of each part of the ECU 100 will be described in detail later.

<Cooling device configuration>
Next, the configuration of the inverter cooling device (that is, the device for cooling the inverter 30) according to the first embodiment will be specifically described with reference to FIG. It is the schematic which shows the structure of the cooling device of the inverter which concerns on 1st Embodiment.

As shown in FIG. 2, the inverter cooling device according to the first embodiment is configured as a device for flowing cooling water from the upper arm to the lower arm of the inverter 20. The cooling device is provided with a water temperature sensor 200 at the inlet portion of the cooling water (that is, on the front side of each switching element of the inverter 30). The cooling water temperature acquisition unit 110 in the ECU 100 described above is configured to acquire the temperature detected by the water temperature sensor 200.
Each switching element of the lower arm is provided with element temperature sensors 301, 302, and 303, respectively. The element temperature sensor 301 detects the temperature of the switching element Qun. The element temperature sensor 302 detects the temperature of the switching element Qvn. The element temperature sensor 302 detects the temperature of the switching element Qwn. The element temperature acquisition unit 120 in the ECU 100 described above is configured to acquire the temperature detected by these element temperature sensors 301, 302, and 303.

<Operation explanation>
Next, the operation of the inverter cooling control system according to the first embodiment (particularly, the operation for determining the cooling conditions) will be described with reference to FIG. FIG. 3 is a flowchart showing an operation flow of the cooling control system of the inverter according to the first embodiment.

As shown in FIG. 3, when the cooling control system of the inverter according to the first embodiment is operated, first, a predetermined current is applied to the three phases (U phase, V phase, W phase) of the upper arm (step S11). The "predetermined current" here is a current for bringing each of the switching elements Up, Qvp, and Qwp of the upper arm to the saturation temperature, and an appropriate value is set in advance.

Subsequently, it is determined whether or not a second has elapsed since the predetermined current was applied (step S12). Here, "a second" is set as a period until the switching elements Cup, Qvp, and Qwp of the upper arm reach the saturation temperature by energizing a predetermined current. When it is determined that a second has not passed since the predetermined current was energized (step S12: NO), the energization of the predetermined current is continued.

When it is determined that a second has passed since the predetermined current was applied (step S12: YES), the element temperature acquisition unit 120 sets the temperatures Tu, Tv, and Tw of the switching elements Qun, Qvn, and Qwn of the lower arm. Acquire each (step S13). The element temperature acquisition unit 120 further acquires the largest value among the acquired temperatures Tu, Tv, and Tw as the maximum temperature Tmax (step S14).

Subsequently, the rising temperature calculation unit 130 raises the rising temperature of each of the lower arm switching elements Qun, Qvn, and Qwn (specifically, each of the upper arms) by energizing the upper arm switching elements Qup, Qvp, and Qwp. The temperature rise due to the heat generated by the switching elements Cup, Qvp, and Qwp being transmitted to the switching elements Qun, Qvn, and Qwn of the lower arm via the cooling water) is calculated (step S15). Hereinafter, this rising temperature will be referred to as “rising temperature due to upstream / downstream effect”. The rising temperature due to the upstream / downstream effect is obtained, for example, by subtracting the water temperature of the cooling water acquired by the cooling water temperature acquisition unit 110 from the maximum temperature Tmax acquired by the element temperature acquisition unit 120.

Subsequently, the heat generation allowable temperature calculation unit 140 calculates the heat generation allowable temperature of each of the switching elements Qun, Qvn, and Qwn of the lower arm (step S16). The heat generation allowable temperature is a temperature corresponding to the self-heating component allowed for each of the switching elements Qun, Qvn, and Qwn of the lower arm, and is calculated based on the temperature rise due to the upstream / downstream effect calculated by the rise temperature calculation unit 130. be able to.

Here, the method of calculating the allowable heat generation temperature will be specifically described with reference to FIG. FIG. 4 is a conceptual diagram showing a method of calculating the allowable heat generation temperature by the cooling control system of the inverter according to the first embodiment.

As shown in FIG. 4, the heat generation allowable temperature is the design value of the rising temperature due to the upstream / downstream effect (specifically, the value assuming the maximum thermal resistance deterioration and the maximum loss variation) and the rising temperature due to the upstream / downstream effect. It can be calculated as a difference from the calculated value of (that is, the value calculated by the rising temperature calculation unit 130). Regarding the temperature rise due to the upstream and downstream effects, the actually calculated value is smaller than the design value calculated as the theoretical maximum value, so the difference is the expandable amount of element heat generation at the present time. It will be tolerated.

Returning to FIG. 3, the control unit 150 determines the maximum drive current Imax of the inverter 30 based on the heat generation allowable temperature calculated by the heat generation allowable temperature calculation unit 140 (step S17). Alternatively, the control unit 150 determines the flow rate of the cooling water based on the heat generation allowable temperature calculated by the heat generation allowable temperature calculation unit 140 (step S18). As a result, in the inverter cooling control system according to the first embodiment, the maximum drive current Imax of the inverter 30 or the flow rate of the cooling water is controlled based on the heat generation allowable temperature calculated from the rising temperature due to the upstream / downstream effect. become.

The series of processes described above may be executed when the vehicle is started or stopped (in other words, it may be executed for each trip of the vehicle).

<Technical effect>
Next, the technical effects obtained by the cooling control system of the inverter according to the first embodiment will be described with reference to FIGS. 5 and 6. FIG. 5 is a map showing the expansion effect of the drive current by the cooling control system of the inverter according to the first embodiment. FIG. 6 is a map showing the effect of reducing the flow rate of the cooling water by the cooling control system of the inverter according to the first embodiment.

As shown in FIG. 5, when the permissible heat generation temperature of each of the switching elements Qun, Qvn and Qwn of the lower arm is calculated, the permissible self-heat generation temperature becomes higher than the design value. As a result, the maximum drive current Imax of the inverter 30 is extended to Imax + α during one trip in which the heat generation allowable temperature is calculated. That is, it is possible to increase the maximum drive current of the inverter 30 as compared with the design value. Therefore, the inverter 30 can be operated more efficiently to improve the fuel efficiency of the vehicle.

As shown in FIG. 6, when the heat generation allowable temperature of each switching element Qun, Qvn and Qwn of the lower arm is calculated, the map for determining the flow rate of the cooling water is changed to one having a smaller flow rate. Can be done. As a result, the flow rate of the cooling water is changed to a smaller value during one trip in which the heat generation allowable temperature is calculated. That is, it is possible to reduce the cooling water required for cooling as compared with the design value. Therefore, excessive cooling can be suppressed and the fuel efficiency of the vehicle can be improved.

<Second Embodiment>
Next, the inverter cooling control system according to the first embodiment will be described with reference to FIGS. 7 to 10. The second embodiment is different from the above-described first embodiment only in a part of the configuration and operation, and the other parts are substantially the same as those of the first embodiment. Therefore, in the following, the parts different from the first embodiment will be described in detail, and the overlapping parts will be omitted as appropriate.

<Operation explanation>
The operation of the inverter cooling control system according to the second embodiment (particularly, the operation for determining the cooling conditions) will be described with reference to FIG. 7. FIG. 7 is a flowchart showing an operation flow of the cooling control system of the inverter according to the second embodiment.

As shown in FIG. 7, when the cooling control system of the inverter according to the second embodiment is operated, first, a predetermined current is applied to the three phases (U phase, V phase, W phase) of the lower arm (step S21). The "predetermined current" here is a current for bringing the switching elements Qun, Qvn and Qwn of the lower arm to reach the saturation temperature, and an appropriate value is set in advance.

Subsequently, it is determined whether or not a second has elapsed since the predetermined current was applied (step S22). Here, "a second" is set as a period until the switching elements Qun, Qvn, and Qwn of the lower arm reach the saturation temperature by energizing a predetermined current. When it is determined that a second has not passed since the predetermined current was energized (step S22: NO), the energization of the predetermined current is continued.

When it is determined that a second has passed since the predetermined current was applied (step S22: YES), the element temperature acquisition unit 120 sets the temperatures Tu, Tv, and Tw of the switching elements Qun, Qvn, and Qwn of the lower arm. Acquire each (step S23). The element temperature acquisition unit 120 further acquires the largest value among the acquired temperatures Tu, Tv, and Tw as the maximum temperature Tmax (step S24).

Subsequently, the rising temperature calculation unit 130 calculates the rising temperature of each of the switching elements Qun, Qvn, and Qwn of the lower arm due to self-heating (step S25). The temperature rise due to self-heating is obtained by subtracting the water temperature of the cooling water acquired by the cooling water temperature acquisition unit 110 from, for example, the maximum temperature Tmax acquired by the element temperature acquisition unit 120.

Subsequently, the heat generation allowable temperature calculation unit 140 calculates the heat generation allowable temperature of each of the switching elements Qun, Qvn, and Qwn of the lower arm (step S26). The heat generation allowable temperature is a temperature corresponding to the self-heating component allowed for each of the switching elements Qun, Qvn, and Qwn of the lower arm, and is calculated based on the self-heating rising temperature calculated by the rising temperature calculation unit 130. Can be done.

Here, the method of calculating the allowable heat generation temperature will be specifically described with reference to FIG. FIG. 8 is a conceptual diagram showing a method of calculating the allowable heat generation temperature by the cooling control system of the inverter according to the second embodiment.

As shown in FIG. 8, the permissible heat generation temperature is calculated by calculating the design value of the temperature rise due to self-heat generation (specifically, the value assuming the maximum thermal resistance deterioration and the maximum loss variation) and the temperature rise due to self-heat generation. It can be calculated as a difference from the value (that is, the value calculated by the rising temperature calculation unit 130). Regarding the temperature rise due to self-heating, the actually calculated value is smaller than the design value calculated as the theoretical maximum value, so the difference is acceptable as the expandable amount of element heat generation at the present time. Will be done.

Returning to FIG. 7, the control unit 150 determines the maximum drive current Imax of the inverter 30 based on the heat generation allowable temperature calculated by the heat generation allowable temperature calculation unit 140 (step S27). Alternatively, the control unit 150 determines the flow rate of the cooling water based on the heat generation allowable temperature calculated by the heat generation allowable temperature calculation unit 140 (step S28). As a result, in the inverter cooling control system according to the second embodiment, the maximum drive current Imax of the inverter 30 or the flow rate of the cooling water is controlled based on the heat generation allowable temperature calculated from the temperature rise due to self-heating. Become.

The series of processes described above may be executed when the vehicle is started or stopped (in other words, it may be executed for each trip of the vehicle).

<Technical effect>
Next, the technical effects obtained by the cooling control system of the inverter according to the second embodiment will be described with reference to FIGS. 9 and 10. FIG. 9 is a map showing the expansion effect of the drive current by the cooling control system of the inverter according to the second embodiment. FIG. 10 is a map showing the effect of reducing the flow rate of the cooling water by the cooling control system of the inverter according to the second embodiment.

As shown in FIG. 9, when the heat generation allowable temperature of each switching element Qun, Qvn and Qwn of the lower arm is calculated, the map for determining the maximum drive current Imax of the inverter 30 is changed to one having a larger current. Can be changed to. As a result, the maximum drive current Imax of the inverter 30 is extended to Imax + α during one trip in which the heat generation allowable temperature is calculated. That is, it is possible to increase the maximum drive current of the inverter 30 as compared with the design value. Therefore, the inverter 30 can be operated more efficiently to improve the fuel efficiency of the vehicle.

As shown in FIG. 10, when the heat generation allowable temperature of each switching element Qun, Qvn and Qwn of the lower arm is calculated, the map for determining the flow rate of the cooling water is changed to one having a smaller flow rate. Can be done. As a result, the flow rate of the cooling water is changed to a smaller value during one trip in which the heat generation allowable temperature is calculated. That is, it is possible to reduce the cooling water required for cooling as compared with the design value. Therefore, excessive cooling can be suppressed and the fuel efficiency of the vehicle can be improved.

<Additional notes>
Various aspects of the invention derived from the embodiments described above will be described below.

(Appendix 1)
The cooling control system for the inverter according to Appendix 1 is a cooling control system for the inverter using cooling water flowing from the first switching element group to the second switching element group, and the cooling in the inflow portion to the inverter. A predetermined current is applied to the first acquisition means for acquiring the temperature of water as the first temperature and the first switching element group or the second switching element group, and the temperature is the highest in the second switching element group. Based on the second acquisition means for acquiring the temperature of the element as the second temperature and the first temperature and the second temperature, the heat generated by the first switching element group is transmitted to the second switching element via the cooling water. The second calculation means based on the first calculation means for calculating the rise temperature of the interference component or the rise temperature of the self-heating component in the second switching element, and the rise temperature of the interference component or the self-heating component. A second calculation means for calculating the allowable heat generation temperature that the switching element group can tolerate, and a control means for controlling the flow rate of the cooling water based on the allowable heat generation temperature are provided.

In the inverter cooling control system described in Appendix 1, the cooling water for cooling the inverter is based on the heat generation allowable temperature of the second switching located on the downstream side of the cooling water (in other words, the side where the cooling effect is small). The flow rate is controlled. The heat generation allowable temperature of the second switching is the temperature rise of the interference from the first switching element or the second switching element, which can be calculated by energizing the first switching element or the second switching element with a predetermined current. This is the current value calculated based on the rising temperature of the self-heating portion of.

By using the heat generation allowable temperature described above, it is possible to control the flow rate of the cooling water in consideration of the deterioration of the thermal resistance in the switching element and the loss variation for each element. For example, the temperature of the switching element does not exceed the heat resistant temperature. Within the range, it is possible to cool the inverter efficiently.

The present invention is not limited to the above-described embodiment, and can be appropriately changed within the scope of claims and within the range not contrary to the gist or idea of the invention that can be read from the entire specification, and the cooling control of the inverter accompanied by such a change is possible. The system is also included in the technical scope of the present invention.

10 Battery 12 System Main Relay C1 Smoothing Condenser 20 Converter L1 Reactor Q1, Q2 Switching Elements D1, D2 Rectifier Diode C2 Smoothing Condenser 20 Inverter Cup ~ Qwn Switching Element Dup ~ Dwn Rectifier Diode MG Motor Generator 100 ECU
110 Cooling water temperature acquisition unit 120 Element temperature acquisition unit 130 Rise temperature calculation unit 140 Heat generation allowable temperature calculation unit 150 Control unit 200 Water temperature sensor 301, 202, 303 Element temperature sensor

Claims (1)

An inverter cooling control system that uses cooling water that flows from the first switching element group to the second switching element group.
The first acquisition means for acquiring the temperature of the cooling water in the inflow portion to the inverter as the first temperature,
A second acquisition means that applies a predetermined current to the first switching element group or the second switching element group and acquires the temperature of the hottest element in the second switching element group as the second temperature.
Based on the first temperature and the second temperature, the temperature rise of the interference caused by the heat generated by the first switching element group to the second switching element via the cooling water, or the self-heating in the second switching element. The first calculation means for calculating the rising temperature of the minute,
A second calculation means for calculating the heat generation allowable temperature that the second switching element group can tolerate based on the temperature rise of the interference component or the temperature rise of the self-heating component.
An inverter cooling control system including a control means for controlling the flow rate of the cooling water based on the heat generation allowable temperature.

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