JP2015053774A - Power converter, and electric vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power converter and an electric vehicle capable of securing the safety.SOLUTION: A power converter comprises: an inverter 26 obtained by parallel-connecting switch circuits each having a pair of semiconductor switches connected in series; a cooling unit 27 having therein a cavity where cooling medium circulates; an insulator 25 arranged between the inverter 26 and the cooling unit 27; a controller 22 including a deterioration diagnosis part 22D having temperature input parts 221 and 222 to which information on a temperature of the semiconductor switch and information on a temperature of the cooling medium are inputted, calculating a heat resistance on the basis of the information on the temperature of the semiconductor switch and the information on the temperature of the cooling medium inputted to the temperature input parts 221 and 222, determining whether or not the temperature change of the cooling medium is a predetermined value or more, and when the temperature change of the cooling medium is the predetermined value or more and when the heat resistance is a predetermined value or more, determining that cooling performance is deteriorated.

Description

  Embodiments described herein relate generally to a power converter and an electric vehicle.

  The power converter has a plurality of switching elements. The switching element may generate heat when it is conductive and current flows, resulting in performance degradation, failure, and life reduction. In order to suppress the temperature rise of the switching element, a cooling device is attached to the power converter.

  In the cooling device attached to the power converter, for example, an insulator that insulates a high voltage or grease is used to increase the heat transfer rate between components. When the power converter is used for a long time, the insulator and grease deteriorate due to heat and aging. If a part such as an insulator is deformed or grease is removed, the cooling performance of the cooling device may deteriorate.

  When the cooling performance of the cooling device is lowered, not only the performance of the power converter is lowered, but the power converter may become high temperature and stop abnormally during operation. For example, when installed in systems where it is difficult to abnormally stop power converters, such as semiconductor manufacturing plants, nuclear power plant equipment, medical equipment, transportation equipment such as trains and cars, and elevators It is desirable to detect deterioration in cooling performance before an abnormal stop.

Japanese Patent No. 4951642

  According to an embodiment of the present invention, an object is to provide a power converter that ensures safety and an electric vehicle.

  According to the embodiment, an inverter in which a switch circuit including a pair of semiconductor switches connected in series is connected in parallel, a cooler having a cavity in which a cooling medium circulates, and between the inverter and the cooler. And the temperature information of the semiconductor switch input to the temperature input unit, and the temperature input unit to which the temperature information of the semiconductor switch and the temperature information of the cooling medium are input. Calculating a thermal resistance based on the information on the temperature of the cooling medium, determining whether the temperature change of the cooling medium is equal to or greater than a predetermined value, the temperature change of the cooling medium is equal to or greater than a predetermined value, and There is provided a power converter comprising: a controller including a deterioration diagnosis unit that determines that the cooling performance is deteriorated when the thermal resistance is equal to or greater than a predetermined value.

FIG. 1 is a block diagram schematically illustrating a configuration example of an electric vehicle according to an embodiment. FIG. 2 is a diagram schematically illustrating a configuration example of the power converter. FIG. 3 is a diagram schematically illustrating an example of the configuration of the semiconductor switch and the cooling device of the power converter. FIG. 4 is a block diagram for explaining an example of the configuration of the deterioration diagnosis unit. FIG. 5 is a diagram showing an example of a simple thermal circuit ignoring the heat capacity of each component from the cooling medium to the semiconductor switch. FIG. 6 is a flowchart for explaining an example of the operation of deterioration determination in the determination unit. FIG. 7 is a block diagram for explaining an example of the configuration of the deterioration diagnosis unit. FIG. 8 is a diagram illustrating an example of a simple thermal circuit from the cooling medium to the semiconductor switch using the temperature change of the cooling medium as a heat source. FIG. 9 is a diagram for explaining an example of the relationship between the temperature change of the cooling medium and the temperature change of the semiconductor switch. FIG. 10 is a flowchart for explaining an example of the deterioration determination operation in the cooling medium temperature change detection unit, the time measurement threshold value setting unit, and the determination unit. FIG. 11 is a diagram for explaining an example of the relationship between the temperature change of the cooling medium and the temperature change of the semiconductor switch. FIG. 12 is a diagram illustrating an example of a simple thermal circuit from the cooling medium to the semiconductor switch when there is a heat source other than the temperature change of the cooling medium. FIG. 13 is a block diagram schematically illustrating another configuration example of the electric vehicle according to the embodiment.

  Hereinafter, the power converter of an embodiment and an electric vehicle are explained with reference to drawings.

FIG. 1 is a block diagram schematically showing a configuration example of the electric vehicle according to the first embodiment.
The electric vehicle according to the present embodiment includes, for example, an electric battery including a battery 10, a power converter, a motor 30, a wheel WL, an axle 40 that transmits the rotational power of the motor 30 to the wheel WL, and a vehicle ECU 60. It is a car. The power conversion device includes a power converter 20 and a cooling device including a cooling medium supply device 50.

  The electric vehicle other than the electric vehicle is a vehicle equipped with an inverter, such as a hybrid electric vehicle equipped with a gasoline engine and a fuel cell vehicle.

  The battery 10 includes a storage battery such as a lithium ion battery or a nickel metal hydride battery. The DC power output from the battery 10 is supplied to the power converter 20 and charges electrical energy generated by a device connected via the power converter 20, for example, the motor 30.

  The power converter 20 converts the DC power of the battery 10 into, for example, three-phase AC power and supplies it to the motor 30. As shown in FIG. 2 later, the power converter 20 includes an inverter including a plurality of switching elements and a controller 22, and controls the current supplied to the motor 30 by the controller 22 opening and closing the plurality of switching elements. I do.

  The motor 30 generates torque by the current supplied from the power converter 20, converts the torque into driving force, and powers the vehicle. The driving force of the motor 30 is transmitted to the wheels WL via the axle 40. Further, the motor 30 performs a regenerative operation by reversely converting the driving force into electric power. The electric power generated by the regenerative operation of the motor 30 is converted into DC power by the power converter 20 and charged to the battery 10.

  The cooling medium supply device 50 supplies the cooling medium to the power converter 20. As the medium, pure water, hydrogen, chlorofluorocarbons, ammonia, carbon dioxide and the like can be employed in addition to water and air added such as ethylene glycol. For example, when the cooling medium is a liquid, the cooling medium supply device 50 is a pump. For example, when the cooling medium is a gas, the cooling medium supply device 50 is a blower fan. The cooling medium supply device 50 is included in the cooling device together with a heat sink described later.

  A vehicle ECU (electric control unit) 60 cooperatively controls the operation of equipment mounted on the electric vehicle. For example, the vehicle ECU 60 receives a deterioration determination signal from the power converter 20 and turns on a warning lamp according to the value of the deterioration determination signal.

FIG. 2 is a diagram schematically showing a configuration example of the power converter 20.
The power converter 20 includes a controller 22, an input voltage detection unit 24, an inverter 26, and a load current detection unit 28.

  The input voltage detection unit 24 detects the voltage of the power supply in the connection line between the power supply and the inverter 26 and outputs the detected voltage to the controller 22 as input voltage information. In addition, although the battery 10 is employ | adopted as a power supply in an electric vehicle, an alternating current power supply is also applicable as a power supply. When there is no need to monitor the voltage of the power supply, such as when the voltage of the power supply is constant, the input voltage detection unit 24 can be omitted.

  The inverter 26 includes a plurality of semiconductor switches that switch electrical connection between a power source and a load. The inverter 26 includes, for example, three switching circuits connected in parallel. Each of the three switching circuits includes two semiconductor switches connected in series, for example, two IGBT (Insulated Gate Bipolar Transistor) elements. As a semiconductor switch other than the IGBT element, a transistor, a field effect transistor (FET), a thyristor, a gate turn-off thyristor (GTO), or the like can be employed.

  The load current detection unit 28 detects a current flowing from the power converter 20 to the load (or a current flowing from the load to the power converter 20), and outputs the detected current to the controller 22 as load current information. In addition, although the motor 30 is employ | adopted as a load in an electric vehicle, the resistive load etc. which generate | occur | produce a thermal energy are applicable as other loads.

  The controller 22 includes a current command setting unit 22A, a load current control unit 22B, a switch signal conversion unit 22C, and a deterioration diagnosis unit 22D.

  The current command setting unit 22A sets, for example, a load current command that causes the motor 30 to achieve a predetermined torque based on a torque command that is a power converter operation command, and outputs the load current command to the load current control unit 22B.

  The load current control unit 22B sets a voltage command to be applied to the load from the load current detected by the load current detection unit 28 and the load current command set by the current command setting unit 22A.

  The switch signal conversion unit 22C sets an open / close signal for the semiconductor switch 26 from the power supply voltage detected by the input voltage detection unit 24 and the voltage command set by the load current control unit 22B.

  The deterioration diagnosis unit 22D determines deterioration of the cooling performance based on the semiconductor switch temperature signal (information on the temperature of the semiconductor switch) and the cooling medium temperature signal (information on the temperature of the cooling medium), and a deterioration determination signal indicating the result Is output to the vehicle ECU 60 which is the host control device.

  When the deterioration diagnosis unit 22D performs the deterioration diagnosis, when the temperature of the cooling medium is forcibly changed, the deterioration diagnosis unit 22D starts or stops the cooling medium supply device 50. Alternatively, a stop signal may be output to the cooling medium supply device 50. When the temperature of the cooling medium is not forcibly changed, the cooling medium supply device start signal and the stop signal output from the deterioration diagnosis unit 22D are omitted.

  FIG. 3 is a diagram schematically showing an example of the configuration of the inverter and the cooler of the power converter.

  Below the inverter 26 of the power converter 20, a cooler 27 of a cooling device is disposed via an insulator 25.

  The insulator 25 is formed of, for example, a resin material or ceramic, and insulates the inverter 26 and the electrode from the cooler 27. The insulator 25 may be a part of a case that houses the power converter 20, for example. The insulator 25 is interposed between the inverter 26 and the cooler 27, and a high voltage is applied to the cooling medium and the casing of the cooler 27, causing leakage to the outside of the power converter 20, and human electric shock due to leakage. Is preventing.

  The inverter 26 receives the switch open / close signal, and electrically connects or opens between the two electrodes by the semiconductor switch to control the amount of electric energy output from the power converter 20. When the semiconductor switch of the inverter 26 is turned on, a current flows through the semiconductor switch and the semiconductor switch generates heat.

  It is known that the inverter 26 and the insulator 25 are thermally destroyed or have a reduced life due to a temperature rise caused by conduction and current flow. For this reason, a cooling device is attached to a power converter with severe environmental conditions and usage conditions to achieve high output and long life.

  The cooling device includes the above-described cooling medium supply device 50 and a cooler 27 provided with a cavity through which the cooling medium circulates. The cooling medium discharged from the cooling medium supply device 50 circulates in the cavity of the cooler 27, and the inverter 26 is cooled by the casing of the cooler 27 cooled by the cooling medium. The cooling medium discharged from the cooling medium supply device 50 circulates in the cavity of the cooler 27 and then returns to the cooling medium supply device 50 again. The cooler 27 may have a pipe line through which the cooling medium circulates as described above, or may be a heat sink.

  FIG. 4 is a block diagram for explaining an example of the configuration of the deterioration diagnosis unit of the control device for the power converter.

  The deterioration diagnosis unit 22D includes a cooling medium temperature input unit 221, a semiconductor switch temperature input unit 222, a cooling medium temperature change detection unit 223, a cooling device thermal resistance calculation unit 224, and a determination unit 225.

  The cooling medium temperature input unit 221 receives a temperature signal (temperature information) [V] of the cooling medium. The temperature of the cooling medium is measured by a temperature sensor (not shown) attached to the casing of the cooler 27 so as to come into contact with the cooling medium or attached to the casing near the cooling medium of the cooler 27. Detected. When the cooler 27 is a heat sink, the temperature sensor is attached to the heat sink. The cooling medium temperature input unit 221 converts the temperature signal [V] received from the temperature sensor into temperature information [° C.] and outputs the temperature information to the cooling medium temperature change detection unit 223 and the cooling device thermal resistance calculation unit 224.

  The semiconductor switch temperature input unit 222 receives a semiconductor switch temperature signal (temperature information) [V]. The temperature of the semiconductor switch is detected by a temperature sensor (not shown) attached to at least one semiconductor switch. The semiconductor switch temperature input unit 222 converts the temperature signal [V] received from the temperature sensor into temperature information [° C.] and outputs it to the cooling device thermal resistance calculation unit 224. When temperature sensors are attached to a plurality of semiconductor switches, the semiconductor switch temperature input unit 222 may receive a plurality of temperature signals [V].

  The cooling medium temperature change detection unit 223 calculates the temperature of the cooling medium that has changed during a predetermined period from the received cooling medium temperature information [° C.] and outputs the calculated temperature to the determination unit 225.

  The cooling device thermal resistance calculation unit 224 includes the temperature information [° C.] of the cooling medium, the temperature information [° C.] of the semiconductor switch, the thermal resistance of heat conduction of the cooling device, the heat transfer between the cooling device and the semiconductor switch, and the semiconductor. The thermal resistance of the cooling device is calculated using the thermal resistance of the heat conduction of the switch and the thermal resistance of the heat transfer to the outside of the power converter 20.

  FIG. 5 is a diagram showing an example of a simple thermal circuit ignoring the heat capacity of each component from the cooling medium to the semiconductor switch.

  Here, the temperature of the cooling medium is used as a heat source, and the heat source is the heat resistance R1 [° C / W] of the heat conduction of the cooling device, the heat transfer between the cooling device and the semiconductor switch, and the semiconductor switch heat resistance R2 [° C / W]. ], It is transmitted to the outside of the semiconductor switch.

  The heat transfer to the outside of the semiconductor switch is the heat transfer from the semiconductor switch to the ambient air or the heat transfer to the electric wire of the power converter through the electrode of the semiconductor switch, and its thermal resistance R3 [° C./W] is The value is larger than the thermal resistance R1 [° C./W] and the thermal resistance R2 [° C./W] related to the cooling device. Each component has a heat capacity, but can be ignored on the condition that a sufficient time has passed for the temperature of the cooling medium to be transferred to the semiconductor switch.

Based on the circuit shown in FIG. 5, the temperature change V2 of the semiconductor switch can be expressed by the following (formula 1).
V2 = (R3 / (R1 + R2 + R3)) * V (Formula 1)
Here, V is a temperature change of the cooling medium.

From (Equation 1), when the insulator 25 between the cooling device and the semiconductor switch deteriorates and the thermal resistance value R2 increases, the temperature change V2 of the semiconductor switch decreases. Therefore, the thermal resistance (R1 + R2) [° C./W] indicating the deterioration of the cooling device and the semiconductor switch can be obtained from the ratio between the cooling medium temperature change V and the temperature change V2 of the semiconductor switch as shown in (Expression 2).
(R1 + R2) = R3 ((V / V2) -1) (Formula 2)
In (Equation 2), the heat resistance R3 [° C./W] for heat transfer to the outside of the semiconductor switch needs to be known, but the structure and ambient conditions of the semiconductor switch are the inverter 26 and the power mounted on the semiconductor switch. Since it can be grasped in advance from the structure of the converter 20, the value of the thermal resistance R <b> 3 [° C./W] can be stored in the cooling device thermal resistance calculation unit 224 in advance.

  In addition, according to the above (Formula 2), the thermal resistance (R1 + R2) [° C./W] cannot be obtained when the temperature of the cooling medium changes. When the temperature change V2 is minimal, it is determined from Equation (2) that (R1 + R2) is a large value and the thermal resistance has increased, that is, has deteriorated. When the temperature change V2 is 0, the denominator of the equation (2) is 0, and (R1 + R2) is an infinite value, and it is determined that the thermal resistance has increased, that is, has deteriorated. Therefore, the thermal resistance (R1 + R2) [° C./W] can be obtained when the temperature of the cooling medium changes or when both the temperature of the cooling medium and the temperature of the semiconductor switch change.

  FIG. 6 is a flowchart for explaining an example of the deterioration determination operation in the determination unit of the deterioration diagnosis unit.

  The determination unit 225 receives the temperature of the cooling medium that has changed over a predetermined period from the cooling medium temperature change detection unit 223, and receives the thermal resistance (R1 + R2) [° C./W] from the cooling device thermal resistance calculation unit 224 (step STA1). ).

  Subsequently, the determination unit 225 determines whether or not the temperature of the changed cooling medium is equal to or higher than a threshold value. If the determination unit 225 determines that the temperature change V of the cooling medium is less than the threshold value, the determination unit 225 ends the process without determining whether or not the cooling performance has deteriorated (step STA2).

  The determination unit 225 determines whether or not the cooling performance has deteriorated only when the temperature change V of the cooling medium is equal to or greater than the threshold value. When the heat capacity of the cooling medium is larger than the heat capacity of the semiconductor switch, the amount of change in the cooling medium temperature due to the temperature change of the semiconductor switch is small. Therefore, the calculation of the thermal resistance (R1 + R2) [° C / W] based on the amount of change in the temperature of the semiconductor switch when the temperature of the cooling medium changes is not affected by signal noise and the like. The thermal resistance (R1 + R2) [° C./W] can be calculated. For this reason, the determination unit 225 determines that the cooling performance is lowered when the temperature change V of the cooling medium received from the cooling medium temperature change detection unit 223 is equal to or greater than a threshold value.

  When the determination unit 225 determines that the temperature change V of the cooling medium is equal to or greater than the threshold value, the value of the thermal resistance (R1 + R2) [° C./W] received from the cooling device thermal resistance calculation unit 224 is equal to or greater than the threshold value. (Step STA3).

  When the value of the thermal resistance (R1 + R2) [° C./W] is equal to or greater than the threshold value, the determination unit 225 determines that the cooling performance of the cooling device has deteriorated (step STA4).

  When the value of the thermal resistance (R1 + R2) [° C./W] is less than the threshold value, the determination unit 225 determines that the cooling performance of the cooling device has not deteriorated (step STA5).

  Note that the threshold value of the thermal resistance value (R1 + R2) [° C./W] is larger than the thermal resistance value when the cooling performance is not lowered, and the cooling performance is lowered and the power converter is It is necessary to make the value smaller than the thermal resistance value (R1 + R2) [° C./W] when stopping.

  After step STA4 and step STA5, determination unit 225 outputs a deterioration determination signal indicating the cooling performance deterioration determination result to vehicle ECU 60 (step STA6). If it is determined in step STA5 that there is no deterioration, the output of the deterioration determination signal to the vehicle ECU 60 may be omitted.

  Further, as described above, when there is no change (or a small change) in the cooling medium temperature, the deterioration determination of the cooling performance cannot be performed, and thus the deterioration diagnosis unit 22D outputs a deterioration determination signal under the conditions. It is desirable not to stop the power converter 20 accidentally.

  Since the thermal resistance (R1 + R2) [° C./W] is a value that increases when the temperature change V2 of the semiconductor switch 26 is small, whether or not the temperature change V2 of the semiconductor switch 26 is smaller than a predetermined value in step STA3. It may be judged. In this case, the determination unit 225 determines that the cooling performance has deteriorated when the temperature change V2 of the semiconductor switch 26 is smaller than a predetermined value, and the temperature change V2 of the semiconductor switch 26 is greater than or equal to the predetermined value. At some point, it is determined that the cooling performance has not deteriorated.

  As described above, according to the present embodiment, it is possible to determine the deterioration of the cooling performance of the semiconductor switch 26 without operating the semiconductor switch 26, and the electric power vehicle 20 that ensures safety and the electric vehicle Can be provided.

  The power converter includes a power converter that converts DC electric energy to AC electric energy, and DC electric energy to DC electric energy, AC electric energy to DC electric energy, and AC electric energy to AC electric energy. It can be applied to converters.

  Next, the power converter and electric vehicle of 2nd Embodiment are demonstrated with reference to drawings. In the following description, the same components as those in the first embodiment described above are denoted by the same reference numerals and description thereof is omitted.

  The power converter and the electric vehicle of the present embodiment are different from those of the first embodiment described above in the operation of the semiconductor switch and the determination of the cooling performance of the cooling device.

  FIG. 7 is a block diagram for explaining an example of the configuration of the deterioration diagnosis unit. In the description of the block diagram shown in FIG. 7, the same components as those in the block diagram shown in FIG. 4 are denoted by the same reference numerals, and the description of the same components and operations is omitted.

  In the present embodiment, the deterioration diagnosis unit 22D does not include the cooling device thermal resistance calculation unit of the first embodiment but includes a time measurement threshold value setting unit 226, a cooling medium temperature change detection unit 223, and a determination unit 225. The operation is different.

  The cooling medium temperature change detection unit 223 receives the cooling medium temperature information [° C.] from the cooling medium temperature input unit 221, and when the cooling medium temperature [° C.] becomes larger than the threshold value, the measurement start command Is output to the time measurement threshold value setting unit 226.

  When the time measurement threshold value setting unit 226 receives a measurement start command, the time measurement threshold value setting unit 226 starts time measurement and sets an arrival temperature threshold value and an arrival time threshold value. The time measurement threshold value setting unit 226 determines a time (measurement time) required from the time when the temperature of the cooling medium exceeds the threshold value to the arrival temperature threshold value, and the arrival time threshold value determination unit. To 225.

Here, an example of the relationship between the temperature change of the cooling medium and the time required for the temperature change will be described.
FIG. 8 is a diagram illustrating an example of a simple thermal circuit from the cooling medium to the semiconductor switch using the temperature change of the cooling medium as a heat source.

  In the present embodiment, in order to examine the temperature change in a relatively short time, the heat resistance R3 of the heat transfer to the outside of the semiconductor switch in the first embodiment is ignored, and the heat capacity C1 of the cooling device and the heat capacity C2 of the semiconductor switch. And is considered.

  The heat flow I is transmitted to the cooling device by the temperature change V of the cooling medium. The heat flow rate I is the heat conduction resistance R1 of the cooling device composed of the cooling medium, the cooler 27 and the insulator 25, the heat capacity C1 of the cooling device, the heat resistance between the cooling device and the semiconductor switch, and the heat conduction of the semiconductor switch. The heat is transferred to the semiconductor switch by the combined thermal resistance R2 and the heat capacity C2 of the semiconductor switch.

In FIG. 7, the transfer function from the temperature change V of the cooling medium to the temperature change V2 of the semiconductor switch is a second-order lag system that combines the first-order lag time constant T1 = (R1C1) and the first-order lag time constant T2 = (R2C2). Yes, it can be expressed by (Formula 3). Note that the symbol s in (Expression 3) is a Laplace operator.
V2 = {1 / (1 + sT1)} × {1 / (1 + sT2)} × V (Formula 3)
When the performance degradation of the insulator occurs due to thermal degradation or aging degradation, the heat transfer resistance R2 between the cooling device of FIG. 7 and the semiconductor switch increases.

FIG. 9 is a diagram for explaining an example of the relationship between the temperature change of the cooling medium and the temperature change of the semiconductor switch.
Here, an example of a temperature change of the semiconductor switch when a cooling medium supply device such as a water circulation pump or a blower fan is started and the cooling medium temperature is forcibly changed suddenly is shown. When the temperature of the cooling medium changes gradually, it is desirable to consider the arrival time threshold for the temperature change of the cooling medium described below.

  This means that when the cooling device deteriorates, the time constants T1 and T2 of the second-order lag system increase. When the time constants T1 and T2 are increased, the transmission of temperature from the cooling medium to the semiconductor switch is delayed. The thermal resistance of the cooling device can be obtained from the above-described changes in the cooling medium temperature and the semiconductor switch temperature.

  Graph 8A shows the case where the first-order lag time constant T1 = 0.8 seconds, the first-order lag time constant T2 = 0.08 seconds, and the cooling medium temperature change V = 100 ° C. are applied to the above (Equation 3). The semiconductor switch temperature change V2 is shown. That is, the graph 8A shows the temperature change of the semiconductor switch 26 when the temperature of the cooling medium changes from 0 ° C. to 100 ° C. when the cooling performance is not deteriorated.

  Since (Equation 3) is a second-order lag system, the time for the semiconductor switch temperature to reach 63.2% with respect to 100 ° C. is the first-order lag time constant T1 = 0.8 seconds and the first-order lag time constant. The total time of T2 = 0.08 seconds is longer than 0.88 seconds and takes 1.21 seconds.

  Graph 8B shows the semiconductor switch temperature when the above-described (Equation 3) primary delay time constant T1 = 0.8 seconds, primary delay time constant T2 = 0.16 seconds, and temperature change V = 100 ° C. is applied. It shows a change. This graph 8B shows the case where the first-order lag time constant T2 is 0.16 seconds, which is twice that of the graph 8A, due to the decrease in cooling performance. Shows the temperature change of the semiconductor switch when the temperature changes from 0 ° C. to 100 ° C. FIG.

  At this time, it takes 1.44 seconds for the temperature change of the semiconductor switch 26 to reach 63.2% with respect to 100 ° C., and the increase in the temperature of the semiconductor switch increases by 0.23 seconds due to the decrease in cooling performance. .

  As described above, when the temperature of the cooling medium changes, the time until the temperature of the semiconductor switch reaches the set temperature threshold is measured, and the measurement time is regarded as the thermal resistance in the first embodiment. It is also possible to perform a switch and cooling performance degradation determination.

  The reached temperature threshold value is a value between the temperature before the change of the cooling medium and the temperature after the change of the cooling medium. The closer this reached temperature threshold is to the temperature after the change of the cooling medium, the greater the difference in the arrival time of the semiconductor switch temperature between when there is no deterioration and when there is deterioration, and the deterioration determination accuracy can be improved.

  As described above, it is desirable that the time required for the semiconductor switch to reach the reached temperature threshold value is at least larger than the total value of the first-order lag time constant T1 and the first-order lag time constant T2.

  FIG. 10 is a flowchart for explaining an example of the deterioration determination operation in the cooling medium temperature change detection unit, the time measurement threshold value setting unit, and the determination unit.

  The cooling medium temperature change detection unit 223 receives the temperature information [° C.] of the cooling medium from the cooling medium temperature input unit 221 (step STB1).

  The cooling medium temperature change detection unit 223 determines whether or not the temperature change V of the cooling medium that has changed during a predetermined period is greater than a threshold value (step STB2). Here, it is desirable that the cooling medium temperature change threshold value is a value that is not affected by the noise component included in the temperature signal.

  When the temperature change V of the cooling medium is equal to or less than the threshold value, the cooling medium temperature change detection unit 223 returns to step STB1 again to perform processing. When the temperature change V of the cooling medium is larger than the threshold value, the cooling medium temperature change detection unit 223 transmits a measurement start command to the time measurement threshold value setting unit 226.

  When the time measurement threshold value setting unit 226 receives a measurement start command, the time measurement threshold value setting unit 226 starts time measurement, and sets an arrival temperature threshold value and an arrival time threshold value. The reached temperature threshold is a value between before and after the temperature change of the cooling medium, for example, a value of 63.2% of the change V in the cooling medium temperature. The arrival time threshold is larger than the total value of the time constant T1 and the time constant T2 when the cooling performance is not deteriorated, and the time constant T2 such that the cooling performance is deteriorated and the output performance of the power converter is deteriorated. And a value smaller than the total value of the time constant T1. In addition, the arrival time threshold reaches the semiconductor switch temperature threshold set above in the thermal circuit at the time of thermal resistance in which the cooling performance of the semiconductor switch 26 deteriorates and the power converter 20 stops. A value smaller than the time is set as the threshold value for deterioration determination. (Step STB3).

  The time measurement threshold setting unit 226 receives the semiconductor switch temperature information [° C.] from the semiconductor switch temperature input unit 222 (step STB4).

  The time measurement threshold value setting unit 226 determines whether or not the temperature information [° C.] of the semiconductor switch has reached the reached temperature threshold value (step STB5). When the temperature information [° C.] of the semiconductor switch does not reach the reached temperature threshold value, the process returns to step STB4 and receives the temperature information of the semiconductor switch.

  When the temperature information [° C.] of the semiconductor switch reaches the reaching temperature threshold, the time measurement threshold setting unit 226 measures the time when the temperature information [° C.] of the semiconductor switch reaches the reaching temperature threshold. Is recorded (step STB6), and the measurement time and arrival time threshold value are output to the determination unit 225.

  The determination unit 225 determines whether or not the measurement time exceeds the arrival time threshold value (step STB7). When determining that the measurement time exceeds the arrival time threshold value, the determination unit 225 determines that there is a decrease in cooling performance (step STB8) and determines that the measurement time is equal to or less than the arrival time threshold value. In this case, it is determined that there is no decrease in cooling performance (step STB9).

  After step STB8 and step STB9, determination unit 225 outputs a deterioration determination signal for notifying the determination result to vehicle ECU 60 (step STB10). When it is determined in step STB9 that there is no deterioration, the output of the deterioration determination signal to the vehicle ECU 60 may be omitted.

  As described above, according to the present embodiment, it is possible to determine a decrease in cooling performance without operating a semiconductor switch, and it is possible to provide a power converter that ensures safety and an electric vehicle. .

  Next, the power converter and electric vehicle of 3rd Embodiment are demonstrated with reference to drawings.

  In the present embodiment, before the deterioration diagnosis is performed, the switch open / close signal is set so that a current is applied to the semiconductor switch. Due to the current flowing through the semiconductor switch, the semiconductor switch temperature becomes higher than the cooling medium temperature at the start of the deterioration diagnosis.

FIG. 11 is a diagram for explaining an example of the relationship between the temperature change of the cooling medium and the temperature change of the semiconductor switch.
Here, the time change of the semiconductor switch temperature when the current of the semiconductor switch is set to 0 A after flowing the current through the semiconductor switch of the inverter 26 to increase the temperature to 100 ° C. is shown. In this graph, when the cooling performance is not lowered, the first-order lag time constant T1 = 0.8 seconds and T2 = 0.08 seconds. When the cooling performance is degraded, the first-order lag time constant T1 = 0.8 seconds and T2 = 0.16 seconds.

  The semiconductor switch temperature after stopping the open / close signal of the semiconductor switch becomes a response characteristic of a second-order lag system by the thermal circuit shown in FIG. 8, and approaches the cooling medium temperature. In this example, the cooling medium temperature does not change, and the temperature of the semiconductor switch changes from a value increased by the flow of current to the cooling medium temperature. This can be handled in the same manner as the temperature change behavior of the semiconductor switch when the coolant temperature changes in the first embodiment described above, and by the same method as in the first embodiment and the second embodiment, Deterioration diagnosis can be performed.

  FIG. 11 shows an example of the result of measuring the reaching time by setting the reaching temperature threshold value of the semiconductor switch temperature as in the second embodiment. When the cooling performance is degraded, the arrival time of the semiconductor switch to the arrival temperature threshold is 0.11 seconds. When the cooling performance is degraded, the arrival time changes to 0.19 seconds.

  As described above, a difference of 0.08 seconds occurs until the temperature of the semiconductor switch reaches a predetermined temperature depending on the presence or absence of the cooling performance. Therefore, this time is measured and compared with a predetermined threshold value. It is possible to determine whether the cooling performance is reduced.

  The cooling medium temperature change detection unit 223 receives the temperature information [° C.] of the cooling medium from the cooling medium temperature input unit 221. The cooling medium temperature change detection unit 223 receives the semiconductor switch temperature information [° C.] from the semiconductor switch temperature input unit 222.

  The coolant temperature change detection unit 223 determines whether or not the temperature of the semiconductor switch of the inverter 26 has increased to a predetermined value.

  When the temperature change of the semiconductor switch becomes a predetermined value or more, the coolant temperature change detection unit 223 transmits a measurement start command to the time measurement threshold value setting unit 226.

  When the time measurement threshold value setting unit 226 receives a measurement start command, the time measurement threshold value setting unit 226 starts time measurement, and sets an arrival temperature threshold value and an arrival time threshold value. The reached temperature threshold is a value between before and after the temperature change of the semiconductor switch, for example, a value of 36.8% of the change V of the semiconductor switch temperature. The arrival time threshold value is larger than the total value of the time constant when the cooling performance is not deteriorated and smaller than the total value of the time constant such that the cooling performance is reduced and the output performance of the power converter is reduced. Set.

  The time measurement threshold setting unit 226 receives the semiconductor switch temperature information [° C.] from the semiconductor switch temperature input unit 222.

  The time measurement threshold value setting unit 226 determines whether or not the temperature information [° C.] of the semiconductor switch has reached the ultimate temperature threshold value. When the temperature information [° C.] of the semiconductor switch does not reach the temperature threshold value, the temperature information of the semiconductor switch is received again.

  When the temperature information [° C.] of the semiconductor switch reaches the reaching temperature threshold, the time measurement threshold setting unit 226 measures the time when the temperature information [° C.] of the semiconductor switch reaches the reaching temperature threshold. And the measurement time and the arrival time threshold value are output to the determination unit 225.

  The determination unit 225 determines whether or not the measurement time exceeds the arrival time threshold value. If the determination unit 225 determines that the measurement time exceeds the arrival time threshold value, the determination unit 225 determines that there is a decrease in cooling performance, and determines that the measurement time is equal to or less than the arrival time threshold value. It is determined that there is no decrease in

  Subsequently, the determination unit 225 outputs a deterioration determination signal that notifies the determination result to the vehicle ECU 60. When it is determined that there is no deterioration, the output of the deterioration determination signal to the vehicle ECU 60 may be omitted.

  In the present embodiment, the current flowing through the semiconductor switch before the start of the deterioration determination may be a current applied to the load or a current that short-circuits the power supply.

  As described above, even if the deterioration of the cooling performance is diagnosed by changing the temperature of the semiconductor switch of the inverter 26, the same effects as those of the first and second embodiments can be obtained.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  When the semiconductor switch temperature change V3 is caused by a heat source other than the temperature change of the cooling medium after the deterioration diagnosis is started, the reached temperature threshold value is the ambient temperature of the semiconductor switch or the heat transferred to other parts. It is desirable to determine in consideration of the influence of the thermal circuit omitted on the thermal circuit shown in FIG. When there is a factor that increases the temperature of the semiconductor switch other than the cooling medium temperature, such as when a current flows through the semiconductor switch and generates heat, the above reached temperature threshold is set to the temperature before and after the change of the cooling medium. It may be set to a value that is not between.

  FIG. 12 is a diagram illustrating an example of a simple thermal circuit from the cooling medium to the semiconductor switch when there is a heat source other than the temperature change of the cooling medium. When a heat source other than a temperature change should be taken into consideration for the power converter, the thermal circuit shown in FIG. 12 is adopted to determine the deterioration of the cooling performance as in the first to third embodiments described above. be able to. At this time, when the semiconductor switch heat capacity C2 is sufficiently smaller than the cooling device heat capacity C1, it is possible to treat that the cooling device temperature change V1 and the cooling medium temperature change V are hardly increased.

  Moreover, although the above-mentioned embodiment demonstrated the example which mounted the power converter in the electric vehicle, even if it mounts the above-mentioned power converter in another apparatus, the same effect can be acquired. For example, it is difficult for a power converter used for a device that operates continuously to periodically perform life diagnosis and maintenance by stopping the device and removing the power converter. On the other hand, when the power converter is stopped due to a semiconductor switch of the power converter and a decrease in cooling performance during continuous operation of the device, the entire device that is continuously operated stops abnormally, resulting in great damage. For example, when the continuously operating device is a semiconductor manufacturing apparatus or a nuclear power plant device, the entire plant is stopped, and a lot of manpower and time are required for recovery. In addition, for example, when a continuously operating device is a transportation device such as an automobile or a train, a mobile device such as an elevator, or a medical device used in a hospital or the like, the continuously operating device may be related to the life of the user. is there.

  For this reason, it is necessary to prevent the power converter from stopping abnormally in equipment that performs continuous operation. In the power converter of the above-described embodiment, the performance deterioration determination of the cooling performance is performed and a warning signal is output. Thus, it is possible to prevent the power converter from unexpectedly stopping abnormally.

  Moreover, the power converter of the above-mentioned embodiment can also be applied to a train.

  FIG. 13 is a block diagram schematically illustrating another configuration example of the electric vehicle according to the embodiment. In this example, the difference from the electric vehicle of the above-described embodiment is that there is no battery 10 in the electric vehicle and that the power converter 20 is a converter.

  The train is supplied with voltage from an external power source via an overhead line or the like. The voltage of the external power supply may be alternating current or direct current.

  The converter is supplied with a voltage from an external power source and passes a current to the motor so that the train motor generates a desired torque. When the external power supply is an AC power supply, the converter may convert the AC voltage into a DC voltage and then convert it into an AC voltage applied to the motor. For example, like a matrix converter, the converter directly converts the AC voltage to the motor. An alternating voltage to be applied may be generated.

  Even when the power converter of the above-described embodiment is mounted on a train, the same effects as those of the above-described embodiment can be obtained.

  WL ... wheel, V2 ... temperature change of semiconductor switch, V ... temperature change of cooling medium, 10 ... power supply (battery) 20 ... power converter, 22 ... controller, 22A ... current command setting unit, 22B ... load current control unit, 22C: Switch signal conversion unit, 22D: Degradation diagnosis unit, 24: Input voltage detection unit, 25 ... Insulator, 26 ... Inverter (or converter), 27 ... Cooler, 28 ... Load current detection unit, 30 ... Load (motor) ), 40... Axle, 50... Cooling medium supply device, 60... Higher control device (vehicle ECU), 221... Cooling medium temperature input unit, 222. Cooling device thermal resistance calculation unit, 225... Determination unit, 226.

Claims (6)

An inverter connected in parallel with a switch circuit comprising a pair of semiconductor switches connected in series;
A cooler having a cavity in which a cooling medium circulates;
An insulator disposed between the inverter and the cooler;
A temperature input unit for inputting information on the temperature of the semiconductor switch and information on the temperature of the cooling medium, and information on the temperature of the semiconductor switch and information on the temperature of the cooling medium input to the temperature input unit; And calculating whether the temperature change of the cooling medium is equal to or greater than a predetermined value, the temperature change of the cooling medium is equal to or greater than a predetermined value, and the thermal resistance is equal to or greater than a predetermined value. And a controller including a deterioration diagnosis unit that determines that the cooling performance is deteriorated when the power converter is the power converter. An inverter connected in parallel with a switch circuit comprising a pair of semiconductor switches connected in series;
A cooler having a cavity in which a cooling medium circulates;
An insulator disposed between the inverter and the cooler;
Whether the temperature change of the cooling medium is greater than or equal to a predetermined value from the value input to the temperature input unit, the temperature input unit to which the temperature information of the semiconductor switch and the temperature information of the cooling medium are input When the temperature change of the cooling medium is equal to or higher than a predetermined value, the time until the semiconductor switch temperature reaches a predetermined value is measured, and the cooling is performed when the measured time exceeds the predetermined value. A power converter comprising: a deterioration diagnosis unit that determines that the performance has deteriorated. A cooling medium supply device for delivering the cooling medium to a cavity in the cooler;
3. The power converter according to claim 1, wherein the deterioration diagnosis unit outputs a start signal or a stop signal to the cooling medium supply device prior to determination of deterioration of cooling performance. An inverter connected in parallel with a switch circuit comprising a pair of semiconductor switches connected in series;
A cooler having a cavity in which a cooling medium circulates;
An insulator disposed between the inverter and the cooler;
It has a temperature input unit for inputting information on the temperature of the semiconductor switch and information on the temperature of the cooling medium, and switches the semiconductor switch prior to the determination of the deterioration of cooling performance to flow current to the semiconductor switch, Information on the temperature of the semiconductor switch is received, and it is determined whether the temperature change of the semiconductor switch is greater than or equal to a predetermined value from the value input to the temperature input unit, and the temperature change of the semiconductor switch is greater than or equal to a predetermined value A deterioration diagnosis unit that measures a time until the temperature of the semiconductor switch reaches a predetermined value and determines that the cooling performance has deteriorated when the measured time exceeds a predetermined value. And a power converter characterized by comprising:   The power converter according to any one of claims 1 to 4, wherein the deterioration diagnosis unit outputs a signal indicating a determination result to the host controller when it is determined that the cooling performance has deteriorated. Power supply,
A power converter according to any one of claims 1 to 5,
An AC electric motor that operates with electric power supplied from the power converter;
An axle driven by the power of the AC motor,
The AC motor is connected to a series connection point of a pair of semiconductor switches connected in series.

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