JP7119932B2 - Power converter for electric vehicles - Google Patents

Description

The technology disclosed in this specification relates to a power converter for an electric vehicle.

An electric vehicle is equipped with a power conversion device that converts electric power from an on-board power source into electric power for driving a motor for running. Since the electric power for driving the driving motor is as large as several tens of kilowatts, the amount of heat generated by the switching elements for power conversion, which are the main components of the power converter, is large. Therefore, the power conversion device also includes a cooler that cools the switching elements for power conversion. In order to keep the coolant temperature of the cooler within an appropriate temperature range, the cooler is equipped with a temperature sensor that measures the coolant temperature. It should be noted that the electric vehicle in this specification only needs to have a motor for running, and includes a hybrid vehicle that has a motor and an engine. In addition, a fuel cell vehicle equipped with a fuel cell and a battery is also included in the electric vehicle in this specification.

Patent Literature 1 discloses a technique for detecting an abnormality in a temperature sensor of a cooler of a power converter. The technique of Patent Document 1 calculates the estimated temperature of the coolant from the measured value of the temperature sensor that measures the temperature of the switching element. When the absolute value of the difference between the measured temperature measured by the temperature sensor of the cooler and the estimated temperature exceeds a predetermined value, the water pump is driven in Hi drive mode. When the absolute value of the difference between the measured temperature and the estimated temperature exceeds a predetermined value even when the water pump is Hi-driven, it is determined that the temperature sensor of the cooler is abnormal.

Japanese Patent Application Laid-Open No. 2014-193001

With the technique of Patent Document 1, it is not possible to determine which of the temperature sensor of the cooler and the temperature sensor that measures the temperature of the switching element has an abnormality. This specification provides a technique for identifying a temperature sensor in which an abnormality has occurred.

A power converter disclosed in this specification includes an inverter, a charger, a cooler, first to third temperature sensors, and a controller. The inverter includes a first switching element for power conversion, and converts the DC power of the vehicle-mounted power source into the driving power (AC power) of the motor for running. The charger includes a second switching element for power conversion, and converts the power of the external power source into charging power of the onboard power source. A cooler cools the first switching element and the second switching element. A first temperature sensor measures the temperature of the first switching element. A second temperature sensor measures the temperature of the second switching element. A third temperature sensor measures the temperature of the coolant in the cooler.

The controller calculates a first estimated temperature of the refrigerant from the measured value of the first temperature sensor and calculates a second estimated temperature of the refrigerant from the measured value of the second temperature sensor. The controller compares the measured temperature measured by the third temperature sensor with the first estimated temperature and the second estimated temperature. When the absolute value of the temperature difference between any one temperature and each of the other two temperatures exceeds a predetermined allowable temperature difference, the controller determines that the temperature sensor corresponding to the one temperature is abnormal. Outputs a signal indicating that

In the power conversion device disclosed in this specification, by comparing the three temperatures (the first and second estimated temperatures and the measured temperature), it is possible to identify the temperature sensor in which an abnormality has occurred. Details and further improvements of the technique disclosed in this specification are described in the following "Mode for Carrying Out the Invention".

1 is a block diagram of an electric vehicle including a power conversion device of an embodiment; FIG. 8 is a flowchart of temperature sensor monitoring processing;

A power converter according to an embodiment will be described with reference to the drawings. A power conversion device 10 of the embodiment is mounted on an electric vehicle 100 . FIG. 1 shows a block diagram of an electric vehicle 100 including a power converter 10. As shown in FIG. The power converter 10 is a device that converts the DC power of the battery 2 into drive power (AC power) for the motor 3 for running. The power conversion device 10 also includes a charger that charges the battery 2 using power from a power source external to the vehicle.

The power converter 10 includes a voltage converter 60 , an inverter 20 , a charger 30 , a cooler 40 and a controller 50 . Voltage converter 60 has a step-up function of stepping up the voltage of battery 2 and supplying it to inverter 20 , and stepping down regenerative power sent from inverter 20 (power generated by motor 3 due to inertial energy of the vehicle) and supplying it to battery 2 . It has a voltage step-down function. Voltage converter 60 is a bi-directional DC-DC converter. A detailed description of the circuit configuration of the voltage converter 60 is omitted.

Inverter 20 is a device that converts DC power boosted by a voltage converter into AC power. The inverter 20 can also convert AC regenerated power generated by the motor 3 into DC power.

The inverter 20 has a circuit configuration in which three series-connected sets of an upper arm switching element 21a and a lower arm switching element 21b are connected in parallel. An upper diode 22a is connected in antiparallel to the upper arm switching element 21a. A lower diode 22b is connected in antiparallel to the lower arm switching element 21b. Alternating current is output from the midpoint of each of the three sets of series connections. Hereinafter, the upper arm switching element 21a and the lower arm switching element 21b may be collectively referred to as switching elements 21a and 21b.

The switching elements 21 a and 21 b are controlled by a controller 50 . The inverter 20 also includes a first temperature sensor 23 that measures the temperatures of the switching elements 21a and 21b. The controller 50 controls the switching elements 21a and 21b so that the temperature measured by the first temperature sensor 23 (that is, the temperature of the switching elements 21a and 21b) does not exceed a predetermined first threshold temperature.

Charger 30 is connected to battery 2 and to connector 12 . Although not shown, the connector 12 is provided on the body of the vehicle. The connector 12 is normally hidden from the outside by a cover. Charger 30 converts the power of an AC power source external to the vehicle connected to connector 12 into DC power, boosts it to the voltage of battery 2 , and supplies the DC power to battery 2 . The charger 30 has a boost converter 31 and a rectifier 39 . The rectifier 39 converts AC power supplied from outside the vehicle via the connector 12 into DC power. A specific circuit configuration of the rectifier 39 is omitted from the drawing.

The boost converter 31 includes a boost switching element 32 , diodes 33 and 34 , a reactor 35 , a filter capacitor 36 and a second temperature sensor 37 . The boost switching element 32 is connected between the positive line and the negative line 31c. A diode 33 is connected in anti-parallel to the boost switching element 32 . The reactor 35 is connected between the positive electrode (collector) of the boost switching element 32 and the positive terminal 31b on the rectifier 39 side. A filter capacitor 36 is connected between the positive terminal 31b and the negative terminal 31c. Diode 34 is connected between the middle point of reactor 35 and boost switching element 32 and positive terminal 31 a of boost converter 31 on the battery 2 side. When the boost switching element 32 is turned on, the midpoint between the switching element 32 and the reactor 35 becomes the negative potential, current flows through the reactor 35 , and electrical energy is stored in the reactor 35 and the filter capacitor 36 . When the boost switching element 32 is turned off, the induced electromotive force of the reactor 35 pushes up the potential of the positive terminal 31a. As a result, the potential of the positive terminal 31a on the battery 2 side becomes higher than the potential of the positive terminal 31b on the rectifier 39 side. That is, the DC voltage supplied from the rectifier 39 increases.

A second temperature sensor 37 measures the temperature of the boost switching element 32 . Boost switching element 32 is also controlled by controller 50 . The controller 50 controls the boost switching element 32 so that the measured value of the second temperature sensor 37 (that is, the temperature of the boost switching element 32) does not exceed a predetermined second threshold temperature.

The controller 50 is communicably connected to the upper controller 80 . The host controller 80 is a controller that controls the entire system of the vehicle. The host controller 80 determines the target output of the motor 3 from the vehicle speed and the accelerator opening, and issues a command to the controller 50 . Controller 50 controls voltage converter 60 and inverter 20 such that the received target output is achieved. Alternatively, when the host controller 80 detects that the plug of the external power source is connected to the connector 12 , it commands the controller 50 to start the charger 30 . On the other hand, when an abnormality is detected in the power conversion device 10, the controller 50 transmits a signal indicating the occurrence of abnormality to the host controller 80. FIG.

The cooler 40 has a circulation path 41 , a pump 43 and a third temperature sensor 44 . The circulation path 41 passes through the inverter 20 and the charger 30 and has both ends connected to the external radiator 70 . Although the circulation path 41 also passes through the voltage converter 60, its illustration is omitted. Below, description of the relationship between the voltage converter 60 and the cooler 40 is omitted.

A large amount of power can flow through the switching elements 21 a and 21 b and the boost switching element 32 . A cooler 40 is provided to keep the temperatures of the switching elements 21a and 21b and the temperature of the boost switching element 32 within appropriate temperature ranges.

Refrigerant in circuit 41 is pumped by pump 43 and passes through charger 30 and inverter 20 . The refrigerant cools the boost switching element 32 while passing through the charger 30 . The coolant cools the switching elements 21 a and 21 b while passing through the inverter 20 . Cooling that has absorbed heat from the switching elements is returned to the radiator 70 to lower its temperature. The coolant is water or antifreeze. A third temperature sensor 44 measures the temperature of the coolant flowing through the circulation path 41 . Pump 43 is also controlled by controller 50 . The controller 50 controls the pump 43 so that the measured value of the third temperature sensor 44 (that is, the temperature of the coolant) is kept within a predetermined temperature range.

If the third temperature sensor 44 becomes abnormal, the temperature of the refrigerant cannot be known, and the controller 50 cannot properly control the cooler 40 . If the cooler 40 cannot be properly controlled, there is a possibility that the temperatures of the switching elements 21a and 21b of the inverter 20 cannot be maintained within an appropriate range. In addition, even if the first temperature sensor 23 becomes abnormal, it becomes impossible to know the correct temperature of the switching elements 21a and 21b, and there is a possibility that the temperatures of the switching elements 21a and 21b cannot be maintained within an appropriate range. Similarly, when an abnormality occurs in the second temperature sensor 37, there is a possibility that the temperature of the boost switching element 32 cannot be maintained within an appropriate temperature range. Therefore, the controller 50 uses the measured values of the first to third temperature sensors 23, 37, and 44 to monitor whether any temperature sensor is abnormal.

The controller 50 estimates the temperature of the coolant in the cooler 40 from the measured values of the first temperature sensor 23 and the second temperature sensor 37, respectively. Below, the coolant temperature estimated from the measured value of the first temperature sensor 23 is called a first estimated temperature, and the coolant temperature estimated from the measured value of the second temperature sensor 37 is called a second estimated temperature. Also, the coolant temperature measured by the third temperature sensor 44 is referred to as the measured temperature.

The first temperature sensor 23 is arranged near the switching elements 21a, 21b, and the measured value of the first temperature sensor 23 originally indicates the temperature of the switching elements 21a, 21b. On the other hand, a circulation path 41 passes through the vicinity of the switching elements 21a and 21b, and a coolant flows through the inside thereof. If the temperature of the switching elements 21a and 21b rises, the refrigerant temperature also rises. That is, there is a correlation between the temperatures of the switching elements 21 a and 21 b (measured values of the first temperature sensor 23 ) and the refrigerant temperature based on the structural relationship between the switching elements 21 a and 21 b and the circulation path 41 . The correlation is obtained in advance by tests and simulations, and is incorporated in the controller 50 (software of the controller 50). The controller 50 uses the correlation to estimate the coolant temperature (first estimated temperature) from the measured value of the first temperature sensor 23 .

Similarly, there is another correlation between the temperature of the boost switching element 32 (the measured value of the second temperature sensor 37) and the coolant temperature, and this other correlation is also obtained in advance. Another correlation is also built into controller 50 (software of controller 50). The controller 50 estimates the coolant temperature (second estimated temperature) from the measured value of the second temperature sensor 37 using another correlation. The correlation is built into the controller 50 in the form of a mathematical formula or map that relates the temperature sensor measurements and the estimated temperature.

FIG. 2 shows a flowchart of temperature sensor monitoring processing executed by the controller 50 . The temperature sensor monitoring process will be described with reference to FIG. The processing in FIG. 2 is executed at regular intervals (for example, every second).

The controller 50 acquires the measured values of the first to third temperature sensors 23, 37, 44 (step S2). In FIG. 2, the measurement value (that is, the measured temperature) of the third temperature sensor 44 is represented by the symbol Ts.

Next, the controller 50 calculates the first estimated temperature Te1 from the measured value of the first temperature sensor 23 (step S3), and calculates the second estimated temperature Te2 from the measured value of the second temperature sensor 37 (step S4). The method of estimating the coolant temperature from the measured value of the temperature sensor is as described above.

Next, the controller 50 compares the absolute value of the temperature difference between the first estimated temperature Te1 and the measured temperature Ts with a predetermined allowable temperature difference Tth (step S5). If the absolute value of the temperature difference (Te1-Ts) does not exceed the allowable temperature difference Tth (step S5: YES), it can be determined that the first temperature sensor 23 and the third temperature sensor 44 are normal. In that case, the controller 50 compares the absolute value of the temperature difference between the second estimated temperature Te2 and the measured temperature Ts with a predetermined allowable temperature difference Tth (step S6). If the absolute value of the temperature difference (Te2-Ts) does not exceed the allowable temperature difference Tth in step S6 (step S6: YES), it can be determined that the second temperature sensor 37 is also normal. If the determination in step S6 is YES, it can be determined that all three temperature sensors 23, 37 and 44 are normal. In this case, the controller 50 ends the monitoring process as it is. In this case, the controller 50 controls the pump 43 of the cooler 40 using the measured value (measured temperature Ts) of the third temperature sensor 44 .

If the determination in step S5 is YES, it can be determined that both the first temperature sensor 23 and the third temperature sensor 44 are normal. At this time, when the determination in step S6 is NO (that is, when the absolute value of the temperature difference between the second estimated temperature Te2 and the measured temperature Ts exceeds the allowable temperature difference Tth), the measured value of the second temperature sensor 37 is It turns out to be abnormal. At this time, the controller 50 determines that an abnormality has occurred in the second temperature sensor 37 (step S7).

On the other hand, if the determination in step S5 is NO, it is determined that either the first temperature sensor 23 or the third temperature sensor 44 is abnormal. In this case, in step S8, the controller 50 compares the absolute value of the temperature difference between the second estimated temperature Te2 and the measured temperature Ts with a predetermined allowable temperature difference Tth. If the absolute value of the temperature difference (Te2-Ts) does not exceed the allowable temperature difference Tth in step S8 (step S8: YES), it can be determined that both the second temperature sensor 37 and the third temperature sensor 44 are normal. Ultimately, it is found that the first temperature sensor 23 is abnormal (steps S8: YES, S9). On the other hand, if the absolute value of the temperature difference (Te2-Ts) exceeds the allowable temperature difference Tth in step S8 (step S8: NO), it can be determined that an abnormality has occurred in the third temperature sensor 44 (step S8: NO, S10).

The controller 50 that has executed any of steps S7, S9, and S10 outputs a signal indicating an abnormality of the temperature sensor to the host controller 80 (step S12). The signal indicating the abnormality of the temperature sensor also includes the identifier of the temperature sensor determined to be abnormal. Therefore, the host controller 80 can know which temperature sensor has an abnormality.

Upon receiving the signal indicating the temperature sensor abnormality, the host controller 80 lights the warning light on the instrument panel and stores a message indicating the temperature sensor abnormality (including the identifier of the temperature sensor in which the abnormality has occurred) in the diagnostic memory. do. The diagnostic memory is a memory referenced by vehicle maintenance staff. Maintenance staff can know the state of the vehicle from the information stored in the diagnostic memory.

By the processing of FIG. 2, the controller 50 can identify the temperature sensor in which an abnormality has occurred. The processing from steps S5 to S12 in FIG. 2 can be expressed as follows. The controller 50 compares the measured temperature Ts with the first estimated temperature Te1 and the second estimated temperature Te2. As a result of the comparison, if the absolute value of the temperature difference between any one temperature and each of the other two temperatures exceeds a predetermined allowable temperature difference Tth, the controller 50 detects the temperature sensor corresponding to the one temperature. outputs a signal indicating that an abnormality has occurred. The temperature sensor corresponding to the first estimated temperature Te1 is the first temperature sensor 23, and the temperature sensor corresponding to the second estimated temperature Te2 is the second temperature sensor 37. A temperature sensor corresponding to the measured temperature Ts is the third temperature sensor 44 . Through the above processing, the controller 50 can identify the temperature sensor in which an abnormality has occurred.

If the third temperature sensor 44 is abnormal, the controller 50 continues to control the cooler 40 using the first estimated temperature Te1 or the second estimated temperature Te2. Therefore, even if any temperature sensor malfunctions, the vehicle can continue running for a while. It should be noted that if an abnormality occurs in any of the temperature sensors, the host controller 80 limits the performance of a part of the vehicle and continues running. For example, the host controller 80 sets the upper limit output of the motor 3 lower than normal to continue running.

Also, if the first temperature sensor 23 is abnormal, the controller 50 uses the measured values of the third temperature sensor 44 to estimate the temperatures of the switching elements 21a and 21b. The estimated temperature of the switching elements 21 a and 21 b can be calculated using the correlation used when calculating the first estimated temperature from the measured value of the first temperature sensor 23 . The controller 50 uses the estimated temperature to keep the temperature of the switching elements 21a, 21b within an appropriate temperature range.

Furthermore, if the second temperature sensor 37 is abnormal, the controller 50 estimates the temperature of the boost switching element 32 using the measured value of the third temperature sensor 44 . The estimated temperature of the boost switching element 32 can be calculated using the correlation used when calculating the second estimated temperature from the measured value of the second temperature sensor 37 . Controller 50 uses the estimated temperature to keep the temperature of boost switching element 32 within the proper temperature range.

Points to note regarding the technology disclosed in the present specification are described. The switching elements 21a and 21b of the inverter 20 are an example of a first switching element. The boost switching element 32 is an example of a second switching element. The circuit configurations of inverter 20 and charger 30 are not limited to the circuit configuration of FIG.

Although specific examples of the present invention have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above. The technical elements described in this specification or in the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims as of the filing. In addition, the techniques exemplified in this specification or drawings can simultaneously achieve a plurality of purposes, and achieving one of them has technical utility in itself.

2: Battery 3: Motor 10: Power converter 12: Connector 20: Inverters 21a, 21b, 32: Switching elements 22a, 22b, 33, 34: Diode 23: First temperature sensor 30: Charger 31: Boost converter 35: Reactor 36: Filter capacitor 37: Second temperature sensor 39: Rectifier 40: Cooler 41: Circulation path 43: Pump 44: Third temperature sensor 50: Controller 60: Voltage converter 70: Radiator 80: Host controller 100: Electric vehicle

Claims (1)

an inverter that includes a first switching element for power conversion and converts the DC power of the on-vehicle power source into drive power for the motor for running;
a charger that includes a second switching element for power conversion and converts power from an external power source into charging power for the onboard power source;
a cooler that cools the first switching element and the second switching element;
a first temperature sensor that measures the temperature of the first switching element;
a second temperature sensor that measures the temperature of the second switching element;
a third temperature sensor that measures the temperature of the coolant in the cooler;
a controller;
and
The controller is
calculating a first estimated temperature of the refrigerant from the measured value of the first temperature sensor;
calculating a second estimated temperature of the refrigerant from the measured value of the second temperature sensor;
The measured temperature measured by the third temperature sensor, the first estimated temperature, and the second estimated temperature are compared, and the absolute value of the temperature difference between any one temperature and each of the other two temperatures is a predetermined allowable outputting a signal indicating that an abnormality has occurred in the temperature sensor corresponding to the one temperature when the temperature difference is exceeded;
Power converter for electric vehicles.

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