JP2021078179A - Control device for motor, electric vehicle, and control method for motor - Google Patents

Abstract

To provide a motor of which the dielectric strength can be secured in response to a sudden temperature change.SOLUTION: A control device 2 for a motor 200 which is cooled by a dielectric coolant circulated by a pump comprises: a current command calculation unit 10 which calculates a current command on the basis of a torque command to the motor, a DC voltage applied from a power source to a power conversion circuit 100 and a rotor position of the motor; and a restriction unit 20 which restricts a maximum value of a voltage to be applied to the motor on the basis of the calculated current command, the DC voltage, and a flow rate and a temperature of the dielectric coolant.SELECTED DRAWING: Figure 2

Description

The present invention relates to a motor control device, an electric vehicle, and a control method for the motor.

For a motor that is liquid-cooled by an insulating refrigerant, it is desired to secure the dielectric strength and improve the cooling performance by circulating the refrigerant. Therefore, a technique for controlling the flow rate of the refrigerant based on the temperature of the insulating refrigerant has been proposed.

The following Patent Document 1 is known as a background technique of the present invention. In Patent Document 1, when the temperature of the insulating medium detected by the temperature detecting means exceeds a predetermined value, the temperature detecting means detects the flow rate of the insulating medium circulating between the inside of the electric device and the cooling device from the flow rate in the steady state. An electric device for increasing the flow rate within the range not exceeding the upper limit flow rate in the non-discharge region corresponding to the temperature of the insulating medium is described. As a result, it is possible to secure the dielectric strength and improve the cooling performance at the same time, and to improve the maximum output of the electric device.

Japanese Unexamined Patent Publication No. 2006-32651

In Patent Document 1, when the temperature of the insulating refrigerant suddenly changes, the control of the refrigerant flow rate is delayed. Then, the dielectric strength of the electric device is lowered, and at the same time, the output may be lowered. Therefore, even when the temperature of the insulating refrigerant suddenly changes, it is an issue to secure the dielectric strength of the electric device.

The control device of the motor cooled by the insulating refrigerant circulated by the pump is a current command based on the torque command to the motor, the DC voltage applied from the power supply to the power conversion circuit, and the rotor position of the motor. A limiting unit that limits the maximum value of the voltage applied to the motor based on the calculated current command calculation unit, the calculated current command, the DC voltage, and the flow rate and temperature of the insulating refrigerant. And.

According to the present invention, the electric motor can secure the dielectric strength corresponding to a sudden change in temperature.

It is an overall configuration of a motor and a control device for the motor according to the embodiment of the present invention. It is a control block diagram of the control device of the electric motor which concerns on 1st Embodiment of this invention. It is a processing flowchart of the restriction part provided in the control device of the electric motor which concerns on 1st Embodiment of this invention. It is a voltage waveform pattern applied to a motor at the time of switching which concerns on 1st Embodiment of this invention. It is a processing flowchart of the restriction part provided in the control device of the electric motor which concerns on 2nd Embodiment of this invention. It is a processing flowchart of the restriction part provided in the control device of an electric motor which concerns on 3rd Embodiment of this invention. It is a reference figure of the waveform of the gate voltage applied to the switching element which concerns on 3rd Embodiment of this invention. It is a figure which shows the electric vehicle to which the control device of the electric motor according to this invention is applied.

(Structure of Motor Control Device, and First Embodiment)
FIG. 1 is a diagram showing an overall configuration of a control device related to an electric motor and an inverter control device 2 (hereinafter, simply referred to as a control device 2) according to an embodiment of the present invention.

As shown in FIG. 1, the overall configuration of the motor and the control device of the motor includes an electric system control device 1 (hereinafter, simply referred to as a control device 1), a control device 2, and a pump control device 3 (hereinafter, simply a control device 3). It includes an inverter 100, a motor 200, a position sensor 210, a current sensor 220, a voltage sensor 230, an insulating refrigerant 300, a pump 310, a refrigerant flow sensor 320, and a refrigerant temperature sensor 330.

The control device 1 outputs a torque command to the motor 200 based on a command input from a higher-level control device (not shown). The torque command is input to the control device 2.

The control device 2 is detected by the torque command input from the control device 1, the three-phase AC current detected by the current sensor 220, the rotor position of the motor 200 detected by the position sensor 210, and the voltage sensor 230. Based on the input voltage and the switching signal, the inverter 100 is PWM-controlled. The details of the inside of the control device 2 will be described later.

The control device 3 controls the flow rate of the insulating refrigerant 300 based on the refrigerant flow rate input from the refrigerant flow rate sensor 320 and the refrigerant temperature input from the refrigerant temperature sensor 330 so that the motor 200 does not fail due to overheating. The refrigerant flow rate command of is output to the pump 310.

The inverter 100, which is a power conversion circuit, is composed of switching elements 110a to 110f. The switching element 110a is a U-phase upper arm, the switching element 110b is a U-phase lower arm, the switching element 110c is a V-phase upper arm, the switching element 110d is a V-phase lower arm, the switching element 110e is a W-phase upper arm, and the switching element 110f is W. It is placed on the lower arm.

The switching elements 110a to 110f are configured by combining a metal oxide film type field effect transistor (MOSFET), an insulated gate bipolar transistor (IGBT), or the like with a diode.

Further, the switching elements 110a to 110f are turned on or off, respectively, based on the switching signal generated by the control device 2. As a result, the switching elements 110a to 110f convert the DC voltage applied from the external DC power supply into an AC voltage. The AC voltage converted here is applied to the stator of the motor 200, and an AC current is generated in each of the three-phase coils provided in the stator. This three-phase alternating current generates a rotating magnetic field in the motor 200, whereby the rotor of the motor 200 rotates. The temperatures of the switching elements 110a to 110f are detected by a detection unit (not shown) and fed back to the control device 2.

The position sensor 210 detects the position of the rotor of the motor 200. The rotor position detected here is output to the control device 2.

The current sensor 220 detects the three-phase alternating current flowing through the motor 200. The three-phase alternating current detected here is output to the control device 2.

The voltage sensor 230 detects a DC voltage (hereinafter, simply referred to as an input voltage) applied to the inverter 100 from an external DC power source such as a battery, and outputs the detected input voltage to the control device 2.

The insulating refrigerant 300 is filled inside the motor 200 and circulated by the pump 310. The motor 200 is cooled by circulating the insulating refrigerant 300 between the motor 200 and the pump 310 via a cooling structure (not shown). As the insulating refrigerant 300, a liquid having electrical insulation such as mineral oil for transformers and gear oil is used.

The pump 310 circulates the insulating refrigerant 300 and controls the flow rate based on the refrigerant flow rate command input from the pump control device 3.

The refrigerant flow rate sensor 320 detects the flow rate of the insulating refrigerant 300. The detected refrigerant flow rate is input to the control device 2 and the control device 3.

The refrigerant temperature sensor 330 detects the temperature of the insulating refrigerant 300. The detected refrigerant temperature is input to the control device 2 and the control device 3.

FIG. 2 is a control block diagram of a control device for an electric motor according to the first embodiment of the present invention.

In the block diagram of FIG. 2, the current command calculation unit 10 (hereinafter, simply referred to as the calculation unit 10), the limiting unit 20, the current control unit 30, the PWM signal generation unit 40, and the speed conversion unit 50 are the main structures of the present invention. It is provided inside the control device 2.

The calculation unit 10 includes a torque command input from the control device 1, an angular velocity and rotor position fed back from the motor 200 via the speed conversion unit 50, a switching element temperature fed back from the inverter 100, and a voltage sensor 230. The pre-limit current command is calculated based on the input voltage detected in.

For the calculation of the pre-limit current command output from the calculation unit 10 to the limit unit 20, known methods such as maximum torque current control for the purpose of minimizing the output current and maximum efficiency control for the purpose of minimizing the power loss are known. Calculation technique is used.

Further, in order to prevent the switching elements 110a to 110f of the inverter 100 from being damaged due to overtemperature, the pre-limit current command is controlled based on the switching element temperature. However, depending on the usage conditions of the inverter 100 and the like, the pre-limit current command may be calculated without considering the influence of the switching element temperature. In that case, it is not necessary to feed back the switching element temperature from the inverter 100 to the calculation unit 10.

The limiting unit 20 is restricted based on the pre-limit current command input from the calculation unit 10, the refrigerant flow rate and the refrigerant temperature fed back from the sensors 320 and 330, and the input voltage fed back from the voltage sensor 230, respectively. Calculate the current command. The processing step inside the limiting unit 20 will be described with reference to FIG. 3 described later.

The current control unit 30 is a known technique such as proportional control or integral control based on a predetermined control gain from the post-limit current command input from the limiting unit 20 and the three-phase AC current fed back from the current sensor 220. Outputs a voltage command to the PWM signal generation unit 40.

The PWM signal generation unit 40 generates a switching signal for turning on or off the switching elements 110a to 110f based on the input voltage command. When generating a switching signal, a known technique such as a triangular wave carrier comparison method or a space vector modulation method is used.

The data of the rotor position of the motor 200 detected by the position sensor 210 is fed back to the speed conversion unit 50. The speed conversion unit 50 outputs the angular velocity to the current command calculation unit 10 based on the data of the rotor position of the motor 200.

FIG. 3 is a processing flowchart of the restriction unit 20.

In step S1, the dielectric strength is calculated based on the temperature and flow rate of the insulating refrigerant 300. The withstand voltage of the motor 200 changes depending on the temperature and flow rate of the insulating refrigerant 300. However, since it is affected by the flow charging phenomenon, it is necessary to measure the leakage current in order to evaluate the effect. The leakage current changes depending on the temperature and flow rate of the insulating refrigerant 300, similar to the withstand voltage of insulation. Therefore, the relationship data between the withstand voltage and the leakage current, which is different for each temperature and flow rate of the insulating refrigerant 300, is stored in the limiting unit 20 in advance, and the accurate withstand voltage according to the situation is calculated based on the data.

In step S2, the maximum value of the voltage applied to the motor 200 is calculated. The maximum value of the voltage is generated when the switching elements 110a to 110f are turned on or off. The magnitude of the voltage correlates with the magnitude of the turn-on or turn-off current, that is, the three-phase alternating current. Further, the amplitude of the voltage applied to the motor 200 changes as the input voltage changes. Therefore, for example, it is necessary to store the condition in which the voltage applied to the motor 200 is maximum, that is, the relationship between the three-phase alternating current and the maximum value of the voltage when the input voltage is maximum. Therefore, the relationship data between the three-phase AC current and the instantaneous maximum voltage, which is different for each input voltage, is stored in the limiting unit 20 in advance, and based on the data and the pre-limit current command input from the calculation unit 10, the situation is adjusted. Calculate the exact maximum voltage.

In step S3, the withstand voltage calculated in step S1 is compared with the maximum value of the voltage calculated in step S2, and it is determined whether or not the maximum value of the voltage is less than the withstand voltage. At this time, considering that an error is included in the withstand voltage calculated in step S1 and the maximum value of the voltage calculated in step S2, the sum of the maximum value of the voltage and the withstand voltage margin is less than the withstand voltage. It is desirable to determine whether or not.

The withstand voltage margin is a value set extra for the calculated withstand voltage so that the maximum value of the voltage does not exceed the withstand voltage. Specifically, the calculation error of the dielectric strength due to the detection error of the temperature and the flow rate of the insulating refrigerant 300, the decrease of the dielectric strength due to the aged deterioration of the insulating refrigerant 300, and the maximum value of the voltage due to the fluctuation of the input voltage. It is set when an increase or decrease, an increase or decrease of the maximum value of the voltage due to a change in the switching element temperature, etc. occur in combination. If there are many fluctuation factors that are not taken into consideration when calculating the maximum value of the withstand voltage and the voltage, and the calculation error is large, the value of the withstand voltage margin needs to be set larger.

In step S3, when it is determined that the maximum value of the voltage is less than the dielectric strength, the pre-limit current command is output without limitation, and the flowchart ends. On the other hand, if it is determined that the maximum value of the voltage is equal to or higher than the dielectric strength, the process proceeds to step S4.

In step S4, in the relationship data between the three-phase AC current and the maximum voltage used when calculating the maximum value of the voltage in step S2, the maximum value of the voltage is smaller than the insulation withstand voltage calculated in step S1. The value of the alternating current is calculated as the output current after limiting. Then, the calculated limited current command is output to the current control unit 30, and the flowchart is terminated. As a result, the three-phase alternating current output from the inverter 100 to the motor 200 is limited so that the maximum value of the voltage applied from the inverter 100 to the motor 200 is limited. At this time, it is desirable that the sum of the maximum value of the voltage and the dielectric strength margin is less than the dielectric strength, taking into account the error.

FIG. 4 is an example of a voltage waveform pattern applied to the motor during switching according to steps S3 and S4 in FIG.

For example, in the case 4 where the input voltage is high and the three-phase alternating current is also large, the maximum value of the voltage applied to the motor 200 at the time of switching may exceed the dielectric strength. In step S3 of the limiting unit 20, the control device 2 determines that the maximum value of the voltage is equal to or greater than the dielectric strength. As a result, the process proceeds to step S4 of the limiting unit 20. The limited current command is calculated in step S4, and the maximum value of the voltage is limited to less than the dielectric strength as in case 3 of FIG.

On the other hand, when the input voltage is low and the three-phase alternating current is also low, if the three-phase alternating current is limited, the maximum value of the voltage applied to the motor 200 at the time of switching is excessively limited as in case 1, which is more than necessary. The output of the inverter 100 is reduced. Therefore, in step S2 of FIG. 3, the maximum value of the voltage appropriate for the situation is calculated based on the relationship between the three-phase alternating current stored for each input voltage and the maximum value of the voltage.

According to the first embodiment of the present invention described above, the following effects are exhibited.

(1) The control device 2 of the motor 200, which is cooled by the insulating refrigerant 300 circulated by the pump 310, has a torque command to the motor 200, a DC voltage applied to the inverter 100 from the power supply, and a rotor position of the motor 200. The maximum value of the voltage applied to the motor 200 based on the current command calculation unit 10 that calculates the current command based on the above, the calculated current command, the DC voltage, and the flow rate and temperature of the insulating refrigerant 300. 20 is provided. As a result, the motor 200 can secure an insulation strength corresponding to a sudden change in temperature.

(2) The limiting unit 20 limits the maximum value of the voltage applied to the motor 200 by limiting the three-phase alternating current output from the inverter 100 to the motor 200. Therefore, in the control of the three-phase alternating current carried out by the control device 2, the maximum value of the voltage applied to the motor 200 can be limited.

(3) The limiting unit 20 calculates the withstand voltage of the motor 200 based on the flow rate and temperature of the insulating refrigerant 300 (step S1), and limits the maximum value of the voltage applied to the motor 200 based on the calculated withstand voltage. (Steps S2 to S4). Since this is done, the maximum value of the voltage applied to the motor 200 can be appropriately limited according to the withstand voltage.

(4) The limiting unit 20 calculates the maximum value of the voltage applied to the motor 200 from the current command and the DC voltage (step S2), and the motor 200 is set so that the maximum value of the calculated voltage becomes smaller than the insulation withstand voltage. The maximum value of the voltage applied to is limited (steps S3 and S4). Since this is done, the maximum value of the voltage can be surely set to the withstand voltage or less, and the dielectric strength of the motor 200 can be ensured.

(Second embodiment)
FIG. 5 is a flowchart of processing of the limiting unit 20 that limits the maximum value of the voltage based on the switching element temperature of the inverter 100 according to the second embodiment of the present invention.

The maximum value of the voltage applied to the motor 200 is generated when the switching elements 110a to 110f are turned on or off, and the magnitude of the voltage correlates with the temperature of the switching element when the switching elements are turned on or off.

In step S1, the dielectric strength is calculated based on the temperature and flow rate of the insulating refrigerant 300, as in step S1 of FIG.

In the present embodiment, the relationship data between the three-phase alternating current applied from the inverter 100 to the motor 200 and the maximum value of the voltage is stored in advance in the limiting unit 20 for each switching element temperature. In step S2, among the data on the relationship between the maximum value of the three-phase alternating current and the voltage stored in advance for each switching element temperature, the data corresponding to the switching element temperature fed back from the inverter 100 to the limiting unit 20 is selected. .. Based on the data selected in this way, it is possible to calculate a more accurate maximum value of the voltage from the input voltage fed back and the pre-limit current command input from the calculation unit 10.

In step S3, similarly to step S3 of FIG. 3, when it is determined that the maximum value of the voltage is less than the dielectric strength, the pre-limit current command is output without limitation, and the flowchart ends. On the other hand, if it is determined that the maximum value of the voltage is equal to or higher than the dielectric strength, the process proceeds to step S4.

In step S4, as in step S4 of FIG. 3, the maximum value of the voltage is smaller than the insulation withstand voltage calculated in step S1 from the relationship between the three-phase alternating current selected in step S2 and the maximum value of the voltage. The value of the phase alternating current is calculated as the output current after limiting. Then, the calculated limited current command is output to the current control unit 30, and the flowchart is terminated. At this time, it is desirable that the sum of the maximum value of the voltage and the insulation withstand voltage margin be less than the insulation withstand voltage in consideration of the error.

According to the second embodiment of the present invention described above, the following effects are exhibited.

(5) The limiting unit 20 calculates the maximum value of the voltage applied to the motor 200 based on the current command, the DC voltage, and the temperatures of the switching elements 110a to 110f of the inverter 100 (step S2). Since this is done, the maximum value of the voltage can be calculated from information other than the input voltage, and the motor 200 can secure the dielectric strength corresponding to a sudden change in temperature. Further, this makes it possible to reduce the withstand voltage margin and suppress excessive limitation of the output three-phase alternating current.

(Third Embodiment)
FIG. 6 is a flowchart of processing of the limiting unit 20 that limits the maximum value of the voltage based on the gate voltage according to the third embodiment of the present invention.

The maximum value of the voltage applied to the motor 200 is generated when the switching elements 110a to 110f are turned on or off, and the magnitude thereof correlates with the amplitude of the gate voltage that drives the switching element by turning on or off.

In step S1, the dielectric strength is calculated based on the temperature and flow rate of the insulating refrigerant 300, as in steps S1 of FIGS. 3 and 5.

In the present embodiment, the relationship data between the three-phase alternating current applied from the inverter 100 to the motor 200 and the maximum value of the voltage is stored in advance in the limiting unit 20 for each gate voltage. The gate voltage is controlled by a control unit (not shown) using a known technique so as not to be over-applied. As a result, the gate voltage that drives the switching elements 110a to 110f of the inverter 100 changes. In step S2, the data corresponding to the current gate voltage is selected from the data on the relationship between the three-phase alternating current and the maximum value of the voltage stored in advance for each gate voltage. Based on the data selected in this way, the maximum value of the accurate voltage according to the situation is calculated from the input voltage fed back and the pre-limit current command input from the calculation unit 10.

In step S3, as in steps S3 of FIGS. 3 and 5, when it is determined that the maximum value of the voltage is less than the dielectric strength, the pre-limit current command is output without limitation and the flowchart ends. On the other hand, if it is determined that the maximum value of the voltage is equal to or higher than the dielectric strength, the process proceeds to step S4.

In step S4, the gate voltage is calculated so that the maximum value of the voltage is less than the insulation withstand voltage. When the amplitude of the gate voltage is reduced, the speed at which the gate voltage rises or falls decreases accordingly. As a result, the speed at which the switching elements 110a to 110f turn on or off is reduced, so that the maximum value of the voltage can be limited by reducing the amplitude of the gate voltage.

In step S5, among the relationships between the three-phase alternating current for each gate voltage and the maximum value of the voltage stored in advance in the limiting unit 20, the relationship corresponding to the gate voltage calculated in step S4 is selected. Then, from the relationship between the selected three-phase AC current and the maximum value of the voltage, the value of the three-phase AC current such that the maximum value of the voltage is smaller than the insulation withstand voltage calculated in step S1 is calculated as the output current after limitation. .. After that, the calculated limited current command is output to the current control unit 30, and the flowchart ends.

FIG. 7 is a reference diagram of the waveform of the gate voltage applied to the switching element according to the third embodiment.

If the gate voltage for turning on or off the switching elements 110a to 110f as shown in FIG. 7 is reduced from ± 15V at the time of application to ± 12V, the amplitude becomes smaller by 6V. When the amplitude of the gate voltage is reduced, the maximum value of the related voltage is also lowered, and the dielectric strength margin can be reduced.

According to the third embodiment of the present invention described above, the following effects are exhibited.

(6) The limiting unit 20 calculates the maximum value of the voltage applied to the motor 200 based on the current command, the DC voltage, and the gate voltage for driving the switching elements 110a to 110f of the inverter 100 (step). S2). Since this is done, the maximum value of the voltage can be calculated from information other than the input voltage, and the motor 200 can secure the dielectric strength corresponding to a sudden change in temperature. In addition, the dielectric strength margin can be reduced, and excessive limitation of the output three-phase alternating current can be prevented.

(Electric vehicle)
FIG. 8 is a diagram showing an electric vehicle 600 to which the control device 2 according to the present invention is applied. The electric vehicle 600 has a power train in which the motor 200 is applied as a motor / generator.

A front wheel axle 601 is rotatably supported on the front portion of the electric vehicle 600, and front wheels 602 and 603 are provided at both ends of the front wheel axle 601. A rear wheel axle 604 is rotatably supported at the rear portion of the electric vehicle 600, and rear wheels 605 and 606 are provided at both ends of the rear wheel axle 604.

A differential gear 611, which is a power distribution mechanism, is provided at the center of the front wheel axle 601 to distribute the rotational driving force transmitted from the engine 610 via the transmission 612 to the left and right front wheel axles 601. ing. The engine 610 and the motor 200 are mechanically connected via a belt provided on the crankshaft of the engine 610 and between pulleys provided on the rotating shaft of the motor 200.

As a result, the rotational driving force of the motor 200 can be transmitted to the engine 610, and the rotational driving force of the engine 610 can be transmitted to the motor 200. The motor 200 rotates the rotor by supplying the three-phase AC power output from the inverter 100 to the stator coil of the stator under the control of the control device 2, and exerts a rotational driving force according to the three-phase AC power. appear.

That is, while the motor 200 is controlled by the control device 2 and operates as an electric motor, the motor 200 operates as a generator that generates three-phase AC power by rotating the rotor in response to the rotational driving force of the engine 610.

The inverter 100 is a power conversion device that converts DC power supplied from a high-voltage battery 622, which is a high-voltage (42V or 300V) power supply, into three-phase AC power, and is based on an operation command value and a magnetic pole position of a rotor. , Controls the three-phase AC current flowing through the stator coil of the motor 200.

The three-phase AC power generated by the motor 200 is converted into DC power by the inverter 100 to charge the high-voltage battery 622. The high voltage battery 622 is electrically connected to the low voltage battery 623 via a DC / DC converter 624. The low-voltage battery 623 constitutes a low-voltage (14v) system power supply for the electric vehicle 600, and is used as a power source for a starter 625, a radio, a light, etc. that initially starts (cold start) the engine 610.

When the electric vehicle 600 is stopped (idle stop mode) such as waiting for a traffic light, the engine 610 is stopped, and when the engine 610 is restarted (hot start) when the vehicle reoccurs, the inverter 100 drives the motor 200 to drive the engine. Restart 610.

In the idle stop mode, when the charge amount of the high-pressure battery 622 is insufficient or the engine 610 is not sufficiently warm, the engine 610 is not stopped and the drive is continued. Further, in the idle stop mode, it is necessary to secure a drive source for auxiliary machinery such as an air conditioner compressor that uses the engine 610 as a drive source. In this case, the motor 200 is driven to drive the accessories.

Even in the acceleration mode or the high load operation mode, the motor 200 is driven to assist the driving of the engine 610. On the contrary, when the high-voltage battery 622 is in the charging mode that requires charging, the engine 610 generates the motor 200 to charge the high-voltage battery 622. That is, the motor 200 is regeneratively operated during braking or deceleration of the electric vehicle 600.

The electric vehicle 600 has a DC voltage due to a control device 2 that issues a command to limit the three-phase AC current applied to the motor 200 based on the temperature and flow rate of the insulating refrigerant, and a limited PWM pulse output from the control device 2. The inverter 100 drives the motor 200 by converting the voltage into an AC voltage, and the DC / DC converter 624 that boosts the DC voltage. As a result, the insulating refrigerant 300 can be stably controlled even while the vehicle is being driven.

The embodiments and various modifications described above are merely examples, and the present invention is not limited to these contents as long as the features of the invention are not impaired. Moreover, although various embodiments and modifications have been described above, the present invention is not limited to these contents. Other aspects conceivable within the scope of the technical idea of the present invention are also included within the scope of the present invention.

1 Electric system control device 2 Inverter control device 3 Pump control device 10 Current command calculation unit 20 Limiting unit 30 Current control unit 40 PWM signal generation unit 50 Speed conversion unit 100 Inverter 110a U-phase upper arm switching element 110b U-phase lower arm switching element 110c V-phase upper arm switching element 110d V-phase lower arm switching element 110e W-phase upper arm switching element 110f W-phase lower arm switching element 200 Motor 210 Position sensor 220 Current sensor 230 Voltage sensor 300 Insulated refrigerant 310 Pump 320 Refrigerator Flow sensor 330 Refrigerator Temperature sensor 600 Electric vehicle

Claims (8)

A control device for a motor that is cooled by an insulating refrigerant circulated by a pump.
A current command calculation unit that calculates a current command based on a torque command for the motor, a DC voltage applied from a power source to the power conversion circuit, and a rotor position of the motor.
A control device including a limiting unit that limits a maximum value of a voltage applied to the motor based on the calculated current command, the DC voltage, and the flow rate and temperature of the insulating refrigerant. The control device according to claim 1.
The limiting unit is a control device that limits the maximum value of the voltage by limiting the three-phase alternating current output from the power conversion circuit to the motor. The control device according to claim 1.
The limiting unit is a control device that calculates the dielectric strength of the motor based on the flow rate and temperature of the insulating refrigerant, and limits the maximum value of the voltage based on the calculated dielectric strength. The control device according to claim 3.
The limiting unit is a control device that calculates the maximum value of the voltage from the current command and the DC voltage, and limits the maximum value of the voltage so that the maximum value of the voltage is smaller than the dielectric strength. The control device according to claim 4.
The limiting unit is a control device that calculates the maximum value of the voltage based on the current command, the DC voltage, and the temperature of the switching element of the power conversion circuit. The control device according to claim 4.
The limiting unit is a control device that calculates the maximum value of the voltage based on the current command, the DC voltage, and the gate voltage that drives the switching element of the power conversion circuit. An electric vehicle provided with the control device according to any one of claims 1 to 6. The step of obtaining the dielectric strength and the leakage current from the temperature and flow rate of the insulating refrigerant circulated by the pump, respectively, and calculating the dielectric strength of the motor from the relationship between the insulation resistance and the leakage current.
In the power conversion circuit, the relationship between the current at the time of output and the maximum value of the voltage, which is different for each voltage input to the switching element, is stored in advance.
The step of confirming that the dielectric strength is larger than the calculated maximum value of the voltage, and
A method for controlling an electric motor, comprising: a step of calculating a current for limiting the maximum value of the voltage when the dielectric strength is smaller than the maximum value of the voltage.

Images