Power conversion device, rotary electric machine device, and method for controlling power conversion device

Abstract

To prevent a specific switching element from generating heat by changing a current amplitude and a current phase within an electrical angle period according to the temperature of the switching element.SOLUTION: Calculating a current command value defined by a current amplitude and a current phase in d-axis current and q-axis current coordinates based on a power conversion circuit having a plurality of legs each provided with a positive electrode side switching element, a negative electrode side switching element, and a power supply line connecting a connection point where the positive electrode side switching element and the negative electrode side switching element are connected in series to a coil of a rotating electric machine, a temperature detector configured to detect a temperature of the switching element, and a command value, and performing on / off control of the switching element of the power conversion circuit based on the current command value; A control unit configured to change the current amplitude and the current phase within an electrical angle period according to a temperature of the switching element detected by a temperature detector.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a power conversion device, a rotating electrical machine device, and a method for controlling a power conversion device. [Background technology]

[0002] Electric power from a DC power source is converted into the rotational force of a rotating electric machine by a power conversion device. Electric motors and generators are collectively called rotating electric machines. An inverter that converts DC power to AC power is commonly used as a power conversion device that converts the form of power output to control the rotating electric machine. The power conversion devices that control these rotating electric machines are often configured with semiconductor switching elements. A rotating electric machine device is made up of a combination of a rotating electric machine and a power conversion device that controls it.

[0003] As a technology related to power conversion devices that control rotating electrical machines, a technology for controlling current phase and current amplitude to suppress heat generation in switching elements is generally known. Regarding electric motors that drive electric brakes, a technology has been disclosed that prevents heat generation from being concentrated in switching elements that energize specific phases when locking energization is applied to an electric motor having multi-phase coils. A technology has also been disclosed that changes the phase of a current command value according to time so that energization at the same current phase does not continue for more than a predetermined time (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2023-82656 Summary of the Invention [Problem to be solved by the invention]

[0005] The control technology disclosed in Patent Document 1 changes the phase of a current command value when the motor is locked so that the current phase that flows through it does not remain fixed for a predetermined time. Changing the current phase prevents drive from concentrating on a specific switching element and equalizes the temperature of each switching element. However, this technology does not take into account changes in the temperature of the switching elements before and after changing the current phase. If the temperature of the switching elements rises before the predetermined time has elapsed, it may not be possible to respond, and the switching elements may exceed their operating limit temperature, which could result in performance degradation and a shortened lifespan.

[0006] The present disclosure has been made to solve the above-mentioned problems. It is an object of the present disclosure to provide a power conversion device that drives a rotating electric machine by controlling the on / off of switching elements, and to prevent a specific switching element from generating heat by changing the current amplitude and current phase within an electrical angle period in accordance with the temperature of the switching element detected by a temperature detector. It is also an object of the present disclosure to provide a rotating electric machine device that uses such a power conversion device. It is also an object of the present disclosure to provide a control method for such a power conversion device. [Means for solving the problem]

[0007] The power conversion device according to the present disclosure comprises: a power conversion circuit having a plurality of legs each provided with a positive-side switching element connected to a positive side of a DC power supply, a negative-side switching element connected to a negative side of the DC power supply, and a power supply line connecting a connection point at which the positive-side switching element and the negative-side switching element are connected in series to a coil of a rotating electric machine; a temperature detector for detecting the temperature of a switching element of the power conversion circuit; and The inverter includes a control unit that calculates a current command value defined by the current amplitude and current phase in the d-axis current and q-axis current coordinates based on the command value, controls the on / off of the switching elements of the power conversion circuit based on the current command value, and changes the current amplitude and current phase within an electrical angle period according to the temperature of the switching elements detected by a temperature detector.

[0008] A rotating electric machine device according to the present disclosure includes: A rotating electric machine comprising a stator around which a coil is wound and a rotor on whose surface a permanent magnet is arranged; It is equipped with a power conversion device.

[0009] A control method for a power conversion device according to the present disclosure includes: a first step in which, for a power conversion circuit having a plurality of legs each having a positive-side switching element connected to a positive side of a DC power supply, a negative-side switching element connected to a negative side of the DC power supply, and an external connection point connecting the positive-side switching element and the negative-side switching element in series and connected to a coil of a rotating electric machine, a control unit calculates a current command value defined by a current amplitude and a current phase in d-axis current and q-axis current coordinates based on a command value, determines the current command value at a current amplitude and current phase that become a minimum current operating point that realizes a target torque, and controls on and off the switching elements of the power conversion circuit based on the current command value; The power conversion circuit further includes a second step of changing the current phase of the current command value on an equal torque curve by changing the current phase of the current command value from the minimum current operating point in a predetermined angle leading direction and lagging direction within an electrical angle period when the temperature of the switching element detected by a temperature detector that detects the temperature of the switching element of the power conversion circuit is higher than a predetermined temperature threshold value. [Effects of the Invention]

[0010] According to the power conversion device disclosed herein, in a power conversion circuit that drives a rotating electric machine by controlling the on / off of switching elements, the current amplitude and current phase can be changed within an electrical angle period in accordance with the temperature of the switching element detected by a temperature detector to prevent specific switching elements from overheating. Therefore, control can be performed in accordance with changes in the temperature of the switching elements before and after changing the current amplitude and current phase, and the switching elements do not exceed their operating limit temperatures, which could cause performance degradation and shortened lifespan. This prevents performance degradation due to overheating of the switching elements, resulting in a highly reliable power conversion device.

[0011] A rotating electric machine using such a power converter can be obtained, thereby improving the reliability of the rotating electric machine. Furthermore, a control method for such a power converter can be implemented to prevent a specific switching element from generating heat by changing the current amplitude and current phase in accordance with the temperature of the switching element detected by the temperature detector. Thus, a highly reliable control method for a power converter can be achieved. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a configuration diagram of a power conversion device and a rotating electrical machine device according to an embodiment; [Figure 2] FIG. 2 is a hardware configuration diagram of a control unit of a power conversion device according to an embodiment. [Figure 3] FIG. 2 is a functional block diagram of a control unit of the power conversion device according to the embodiment. [Figure 4] 4A and 4B are diagrams illustrating current phases and current amplitudes in d-axis and q-axis current coordinates of the power conversion device according to the embodiment. [Figure 5] 4 is a characteristic diagram of the rotation speed and torque of the rotating electric machine according to the embodiment; FIG. [Figure 6] 5 is a diagram showing the relationship between the current flowing through the power supply line and the temperature of the switching element of the power conversion device according to the embodiment. FIG. [Figure 7]4A and 4B are diagrams illustrating the electrical angle, the temperature, the current value, the current phase, and the torque of the switching elements of the power conversion device according to the embodiment. [Figure 8] 10A and 10B are diagrams illustrating absolute values ​​of phase currents in the case of a minimum current phase and in the case of an arbitrary current phase of the power conversion device according to the embodiment. [Figure 9] 10A and 10B are diagrams illustrating currents and temperatures of switching elements when maximum torque control and instantaneous current suppression are applied in the power conversion device according to the embodiment. [Figure 10] 10 is a diagram showing a comparison of the temperatures of the switching elements when maximum torque control and instantaneous current suppression are applied during high rotation of the power conversion device according to the embodiment. FIG. [Figure 11] 10 is a diagram showing the phase current and the temperature of the switching element when instantaneous current suppression is applied to the U phase of the power conversion device according to the embodiment. FIG. [Figure 12] 10 is a diagram showing phase currents and temperatures of switching elements when instantaneous current suppression is applied to the U phase and V phase of the power conversion device according to the embodiment. FIG. [Figure 13] 10A and 10B are diagrams illustrating currents when maximum torque control is applied and when instantaneous current suppression is applied in the electrical angle of the power conversion device according to the embodiment. [Figure 14] 1 is a cross-sectional view of a rotating electric machine according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] A power conversion device according to an embodiment of the present disclosure will be described with reference to the drawings. The drawings are schematic, and for the sake of convenience, components are omitted or simplified. Furthermore, the relative sizes and positions of components shown in different drawings are not necessarily accurately depicted and may be changed as appropriate.

[0014] 1. Embodiment <Configuration of power conversion device and rotating electrical machine device> 1 is a configuration diagram showing a power conversion device 100 according to an embodiment and a rotating electrical machine device 200. The power conversion device 100 is connected to a rotating electrical machine 1, a power supply unit 2, and a command generator 8, and is cooled by a cooler 4.

[0015] The power conversion device 100 includes a power conversion circuit 3, a drive circuit 34, and a control unit 9. The power conversion device 100 also includes a current detector 32 that detects the current that drives the coils 11, 12, and 13 of the rotating electric machine 1, an amplifier circuit 33, and a switching element temperature detector 7 that detects the temperature of the switching elements. The detected and amplified current and the temperature of the switching elements are transmitted to the control unit 9.

[0016] The rotating electric machine 1 is equipped with a rotation angle detector 5 and a rotating electric machine temperature detector 6. The detected rotation angle and temperature of the rotating electric machine are transmitted to a control unit 9 of the power conversion device 100. The rotating electric machine 1 and the power conversion device 100 are combined to form a rotating electric machine device 200.

[0017] The power conversion device 100 receives DC power from a power supply unit 2 and a control command from an external command generator 8. A control unit 9 of the power conversion device 100 calculates a target current based on the control command, drives the switching elements 311 to 316 of the power conversion circuit 3 on and off via a drive circuit 34, supplies current to the rotating electric machine 1, and recovers regenerative power.

[0018] <Rotating electric machines> The rotating electric machine 1 is a concept that includes an electric motor (motor) and a generator (electric power generator). The rotating electric machine 1 connected to the power conversion device 100 may be interpreted as either an electric motor or a generator. The rotating electric machine 1, which has the functions of both an electric motor and a generator, can convert electric power into driving force for power running, and can also convert the driving force back into electric power for regenerative operation with the same structure. The electric motor and the generator basically have the same structure, and both are capable of power running and regenerative operation.

[0019] The rotating electric machine 1 is controlled according to the PWM (Pulse Width Modulation) method. The rotor has a disk-shaped or cylindrical core member. A permanent magnet is attached to the surface of the core member, and the rotor has magnetic poles.

[0020] The stator accommodates the rotor within it so that they can rotate relative to each other. The stator has protrusions that face the rotor and protrude radially inward at preset angles. U-phase coil 11, V-phase coil 12, and W-phase coil 13 are wound around these protrusions.

[0021] In FIG. 1, the rotating electric machine 1 is depicted as a three-phase AC rotating electric machine having coils 11 to 13. The number of coils may be two-phase or a rotating electric machine with more than three phases. In FIG. 1, the rotating electric machine 1 is shown as being star-connected. In this case, the neutral point may be grounded, or may be floating. The coils of the rotating electric machine 1 may also be delta-connected.

[0022] <DC power supply> The power supply unit 2 is provided with a DC power supply 21, which serves as a drive source for the power conversion device 100. The DC power supply 21 is also called a battery, and supplies DC power to the power conversion device 100 to drive the rotating electric machine 1. The power supply unit 2 is provided with a smoothing capacitor 22 and a choke coil 23.

[0023] Smoothing capacitor 22 and choke coil 23 are disposed between DC power supply 21 and power conversion circuit 3, and form a power filter. With this configuration, it is possible to reduce noise transmitted from other devices that share DC power supply 21 to power conversion circuit 3, and also to reduce noise transmitted from power conversion circuit 3 to other devices that share DC power supply 21.

[0024] By storing electric charge, smoothing capacitor 22 assists in supplying power to switching elements 311 to 316 and also suppresses noise components such as surge currents. Furthermore, power supply voltage Vbat of DC power supply 21 and capacitor voltage Vcon of smoothing capacitor 22 may be detected by control unit 9 (power supply voltage Vbat is not shown).

[0025] <Power conversion circuit> The power conversion circuit 3 converts DC power supplied from the power supply unit 2 into AC power and outputs the converted AC power to the rotating electric machine 1. The power conversion circuit 3 has switching elements 311 to 316. The power conversion circuit 3 may include a smoothing capacitor 22 and a choke coil 23. The power conversion circuit 3 may also include a current detector 32, an amplifier circuit 33, a drive circuit 34, a switching element temperature detector 7, and a capacitor temperature detector 24 (the capacitor temperature detector 24 is not shown).

[0026] The power conversion circuit 3 has three pairs of legs, each consisting of an upper arm and a lower arm. The legs are also called half-bridge circuits. The power conversion circuit 3 has three pairs of half-bridge circuits connected in parallel, each having switching elements 311 to 313 as upper arms and switching elements 314 to 316 as lower arms. The switching elements 311 to 316 are controlled to switch on and off in accordance with a PWM signal, thereby converting the DC power output from the power supply unit 2 into AC power. The converted AC power is output to the rotating electric machine 1 via a power supply line.

[0027] Switching elements 311 and 314, switching elements 312 and 315, and switching elements 313 and 316 each constitute three pairs of legs, each with a positive side (upper stage) switching element and a negative side (lower stage) switching element connected in series, and are connected in parallel to DC power supply 21. The connection point of switching elements 311 and 314 is connected to U-phase coil 11 of rotating electric machine 1 by a power supply line. The connection point of switching elements 312 and 315 is connected to V-phase coil 12 of rotating electric machine 1. The connection point of switching elements 313 and 316 is connected to W-phase coil 13 of rotating electric machine 1. Power conversion circuit 3 is a three-phase inverter, and switches the energization of U-phase coil 11, V-phase coil 12, and W-phase coil 13.

[0028] <Switching element> The switching elements 311 to 316 may be MOSFETs (Metal Oxide Semiconductor Field Effect Transistors), which are a type of field effect transistor. Other transistors than MOSFETs, such as IGBTs (Insulated Gate Bipolar Transistors), may also be used. The following describes an example in which MOSFETs are used as switching elements. The switching elements 311 to 316 are denoted as SW311 to 316.

[0029] The drains of the three SW311 to 313 are connected to the positive electrode side of the DC power supply 21. The sources of SW311 to 313 are connected to the drains of SW314 to 316, respectively. The sources of SW314 to 316 are connected to the negative electrode side of the DC power supply 21. A connection point connecting the pair of SW311 and SW314 is connected to one end of the U-phase coil 11. A connection point connecting the pair of SW312 and SW315 is connected to one end of the V-phase coil 12. A connection point connecting the pair of SW313 and SW316 is connected to one end of the W-phase coil 13.

[0030] In the following description, the switching elements SW311 to SW313 arranged on the positive side may be referred to as "upper SW" or "H_SW," and the switching elements SW314 to SW316 arranged on the negative side may be referred to as "lower SW" or "L_SW." In addition, in this embodiment, for ease of understanding, the potential on the negative side will be described as 0V.

[0031] <Current detector> The current detector 32 includes a U-phase current detector 321, a V-phase current detector 322, and a W-phase current detector 323. The U-phase current detector 321, the V-phase current detector 322, and the W-phase current detector 323 may be configured using, for example, shunt resistors. Alternatively, a current detector using a Hall element or the like may be used. In the following description, the U-phase current detector 321, the V-phase current detector 322, and the W-phase current detector 323 will be referred to as current detectors 321 to 323 as appropriate.

[0032] The U-phase current detector 321 detects the U-phase current Iu as the current flowing through the U-phase coil 11. The V-phase current detector 322 detects the V-phase current Iv as the current flowing through the V-phase coil 12. The W-phase current detector 323 detects the W-phase current Iw as the current flowing through the W-phase coil 13. The detected values ​​detected by the current detectors 321 to 323 are input to the control unit 9 via an amplifier circuit 33. The amplifier circuit 33 is intended to enable the detected values ​​detected by the current detectors 321 to 323 to be taken in as appropriate values ​​that can be processed within the control unit 9.

[0033] <Drive circuit> The drive circuit 34 transmits a signal input from the control unit 9 to the switches SW314 to SW316 of the power conversion circuit 3. The drive circuit 34 has a function of switching on and off each of the switches SW314 to SW316 based on a PWM signal input from the control unit 9. The function of the drive circuit 34 may be included in the control unit 9.

[0034] <Cooler> The cooler 4 cools the smoothing capacitor 22, the choke coil 23, and the power conversion circuit 3. The cooler 4 may be, for example, a water-cooled cooler. Specifically, the cooler 4 may be configured such that a hose connects the water-cooled cooler to a water pump driven by an electric motor.

[0035] A cooling medium such as water, oil, or LLC (Long Life Coolant) flows into the water-cooled cooler using a water pump. After cooling the object to be cooled and absorbing heat, the cooling medium is cooled by the radiator and returns to the water pump.

[0036] The cooler 4 is not limited to a water-cooled cooler, but may be an air-cooled cooler, etc. The DC power supply 21 may be cooled by the cooler.

[0037] <Rotation angle detector> The rotation angle detector 5 is attached to the rotating electric machine 1 and detects position information indicating the rotor position of the rotating electric machine 1, specifically, the rotation angle θm of the rotor. The rotation angle detector 5 may be configured using, for example, a resolver. Alternatively, the rotation angle detector 5 may use an optical sensor, a Hall element, a sensor using the giant magnetoresistance (GMR) effect, or a sensor using the tunnel magnetoresistance (TMR) effect. Alternatively, the rotation angle may be detected sensorlessly using an induced voltage.

[0038] The rotation angle detector 5 is configured to convert the detected rotation angle θm into an electrical angle θe based on the number of pole pairs of the permanent magnet of the rotating electric machine 1. The rotation angle θm and the electrical angle θe are acquired by the control unit 9.

[0039] <Rotating electrical machine temperature detector> The rotating electric machine temperature detector 6 detects the temperature of the rotating electric machine 1. The rotating electric machine temperature detector 6 may be configured by a thermistor or the like, and may include a permanent magnet temperature detector 25 that detects the temperature of a permanent magnet provided in the motor, and a coil temperature detector 26 that detects the temperatures of the U-phase coil 11, the V-phase coil 12, and the W-phase coil 13 (the permanent magnet temperature detector 25 and the coil temperature detector 26 are not shown).

[0040] The rotating electric machine temperature detector 6 may detect the coil temperature by calculation using a thermal network. The detection value temp_mag by the permanent magnet temperature detector 25 and the detection value temp_coil by the coil temperature detector 26 of the rotating electric machine 1 are acquired by the control unit 9 (detection values ​​temp_mag and temp_coil are not shown).

[0041] If a temperature detector cannot be directly attached to the permanent magnet provided in the rotating electric machine 1, the temperature of the permanent magnet may be estimated from the temperature of another part. For example, the control unit 9 may indirectly estimate the temperature of the permanent magnet based on the detected value temp_coil of the coil temperature detector, the operating conditions of the power conversion circuit 3, etc.

[0042] <Switching element temperature detector> The switching element temperature detector 7 may include a temperature detector that detects the temperature of each of SW311 to SW316. Specifically, for example, the temperature temp_Tj of the switching elements detected by the switching element temperature detector 7 is a detected value obtained by individually detecting the temperature of each of SW311 to SW316 using a temperature detector installed near SW311 to SW316.

[0043] Each leg, i.e., each pair of upper and lower SWs, may be provided with a temperature detector for detecting the temperatures of the U-phase leg, V-phase leg, and W-phase leg. Alternatively, a single temperature detector may be provided for detecting the temperature of the entire SW311 to SW316. Furthermore, the temperature of the entire SW311 to SW316 may be measured indirectly. The detected values ​​of the temperature detectors are acquired by the control unit 9.

[0044] <Command generator> The command generator 8 is a device that generates control commands for controlling the rotating electric machine 1 and outputs the control commands to the control unit 9. The control commands output by the command generator 8 are periodically transmitted to the control unit 9 via communication.

[0045] Examples of control commands for controlling the rotating electric machine 1 include a torque command, a current command, and a voltage command. In this embodiment, a torque command Trq* is used as the control command. The control command is also referred to as an output command value. The function of the command generator may be incorporated into the control unit 9.

[0046] <Hardware configuration of the control unit> 2 is a hardware configuration diagram of a control unit 9 of a power conversion device 100 according to an embodiment. In this embodiment, the control unit 9 is a control device that controls the power conversion device 100. Each function of the control unit 9 is realized by a processing circuit provided in the control unit 9. Specifically, the control unit 9 includes, as processing circuits, an arithmetic processing device 80 (computer) such as a CPU (Central Processing Unit), a storage device 81 that exchanges data with the arithmetic processing device 80, an input circuit 82 that inputs external signals to the arithmetic processing device 80, and an output circuit 83 that outputs signals from the arithmetic processing device 80 to the outside.

[0047] The arithmetic processing device 80 may be an application-specific integrated circuit (ASIC), an integrated circuit (IC), a digital signal processor (DSP), a field programmable gate array (FPGA), various logic circuits, various signal processing circuits, etc. Furthermore, a plurality of the same or different types of arithmetic processing devices 80 may be provided, with each device performing a different process. The storage device 81 may be a random access memory (RAM) configured to be able to read and write data from the arithmetic processing device 80, or a read-only memory (ROM) configured to be able to read data from the arithmetic processing device 80. The input circuit 82 includes the rotation angle detector 5, the rotating electrical machine temperature detector 6, the switching element temperature detector 7, the command generator 8, and an amplifier circuit 33 for the current detector 32. The input circuit 82 is connected to various sensors and switches, and includes interface circuits such as an AD converter and an input circuit that inputs output signals from these sensors and switches to the arithmetic processing device 80. The output circuit 83 includes a drive circuit 34, and is connected to electrical loads such as switching elements and actuators. The output circuit 83 is equipped with interface circuits such as a drive circuit that converts and outputs output signals from the arithmetic processing unit 80 to these electrical loads, and a communication circuit.

[0048] Each function of the control unit 9 is realized by the arithmetic processing device 80 executing software (programs) stored in a storage device 81 such as a ROM, and working in cooperation with other hardware of the control unit 9 such as the storage device 81, an input circuit 82, and an output circuit 83. Setting data such as thresholds and judgment values ​​used by the control unit 9 is stored in the storage device 81 such as a ROM as part of the software (programs).

[0049] Each function installed inside the control unit 9 may be configured as a software module, or may be configured as a combination of software and hardware.

[0050] <Controller function block> 3 is a functional block diagram showing the signal processing process of the control unit 9 of the power conversion device 100 according to the embodiment. The control unit 9 has a rotation speed calculation unit 91, a torque / current command conversion unit 93, a three-phase to two-phase conversion unit 94, a voltage command generation unit 95, a two-phase to three-phase conversion unit 96, a duty conversion unit 97, and a PWM signal generation unit 98.

[0051] The rotation speed calculation unit 91 integrates the rotation angle θm acquired from the rotation angle detector 5 and converts it into the rotation speed N of the rotating electrical machine 1. The rotation speed calculation unit 91 outputs the rotation speed N to the torque / current command conversion unit 93.

[0052] The torque / current command conversion unit 93 calculates a d-axis current command Id* and a q-axis current command Iq* from the rotation speed N of the rotating electric machine 1, the torque command Trq*, the temperature temp_Tj of the switching element, and the rotation angle θm acquired from the rotation speed calculation unit 91. Specifically, for example, the torque / current command conversion unit 93 is configured to convert these values ​​into the MTPA control d-axis current command Id*_mtpa by using a torque / current command conversion table with the rotation speed N of the rotating electric machine 1 and the torque command Trq* as axes.

[0053] In this embodiment, the torque / current command conversion table is generated so as to minimize the amplitude of the three-phase current, that is, to calculate the MTPA control d-axis current command Id*_mtpa when maximum torque control is applied, but this is not limitative. Furthermore, the torque / current command conversion unit 93 may be configured to calculate the MTPA control d-axis current command Id*_mtpa without using the torque / current command conversion table.

[0054] The d-axis current command Id* and the q-axis current command Iq* are also referred to as the target d-axis current and the target q-axis current. The torque / current command conversion unit 93 will be described in more detail later. The three-phase to two-phase conversion unit 94 acquires the U-phase current Iu, the V-phase current Iv, and the W-phase current Iw, i.e., the three-phase currents Iu, Iv, and Iw, using current detectors 321 to 323. The d-axis current Id and the q-axis current Iq are calculated from the three-phase currents Iu, Iv, and Iw and the electrical angle θe acquired from the rotation angle detector 5.

[0055] The voltage command generation unit 95 calculates a d-axis voltage command Vd* and a q-axis voltage command Vq* by performing current feedback calculations from the d-axis current command Id*, the q-axis current command Iq*, and the d-axis current Id and the q-axis current Iq. Specifically, for example, the voltage command generation unit 95 is configured to calculate the d-axis voltage command Vd* and the q-axis voltage command Vq* so that a current deviation ΔId, which is the deviation between the d-axis current command Id* and the d-axis current Id, and a current deviation ΔIq, which is the deviation between the q-axis current command Iq* and the q-axis current Iq, converge to 0 (ΔId and ΔIq are not shown).

[0056] The two-phase to three-phase conversion unit 96 calculates three-phase voltage commands Vu*, Vv*, and Vw* from the d-axis voltage command Vd* and q-axis voltage command Vq* obtained from the voltage command generation unit 95 and the electrical angle θe obtained from the rotation angle detector 5. It is preferable that the three-phase voltage commands Vu*, Vv*, and Vw* are set to be equal to or less than the DC power supply voltage input to the power conversion circuit 3, i.e., the capacitor voltage Vcon of the smoothing capacitor 22.

[0057] The duty conversion unit 97 acquires the three-phase voltage commands Vu*, Vv*, Vw* from the two-phase to three-phase conversion unit 96. Then, it generates duty commands Du, Dv, Dw for each phase from the three-phase voltage commands Vu*, Vv*, Vw* and the capacitor voltage Vcon of the smoothing capacitor 22. In this way, the duty conversion unit 97 generates a duty command corresponding to the optimal correction control command and outputs the duty command.

[0058] The PWM signal generation unit 98 of the control unit 9 generates PWM signals for controlling the on and off switching of each of SW311 to 316 based on the duty commands Du, Dv, and Dw of each phase obtained from the duty conversion unit 97. Specifically, for example, the PWM signal generation unit 98 generates PWM signals by comparing the duty commands Du, Dv, and Dw of each phase with a carrier wave.

[0059] The PWM signal generation unit 98 of the control unit 9 outputs an on / off signal UH_SW to the switching element 311 via the drive circuit 34. Similarly, an on / off signal UL_SW is output to the switching element 314. Similarly, an on / off signal VH_SW is output to the switching element 312. Similarly, an on / off signal VL_SW is output to the switching element 315. Similarly, an on / off signal WH_SW is output to the switching element 313. Similarly, an on / off signal WL_SW is output to the switching element 316.

[0060] The PWM signal generation unit 98 is configured to generate PWM signals by adopting, for example, a triangular wave comparison method using a triangular wave with equal rising and falling speeds as a carrier wave, and a sawtooth wave comparison method. In the torque / current command conversion unit of the control unit 9, the current phase and current amplitude are controlled within the electrical angle period according to the temperature of the switching element. The electrical angle period is the rotation period in electrical angle.

[0061] <d-axis current, q-axis current coordinates> FIG. 4 is a diagram showing the current phase Φ and current amplitude Ia of the power conversion device 100 in coordinates with the q-axis current Iq on the vertical axis and the d-axis current Id on the horizontal axis. In FIG. 4, the current phase Φ is an angle in the counterclockwise direction with respect to the d-axis as a reference. Also, the magnitude of the vector obtained by adding the q-axis current Iq and the d-axis current Id is the current amplitude Ia, which is represented by Equation (1). The q-axis current Iq and the d-axis current Id are each represented by Equation (2) using the current amplitude Ia and the current phase Φ. When controlling the current phase Φ and the current amplitude Ia in the present disclosure, it is possible to control the current phase Φ and the current amplitude Ia by the d-axis current Id and the q-axis current Iq based on Equation (1) and Equation (2).

[0062]

number

[0063]

number

[0064] Torque τ can be calculated using equation (3) using the number of pole pairs p of the rotating electrical machine 1, the magnetic flux φmag per pole pair, the d-axis inductance Ld, and the q-axis inductance Lq. The equal torque curves in Figure 4 can be calculated based on equation (3) and represent the combinations of d-axis current and q-axis current that can produce equal torque at any electrical angle. Furthermore, torque and current amplitude can be expressed by equation (4), which is obtained by substituting equation (2) into equation (3).

[0065] <Torque and phase> Here, the magnet magnetic flux φmag, d-axis inductance Ld, and q-axis inductance Lq may be treated as functions of the electrical angle θe. Point P in Fig. 4 is the point on the equal torque curve that indicates the target torque where the current amplitude is smallest, and is the minimum current operating point. Control in which the d-axis current and q-axis current that result in the current phase and current amplitude like point P are used as current command values ​​is defined as maximum torque control.

[0066] When maximum torque control is applied, maximum torque is obtained with the current amplitude Ia, which is the minimum effective value. The vector OP (solid line) on the Id-Iq coordinate system indicates minimum current operation. The current phase at this time is defined as the minimum current phase φMT.

[0067] In the power conversion device 100 of the present disclosure, when controlling the current phase Φ and current amplitude Ia on a constant torque, the current phase Φ and current amplitude Ia that result in constant torque are selected based on equation (3). By controlling the current phase Φ and current amplitude Ia on a constant torque, the effect of maintaining drive without reducing torque is achieved. The current phase Φ is gradually changed in the leading and lagging directions by a predetermined angle with respect to the vector OP (solid line) on the Id-Iq coordinate system at the same torque. As a result, the current phase Φ changes within a predetermined angle range, changing the range from vector OP1 (dashed line) to vector OP2 (dashed line).

[0068]

number

[0069]

number

[0070] <Constant torque operation> FIG. 5 is a characteristic diagram of the rotation speed and torque of the rotating electric machine 1 according to the embodiment. FIG. 5 shows the characteristics of the rotating electric machine 1 with torque on the vertical axis and rotation speed on the horizontal axis. The characteristics of the rotating electric machine 1 can be divided into a constant torque line where torque is constant with respect to rotation speed, and a constant output line where output is constant with respect to rotation speed. The constant torque line is determined by the maximum current that the power conversion circuit 3 can output. On the other hand, the constant output line is determined by the maximum voltage and maximum current that the power conversion circuit 3 can output.

[0071] The power conversion device 100 of the present disclosure is used at any rotation speed and torque in the characteristic diagram of the rotating electric machine 1. In the control unit 9, the current phase Φ and the current amplitude Ia are controlled according to the rotation speed within an electrical angle cycle in accordance with the temperature temp_Tj of the switching elements 311 to 316, thereby enabling control that utilizes the difference in temperature rise between low rotation speed and high rotation speed, and achieving the effect of sustaining drive over a wide range.

[0072] That is, when the temperature temp_Tj of the switching elements 311 to 316 is higher than a predetermined temperature threshold Tth, the current phase Φ of the current command value can be alternately changed in the leading and lagging directions by a predetermined angle around the minimum current operating point (the predetermined temperature threshold Tth is not shown). By doing so, it is possible to prevent an overheating state due to current concentration in a switching element of a specific phase. In this embodiment, the period during which the current phase is alternately changed may be shorter than one electrical angle period.

[0073] Furthermore, if the temperature temp_Tj of the switching elements 311 to 316 is higher than a predetermined temperature threshold Tth, the current phase Φ of the switching element in the hottest leg may be changed. This is significant because it can suppress the temperature rise of the switching element that is most overheated. The temperature of the switching element in that leg can then be kept below the operating limit temperature and allowable temperature. Here, the temperature threshold at which the performance of the switching element may deteriorate or its lifespan may be shortened is referred to as the "operating limit temperature," and the temperature threshold at which control to reduce torque and current amplitude Ia is applied is referred to as the "allowable temperature." This control is not limited to the temperature of the switching elements. It can also be performed to reduce the current in the hottest phase among the coils of the rotating electric machine 1 and distribute the current to other phases. In this case, a temperature detector can be installed for each coil of the rotating electric machine 1, and the current amplitude and current phase can be changed according to the detected temperature.

[0074] <Temperature rise at low rotation speed> 6 is a diagram showing the relationship between the current flowing in a specific power supply line (for example, U-phase) of the power conversion device 100 according to the embodiment and the temperature Tj of a specific switching element (for example, switching elements 311 and 314). The diagram shows the current flowing in the switching element at points P and Q, which are operating points shown in FIG. 5, and the temperature Tj of the switching element at that time, as intervals P and Q (here, the temperature temp_Tj of the switching element is abbreviated as temperature Tj).

[0075] The current amplitude Ia is equal between the currents flowing through switching elements 311 to 316 at points P and Q, assuming maximum torque control is applied. The current frequency is proportional to the rotation speed, so the current fluctuation frequency is higher at point P, where the rotation speed is higher, than at point Q. The temperature Tj of the switching elements can be calculated from the loss caused by the current flowing through switching elements 311 to 316 and the heat capacity and thermal resistance of switching elements 311 to 316.

[0076] As shown in Figure 6, the temperature of the switching elements fluctuates at the same frequency as the frequency of the current flowing through them. This is because the current flowing through any one switching element is a half-wave of the phase current, and losses also occur at the same cycle. Here, the current amplitude Ia of the current flowing through the switching elements is the same in sections P and Q, so the average value (average temperature) of the temperature Tj of the switching elements is the same.

[0077] On the other hand, the amount of change in the temperature Tj of the switching element is different between intervals P and Q. This is because the temperature Tj of the switching element is determined by the loss due to the current, thermal resistance, and heat capacity, and changes transiently in response to the loss. Here, point A in FIG. 6 represents the point where the current amplitude is maximum, and point B represents the point where the temperature of the switching element is maximum. The difference in time between points A and B is the delay time of the temperature of the switching element relative to the loss, and in this disclosure, this delay time is referred to as the "response time." The thermal resistance and heat capacity of a switching element have specific values, and the thermal resistance and heat capacity can be calculated by analysis (calculation) and experiment (actual measurement).

[0078] Therefore, the response time can be obtained in advance through analysis (calculation) and experiment (measurement). When the current cycle is sufficiently small compared to this response time, i.e., when the frequency is high, heat is generated during the diffusion of heat caused by losses in the switching element one cycle before, causing the temperature to rise. After a sufficient amount of time has passed, the heat dissipation and heat generation balance out, and the average temperature converges to a constant value.

[0079] Therefore, in section P where the current fluctuation frequency is high, the temperature Tj is leveled out and converges to near the average temperature. In contrast, in section Q where the current fluctuation frequency is low, the period of loss caused by current fluctuations is close to the response time. The next heat generation occurs after the heat gained in the previous period has been sufficiently dissipated. In addition, the time over which losses are added is longer, causing the temperature of the switching element to rise. Therefore, in areas where the current frequency is low, such as section Q, the temperature fluctuations of the switching element become greater.

[0080] In this case, if the current phase Φ is constant, a situation may occur in which the operating temperature or allowable temperature of a switching element is exceeded when current continues to flow to a specific switching element and the temperature Tj of the switching element reaches a maximum, as shown in Figure 6. If the temperature Tj of the switching element exceeds the operating temperature limit, the performance of the switching element may deteriorate and its lifespan may be shortened.

[0081] When the temperature exceeds the allowable temperature, the current amplitude Ia can be reduced to prevent deterioration in the performance of the switching elements and shortened lifespan, but this would result in a decrease in torque. In the configuration of the present disclosure, the current amplitude and current phase Φ are changed within the electrical angle period in response to the temperature rise of the switching elements or the rotation speed of the rotating electric machine 1, thereby making it possible to expand the driving range while maintaining torque. In other words, it becomes possible to maintain continuous driving while maintaining torque.

[0082] In other words, when the rotation speed is lower than a predetermined rotation speed threshold, the current phase Φ is changed in the advance and lag directions from the minimum current operating point by a predetermined angle, and the current command value is changed on the constant torque curve. This changes the switching elements that are energized, making it possible to prevent current concentration in a specific switching element. By controlling the current amplitude Ia and current phase Φ according to the current fluctuation frequency, it is possible to level out the temperature of each element at low rotation speeds.

[0083] For example, when the temperature Tj of the switching elements is higher than a predetermined temperature threshold, and the rotation speed of the rotating electric machine 1 (or the fluctuation frequency of the drive current) is lower than a first rotation speed threshold, the current phase Φ may be varied at a frequency twice the rotation speed. Furthermore, when the temperature Tj of the switching elements is higher than the predetermined temperature threshold, and the rotation speed of the rotating electric machine 1 (or the fluctuation frequency of the drive current) is lower than a second rotation speed threshold that is lower than the first rotation speed threshold, the current amplitude Ia and the current phase Φ may be varied at a predetermined frequency.

[0084] <Temperature reduction by changing the current phase> 7 is a diagram showing the electrical angle θe, switching element temperature Tj, U-phase current Iu, current phase Φ, and torque T of power conversion device 100 according to the embodiment. In Fig. 7, the horizontal axis represents the electrical angle θe, and the vertical axis represents the switching element temperature Tj of SW311, U-phase current Iu, current phase Φ, and torque T.

[0085] The temperature threshold value Tth of the switching element in Fig. 7 may be a value calculated in advance through thermal analysis (calculation) or experiment (actual measurement). For example, the temperature threshold value Tth can be set taking into account the temperature rise that is delayed by the response time relative to the operating limit temperature or allowable temperature of the switching element. It is also possible to set the temperature threshold value Tth by temperature derating.

[0086] The dashed lines in Fig. 7 show the temperature waveform Tjps, current waveform Iups, and current phase Φps when the current amplitude Ia and current phase Φ are constant. Point θa shown in Fig. 7 is the electrical angle when the detection value of switching element temperature detector 7 exceeds the temperature threshold value Tth. Point θb is the electrical angle when the detection value of switching element temperature detector 7 falls below the temperature threshold value Tth.

[0087] In the section from point θa to point θb, as shown in FIG. 7, the current phase shown in FIG. 7 is changed to Φpd so that the absolute value of the instantaneous current decreases while maintaining the torque as shown. By changing the current phase to Φpd and suppressing the current flowing through SW311 to a current waveform Iupd, the loss generated in SW311 is reduced. As a result, the switching element temperature Tj takes on a temperature waveform Tjpd and its peak decreases. The control unit 9 has an arbitrary temperature threshold Tth for the temperature Tj of any switching element, and controls the current phase Φ and current amplitude Ia to lower the switching element temperature Tj when the detected switching element temperature Tj exceeds the temperature threshold Tth. The control unit 9 achieves the effect of lowering the temperature Tj of any switching element while maintaining the torque T.

[0088] <Instantaneous current limit> The control unit 9 controls the power conversion circuit 3 so as to reduce the maximum absolute value of the instantaneous current of each phase. In this disclosure, the current at which the absolute value of each phase current is maximum at any electrical angle is referred to as the "maximum instantaneous current," and the phase through which the maximum instantaneous current flows is referred to as the "maximum current phase." Here, a method for deriving the current phase Φ that suppresses the maximum instantaneous current will be described. The current flowing in each phase at any electrical angle θe and current phase Φ can be calculated using equation (4).

[0089] Equation (5) is obtained by substituting equation (2) into equation (4). Furthermore, the relationship between the current amplitude Ia and the current phase on the equal torque curve when Ld ≠ Lq and cosφ ≠ 0 can be expressed by equation (7) from equation (4). Furthermore, when Ld = Lq or cosφ = 0, equation (8) is obtained. Equations (7) and (8) express the relationship between the current amplitude and the current phase. The relationship between the phase current and the current phase at any electrical angle can be expressed by substituting equation (7) or equation (8) into equation (5).

[0090] Fig. 8 shows the absolute values ​​of the three-phase current when the current phase is set to the minimum current phase φMT and an arbitrary current phase φa. In the example of Fig. 8, the current phase φa is set to a value smaller than the minimum current phase φMT. Fig. 8 also shows the section θU in which the U phase is the maximum current phase in the three-phase current when the current phase is the minimum current phase φMT.

[0091] For example, when checking the instantaneous current of the U phase at any electrical angle θ1 within the section θU, the instantaneous current at the current phase φa is smaller than that at the minimum current phase. When checking the absolute values ​​of the instantaneous current of the other phases at the current phase φa, the V phase is larger but smaller than the U phase, and the W phase is similarly small. Therefore, in the example shown, the maximum instantaneous current can be reduced by controlling the current so that the current phase is φa at any electrical angle θ1. Therefore, it is sufficient to select a current phase that reduces the maximum instantaneous current for each electrical angle. Furthermore, by selecting the current amplitude and current phase that suppress the maximum instantaneous current according to the switching element temperature Tj, it is possible to suppress the switching element temperature Tj and reduce the average temperature rise of the switching elements.

[0092]

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[0093]

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[0094]

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[0095]

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[0096] <Suppression of instantaneous current> 9 is a diagram showing the current and the temperature Tj of the switching elements when maximum torque control and instantaneous current suppression are applied in the power conversion device 100 according to the embodiment. The instantaneous current suppression controls the current phase Φ and the current amplitude Ia so that the maximum instantaneous current that constantly flows through the switching elements is minimized. This makes it possible to suppress the maximum value of the temperature Tj of the switching elements compared to when maximum torque control is applied.

[0097] <Temperature difference of switching element> 10 is a diagram showing a comparison of the temperature Tj of the switching elements when maximum torque control and instantaneous current suppression are applied during high rotation of the power conversion device 100 according to the embodiment. In the high rotation speed region where the current fluctuation frequency is sufficiently large relative to the response time, the temperature Tj of the switching elements is lower when maximum torque control is applied than when instantaneous current suppression, in which the effective value of the current is large.

[0098] The control unit 9 of the power conversion device 100 of the present disclosure has a temperature difference threshold Tdth for the temperature difference ΔTj of the temperatures Tj of the switching elements in any one cycle of each of the switching elements 311 to 316 (the temperature difference ΔTj and the temperature difference threshold Tdth are not shown).When the temperature difference ΔTj exceeds the temperature difference threshold Tdth, the control unit 9 controls the current phase Φ and the current amplitude Ia so as to reduce the temperature difference ΔTj.

[0099] With this configuration, when the temperature difference ΔTj of each switching element in any one cycle of the switching element is equal to or less than the temperature difference threshold Tdth at high rotation speeds, maximum torque control is applied to suppress the average temperature. On the other hand, at low rotation speeds, instantaneous current suppression is performed to reduce the maximum instantaneous current flowing through the switching element, taking into account the response time of the switching element.

[0100] This makes it possible to suppress the maximum temperature of the switching elements, thereby achieving both the effect of suppressing the maximum temperature of the switching elements at low rotation speeds and the effect of suppressing the average temperature of the switching elements at high rotation speeds, and making it possible to sustain driving over a wide operating range.

[0101] When there is no temperature difference between the cyclic average temperatures of the switching elements, the maximum temperature of all switching elements can be suppressed by selecting the current amplitude Ia and current phase Φ so that the maximum instantaneous current value of the maximum current phase is reduced. However, in reality, due to cooling considerations, it is not possible to cool all switching elements uniformly, so there may be temperature imbalances among the switching elements of some phases. In this case, there will be phases where the cyclic average temperature of the switching elements is high and the switching element temperature exceeds the allowable temperature, while in other phases it does not. Here, only the phases where the switching element temperature exceeds the allowable temperature are subject to instantaneous current suppression, and the current amplitude Ia and current phase Φ are selected so that the maximum instantaneous current is reduced. The current not subject to instantaneous current suppression can be calculated using equation (5) from the selected current phase Φ and electrical angle.

[0102] Fig. 11 is a diagram showing the relationship between the currents flowing through the U-phase, V-phase, and W-phase power supply lines of the power conversion device 100 according to the embodiment and the temperatures Tj of the switching elements 311, 315, and 316. In section A of Fig. 11, only the temperature Tj_UH of the switching element 311 exceeds the allowable temperature, while the temperature Tj_VL of the switching element 315 and the temperature Tj_WL of the switching element 316 have a margin above the allowable temperature.

[0103] In contrast, section B of Figure 11 shows the current waveform and the temperature of the switching element at that time when the U-phase current is selected as the target, i.e., the U-phase is considered to be the phase with the highest current at all times, and the current amplitude Ia and current phase Φ are selected to reduce the maximum instantaneous current of the U-phase in order to suppress heat generation in the switching element 311 that has exceeded the allowable temperature. As shown in section B of Figure 11, the U-phase current decreases, so the temperature of the switching element decreases. However, the current increases in the V-phase and W-phase, so the temperature of the switching element rises. As a result, the maximum temperature values ​​of the switching elements of all phases are uniform, allowing continuous operation.

[0104] 12 is a diagram showing the relationship between the currents flowing in the U-phase, V-phase, and W-phase power supply lines of power conversion device 100 according to the embodiment and the temperatures Tj of switching elements 311, 315, and 316, similar to Fig. 11. In Fig. 12, in section A, the temperature Tj_UH of switching element 311 and the temperature Tj_VL of switching element 315 exceed the allowable temperature, and only the temperature Tj_WL of switching element 316 has a margin above the allowable temperature. In this case, the current amplitude Ia and the current phase Φ are selected so that the instantaneous maximum current is reduced for the U-phase and the V-phase.

[0105] Section B in Figure 12 shows the current waveforms and switching element temperatures when control is performed to reduce the instantaneous maximum currents of the U and V phases. As the maximum instantaneous currents of the U and V phases decrease, the temperatures of switching element 311 and switching element 315 decrease. In contrast, the current of the W phase increases, causing the temperature of switching element 316 to increase. As a result, the maximum temperatures of the switching elements of all phases become uniform, allowing continuous operation.

[0106] Furthermore, the current flowing through the switching elements that reach a relatively high temperature may be reduced by controlling the neutral point potential of the power conversion device 100, and the current of the phase with a temperature margin may be increased to level out the temperature of the switching elements. By controlling the neutral point potential and suppressing the instantaneous current, it is possible to reduce the current amplitude of the maximum current phase and the instantaneous current, and it is possible to more effectively level out the temperature of the switching elements.

[0107] Fig. 13 is a diagram showing the current when maximum torque control is applied and when instantaneous current suppression is applied at an electrical angle θe of the power conversion device 100. When instantaneous current suppression is applied, the current amplitude Ia and current phase Φ are controlled so that the maximum absolute value of the current flowing through the continuous switching element is reduced, resulting in the waveform shown by the solid line in Fig. 13. Near the point where the current at point R is at its maximum, the current value when maximum torque control is applied and the current when control to suppress the instantaneous current is applied match at point S, which is 30 degrees away from point R.

[0108] Here, in the section from point R to point S, the current when instantaneous current is suppressed is smaller than the current value when maximum torque control is applied. This reduces loss and temperature. Therefore, taking into account the response time of the switching element as tj, if the command frequency f satisfies equation (9), a greater effect of suppressing maximum temperature can be achieved by controlling the current phase Φ and current amplitude Ia so that the maximum instantaneous current is reduced.

[0109] That is, the control unit 9 changes the current command value so that the absolute value of the instantaneous current decreases when the frequency of the current command value is equal to or less than the reciprocal of the response time tj of the switching element multiplied by 12. This makes it possible to obtain a greater effect of suppressing the maximum temperature.

[0110]

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[0111] The control unit 9 controls the current amplitude Ia and current phase Φ so that the maximum instantaneous current is minimized at each position within the electrical angle cycle. In FIG. 13, it is also possible to switch between instantaneous suppression control and maximum torque control at each position within the electrical angle cycle. By switching control according to the temperature of the switching element at each position within the electrical angle cycle, it is possible to suppress the temperature of any switching element. This provides the effect of leveling the temperature of the switching elements.

[0112] In the power conversion device 100 according to the embodiment, the power conversion circuit 3 has six switching elements made of silicon carbide connected in a full bridge configuration. The use of silicon carbide in the switching elements enables high-speed switching in the power conversion device 100. This also enables the temperature of the switching elements to be leveled across a wide operating range, from low rotation speeds to high rotation speeds. Furthermore, since it is possible to set the temperature threshold of the switching elements high, it becomes possible to maintain torque and continue continuous operation for a longer period of time.

[0113] It is also possible to apply a multilevel inverter to the power conversion circuit of the power conversion device described in this embodiment. When a multilevel inverter is applied, the number of switching elements increases, so that the effect of suppressing the maximum temperature of any switching element can be more significantly obtained.

[0114] Positive-side switching elements 311, 312, and 313 are connected to the positive side of DC power supply 21, and negative-side switching elements 314, 315, and 316 are connected to the negative side of DC power supply 21, with the positive-side switching elements and negative-side switching elements being connected in series. A power supply line is connected from this series connection point to the coil of rotating electric machine 1. A power conversion circuit 3 is provided with a plurality of legs in which these lines are provided. A control unit 9 calculates a current command value defined by a current amplitude Ia and a current phase Φ on the d-axis coordinate and the q-axis coordinate, based on the command value.

[0115] <Method for controlling a rotating electrical machine> In a first step, a current command value is determined at a current amplitude and current phase that result in a minimum current operating point that realizes a target torque, and on / off control is performed on switching elements 311 to 316 of power conversion circuit 3 based on the current command value. Then, in a second step, when the temperature of switching elements 311 to 316 detected by switching element temperature detector 7 that detects the temperature of switching elements 311 to 316 of power conversion circuit 3 is higher than a predetermined temperature threshold Tth, the current phase Φ of the current command value is changed in the advance and lag directions of a predetermined angle within an electrical angle cycle from the minimum current operating point, thereby changing the current command value on the constant torque curve.

[0116] <Configuration of rotating electric machine> In the power conversion device 100 according to the embodiment, the rotating electric machine 1 is composed of a stator 14 around which coils 11 to 13 are wound, and a rotor 17 that rotates around a rotating shaft 18. The rotor 17 is characterized by having permanent magnets arranged on its surface.

[0117] FIG. 14 shows a cross-sectional view of a rotating electric machine 1 in which permanent magnets are arranged on the surface of a rotor 17. Coils 11 to 13 are wound in air gaps 16 around teeth 15 of a stator 14. Because a surface-type permanent magnet rotating electric machine is driven solely by magnetic torque, torque changes with respect to current amplitude Ia and current phase Φ are smaller than those of a rotating electric machine driven by reluctance torque. This allows for a constant torque curve to be obtained while minimizing changes in current amplitude Ia, making it possible to further expand the control range for current phase Φ and current amplitude Ia. Therefore, a surface-type permanent magnet rotating electric machine can more effectively level the temperature of switching elements.

[0118] The control method for the power conversion device 100 according to the embodiment includes a rotating electric machine 1 driven by a power conversion circuit 3, a power conversion circuit 3 that converts DC power input from a power supply unit 2 using switching elements 311 to 316 to output AC power, and a control unit that controls the power conversion circuit, and the switching elements have temperature detectors that detect the temperatures of the switching elements and control the current phase and current amplitude within an electrical angle period according to the temperature of the switching elements.

[0119] Although exemplary embodiments are described in this disclosure, the various features, aspects, and functions described in the embodiments are not limited to the application of a particular embodiment, but may be applied to the embodiments alone or in various combinations. Therefore, countless variations not illustrated are anticipated within the scope of the technology disclosed in the specification. For example, variations in, addition to, or omission of at least one component are included.

[0120] Various aspects of the present disclosure are summarized below as appendices.

[0121] (Appendix 1) a power conversion circuit having a plurality of legs each provided with a positive-side switching element connected to a positive side of a DC power supply, a negative-side switching element connected to a negative side of the DC power supply, and a power supply line connecting a connection point at which the positive-side switching element and the negative-side switching element are connected in series to a coil of a rotating electric machine; a temperature detector for detecting the temperature of a switching element of the power conversion circuit; and a control unit that calculates a current command value defined by a current amplitude and a current phase in d-axis current and q-axis current coordinates based on a command value, controls the on / off of switching elements of the power conversion circuit based on the current command value, and changes the current amplitude and the current phase within an electrical angle cycle in accordance with the temperature of the switching element detected by the temperature detector. (Appendix 2) The power conversion device according to claim 1, wherein the control unit, when the temperature of the switching element detected by the temperature detector is higher than a predetermined temperature threshold, alternately changes the current phase of the current command value in a leading direction and a lagging direction by a predetermined angle around a minimum current operating point that realizes a target torque. (Appendix 3) 3. The power conversion device according to claim 2, wherein the control unit changes the current command value along an equal torque curve when changing the current amplitude and the current phase of the current command value. (Appendix 4) 4. The power conversion device according to claim 2, wherein the control unit changes the angle by which the current phase is changed in accordance with the rotation speed of a rotating electric machine driven by the power conversion circuit. (Appendix 5) 5. The power conversion device according to claim 2, wherein the control unit changes a current amplitude and a current phase of the current command value when the rotational speed of the rotating electric machine driven by the power conversion circuit is lower than a predetermined rotational speed threshold. (Appendix 6) 6. The power conversion device according to any one of claims 1 to 5, wherein the control unit changes the current amplitude and the current phase so that an absolute value of an instantaneous current of the current command value decreases when the temperature of the switching element detected by the temperature detector is higher than a predetermined temperature threshold. (Appendix 7) 7. The power conversion device according to claim 6, wherein the control unit changes the current amplitude and the current phase so that an absolute value of an instantaneous current of the current command value decreases when the frequency of the current command value is equal to or less than the reciprocal of 12 times the response time of the switching element. (Appendix 8) the temperature detector is provided for each leg of the power conversion circuit, The power conversion device according to any one of appendixes 1 to 7, wherein, when a difference in temperature of the switching elements detected by the temperature detector is greater than a predetermined temperature difference threshold, the control unit changes a current amplitude and a current phase of a current command value for each coil of the rotating electric machine to make the difference in temperature of the switching elements equal to or less than the temperature difference threshold. (Appendix 9) 9. The power conversion device according to claim 8, wherein the control unit changes a current amplitude and a current phase of a current command value of a leg having a switching element with the highest temperature detected by the temperature detector, thereby reducing a current flowing through the switching element of the leg. (Appendix 10) the temperature detector is provided for each leg of the power conversion circuit, The power conversion device according to any one of appendixes 1 to 9, wherein the control unit changes the current amplitude and the current phase of the current command value of the leg in which the temperature of the switching element detected by the temperature detector is higher than a predetermined temperature threshold, so as to keep the temperature of the switching element equal to or lower than a permissible temperature at which output limiting is started to prevent performance degradation. (Appendix 11) 11. The power conversion device according to claim 1, wherein the switching elements of the power conversion circuit use silicon carbide semiconductors. (Appendix 12) A rotating electric machine comprising a stator around which a coil is wound and a rotor on whose surface a permanent magnet is arranged; A rotating electrical machine including the power conversion device according to any one of appendixes 1 to 11. (Appendix 13) a first step in which, for a power conversion circuit having a plurality of legs each having a positive-side switching element connected to a positive side of a DC power supply, a negative-side switching element connected to a negative side of the DC power supply, and an external connection point connecting the positive-side switching element and the negative-side switching element in series and connected to a coil of a rotating electric machine, a control unit calculates a current command value defined by a current amplitude and a current phase in a d-axis coordinate and a q-axis coordinate based on a command value, determines the current command value at a current amplitude and a current phase that result in a minimum current operating point that realizes a target torque, and controls on and off of the switching elements of the power conversion circuit based on the current command value; a second step of changing the current phase of the current command value on an equal torque curve by changing the current phase of the current command value from the minimum current operating point by a predetermined angle in a leading direction and a lagging direction within an electrical angle period, when a temperature of a switching element detected by a temperature detector that detects a temperature of the switching element of the power conversion circuit is higher than a predetermined temperature threshold. [Explanation of symbols]

[0122] 1 rotating electric machine, 2 power supply unit, 3 power conversion circuit, 7 switching element temperature detector, 9 control unit, 11, 12, 13 coil, 21 DC power supply, 100 power conversion device, 200 rotating electric machine device, 311, 312, 313, 314, 315, 316 switching elements

Claims

1. a power conversion circuit having a plurality of legs each provided with a positive-side switching element connected to a positive side of a DC power supply, a negative-side switching element connected to a negative side of the DC power supply, and a power supply line connecting a connection point at which the positive-side switching element and the negative-side switching element are connected in series to a coil of a rotating electric machine; a temperature detector for detecting the temperature of a switching element of the power conversion circuit; and a control unit that calculates a current command value defined by a current amplitude and a current phase in d-axis current and q-axis current coordinates based on a command value, controls on and off of switching elements of the power conversion circuit based on the current command value, and changes the current amplitude and the current phase within an electrical angle cycle in accordance with temperatures of the switching elements detected by the temperature detector.

2. 2. The power conversion device according to claim 1, wherein, when the temperature of the switching element detected by the temperature detector is higher than a predetermined temperature threshold, the control unit alternately changes the current phase of the current command value in a leading direction and a lagging direction by a predetermined angle around a minimum current operating point that realizes a target torque.

3. The power conversion device according to claim 2 , wherein the control unit changes the current command value along an equal torque curve when changing the current amplitude and the current phase of the current command value.

4. The power conversion device according to claim 2 , wherein the control unit changes the angle by which the current phase is changed in accordance with the rotational speed of a rotating electric machine driven by the power conversion circuit.

5. 3. The power conversion device according to claim 2, wherein the control unit changes the current amplitude and the current phase of the current command value when the rotational speed of the rotating electric machine driven by the power conversion circuit is lower than a predetermined rotational speed threshold value.

6. 2. The power conversion device according to claim 1, wherein the control unit changes the current amplitude and the current phase so that an absolute value of an instantaneous current of the current command value decreases when the temperature of the switching element detected by the temperature detector is higher than a predetermined temperature threshold value.

7. 7. The power conversion device according to claim 6, wherein the control unit changes the current amplitude and the current phase so that an absolute value of an instantaneous current of the current command value decreases when a frequency of the current command value is equal to or less than an inverse of 12 times a response time of the switching element.

8. the temperature detector is provided for each leg of the power conversion circuit, 2. The power conversion device according to claim 1, wherein, when a difference in temperature of the switching elements detected by the temperature detector is greater than a predetermined temperature difference threshold, the control unit changes a current amplitude and a current phase of a current command value for each coil of the rotating electric machine to make the difference in temperature of the switching elements equal to or less than the temperature difference threshold.

9. 9. The power conversion device according to claim 8, wherein the control unit changes a current amplitude and a current phase of a current command value for a leg having a switching element with the highest temperature detected by the temperature detector, thereby reducing the current flowing through the switching element of the leg.

10. the temperature detector is provided for each leg of the power conversion circuit, 2. The power conversion device according to claim 1, wherein the control unit changes the current amplitude and the current phase of the current command value for a leg in which the temperature of the switching element detected by the temperature detector is higher than a predetermined temperature threshold, so as to keep the temperature of the switching element at or below a permissible temperature at which output limitation is started to be started in order to prevent performance degradation.

11. The power conversion device according to claim 1 , wherein the switching elements of the power conversion circuit are made of silicon carbide semiconductors.

12. A rotating electric machine comprising a stator around which a coil is wound and a rotor on whose surface a permanent magnet is arranged; A rotating electrical machine comprising the power conversion device according to any one of claims 1 to 10.

13. a first step in which, for a power conversion circuit having a plurality of legs each having a positive-side switching element connected to a positive side of a DC power supply, a negative-side switching element connected to a negative side of the DC power supply, and an external connection point connecting the positive-side switching element and the negative-side switching element in series and connected to a coil of a rotating electric machine, a control unit calculates a current command value defined by a current amplitude and a current phase in a d-axis coordinate and a q-axis coordinate based on a command value, determines the current command value at a current amplitude and a current phase that result in a minimum current operating point that realizes a target torque, and controls on and off the switching elements of the power conversion circuit based on the current command value; a second step of changing the current phase of the current command value on an equal torque curve by changing the current phase of the current command value from the minimum current operating point by a predetermined angle in a leading direction and a lagging direction within an electrical angle period, when a temperature of a switching element detected by a temperature detector that detects a temperature of the switching element of the power conversion circuit is higher than a predetermined temperature threshold.

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