Rotating electric machine control device

Abstract

To provide a rotary electric machine control device capable of performing both an over-voltage protection at the time of separating an inverter circuit from a DC power source, and a prevention of an inverter operation stop due to an erroneous detection.SOLUTION: A rotary electric machine control device comprises: a power conversion circuit having multiple legs each having a switching element at a positive electrode side, a switching element at a negative electrode side, and an external connection point connecting both switching elements in series and connected to a rotary electric machine; a capacitor connected to the positive electrode and the negative electrode; a voltage sensor detecting voltage between the positive electrode and the negative electrode; a temperature sensor detecting temperature of the power conversion circuit; and a control unit controlling ON / OFF of the switching elements of the power conversion circuit and executing a protection control when the voltage detected by the voltage sensor is larger than determination voltage calculated based on temperature detected by the temperature sensor.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present application relates to a rotating electrical machine control device. [Background technology]

[0002] Electric vehicles using rotating electric machines as a driving force source are known. In electric vehicles, the rotating electric machine is operated in a power running mode to generate driving torque during travel, and is operated in a regenerative mode to generate regenerative braking torque during braking.

[0003] The drive system of an electric vehicle has a DC power supply consisting of a secondary battery such as a lithium-ion battery, an inverter circuit consisting of a capacitor and multiple semiconductor switches and connected to the DC power supply, and a rotating electric machine connected as a load to the inverter circuit.

[0004] In a drive system using a three-phase synchronous rotating electric machine, an inverter circuit is configured by connecting three sets of series circuits, each set having an upper-stage switching element and a lower-stage switching element connected in series, in parallel with a DC power supply, and the midpoint of each of the three sets of series circuits is connected to the inputs of the U-phase, V-phase, and W-phase of the three-phase synchronous rotating electric machine, respectively.

[0005] The drive system of an electric vehicle is provided with a switching device that disconnects the battery, which is a DC power source, from the inverter circuit as needed to protect the battery from overvoltage or overcurrent. Conditions for opening this switching device include when the battery voltage exceeds a predetermined value during regenerative operation of the rotating electric machine, when the battery voltage falls below a predetermined value due to battery depletion, or when the current flowing through the battery exceeds a predetermined value. The switching device may also be opened due to a vehicle malfunction or collision.

[0006] In such a drive system, the switching device may be opened during regenerative operation of the rotating electric machine, disconnecting the inverter circuit from the battery. Even in a drive system without a switching device, the inverter circuit may be disconnected from the battery due to a break in the power line between the battery and the inverter circuit.

[0007] When the inverter circuit is disconnected from the battery, the regenerative power flowing from the rotating electric machine to the inverter circuit cannot be used to charge the battery, but is instead used to charge the inverter circuit's capacitor, which may result in overvoltage being applied to the capacitor and switching elements, potentially damaging them.

[0008] In such a case, when the inverter circuit is disconnected from the DC power supply, the input voltage of the inverter circuit reaches a high voltage state that would not occur under normal operation. This voltage rise can be detected to determine whether the inverter circuit has been disconnected from the DC power supply. A technique has been disclosed in which, when it is determined that the inverter circuit has been disconnected from the DC power supply, a six-switch open process is executed to turn off all switching elements in the inverter circuit and stop inverter operation. This prevents the capacitor from regenerating power (see, for example, Patent Document 1).

[0009] Another countermeasure is disclosed in which, when it is determined that the inverter circuit and the DC power supply are disconnected, instead of executing the six-switch open process, all of the upper-stage switching elements or all of the lower-stage switching elements of the inverter circuit are turned on, and three-phase short-circuiting process is executed to short-circuit each phase of the rotating electric machine. By doing so, it is possible to prevent the capacitor from regenerating power (for example, Patent Document 2).

[0010] However, in either of the above protective operations, there is a delay between when the inverter circuit determines that it has been disconnected from the DC power source based on its input voltage and when the protective operation is actually performed. During this time, the voltage applied to the capacitor continues to rise due to the inflow of regenerative power. Furthermore, the inverter circuit continues switching until protection is performed. As a result, the switching element is subjected to a surge voltage during switching in addition to the capacitor voltage increased by the regenerative power.

[0011] Therefore, in order to protect the switching elements from overvoltage, it is necessary to quickly determine that the inverter circuit has been disconnected from the DC power supply, and for this reason, it is desirable to set the threshold voltage for the input voltage of the inverter circuit as low as possible.

[0012] On the other hand, if the above-mentioned determination voltage is set too low, a false detection of an overvoltage may occur due to voltage ripples that occur during normal inverter operation, and a protective action may be taken to stop the inverter operation even though there is no abnormality. In order to prevent the inverter from stopping due to such a false detection, it is desirable to set the determination voltage of the input voltage of the inverter circuit, which determines whether the inverter circuit is disconnected from the DC power supply, to as high a value as possible.

[0013] As described above, the threshold voltage for the inverter circuit's input voltage, which determines whether the inverter circuit is disconnected from the DC power source, creates a trade-off between rapid overvoltage protection and preventing false detection. Satisfying both of these requirements requires reducing switching surge voltages, reducing voltage ripples that occur during normal inverter operation, suppressing the voltage rise across the capacitor terminals during regenerative operation, and increasing the voltage resistance of circuit components. These factors lead to larger component sizes and higher costs, making it difficult to achieve smaller and less costly inverter circuits. This poses a major challenge to miniaturizing inverter circuits for electric vehicles, which must be placed in the limited space available in the vehicle.

[0014] Furthermore, the voltage resistance of components and the capacitance of capacitors change depending on the temperature of the components. Therefore, the threshold voltage of the inverter circuit input voltage, which determines whether the inverter circuit is disconnected from the DC power supply, must be determined taking into account the lowest voltage resistance of the components and the lowest capacitance of the capacitor within the operating temperature range. To ensure overvoltage protection and false detection prevention in all possible cases, components would need to be larger and more expensive. [Prior art documents] [Patent documents]

[0015] [Patent Document 1] Japanese Patent Application Publication No. 10-117490 [Patent Document 2] Patent Publication No. 2021-97476 Summary of the Invention [Problem to be solved by the invention]

[0016] Patent Documents 1 and 2 describe a technique for stopping switching to protect inverter circuit components such as inverter switching elements and capacitors when it is determined that an inverter circuit has been disconnected from a DC power supply. However, they do not describe how to address the trade-off between quickness of determination and prevention of erroneous detection when determining a predetermined determination voltage for comparing the input voltage of the inverter circuit to detect disconnection of the inverter circuit from a DC power supply.

[0017] The present invention has been made to solve the above-mentioned problems, and has an object to provide a rotating electrical machine control device that can simultaneously protect against overvoltage when the inverter circuit is disconnected from the DC power supply and prevent inverter operation from stopping due to erroneous detection, without requiring increased costs due to increased component size or improved voltage resistance of circuit components. [Means for solving the problem]

[0018] The rotating electrical machine control device according to the present application comprises: a power conversion circuit having a plurality of legs, each of which is provided with a positive-side switching element connected to a positive electrode of a DC power supply, a negative-side switching element connected to a negative electrode of the DC power supply, and an external connection point that connects the positive-side switching element and the negative-side switching element in series and is connected to a rotating electric machine; a capacitor connected to the positive and negative terminals of the power conversion circuit; a voltage sensor for detecting a voltage between the positive and negative poles of the power conversion circuit; a temperature sensor for detecting the temperature of the power conversion circuit; a capacitor temperature sensor for detecting the temperature of the capacitor; and, A rotating electrical machine control device including a control unit that controls on / off of a switching element of a power conversion circuit, The upper limit of the protection voltage threshold determined from the withstand voltage of the switching element has a positive correlation with the temperature of the power conversion circuit, a lower limit of a protection voltage threshold determined from a voltage ripple superimposed on a voltage applied to a capacitor during operation of the power conversion circuit has a positive correlation with the temperature of the capacitor; The control unit detects that the voltage detected by the voltage sensor 、 The temperature detected by the temperature sensor The capacitor temperature detected by the capacitor temperature sensor Based on The protection voltage threshold must be greater than the lower limit and smaller than the upper limit. If the voltage is greater than the calculated judgment voltage, protective control is executed to turn off all switching elements, or to turn on all positive side switching elements and turn off all negative side switching elements, or to turn off all positive side switching elements and turn on all negative side switching elements. [Effects of the Invention]

[0019] According to the rotating electric machine control device of the present application, by setting the judgment voltage taking into account the temperature characteristics of the circuit components, it is possible to obtain a rotating electric machine control device that can achieve both overvoltage protection when the inverter circuit is disconnected from the DC power supply and prevention of inverter operation stopping due to erroneous detection, without requiring increased costs due to increased component size or improved voltage resistance performance. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a configuration diagram of a rotary electric machine control device according to a first embodiment. [Figure 2]2 is a hardware configuration diagram of a control unit of the rotary electric machine control device according to the first embodiment. FIG. [Figure 3] 4 is a time chart showing a DC bus voltage during a protective operation of the rotary electric machine control device according to the first embodiment. [Figure 4] 4 is a diagram showing temperature characteristics with respect to withstand voltage of a switching element of the rotary electric machine control device according to the first embodiment. FIG. [Figure 5] 4 is a diagram showing temperature characteristics relative to the capacitance of a capacitor in the rotary electric machine control device according to the first embodiment. FIG. [Figure 6] 5 is a flowchart showing the processing of a control unit of the rotary electric machine control device according to the first embodiment. [Figure 7] 5 is a diagram showing the setting of a protection voltage threshold value of the rotary electric machine control device according to the first embodiment. FIG. [Figure 8] FIG. 10 is a configuration diagram of a rotary electric machine control device according to a second embodiment. [Figure 9] 10 is a flowchart showing the processing of a control unit of a rotary electric machine control device according to a second embodiment. [Figure 10] FIG. 10 is a diagram showing the setting of a carrier frequency switching temperature threshold value of the rotary electric machine control device according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, preferred embodiments of the rotary electric machine control device according to the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals.

[0022] 1. First Embodiment A rotating electric machine, which is a concept that includes electric motors and generators, converts electric power into driving force and operates as a power generator. Rotating electric machines can also operate as a regenerative machine by converting driving force back into electric power without changing their structure. Electric motors and generators basically have the same structure, and both are capable of both power and regenerative operation. In this specification, a rotating electric machine will be described as a rotating device that has the functions of both an electric motor and a generator. The term "rotating electric machine" may be read as either an electric motor or a generator.

[0023] An inverter circuit that drives a rotating electric machine converts DC power from a DC power source into AC power by turning on and off multiple semiconductor switches at a predetermined carrier frequency, and adjusts the torque and rotation speed of the rotating electric machine (load). Depending on the operating conditions, the rotating electric machine can also function as a generator, charging the DC power source with regenerative power generated by the generator. Note that efficient permanent magnet three-phase synchronous rotating electric machines are often used as rotating electric machines for electric vehicles.

[0024] The inverter circuit is provided with legs in which upper-stage switching elements and lower-stage switching elements are connected in series. Three sets of legs are connected in parallel to a DC power supply, and the midpoints of the three sets of series circuits are connected to the inputs of the U-phase, V-phase, and W-phase of the three-phase synchronous rotating electric machine, respectively.

[0025] By sequentially turning on and off the switching elements provided for each phase of the inverter circuit, AC power with a phase difference of 120 degrees is supplied to each phase of the three-phase synchronous rotating electric machine, thereby driving the three-phase synchronous rotating electric machine. Hereinafter, unless otherwise specified, the rotating electric machine refers to a three-phase synchronous rotating electric machine. The operating principle of the inverter circuit is generally well known, so a description thereof will be omitted here.

[0026] <Configuration of a rotating electrical machine control device> FIG. 1 is a configuration diagram of a rotating electric machine control device 1 according to a first embodiment. FIG. 1 shows a DC power supply 90 that supplies DC power to an inverter circuit 20 and is charged with regenerative power. The DC power supply 90 may be, for example, a lead battery or a lithium ion battery. The inverter circuit 20 is connected to coils of each phase of a rotating electric machine 10 that is to be controlled. The entire combination of the rotating electric machine control device 1 and the rotating electric machine 10 constitutes a rotating electric machine device 100.

[0027] The rotating electric machine control device 1 is connected to a DC power source 90 by DC buses 21a and 21b via a power switch 70. Driving power or regenerative power is exchanged with the DC power source 90. The rotating electric machine control device 1 is also connected to a rotating electric machine 10 by an AC bus 2, and driving power or regenerative power is exchanged with the rotating electric machine 10.

[0028] The rotating electric machine 10 is equipped with a rotation angle sensor 60 that detects the rotation speed from the rotation angle of the rotor of the rotating electric machine 10. The rotating electric machine 10 drives a load to rotate and is also capable of regenerating the rotational energy of the load as electrical energy. As the rotating electric machine 10, a three-phase brushless motor such as a permanent magnet three-phase AC synchronous motor or the like is used.

[0029] The rotating electric machine control device 1 is also composed of an inverter circuit 20 and a control unit 40. The inverter circuit 20 is composed of a capacitor 22 connected between DC buses 21a and 21b on the power supply input side, a voltage sensor 23 that detects the voltage between the DC buses 21a and 21b of the inverter circuit 20, and a power conversion circuit 30. The power conversion circuit 30 is composed of a plurality of switching elements 31, 32, 33, 34, 35, and 36. The rotating electric machine control device 1 is equipped with the power conversion circuit 30 that performs DC / AC power conversion, a current detection unit 24 that detects the current flowing in the AC bus 2 of the rotating electric machine 10, and a temperature sensor 50 that detects the temperature of the power conversion circuit 30.

[0030] Capacitor 22 has the functions of suppressing ripples in the DC bus voltage, lowering the power supply impedance of inverter circuit 20 to improve the AC current driving capability of inverter circuit 20, and absorbing surge voltage. Voltage sensor 23 divides, for example, the voltage between DC buses 21a and 21b using a voltage dividing resistor to a voltage that can be read by control unit 40, and outputs DC bus voltage information to control unit 40.

[0031] <Power conversion circuit> The power conversion circuit 30 is configured by a generally known circuit in which six switching elements are connected in a full bridge configuration. That is, as shown in Fig. 1, switching elements 31 and 32, switching elements 33 and 34, and switching elements 35 and 36 are connected in series with each other and are each connected in parallel to a DC power supply 90.

[0032] The midpoints of switching element 31 and switching element 32 are connected to the U-phase winding of rotating electric machine 10, the midpoints of switching element 33 and switching element 34 are connected to the V-phase winding of rotating electric machine 10, and the midpoints of switching element 35 and switching element 36 are connected to the W-phase winding of rotating electric machine 10. Here, switching elements 31, 33, and 35 connected to the positive electrode side of DC power supply 90, i.e., DC bus 21a, are referred to as upper-stage switching elements, and switching elements 32, 34, and 36 connected to the negative electrode side of DC power supply 90, i.e., DC bus 21b, are referred to as lower-stage switching elements. A pair of an upper-stage switching element and a lower-stage switching element connected in series is referred to as a leg.

[0033] As the switching element, for example, a MOSFET (Metal-Oxide-Semiconductor Field-Effect-Transistor) as shown in Fig. 1 is generally used. Alternatively, an IGBT (Insulated Gate Bipolar Transistor) may also be used. Note that a free wheel diode (FWD) is formed in parallel with each MOSFET of the switching element, with the forward direction being the direction from the negative side to the positive side of the DC power supply 90, i.e., the direction from the lower side to the upper side.

[0034] The current detection unit 24 detects the rotating electric machine current flowing through the AC bus 2, converts the current into a voltage, and outputs rotating electric machine current information to the control unit 40. In Fig. 1, as an example, a configuration is shown in which the current is detected using a shunt resistor. Note that the current detection unit 24 may alternatively be a current sensor using a Hall element.

[0035] The power switch 70 controls the exchange of power between the DC power supply 90 and the rotating electric machine control device 1. Specifically, the power switch 70 is controlled to an open state when the voltage of the DC power supply 90 exceeds a set value during regenerative operation of the rotating electric machine 10. The power switch 70 is also controlled to an open state when the voltage of the DC power supply 90 falls below a set value due to consumption of the DC power supply 90. The power switch 70 is then controlled to an open state when the current flowing through the DC power supply 90 exceeds a set value, when a vehicle malfunction is detected, or when a vehicle collision is detected. The power switch 70 is controlled to an open state by a system higher than the rotating electric machine control device 1 (not shown). The power switch 70 may be configured to be controlled by the control unit 40.

[0036] The rotation angle sensor 60 detects the rotation angle of the rotor of the rotating electrical machine 10 using a resolver or an encoder. The rotation angle of the rotor detected by the rotation angle sensor 60 is output to the control unit 40. The control unit 40 uses the rotation angle of the rotor as a rotation speed.

[0037] The temperature sensor 50 is configured, for example, by a thermistor, and detects the temperature of the power conversion circuit 30. The temperature sensor 50 may be provided in the inverter circuit 20. If the entire rotating electric machine control device 1 is housed in a single housing, the temperature sensor 50 may be provided in another location within the housing. The temperature detected by the temperature sensor 50 is output to the control unit 40. Alternatively, the temperature sensor 50 may be a temperature sensor using a diode.

[0038] <Control unit> The control unit 40 is responsible for overall control of the rotating electrical machine control device 1, has an arithmetic processing device, and can execute the functions of a switching control signal generation unit 41, a protection voltage threshold determination unit 42, and an abnormal state determination unit 43. It also receives operation commands from the outside. Examples of operation commands include target torque, target rotation speed, target current, and target voltage.

[0039] A switching control signal generator 41 generates an on / off control signal for controlling the on / off of a plurality of switching elements 31 to 36 that constitute the power conversion circuit 30. A protection voltage threshold determiner 42 determines a threshold voltage that is used by an abnormal state determiner 43 to determine whether or not an abnormal state (overvoltage state) exists, based on the temperature of the power conversion circuit 30 detected by a temperature sensor 50. This threshold voltage is hereinafter referred to as a protection voltage threshold Vppc.

[0040] The abnormal state determination unit 43 determines whether the DC power supply is in an abnormal state, such as being disconnected, based on the DC bus voltage information input from the voltage sensor 23 and the protection voltage threshold Vppc input from the protection voltage threshold determination unit 42. If it is determined that the DC power supply is in an abnormal state, a protective operation is performed. Examples of the protective operation include a six-switch open process that turns off all switching elements 31 to 36 of the power conversion circuit 30, a process that turns on all positive-side switching elements 31, 33, and 35 and turns off all negative-side switching elements 32, 34, and 36, and a process that turns off all positive-side switching elements 31, 33, and 35 and turns on all negative-side switching elements 32, 34, and 36. These processes are also referred to as protective control.

[0041] The switching control signal generation unit 41 receives inputs of DC bus voltage information from the voltage sensor 23, rotation angle information (rotational speed) of the rotating electric machine 10 from the rotation angle sensor 60, rotating electric machine current information from the current detection unit 24, and an abnormality response processing command from the abnormal state determination unit 43. The switching control signal generation unit 41 outputs on / off control signals to each of the switching elements 31 to 36 of the power conversion circuit 30 in accordance with this input information and the torque command value and current command value of the rotating electric machine 10 input from outside as operation commands.

[0042] The switching elements 31 to 36 are each turned on and off by an on / off control signal from a switching control signal generation unit 41. The switching elements 31 to 36 convert DC power into AC power and supply it to the rotating electric machine 10. The switching elements 31 to 36 also convert regenerative power generated in the regenerative state of the rotating electric machine 10 into DC power and charge it into the DC power supply 90.

[0043] <Hardware configuration of the control unit> FIG. 2 is a hardware configuration diagram of the control unit 40 of the rotating electric machine control device 1 according to the first embodiment. The hardware configuration diagram in FIG. 2 can also be applied to the control unit 40a. Here, the control unit 40 will be used as a representative example for explanation. In this embodiment, each function of the control unit 40 is realized by a processing circuit provided in the control unit 40. Specifically, as shown in FIG. 2, the control unit 40 includes, as processing circuits, an arithmetic processing device 44 (computer) such as a CPU (Central Processing Unit), a storage device 45 that exchanges data with the arithmetic processing device 44, an input device 46 that inputs external signals to the arithmetic processing device 44, and an output device 47 that outputs signals from the arithmetic processing device 44 to the outside.

[0044] The arithmetic processing device 44 may include an application-specific integrated circuit (ASIC), an integrated circuit (IC), a digital signal processor (DSP), a field programmable gate array (FPGA), various logic circuits, and various signal processing circuits. Furthermore, the arithmetic processing device 44 may include a plurality of devices of the same or different types, each performing a different process. The storage device 45 may include a random access memory (RAM) configured to be able to read and write data from the arithmetic processing device 44, a read-only memory (ROM) configured to be able to read data from the arithmetic processing device 44, a flash memory, etc. The input device 46 is connected to various sensors and switches, such as the voltage sensor 23, the temperature sensor 50, and the rotation angle sensor 60, and includes an A / D converter and the like that inputs output signals from these sensors and switches to the arithmetic processing device 44. The output device 47 is connected to electrical loads, such as the switching elements 31 to 36, and includes a drive circuit and the like that converts and outputs control signals from the arithmetic processing device 44 to these electrical loads.

[0045] Each function of the control unit 40 is realized by the arithmetic processing unit 44 executing software (programs) stored in a storage device 45 such as a ROM, and cooperating with other hardware of the control unit 40, such as the storage device 45, input device 46, and output device 47. Setting data such as thresholds and judgment values ​​used by the control unit 40 are stored in the storage device 45 such as a ROM as part of the software (programs). The functions of the components of the control unit 40 will be described below. Each function of the control unit 40 may be configured as a software module, or may be configured as a combination of software and hardware. The software may be firmware built into the device, or may be frequently updated software that is read from an external device each time it is executed.

[0046] <Controller Functions> The arithmetic processing device 44 reads and executes processing programs stored in the storage device 45, thereby realizing the functions of each part of the control unit 40. That is, the control unit 40 executes a processing step by the arithmetic processing device 44 for taking in a signal input from the voltage sensor 23, which detects the DC bus voltage of the inverter circuit 20, to the abnormal state determination unit 43 and the switching control signal generation unit 41. Then, the control unit 40 executes a processing step by the arithmetic processing device 44 for taking in a signal input from the current detection unit 24, which detects the AC bus current of the inverter circuit 20, and the rotation angle sensor 60, which detects the rotation angle of the rotating electric machine 10, to the switching control signal generation unit 41.

[0047] Furthermore, the control unit 40 executes a processing step, using the arithmetic processing device 44, for inputting a signal input from the temperature sensor 50 that detects the temperature of the power conversion circuit 30 into the protection voltage threshold determination unit 42. Then, the control unit 40 executes a processing step, using the arithmetic processing device 44, for outputting an abnormality response processing command from the abnormal state determination unit 43 to the switching control signal generation unit 41. Furthermore, the control unit 40 executes a processing step, using the arithmetic processing device 44, for outputting an on / off signal, generated by the switching control signal generation unit 41, to the switching element of the power conversion circuit 30 via the output device 47. The storage device 45 stores programs related to these executed processing steps.

[0048] It can be said that these processing programs cause a computer to execute the operating procedures or methods of the control unit 40. Here, the storage device 45 may be, for example, a RAM, a ROM, a flash memory, or a non-volatile or volatile semiconductor memory such as an EPROM or an EEPROM, a magnetic disk, a flexible disk, an optical disk, a compact disk, a minidisk, a DVD, or the like.

[0049] The storage device 45 stores programs for executing the above-mentioned processing steps, as well as data acquired from a higher-level system, data at the time of an abnormality occurrence, and the processing results thereof. The input device 46 corresponds to some functions of the switching control signal generation unit 41, the protection voltage threshold determination unit 42, and the abnormal state determination unit 43, and acquires information output from a higher-level system (not shown). The output device 47 corresponds to some functions of the switching control signal generation unit 41.

[0050] A feature of the rotating electric machine control device 1 according to this embodiment 1 is that the control unit 40 is provided with a protection voltage threshold determination unit 42, which determines a protection voltage threshold Vppc for determining whether the power supply side is in an abnormal state based on the temperature of the power conversion circuit 30 acquired by the temperature sensor 50.

[0051] This configuration makes it possible to prevent damage to the switching elements due to overvoltage when the inverter circuit 20 is disconnected from the DC power supply 90, and to prevent the inverter operation from stopping due to erroneous detection. At this time, there is no need to increase the size of components or increase costs due to improving the voltage resistance performance of components. This will be explained in more detail below.

[0052] As described above, there are cases where the power switch 70 is opened during regenerative operation of the rotating electric machine 10. There is also a possibility that the power line between the DC power supply 90 and the inverter circuit 20 is broken, causing the inverter circuit 20 to be disconnected from the DC power supply 90. In these cases, the regenerative power flowing from the rotating electric machine 10 to the inverter circuit 20 cannot be charged to the DC power supply 90, and is charged instead to the capacitor 22 of the inverter circuit 20. As a result, the voltage applied to the capacitor 22 increases, which may result in problems such as overvoltage damaging inverter circuit components such as switching elements and capacitors.

[0053] As a countermeasure, there is a method in which, when the voltage value detected by voltage sensor 23 exceeds protection voltage threshold Vppc, it is determined that the power supply side is in an abnormal state and a protective operation is performed to stop inverter operation. Protective operations include a six-switch open process that turns off all switching elements 31 to 36 of power conversion circuit 30, a process that turns on all positive-side switching elements 31, 33, 35 and turns off all negative-side switching elements 32, 34, 36, or a process that turns off all positive-side switching elements 31, 33, 35 and turns on all negative-side switching elements 32, 34, 36.

[0054] <Power supply voltage behavior during protection operation> FIG. 3 is a time chart showing the DC bus voltage Vdc applied to the DC buses 21a, 21b connected to the DC power supply 90 during a protective operation of the rotating electric machine control device 1 according to the first embodiment. The vertical axis represents voltage [V], and the horizontal axis represents time [s]. At time T1, the DC power supply 90 is disconnected. At time T2, the DC bus voltage Vdc detected by the voltage sensor 23 exceeds the protection voltage threshold Vppc, which is detected by the control unit 40. The control unit 40 then executes a protective operation and instructs the switching elements to stop switching. This protective operation is executed at time T3. After time T3, the switching operations of the switching elements are stopped. Time T3 is also referred to as the time when protective control is executed.

[0055] A delay time Td occurs between when the control unit 40 determines that the DC power supply side is in an abnormal state and when it executes a protective operation, due to the characteristics of the sensor and control circuit. During the delay time Td, regenerative power flows into the capacitor 22, so the DC bus voltage Vdc applied to the capacitor continues to rise. At time T3, the DC bus voltage Vdc rises to the protective operation execution DC voltage Vpex.

[0056] Until the protective operation is performed, the control unit 40 continues to cause the power conversion circuit 30 to perform inverter operation. As a result, a surge voltage occurs in the switching elements 31 to 36 due to the switching operation, and a surge voltage Vsco at the time of DC power supply cut-off is applied, which is the DC voltage Vpex at the time of protective operation, which is the capacitor voltage increased by regenerative power, plus a surge voltage width Vrco due to switching, as the maximum voltage applied to each switching element.

[0057] To protect the switching elements from this overvoltage, it is necessary to consider the rise in capacitor voltage after an abnormality occurs and the impact of switching surges when regenerative operation is performed at maximum regenerative power. Taking these factors into consideration, it is necessary to set the protection voltage threshold Vppc so that the voltage applied to each component does not exceed its respective withstand voltage.

[0058] <Normal ripple> On the other hand, during normal operation of the inverter, the voltage applied to the capacitor 22 is superimposed not only on the normal DC power supply voltage Vn supplied from the DC power supply 90 but also on a normal ripple voltage width Vrn resulting from the inverter operation of the inverter circuit 20. If the capacitor voltage superimposed with this ripple (maximum voltage Vsn during normal ripple application) exceeds the above-mentioned protection voltage threshold Vppc, it is determined that the power supply side is in an abnormal state even though it is not, and a protection operation is performed to stop the inverter operation.

[0059] To prevent such erroneous detection, it is necessary to set the protection voltage threshold Vppc so that the voltage applied to the capacitor 22 does not exceed the protection voltage threshold Vppc even when the maximum voltage ripple is superimposed when the maximum voltage is supplied from the DC power supply 90.

[0060] In other words, the protection voltage threshold Vppc must be set between the upper and lower limits, with an upper limit determined from the perspective of overvoltage protection and a lower limit determined from the perspective of preventing erroneous detection. Figure 3 shows the behavior of the inverter circuit when the protection voltage threshold Vppc is set near the upper limit of the above-mentioned settable range of the protection voltage threshold Vppc. The lower limit of the protection voltage threshold is the maximum voltage Vsn under normal ripple application. After the DC power supply 90 is turned off, the DC bus voltage Vdc rises to the DC power supply cut-off surge voltage Vsco. In Figure 3, the DC power supply cut-off surge voltage Vsco reaches near the switching element's withstand voltage Vws. The protection voltage threshold Vppc at which the DC power supply cut-off surge voltage Vsco reaches the switching element's withstand voltage Vws is the upper limit of the protection voltage threshold.

[0061] The protection voltage threshold Vppc must be set between the upper and lower limits of the protection voltage threshold. However, there may be cases where it is not possible to set the protection voltage threshold Vppc, such as when the upper and lower limits are reversed. In such cases, it may be necessary to raise the upper limit of the protection voltage threshold Vppc by reducing switching surges, suppressing capacitor voltage rises, and strengthening component withstand voltages, or to lower the lower limit of the protection voltage threshold Vppc by reducing voltage ripple.

[0062] Here, the theoretical formula for the switching surge Vsurge, which greatly contributes to determining the protection voltage threshold Vppc, is shown in formula (1).Then, when the DC power supply 90 is cut off and an abnormality occurs on the power supply side, the theoretical formula for the maximum voltage Vcharge applied to the capacitor that increases due to regenerative power is shown in formula (2).Furthermore, the theoretical formula for the voltage ripple Vripple is shown in formula (3).

[0063]

number

[0064]

number

[0065]

number

[0066] Using equation (1), we can calculate the voltage jump due to the current gradient di / dt and inductance Ls during switching. The switching surge in Figure 3 can be calculated using equation (1).

[0067] Equation (2) can be used to calculate the voltage that increases due to regenerative power flowing in during the delay time Td after the DC bus voltage Vdc has risen to the protection voltage threshold Vppc. The DC voltage Vpex when the protection operation is performed in Figure 3 can be calculated from equation (2).

[0068] The fluctuation of the DC bus voltage Vdc due to the current flowing into the capacitor during normal switching operation can be calculated using equation (3). The normal ripple voltage amplitude Vrn in Figure 3 can be obtained from equation (3).

[0069] <Temperature characteristics of switching elements> 4 is a diagram showing temperature characteristics related to the withstand voltage of the switching elements of the rotating electrical machine control device 1 according to the first embodiment. The vertical axis represents voltage [V], and the horizontal axis represents temperature [deg]. The graph shows an example of the relationship between the withstand voltage and temperature of the switching elements used in the power conversion circuit 30.

[0070] Generally, the higher the temperature of a semiconductor switching element, the higher the breakdown voltage becomes, and the lower the temperature of the element, the lower the breakdown voltage becomes. As a result, the upper limit of the protection voltage threshold Vppc becomes lower as the temperature of the element decreases.

[0071] <Temperature characteristics of capacitors> FIG. 5 is a diagram showing the temperature characteristics versus capacitance of the capacitor of the rotating electrical machine control device 1 according to the first embodiment. The vertical axis shows capacitance [F], and the horizontal axis shows temperature [deg]. Inverter circuits 20 mounted on the drive systems of electric vehicles often use film capacitors with a polypropylene base material. The graph shows an example of the relationship between capacitance C and temperature of a film capacitor with a polypropylene base material.

[0072] Generally, with polypropylene film capacitors, the higher the temperature of the element, the lower the capacitance C, and the lower the temperature of the element, the higher the capacitance C. As a result, the voltage ripple caused by inverter operation becomes larger as the element temperature becomes higher, and becomes smaller as the element temperature becomes lower. As a result, the lower limit of the protection voltage threshold Vppc becomes higher as the element temperature becomes higher.

[0073] Consider a case where the protection voltage threshold Vppc is a preset fixed value in the rotating electrical machine control device 1. In this case, it is necessary to prevent damage to switching elements due to overvoltage and to prevent inverter operation from stopping due to erroneous detection under all conditions. To achieve this, it is necessary to take into account the changes in characteristics due to component temperature as described above and set the protection voltage threshold Vppc so that it is valid under the conditions where each characteristic is lowest.

[0074] In other words, the upper limit of the protection voltage threshold Vppc determined from the viewpoint of overvoltage protection must be determined according to low temperatures when the withstand voltage Vws of the switching element is lowest, while the lower limit of the protection voltage threshold Vppc determined from the viewpoint of preventing erroneous detection must be determined according to high temperatures when the capacitance C of the capacitor is low and the voltage ripple is large.

[0075] To appropriately set the protection voltage threshold Vppc under the above constraints, it is necessary to increase the capacitor capacitance C, strengthen the component voltage resistance, and reduce the switching speed, as can be understood from the theoretical equations (1) to (3) above. These measures lead to larger component sizes and higher costs. Reducing the switching speed reduces surges by lowering di / dt, but it also increases switching losses, leading to lower power conversion efficiency and increased heat generation. This leads to larger components and higher costs.

[0076] <Overvoltage protection operation processing> Fig. 6 is a flowchart showing the processing of the control unit 40 of the rotating electrical machine control device 1 according to the first embodiment. The processing shown in Fig. 6 shows the processing of the overvoltage protection operation executed by the arithmetic processing device 44 of the control unit 40. This processing may be executed at predetermined time intervals (for example, every 1 ms). Instead of at predetermined time intervals, it may be executed in response to an event, such as each time A / D conversion of signals detected by the voltage sensor 23 and the temperature sensor 50 is completed.

[0077] 6 starts, and in step S101, the protection voltage threshold determination unit 42 determines the protection voltage threshold Vppc. The protection voltage threshold Vppc is determined based on the detection value of the temperature sensor 50 that detects the temperature of the power conversion circuit 30.

[0078] In step S102, the abnormal state determination unit 43 determines whether the DC bus voltage Vdc detected by the voltage sensor 23 is greater than the protection voltage threshold Vppc. If the DC bus voltage Vdc is greater than the protection voltage threshold Vppc (determination is Yes), a protective operation is performed in step S103, and then the process ends. If the DC bus voltage Vdc is not greater than the protection voltage threshold Vppc (determination is No), normal drive control is performed in step S104, and then the process ends. For the determination in step S102, hysteresis may be applied to the determination value.

[0079] In step S102, it is determined whether the abnormal state on the power supply side is an abnormal state on the power supply side in which it is impossible to charge the regenerative power to the DC power supply 90. Specifically, when the DC bus voltage Vdc detected by the voltage sensor 23 is greater than the protection voltage threshold Vppc determined by the protection voltage threshold determination unit 42, the abnormal state determination unit 43 determines that the power supply side is in an abnormal state and that it is impossible to charge the DC power supply 90 with the regenerative power. In other cases, it determines that the power supply side is in a normal state.

[0080] When the power switch 70 is in an open state, the rotating electric machine 10 performs a regenerative operation, and the regenerative power is stored in the capacitor 22. Then, the voltage across the capacitor 22, i.e., the DC bus voltage Vdc, becomes a high-voltage state that does not occur in normal operation. Alternatively, even if the power switch 70 is in a conductive state, the DC power supply 90 may become a high-voltage state that does not occur in normal operation. In this way, when the regenerative power cannot be charged to the DC power supply 90, it can be determined that the power supply side is in an abnormal state.

[0081] When the abnormal state determination unit 43 determines an abnormal state, an abnormality response processing command is output to the switching control signal generation unit 41. The switching control signal generation unit 41 performs processing such as opening the six switches.

[0082] When the abnormal state determination unit 43 determines that the power supply side is in a normal state, normal drive control is executed. At this time, the rotating electric machine 10 is in a state where it can perform power running or regenerative operation. No abnormal state determination unit 43 outputs an abnormality response processing command to the switching control signal generation unit 41. When no abnormality response processing command is input from the abnormal state determination unit 43, the switching control signal generation unit 41 executes normal drive control of the inverter circuit.

[0083] In the case of normal drive control, a target torque or target current of the rotating electric machine 10 is input as an operation command via a communication line from another control device such as a vehicle ECU (Electronic Control Unit) not shown. Then, the switching control signal generator 41 performs current feedback control using DC bus voltage information input from the voltage sensor 23, rotation angle information of the rotating electric machine 10 input from the rotation angle sensor 60, and rotating electric machine current information input from the current detector 24. The switching control signal generator 41 calculates on / off control signals for each of the switching elements 31 to 36 of the power conversion circuit 30 so as to obtain the target torque or target current of the rotating electric machine 10, and outputs the on / off control signals to the power conversion circuit 30. Note that current feedback control is well known, and therefore a detailed description thereof will be omitted here.

[0084] <Protection voltage threshold setting> The protection voltage threshold Vppc determined by the protection voltage threshold determiner 42 is set to a higher voltage value as the temperature of the power conversion circuit 30 acquired by the temperature sensor 50 increases. As described above, the withstand voltage Vws of the switching element has a positive correlation with temperature. The voltage ripple superimposed on the voltage applied to the capacitor also has a positive correlation with temperature. The upper and lower limits of the protection voltage threshold Vppc determined based on these also have a positive correlation with temperature. Therefore, the protection voltage threshold Vppc is set to a higher value as the temperature of the power conversion circuit 30 increases. This makes it possible to prevent damage to inverter circuit components, such as switching elements and capacitors, due to overvoltage and prevent inverter operation from being stopped due to false detection, without increasing the component size or increasing costs associated with improved withstand voltage performance, compared to when the protection voltage threshold Vppc is a preset fixed value.

[0085] FIG. 7 is a diagram illustrating the setting of the protection voltage threshold Vppc of the rotary electric machine control device 1 according to the first embodiment. In FIG. 7, the surge voltage Vsco at the time of DC power supply disconnection is close to the withstand voltage Vws of the switching element. Therefore, the protection voltage threshold Vppc set in FIG. 7 is a value close to the upper limit of the protection voltage threshold. The maximum voltage Vsn under normal ripple application corresponds to the lower limit of the protection voltage threshold Vppc. This is because if the protection voltage threshold Vppc is set to a value below this, fluctuations in the bus voltage caused by the ripple voltage due to normal inverter operation will be determined to be abnormal.

[0086] In the example shown in Figure 7, if we try to set a constant protection voltage threshold Vppc without changing the parameters according to temperature, the upper limit of the protection voltage threshold at low temperatures within the operating temperature range will be lower than the maximum voltage Vsn during normal ripple application at high temperatures. In other words, it is not possible to set the protection voltage threshold Vppc as a single fixed value. This is because it would be impossible to achieve both overvoltage protection and prevention of false detection.

[0087] The protection operation execution DC voltage Vpex indicates the DC voltage that rises when an overvoltage is detected at the protection voltage threshold Vppc and an overvoltage protection operation is performed, until the switching operation of the switching elements is completely stopped after a delay time Td. The DC power supply cut-off surge voltage Vsco is the voltage obtained by adding the DC power supply cut-off surge voltage width Vrco to this protection operation execution DC voltage Vpex. The rise voltage by which the voltage of the DC power supply 90 rises from the protection voltage threshold Vppc to the protection operation execution DC voltage Vpex over the delay time Td is shown as the delay time rise voltage Vtd.

[0088] To deal with this situation while keeping the protection voltage threshold Vppc at a single fixed value, it is necessary to either reduce the maximum voltage Vsn during normal ripple application by increasing the size of the capacitor, or improve the voltage resistance performance, which would increase the cost of the switching element. The switching speed can also be reduced to reduce the surge voltage. This is because reducing the switching speed reduces the di / dt, which reduces the surge. However, reducing the switching speed increases switching losses, which reduces power conversion efficiency and increases heat generation. This leads to larger components and higher costs. However, this problem can be solved by determining the protection voltage threshold Vppc based on the temperature of the power conversion circuit 30. By setting the protection voltage threshold Vppc to a higher value as the temperature increases, it becomes possible to achieve both overvoltage protection and prevention of false detection without requiring larger components.

[0089] At this time, the protection voltage threshold Vppc is set to an upper limit value that prevents the surge voltage Vsco at DC power supply cut-off, which is the maximum value of the voltage applied to the switching element, from exceeding the withstand voltage Vws of the switching element corresponding to the obtained temperature of the power conversion circuit 30, taking into consideration the rise in capacitor voltage due to regenerative power when an abnormality occurs due to the cut-off of the DC power supply 90 and the influence of switching surges. This makes it possible to minimize the capacitance C of the capacitor while reliably protecting the components from overvoltage, and to suppress cost increases due to larger component sizes and improved withstand voltage performance.

[0090] In this way, with the rotating electrical machine control device 1 according to the first embodiment, the protection voltage threshold Vppc can be set to match the withstand voltage Vws of the components corresponding to the temperature of the power conversion circuit 30. In the low temperature region where the withstand voltage Vws of the switching elements is low but the voltage ripple is small and therefore the maximum voltage Vsn under normal ripple application is also low, the protection voltage threshold Vppc can be set to a low value because there is no risk of operation stopping due to false detection.

[0091] Furthermore, in a high temperature region where the withstand voltage Vws of the switching elements is high and the maximum voltage Vsn under normal ripple application is also high due to a large voltage ripple, the protection voltage threshold Vppc can be set to a high value that does not cause an operation shutdown due to false detection. This makes it possible to obtain a compact rotating electrical machine control device 1 that can achieve both overvoltage protection and false detection prevention without increasing the cost due to increasing the size of components or improving the withstand voltage of components.

[0092] In the description of the first embodiment, the protection voltage threshold Vppc is configured to be set to an upper limit value at which the DC power supply cut-off surge voltage Vsco, which is the maximum value of the voltage applied to the components in consideration of the rise in capacitor voltage due to regenerative power when an abnormality occurs and the influence of switching surges, does not exceed the withstand voltage of the switching elements corresponding to the obtained temperature of the power conversion circuit 30. However, there is no problem in setting the protection voltage threshold Vppc to a value smaller than the upper limit value, as long as the protection voltage threshold Vppc is a value at which the DC power supply cut-off surge voltage Vsco, which is the maximum value of the voltage applied to the components in consideration of the rise in capacitor voltage due to regenerative power when an abnormality occurs and the influence of switching surges, does not exceed the withstand voltage Vws of the switching elements corresponding to the obtained temperature of the power conversion circuit 30.

[0093] In the first embodiment, the temperature of the power conversion circuit 30 acquired by the temperature sensor 50 is preferably the temperature of the switching element. Generally, the heat capacity of a switching element is relatively small, and therefore the response to temperature changes in the rotating electrical machine control device is high, making it possible to provide reliable protection using the detected temperature value. More preferably, the temperature sensor 50 should acquire the temperature of the lowest-temperature switching element in the power conversion circuit 30. As described above, the lower the temperature of a switching element, the lower its withstand voltage. Therefore, from the perspective of overvoltage protection, reliable protection from overvoltage can be achieved by providing protection based on the switching element with the lowest temperature.

[0094] 2. Second Embodiment <Configuration of a rotating electrical machine control device> 8 is a configuration diagram of a rotating electric machine control device 1a according to embodiment 2. In the rotating electric machine control device 1 according to embodiment 1, a protection voltage threshold Vppc is determined based on the temperature of the switching elements acquired by a temperature sensor 50, and is compared with the DC bus voltage Vdc input from a voltage sensor 23 to determine an abnormal state on the power supply side. In contrast, in the rotating electric machine control device 1a according to embodiment 2, a temperature sensor 50a that detects the temperature of the power conversion circuit 30 and a capacitor temperature sensor 50b that detects the temperature of the capacitor 22 are provided in the inverter circuit 20a. The entire combination of the rotating electric machine control device 1a and the rotating electric machine 10 constitutes a rotating electric machine device 100a.

[0095] The control unit 40a acquires temperature information of the switching elements and the capacitors independently, determines the protection voltage threshold Vppc based on the temperatures of the switching elements, and judges whether the power supply is in an abnormal state based on the DC bus voltage Vdc input from the voltage sensor 23, which is the same as in the first embodiment.

[0096] However, the control unit 40a according to the second embodiment further detects the temperature of the capacitor 22 using a capacitor temperature sensor 50b, and determines the carrier frequency switching temperature threshold Tccf based on the capacitor temperature. Then, when the temperature of a switching element falls below the carrier frequency switching temperature threshold Tccf, the switching control signal generation unit 41a performs control to switch the carrier frequency of the on / off control signal output to each switching element 31 to 36 of the power conversion circuit 30.

[0097] The operation of a rotating electrical machine control device 1a according to the second embodiment will be described, focusing on the differences from the first embodiment. In FIG. 8, a DC power supply 90 supplies DC power to an inverter circuit 20a and is charged with regenerative power. A carrier frequency switching temperature threshold determiner 48 and a carrier frequency switching determiner 49 are added to a control unit 40a. The carrier frequency switching temperature threshold determiner 48 determines the carrier frequency switching temperature threshold Tccf based on the detection value of a capacitor temperature sensor 50b. The carrier frequency switching determiner 49 compares the value acquired by the temperature sensor 50a with the carrier frequency switching temperature threshold Tccf, determines whether or not the carrier frequency needs to be switched, and outputs a signal for carrier frequency switching to a switching control signal generator 41a.

[0098] <Overvoltage protection operation processing> Fig. 9 is a flowchart showing the processing of the control unit 40a of the rotating electric machine control device 1a according to the second embodiment. The processing shown in Fig. 9 shows the processing of the overvoltage protection operation executed by the arithmetic processing device 44 of the control unit 40a. This processing may be executed at predetermined time intervals (for example, every 1 ms). Instead of at predetermined time intervals, it may be executed in response to an event, such as each time A / D conversion of signals detected by the voltage sensor 23, the temperature sensor 50a, and the capacitor temperature sensor 50b is completed.

[0099] The flowchart in Fig. 9 differs from the flowchart in Fig. 6 according to the first embodiment only in that steps S111 to S114 are added before step S101. Only the differences will be described.

[0100] 9 starts, and in step S111, the carrier frequency switching temperature threshold determiner 48 determines the carrier frequency switching temperature threshold Tccf. The carrier frequency switching temperature threshold Tccf is determined based on the detection value of the capacitor temperature sensor 50b that detects the temperature of the capacitor 22.

[0101] In step S112, it is determined whether the temperature detected by the temperature sensor 50a that detects the temperature of the power conversion circuit 30 is equal to or lower than the carrier frequency switching temperature threshold Tccf. If the temperature is equal to or lower than the carrier frequency switching temperature threshold Tccf (determination is Yes), in step S113, the carrier frequency is controlled to be switched to the higher frequency side. Specifically, the carrier frequency switching determination unit 49 outputs a signal to instruct the switching control signal generation unit 41a to switch the carrier frequency to the higher frequency side. Then, the process proceeds to step S101.

[0102] If the temperature is not equal to or lower than the carrier frequency switching temperature threshold Tccf (determination is No), the carrier frequency is controlled to the normal frequency in step S114. Specifically, the carrier frequency switching determination unit 49 outputs an instruction signal for the normal carrier frequency to the switching control signal generation unit 41a. Then, the process proceeds to step S101. For the determination in step S112, hysteresis may be applied to the determination value.

[0103] <Controller Functions> The rotating electric machine control device 1a according to the second embodiment enables further miniaturization and cost reduction of the rotating electric machine control device while simultaneously achieving both overvoltage protection and prevention of erroneous detection. The following will explain why the configuration of the second embodiment enables further miniaturization and cost reduction of the rotating electric machine control device while simultaneously achieving both overvoltage protection and prevention of erroneous detection.

[0104] Here, consider the case where only one temperature sensor 50 described in the first embodiment is provided. The voltage resistance performance of the switching element and the magnitude of the voltage ripple of the capacitor 22, which may cause an erroneous detection in the overvoltage protection, are each affected by temperature independently. In an abnormal state on the power supply side where it is impossible to charge the DC power supply 90 with regenerative power from the rotating electric machine 10 (when the DC power supply 90 is disconnected), the switching element is a component to be protected by the overvoltage protection.

[0105] When the temperature of the switching element is high, the withstand voltage Vws is high, so there is little risk of component damage due to overvoltage. However, when the temperature of the capacitor 22 is high, there is a possibility of operation stopping due to false detection due to large voltage ripple. When the temperature of the switching element is low, there is a possibility of component damage due to overvoltage due to low withstand voltage Vws, but when the temperature of the capacitor is low, there is a small voltage ripple, so there is little risk of operation stopping due to false detection. When there is a strong correlation between the temperature of the switching element and the temperature of the capacitor 22, by appropriately setting the protection voltage threshold Vppc according to the temperature, it is possible to obtain a small rotating electrical machine control device 1 that can achieve both overvoltage protection and false detection prevention without requiring larger components or higher costs due to improved withstand voltage.

[0106] This holds true when there is a strong correlation between the temperature of the switching element and the temperature of the capacitor 22. For example, this does not hold true if there is no correlation at all between the temperature of the switching element and the temperature of the capacitor 22, and if there is a case where the temperature of the switching element is low and the temperature of the capacitor 22 is high. In the rotating electric machine control device 1, the power conversion circuit 30 including the switching element and the capacitor 22 are often mounted together in the same housing as the inverter circuit 20. In this case, it is considered that there are few cases where there is a small correlation between the temperature of the switching element and the temperature of the capacitor 22.

[0107] However, when the power conversion circuit and the capacitor are separate, or when the correlation between their temperatures is weak even when they are mounted in the same housing, or when the temperature difference between them is large, a temperature difference will occur between the switching element and the capacitor. Taking this into consideration, a design with sufficient margin is required. In such cases, the effect of obtaining a small rotating electrical machine control device that can achieve both overvoltage protection and false detection prevention without increasing the cost associated with increasing component size and withstanding voltage, which is achieved by appropriately setting the protection voltage threshold Vppc according to the switching element temperature as described in the first embodiment, cannot be fully achieved.

[0108] However, according to the rotating electric machine control device 1a having the configuration of this embodiment 2, the temperature sensor 50a detects the temperature of the switching element, the capacitor temperature sensor 50b acquires the temperature of the capacitor, and the carrier frequency switching temperature threshold determination unit 48 determines the carrier frequency switching temperature threshold Tccf based on the acquired capacitor temperature.

[0109] The carrier frequency switching determination unit 49 compares the temperature of the switching element acquired by the temperature sensor 50a with the carrier frequency switching temperature threshold Tccf, and if the temperature of the switching element is equal to or lower than the carrier frequency switching temperature threshold Tccf, outputs a carrier frequency switching command to the switching control signal generation unit 41. Upon receiving the carrier frequency switching command from the carrier frequency switching determination unit 49, the switching control signal generation unit 41 increases the carrier frequency of the on / off control signal for controlling the on / off of the multiple switching elements 31 to 36 that make up the power conversion circuit 30.

[0110] As shown in equation (3) in the first embodiment, the voltage ripple is proportional to the time integral of the current flowing into the capacitor. Therefore, by increasing the carrier frequency, the time integral of the current flowing into the capacitor during the carrier period decreases. Therefore, by increasing the carrier frequency, it is possible to reduce the voltage ripple value.

[0111] Here, the carrier frequency switching temperature threshold Tccf is set to a higher temperature as the temperature of the capacitor 22 acquired by the capacitor temperature sensor 50b increases. More preferably, when the protection voltage threshold Vppc is set to the lower limit of the protection voltage threshold Vppc determined by the acquired temperature of the capacitor 22, the protection voltage threshold Vppc is set to a lower limit of the switching element temperature at which the DC power supply cut-off surge voltage Vsco, which is the maximum voltage applied to the switching element, does not exceed the switching element withstand voltage Vws determined by the switching element temperature, taking into account the increase in capacitor voltage due to regenerative power when an abnormality occurs and the effects of switching surges. In other words, a switching element temperature is determined at which the protection voltage threshold lower limit determined by the capacitor temperature does not fall below the overvoltage threshold upper limit determined by the switching element temperature. Then, the lower limit of the switching element temperature is set as the carrier frequency switching temperature threshold Tccf.

[0112] <Setting the temperature threshold for carrier frequency switching> 10 is a diagram showing the setting of the carrier frequency switching temperature threshold of the rotary electric machine control device 1a according to Embodiment 2. As described in Embodiment 1, the upper limit of the protection voltage threshold Vppc is determined from the withstand voltage Vws of the switching element, which is determined by the switching element temperature, and the lower limit of the protection voltage threshold Vppc (maximum voltage Vsn under normal ripple application) is determined from the magnitude of the voltage ripple (normal ripple voltage width Vrn) caused by the capacitance C, which is determined by the capacitor temperature.

[0113] There is a strong correlation between the switching element temperature and the capacitor temperature, and there is no problem if the upper and lower limits of the protection voltage threshold Vppc are not reversed. However, there may be cases where the upper and lower limits of the protection voltage threshold Vppc are reversed because the switching element temperature is low and the capacitor temperature is high. In such cases, it becomes impossible to achieve both overvoltage protection and operation shutdown due to false detection.

[0114] In contrast, in the second embodiment, the switching element temperature at which the protection voltage threshold upper limit (the protection voltage threshold Vppc at which the DC power supply disconnection surge voltage Vsco reaches the switching element withstand voltage Vws) matches the protection voltage threshold lower limit (the maximum voltage Vsn under normal ripple application) determined by the acquired capacitor temperature Tsc is calculated backward, and this temperature is set as the carrier frequency switching temperature threshold Tccf. This makes it possible to identify a temperature at which the upper and lower limits of the protection voltage threshold Vppc are reversed—in other words, a temperature at which both overvoltage protection and operation shutdown due to erroneous detection are not achieved. Below this temperature, the carrier frequency is increased to lower the protection voltage threshold Vppc lower limit (the maximum voltage Vsn under normal ripple application), thereby preventing the upper and lower limits of the protection voltage threshold Vppc from being reversed.

[0115] In other words, when the acquired temperature of the switching element is low and the protection voltage threshold Vppc, which is set to a value that can protect the switching element from overvoltage, is small, but the temperature of the capacitor is high and the voltage ripple is large, so there is a possibility of operation stopping due to false detection, by increasing the carrier frequency and reducing the voltage ripple, it is possible to prevent operation stopping due to false detection.

[0116] With this configuration, the protection voltage threshold Vppc is determined based on the temperature of the switching element, thereby reliably protecting the switching element from overvoltage. At the same time, by determining the carrier frequency switching temperature threshold Tccf from the acquired capacitor temperature, it is possible to eliminate the possibility of operation being stopped due to false detection when the protection voltage threshold Vppc determined from the switching element temperature exceeds the maximum voltage Vsn under normal ripple application (protection voltage threshold lower limit), which includes the voltage ripple determined from the capacitor temperature.

[0117] In such cases, when the temperature of the switching element is below the carrier frequency switching temperature threshold Tccf, the carrier frequency can be increased to reduce voltage ripple and prevent operation shutdowns due to false detection. This makes it possible to achieve both reliable protection from overvoltage and prevention of operation shutdowns due to false detection over a wider range.

[0118] As described above, the rotating electric machine control device 1a according to the second embodiment can set the protection voltage threshold Vppc according to the acquired switching element temperature, and can set the carrier frequency switching temperature threshold Tccf according to the capacitor temperature. This allows the carrier frequency to be increased when the acquired switching element temperature is equal to or lower than the carrier frequency switching temperature threshold Tccf. As a result, in addition to the effects described in the first embodiment, it is possible to reliably protect against overvoltage and prevent operation stoppage due to erroneous detection even when the correlation between the switching element temperature and the capacitor temperature is weak or when the temperature difference between the two temperatures is large. This makes it possible to obtain a more compact rotating electric machine control device that can achieve both overvoltage protection and prevention of erroneous detection without requiring excessive margins, larger component sizes, or increased costs due to increased component withstand voltages.

[0119] In the description of the second embodiment, when the protection voltage threshold Vppc is set to the lower limit of the protection voltage threshold Vppc, which is determined by the acquired capacitor temperature, the carrier frequency switching temperature threshold Tccf is set to the lower limit of the switching element temperature at which the maximum value of the voltage applied to the switching element does not exceed the switching element withstand voltage, which changes with the switching element temperature, taking into account the rise in capacitor voltage due to regenerative power when an abnormality occurs and the effects of switching surges. However, as long as the switching element temperature is such that the maximum value of the voltage applied to the switching element does not exceed the switching element withstand voltage, which changes with the switching element temperature, there is no problem in setting the switching element temperature higher than the above lower limit.

[0120] In the second embodiment, it is desirable that the temperature of the capacitor acquired by the temperature sensor 50 is the temperature of the hottest part of the capacitor. As described above, the higher the temperature of the capacitor, the lower the capacitance C. Therefore, from the viewpoint of preventing erroneous detection, by implementing protection based on the hottest part of the capacitor, reliable protection from erroneous detection is possible.

[0121] Furthermore, even in the case where the capacitor temperature sensor 50b is omitted and both the switching element temperature and the capacitor temperature are detected by the temperature sensor 50, as in the rotating electrical machine control device 1 according to the first embodiment, a carrier frequency switching temperature threshold Tccf may be set as a predetermined fixed value, and the carrier frequency may be increased at temperatures equal to or lower than the carrier frequency switching temperature threshold Tccf. This reduces the ripple voltage amplitude due to switching of the switching elements, thereby lowering the maximum voltage Vsn during normal ripple application. Furthermore, the protection voltage threshold Vppc can be lowered in that temperature range, allowing for earlier detection of DC voltage abnormalities and prompt initiation of protective operation. As a result, the maximum voltage applied to the DC bus of the inverter circuit 20 can be reduced. This makes it possible to prevent the DC bus voltage Vdc from reaching the withstand voltage Vws of the switching elements with ease.

[0122] Here, the switching element temperature at which protection from overvoltage and operation shutdown due to erroneous detection are not compatible is identified from the capacitor temperature detected by capacitor temperature sensor 50b and set as carrier frequency switching temperature threshold Tccf, and the carrier frequency is increased when the switching element temperature detected by temperature sensor 50a is equal to or lower than carrier frequency switching temperature threshold Tccf. However, it is also possible to identify the capacitor temperature at which protection from overvoltage and operation shutdown due to erroneous detection are not compatible from the switching element temperature detected by temperature sensor 50a and set as carrier frequency switching capacitor temperature threshold Tccfc, and increase the carrier frequency when the capacitor temperature detected by capacitor temperature sensor 50b is equal to or higher than carrier frequency switching capacitor temperature threshold Tccfc (carrier frequency switching capacitor temperature threshold Tccfc is not shown).

[0123] <Wide bandgap semiconductor element> The type of semiconductor used in the switching elements 31 to 36 in the power conversion circuit 30 is not particularly limited, but wide bandgap semiconductors can be used. Wide bandgap semiconductor elements that can be used include those made of silicon carbide (SiC), gallium nitride (GaN)-based materials, or diamond (C).

[0124] Inverter circuits configured with switching elements formed from such wide bandgap semiconductors are characterized by a high withstand voltage, low loss, and high frequency drive capability compared to conventional inverter circuits configured with switching elements formed from silicon (Si). Hereinafter, inverter circuits configured with switching elements formed from wide bandgap semiconductors will be referred to as wide bandgap inverter circuits, and inverter circuits configured with switching elements formed from silicon (Si) will be referred to as silicon inverter circuits.

[0125] In a rotating electric machine control device using a wide bandgap inverter circuit, the switching elements have a higher withstand voltage than in a rotating electric machine control device using a silicon inverter circuit. Accordingly, capacitors with high withstand voltage specifications are also used. Generally, when a capacitor is made to withstand a higher withstand voltage, its size relative to its capacitance C tends to increase. Therefore, the rotating electric machine control device according to the present application, which does not require an increase in the capacitance of the capacitor, offers significant benefits.

[0126] Furthermore, rotating electrical machine control devices using wide bandgap inverter circuits can achieve faster switching speeds than rotating electrical machine control devices using silicon inverter circuits. However, as switching speeds increase, surge voltages also increase. Therefore, the switching speed must be limited to protect the switching elements from surge voltages.

[0127] One way to increase the switching speed is to increase the capacitance C to expand the setting range of the protection voltage threshold Vppc, thereby reducing the maximum voltage applied to the switching elements when protection is performed. In contrast, the rotating electric machine control device according to the present application enables the switching speed to be increased without increasing the capacitance C of the capacitor, thereby fully utilizing the performance of a wide bandgap inverter circuit capable of high-speed switching. Furthermore, increasing the switching speed also makes it possible to reduce switching losses that occur during switching. This enables highly efficient driving and also enables the miniaturization of switching elements due to reduced heat generation. This enables further miniaturization and cost reduction of rotating electric machine control devices.

[0128] It should be noted that the above-described first and second embodiments are merely examples, and the present invention is not limited to the above-described embodiments as long as the present application is applicable. For example, in the above-described first and second embodiments, the DC power supply 90 and the rotating electrical machine control device 1 are directly connected to each other, but a DC / DC converter that steps up or down the voltage may be disposed between the DC power supply 90 and the rotating electrical machine control device 1. Also, the DC power supply 90 may be connected to the AC power supply via a rectifier or an AC / DC converter that converts AC power from the AC power supply into DC power.

[0129] Furthermore, in the above-described first and second embodiments, a six-switch open process in which all of the switching elements 31 to 36 of the power conversion circuit 30 are turned off has been described as an abnormality response process in which regenerative power is not charged to the capacitor 22. However, a three-phase short-circuit process may also be implemented, which is a method in which, for example, all of the upper-stage switching elements or all of the lower-stage switching elements of the power conversion circuit 30 are turned on to short-circuit the phases of the rotating electric machine with each other, thereby preventing the capacitor from regenerating power.

[0130] In addition, in the above-described first and second embodiments, the rotating electric machine 10 has been described as a three-phase synchronous rotating electric machine, but the present invention may also be applied to a two-phase or four or more phase rotating electric machine.

[0131] In the first and second embodiments, the temperatures of the switching elements and capacitors are acquired using the temperature sensors 50, 50a and the capacitor temperature sensor 50b. However, the component temperatures may be acquired using two temperature sensors to detect their respective temperatures, or using one temperature sensor to detect the temperature of one component and calculate the temperature of the other component from that value. The temperature of another part may also be acquired and the component temperature may be calculated from that value. A component temperature estimated value based on the operating state of the rotating electric machine 10 or the rotating electric machine control device 1, 1a may also be used. Multiple temperature sensors may be used and the minimum, maximum, or average temperature may be used.

[0132] Although the first and second embodiments have been described using an electric vehicle as an example, the present invention may also be applied to a hybrid vehicle that uses both an engine and a rotating electric machine. Furthermore, the application of the rotating electric machine device is not limited to vehicles.

[0133] Although various exemplary embodiments and examples are described in this application, the various features, aspects, and functions described in one or more 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 contemplated within the scope of the technology disclosed in this specification. For example, this includes cases where at least one component is modified, added, or omitted, or where at least one component is extracted and combined with components of another embodiment.

[0134] Various aspects of the present disclosure are summarized below as appendices.

[0135] (Appendix 1) a power conversion circuit having a plurality of legs, each of which is provided with a positive-side switching element connected to a positive electrode of a DC power supply, a negative-side switching element connected to a negative electrode of the DC power supply, and an external connection point which connects the positive-side switching element and the negative-side switching element in series and is connected to a rotating electric machine; a capacitor connected to the positive and negative terminals of the power conversion circuit; a voltage sensor for detecting a voltage between a positive electrode and a negative electrode of the power conversion circuit; a temperature sensor for detecting the temperature of the power conversion circuit; and A rotating electrical machine control device including a control unit that controls on / off of the switching elements of the power conversion circuit, When the voltage detected by the voltage sensor is greater than a judgment voltage calculated based on the temperature detected by the temperature sensor, the control unit executes protection control to turn off all of the switching elements, or to turn on all of the positive electrode side switching elements and turn off all of the negative electrode side switching elements, or to turn off all of the positive electrode side switching elements and turn on all of the negative electrode side switching elements. (Appendix 2) 2. The rotating electrical machine control device according to claim 1, wherein the control unit is configured to increase the determination voltage in accordance with an increase in the temperature detected by the temperature sensor. (Appendix 3) 3. The rotary electric machine control device according to claim 1, wherein the determination voltage of the control unit is set so that the voltage applied between the terminals of each of the switching elements during the period from when the voltage sensor detects a voltage greater than the determination voltage until when the protection control is executed is less than the withstand voltage of the switching element at the temperature detected by the temperature sensor. (Appendix 4) 3. The rotary electric machine control device according to claim 1, wherein the determination voltage of the control unit is set so that, when the DC power supply is disconnected from the power conversion circuit while the rotary electric machine is rotating, the voltage applied between the terminals of each of the switching elements during the period from when the voltage sensor detects a voltage greater than the determination voltage to when the protection control is executed is less than the withstand voltage of the switching element at the temperature detected by the temperature sensor. (Appendix 5) 5. A rotary electric machine control device according to claim 4, wherein the determination voltage of the control unit is set to a maximum value within a range that is less than the withstand voltage of the switching element at the temperature detected by the temperature sensor, the maximum value being a voltage that is applied between the terminals of each switching element to which a surge voltage generated by turning on and off the switching element is applied during the period from when the voltage sensor detects a voltage greater than the determination voltage to when the protection control is executed, when the DC power supply is disconnected from the power conversion circuit while the rotary electric machine is rotating. (Appendix 6) 6. The rotating electrical machine control device according to claim 1, wherein the temperature sensor detects a temperature of the switching element. (Appendix 7) 7. The rotating electrical machine control device according to claim 1, wherein the temperature sensor detects the lowest temperature of a switching element in the power conversion circuit. (Appendix 8) a capacitor temperature sensor for detecting the temperature of the capacitor; 8. The rotating electric machine control device according to claim 1, wherein the control unit calculates the determination voltage based on the temperature detected by the temperature sensor and the capacitor temperature detected by the capacitor temperature sensor. (Appendix 9) 9. The rotating electric machine control device according to claim 1, wherein the control unit increases a carrier frequency for on / off control of the switching elements of the power conversion circuit when the temperature detected by the temperature sensor is equal to or lower than a predetermined judgment temperature. (Appendix 10) a capacitor temperature sensor for detecting the temperature of the capacitor; 10. The rotating electric machine control device according to claim 9, wherein the control unit increases the determination temperature in accordance with an increase in the capacitor temperature detected by the capacitor temperature sensor. (Appendix 11) 11. The rotary electric machine control device according to claim 10, wherein the judgment temperature of the control unit is set by calculating a ripple voltage due to switching during normal operation of the power conversion circuit from a capacitance of the capacitor estimated based on the capacitor temperature, and the maximum value of the ripple voltage is set to be less than the judgment voltage. (Appendix 12) 12. The rotary electric machine control device according to claim 11, wherein the determination temperature of the control unit is set to the lowest temperature within a range in which a maximum value of the ripple voltage is less than the determination voltage by calculating a ripple voltage due to switching during normal operation of the power conversion circuit from a capacitance of the capacitor estimated based on the capacitor temperature. (Appendix 13) 13. The rotating electrical machine control device according to any one of claims 8 and 10 to 12, wherein the capacitor temperature sensor detects the temperature of the hottest part of the capacitor. (Appendix 14) 14. The rotating electrical machine control device according to any one of claims 1 to 13, wherein the capacitor is a film capacitor using polypropylene as a dielectric. (Appendix 15) 15. The rotating electric machine control device according to any one of claims 1 to 14, wherein the switching elements of the power conversion circuit use wide-gap semiconductors. [Explanation of symbols]

[0136] 1, 1a Rotating electric machine control device, 10 Rotating electric machine, 20, 20a Inverter circuit, 21a, 21b DC bus, 22 Capacitor, 23 Voltage sensor, 30 Power conversion circuit, 31, 32, 33, 34, 35, 36 Switching element, 40, 40a Control unit, 50, 50a Temperature sensor, 50b Capacitor temperature sensor, 90 DC power supply

Claims

1. a power conversion circuit having a plurality of legs, each of which is provided with a positive-side switching element connected to a positive electrode of a DC power supply, a negative-side switching element connected to a negative electrode of the DC power supply, and an external connection point which connects the positive-side switching element and the negative-side switching element in series and is connected to a rotating electric machine; a capacitor connected to the positive and negative terminals of the power conversion circuit; a voltage sensor for detecting a voltage between a positive electrode and a negative electrode of the power conversion circuit; a temperature sensor for detecting the temperature of the power conversion circuit; a capacitor temperature sensor for detecting the temperature of the capacitor; and A rotating electrical machine control device including a control unit that controls on / off of the switching elements of the power conversion circuit, a protection voltage threshold upper limit determined from a withstand voltage of the switching element has a positive correlation with a temperature of the power conversion circuit; a protection voltage threshold lower limit determined from a voltage ripple superimposed on a voltage applied to the capacitor during operation of the power conversion circuit has a positive correlation with a temperature of the capacitor; When the voltage detected by the voltage sensor is greater than a judgment voltage calculated based on the temperature detected by the temperature sensor and the capacitor temperature detected by the capacitor temperature sensor so as to be greater than the protection voltage threshold lower limit and less than the protection voltage threshold upper limit, the control unit executes protection control to turn off all of the switching elements, or to turn on all of the positive electrode side switching elements and turn off all of the negative electrode side switching elements, or to turn off all of the positive electrode side switching elements and turn on all of the negative electrode side switching elements.

2. 2. The rotary electric machine control device according to claim 1, wherein the control unit is configured to increase the determination voltage in accordance with an increase in the temperature detected by the temperature sensor.

3. 2. The rotating electric machine control device according to claim 1, wherein the determination voltage of the control unit is set so that a voltage obtained by adding a surge voltage due to the on / off control of the switching element to a DC voltage that has increased due to a delay time from when a voltage greater than the determination voltage is detected by the voltage sensor to when the protection control is executed is less than a withstand voltage of the switching element at the temperature detected by the temperature sensor.

4. 2. The rotating electric machine control device according to claim 1, wherein the determination voltage of the control unit is set so that, when the DC power supply is disconnected from the power conversion circuit while the rotating electric machine is rotating, a voltage obtained by adding a surge voltage due to the on / off control of the switching element to a DC voltage increased due to a delay time between when a voltage greater than the determination voltage is detected by the voltage sensor and when the protection control is executed is less than a withstand voltage of the switching element at a temperature detected by the temperature sensor.

5. The rotating electrical machine control device according to claim 1 , wherein the temperature sensor detects the temperature of the switching element.

6. The rotating electrical machine control device according to claim 1 , wherein the temperature sensor detects the temperature of the lowest temperature switching element in the power conversion circuit.

7. 2. The rotating electrical machine control device according to claim 1, wherein the control unit increases a carrier frequency for on / off control of the switching elements of the power conversion circuit when the temperature detected by the temperature sensor is equal to or lower than a predetermined threshold temperature.

8. a capacitor temperature sensor for detecting the temperature of the capacitor; The rotary electric machine control device according to claim 7 , wherein the control unit increases the determination temperature in accordance with an increase in the capacitor temperature detected by the capacitor temperature sensor.

9. 9. The rotating electric machine control device according to claim 8, wherein the judgment temperature of the control unit is set by calculating a ripple voltage due to switching during normal operation of the power conversion circuit from a capacitance of the capacitor estimated based on the capacitor temperature, and the maximum value of the ripple voltage is set to be less than the judgment voltage.

10. 10. The rotating electric machine control device according to claim 9, wherein the judgment temperature of the control unit is set to the lowest temperature in a range in which a maximum value of the ripple voltage due to switching during normal operation of the power conversion circuit is calculated from a capacitance of the capacitor estimated based on the capacitor temperature, and the judgment temperature of the control unit is set to be less than the judgment voltage.

11. The rotary electric machine control device according to claim 1 , wherein the capacitor temperature sensor detects the temperature of the hottest part of the capacitor.

12. The rotary electric machine control device according to claim 1 , wherein the capacitor is a film capacitor using polypropylene as a dielectric.

13. The rotating electrical machine control device according to claim 1 , wherein the switching elements of the power conversion circuit are made of wide-gap semiconductors.

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