Inverter control device and electric vehicle

Abstract

To provide an inverter control device capable of accurately estimating motor temperature even when the refrigerant flow rate varies.SOLUTION: An inverter control device 200 controls an inverter 100 that drives a motor 300 cooled by a refrigerant. A processor of the inverter control device 200 estimates a refrigerant flow rate (e.g., refrigerant flow rate Q or the change in refrigerant flow rate ΔQ) indicating the refrigerant flow rate (cooling state estimation unit 270). The processor estimates a motor temperature Temp on the basis of the estimated refrigerant flow rate and motor losses (winding loss Pcoil, stator loss Psta, rotor and magnet loss Prot, etc.) (motor temperature estimation unit 280). The processor corrects the current command for motor 300 so that the estimated motor temperature Temp is equal to or less than a threshold (set temperature) (current command correction unit 290).SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an inverter control device and an electric vehicle. [Background technology]

[0002] In an inverter control device that controls an inverter based on a motor output request to rotate and drive a motor, refrigerant cooling is used to continuously drive the motor while maintaining a large motor output. In such an inverter control device, a technique is known that estimates the motor temperature and controls the inverter so that the motor temperature does not exceed a predetermined set value.

[0003] Each component of a motor, such as the rotor and stator, has a thermal design, and exceeding the design temperature leads to motor failure. For this reason, the motor temperature is detected and the motor current is reduced to prevent the design temperature from being exceeded, thereby thermally protecting the motor (motor temperature protection). Furthermore, when a magnet is used in the rotor, the amount of magnetic flux changes according to the magnet temperature, so the desired motor output cannot be obtained even if the motor current is controlled to a constant value. For this reason, there is a demand for technology to detect the motor temperature in order to adjust the motor current according to the motor temperature.

[0004] Since it is difficult to attach a temperature sensor to detect the temperature of a magnet, which is a rotating body, a known technique for estimating magnet temperature is described in Patent Document 1. Patent Document 1 describes an inverter device that estimates magnet temperature by feeding back the difference between a first temperature estimation based on a voltage equation and a second temperature estimation based on a thermal circuit model. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2022-184581 A Summary of the Invention [Problem to be solved by the invention]

[0006] The technology in Patent Document 1 does not calculate the temperature using the flow rate of the refrigerant that cools the motor, so if there is a change in the refrigerant flow rate due to an abnormality in the refrigerant pump or the like, the accuracy of the temperature estimation may decrease.

[0007] An object of the present invention is to provide an inverter control device that can accurately estimate a motor temperature even if the refrigerant flow rate changes. [Means for solving the problem]

[0008] In order to achieve the above-mentioned object, the present invention provides an inverter control device that controls an inverter that drives a motor cooled by a refrigerant, and includes a processor that estimates a refrigerant flow rate that indicates a flow rate of the refrigerant, estimates a motor temperature based on the estimated refrigerant flow rate and losses in the motor, and corrects a current command for the motor so that the estimated value of the motor temperature is below a threshold value. Effect of the Invention

[0009] According to the present invention, the motor temperature can be estimated with high accuracy even if the coolant flow rate changes. Problems, configurations, and effects other than those described above will become apparent from the following description of the embodiments. [Brief description of the drawings]

[0010] [Figure 1] 1 is a block diagram showing the configuration of a motor device having an inverter control device according to an embodiment of the present invention; [Diagram 2] FIG. 4 is an explanatory diagram showing refrigerant flow rate estimation in one embodiment. [Diagram 3] FIG. 4 is an explanatory diagram of a thermal network model according to an embodiment. [Figure 4] FIG. 4 is a block diagram showing a refrigerant estimating unit and a motor temperature estimating unit in one embodiment. [Diagram 5] FIG. 11 is a graph showing the correlation between a motor speed change and a refrigerant flow rate in another embodiment. [Figure 6] FIG. 13 is a block diagram showing a configuration of an inverter control device according to another embodiment. [Figure 7] FIG. 1 is a configuration diagram of an electric vehicle to which a motor device is applied. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] One embodiment of the present invention is an inverter control device that controls the switching operation of a three-phase inverter circuit to drive a motor having a rotor and a stator cooled by a refrigerant. The inverter control device estimates the refrigerant flow rate due to an abnormality in the refrigerant pump or a sudden change in pressure loss in the refrigerant flow path, and estimates the motor temperature using the estimated refrigerant flow rate, thereby accurately estimating the motor temperature of the rotor, stator, etc. of the motor and thermally protecting the motor. Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

[0012] 1 is a block diagram showing the configuration of a motor device 1 having an inverter control device 200 according to one embodiment of the present invention. The motor device 1 is connected to a battery 2, and has an inverter 100, an inverter control device 200, and a motor 300. The inverter control device 200 is, for example, a microcomputer, and is composed of a storage device such as a memory, a processor such as a CPU, an input / output circuit, and the like.

[0013] The battery 2 is a DC voltage source for the inverter 100. The DC voltage DCV of the battery 2 is converted by the inverter 100 into a three-phase AC voltage with variable voltage and variable frequency, and is applied to the motor 300. To cool the motor, the motor refrigerant cooling unit 310 has, for example, a refrigerant pump for circulating cooling oil, a heat exchanger, and an oil reservoir, and a refrigerant flow path is formed by piping up to the motor 300.

[0014] The motor 300 is a synchronous motor that is rotationally driven by the supply of a three-phase AC voltage. A rotational position sensor 320 is attached to the motor 300 in order to control the phase of the three-phase AC voltage applied to the motor 300 from the inverter 100 to match the phase of the induced voltage of the motor 300. Here, the rotational position sensor 320 may be, for example, a resolver composed of an iron core and a winding. Alternatively, the rotational position sensor 320 may be composed of a GMR sensor or a Hall element.

[0015] The inverter control device 200 has a current command unit 210, a current command correction unit 290, a current control unit 220, a PWM pulse generation unit 230, a drive signal generation unit 240, a speed calculation unit 260, a current detection unit 250, a cooling state estimation unit 270 and a motor temperature estimation unit 280.

[0016] The speed calculation unit 260 detects the rotational position θ based on the output signal of the rotational position sensor 320 , and detects the rotational speed ω of the rotor in the motor 300 .

[0017] The current detection unit 250 acquires the three-phase current detection values ​​(Iu, Iv, Iw) flowing through the motor 300 from the current sensor Ict, and obtains the dq-axis current detection values ​​(Id, Iq) by performing a three-phase / two-phase conversion of these current detection values ​​based on the rotational position θ.

[0018] The inverter control device 200 has a current control function for controlling the output of the motor 300. A current command unit 210 controls the motor output based on a torque command T * The current command Id of the dq axis is * , Iq * The current command correction unit 290 outputs the current command Id in accordance with the motor temperature Temp from the motor temperature estimation unit 280. * , Iq * After correcting, the corrected current command Id ** , Iq **The operation of the motor temperature estimation unit 280 and the cooling state estimation unit 270 will be described in detail later. The current control unit 220 outputs the current detection value (Id, Iq) detected by the current detection unit 250 and the corrected current command Id ** , Iq ** The voltage command (Vd * ,Vq * ) to output.

[0019] The PWM pulse generating unit 230 performs three-phase pulse width modulation (PWM) using the voltage commands (Vd*, Vq*) calculated by the current control unit 220, the DC voltage DCV of the battery 2, and the rotational position θ. The drive signal generating unit 240 converts the PWM signal generated by the PWM pulse generating unit 230 into a drive signal DR for controlling the inverter 100, and outputs it to the inverter 100. The inverter 100 has a plurality of semiconductor switch elements corresponding to each phase of the three-phase AC voltage, and each semiconductor switch element is controlled to be turned on / off by the drive signal DR. As a result, the output voltage of the inverter 100 is adjusted according to the control of the inverter control device 200.

[0020] In the above, an example of the configuration of the motor device 1 when controlling the current of the motor 300 according to a current command from a higher-level controller has been described with reference to Fig. 1, but the configuration of Fig. 1 can also be applied when other control methods are adopted. For example, when controlling the rotation speed of the motor 300, the motor rotation speed ω is calculated based on the time change in the rotation position θ, and a voltage command or current command is generated so that it matches the speed command from the higher-level controller. Also, when controlling the output torque of the motor 300, a relational expression or map between the motor current (Id, Iq) and the motor torque is used to generate a current command (Id*, Iq*).

[0021] Next, motor temperature estimation in one embodiment of the present invention will be described with reference to Figures 2, 3, and 4. Figure 2 shows the estimation of the refrigerant flow rate, Figure 3 shows a thermal network model for motor temperature estimation, and Figure 4 shows a block diagram of a cooling state estimation unit and a motor temperature estimation unit.

[0022] FIG. 2 shows the relationship between the motor magnet temperature and the amount of magnetic flux and the relationship between the motor magnet temperature and the coolant flow rate. Using the correlation between the amount of magnetic flux and the amount of coolant flow rate, the estimation of the coolant flow rate based on the amount of magnetic flux in one embodiment will be described.

[0023] The relationship between the motor magnet temperature and magnetic flux amount in Figure 2(a) is that the magnetic flux amount changes depending on the motor temperature. For example, the temperature coefficient of a neodymium magnet is 10% / 100°C. Details of the calculation formula for magnetic flux amount will be explained later. Meanwhile, the relationship between the motor magnet temperature and refrigerant flow rate is that the magnet temperature increases as the refrigerant flow rate decreases, and the magnet temperature decreases as the refrigerant flow rate increases, as shown in Figure 2(b). In other words, by calculating the motor's magnetic flux amount, it is possible to find the correlation K of the refrigerant flow rate that cools the motor.

[0024] In FIG. 3, the heat transfer of the refrigerant flow rate of the motor in the thermal network is explained in a thermal network model in one embodiment. The losses of the motor are the winding loss Pcoil, the stator iron loss Psta, and the magnet loss Prot including the rotor iron loss as the input heat quantity of the model. The input temperatures from the temperature sensors are the motor housing temperature Tcase and the refrigerant temperature Toil. Although it is possible to increase the input temperature by attaching one or more temperature sensors to the winding, it is preferable to derive the winding temperature by calculation using the thermal network model. In addition, when the motor is divided into one or more motor parts Coil, stator core Sta, and magnet Mag, the motor temperatures are the winding temperature Tcoil, stator temperature Tsta, and magnet temperature Tmag.

[0025] One or more motor components have a thermal capacity as a parameter as an element of the thermal network model. Each motor component is connected by thermal resistance. Examples of thermal resistance are the thermal resistance between the stator and winding Rsta-coil, the thermal resistance between the stator and magnet Rsta-rot, the thermal resistance between the magnet and the refrigerant Rrot-oil, and the thermal resistance between the winding and the refrigerant Rcoil-oil.

[0026] The temperatures of the motor components in the thermal circuit model (winding temperature Tcoil, stator temperature Tsta, magnet temperature Tmag) are expressed by differential equations using the thermal network method, and are calculated by discretized numerical integration in the calculation process by a microcomputer. It is also possible to calculate the thermal network method using the cloud, and the input temperature and the input heat amount or the motor operating state required to calculate the input heat amount (rotation speed ω, current Id, Iq, torque command T * ) via communication and receiving the motor temperatures (one or all of the winding temperature Tcoil, stator temperature Tsta, and magnet temperature Tmag), the calculation load on the microcontroller can be reduced.

[0027] Regarding the refrigerant Oil, by ignoring the heat capacity of the refrigerant (ignoring the temperature time constant), the order of the differential equation equal to the number of heat capacities can be reduced by giving the refrigerant temperature Toil, and the calculation processing load on the microcomputer can be reduced. The change in the refrigerant Oil flow rate can be treated as a change in the thermal time constant, and can be treated as a change in heat capacity or as a change in the thermal resistance (thermal resistance Rsta-coil between the stator and winding, and thermal resistance Rsta-rot between the stator and magnet) connecting the refrigerant Oil. For example, the thermal resistance can be set with the design value of the refrigerant flow rate as the reference value, and the thermal resistance can be reduced when the refrigerant flow rate increases and increased when the refrigerant flow rate decreases, making the thermal resistance equal to the thermal time constant caused by the change in the refrigerant flow rate.

[0028] If the motor loss is divided into smaller parts, it is possible to divide and calculate the motor components of the thermal network model as well. The motor can be thermally protected by setting an upper limit for the temperature of each motor component, or the select high of the temperature of each motor component can be treated as the motor temperature. It is preferable to simplify the thermal network model, which simplifies the derivation of parameters for the thermal network model and avoids overfitting.

[0029] FIG. 4 is a block diagram of a refrigerant estimator and a motor temperature estimator in one embodiment of a method for estimating the change in refrigerant flow rate from magnetic flux estimation and estimating the motor temperature by multiplying the thermal resistance of a thermal network model by a gain.

[0030] The d-axis magnetic flux estimation Φd_est of the cooling state estimation unit 270 is calculated by the q-axis voltage command Vq related to the magnet magnetic flux from the motor voltage equation as shown in equation (1). * , q-axis current command Iq * Alternatively, it can be obtained by the time derivative of the q-axis current Iq, the winding resistance R, the rotational speed ω, and the q-axis magnetic flux Φq.

[0031]

number

[0032] The term of the time derivative of the q-axis magnetic flux amount Φq indicates the change in the q-axis magnetic flux due to the change in the magnetic saturation of the motor caused by the motor current, and if the change in the motor current can be ignored, the change in the q-axis magnetic flux can be ignored. Preferably, in a motor utilizing reluctance torque, there is a salient pole ratio between the d-axis and the q-axis, and the change in the magnetic flux amount of the d-axis or q-axis due to the motor current is likely to be large, so the change in the q-axis magnetic flux amount Φq in the transient state is taken into consideration. The q-axis magnetic flux Φq is referenced as an approximate formula or table according to the motor current.

[0033] To estimate the refrigerant flow rate indicating the cooling state of cooling state estimation unit 270, changes in the motor magnet temperature and d-axis magnetic flux Φd due to changes in the refrigerant flow rate are derived regardless of the motor's operating state (voltage, current, rotation speed). Estimation error factors of the d-axis magnetic flux estimation Φd_est include an error in the q-axis magnetic flux amount Φq, a voltage drop error of the inverter 100, a dead time error of the inverter 100, and a voltage detection error of the DC voltage DCV.

[0034] There are methods that use the refrigerant flow rate Q itself, and methods that use the amount of change ΔQ in the refrigerant flow rate, but in this embodiment, the amount of change ΔQ in the refrigerant flow rate is used to derive the motor temperature. The cooling state estimation unit 270 in Fig. 4 shows a method that uses the amount of change ΔQ in the refrigerant flow rate, and by using the difference between a first low-pass filter LPF_std with a long time constant and a second low-pass filter LPF_trn with a short time constant, it finds the amount of change ΔΦd_est in the d-axis magnetic flux while canceling the estimation error factors of the d-axis magnetic flux estimation Φd_est, and outputs the amount of change ΔQ in the refrigerant flow rate from the amount of change ΔΦd_est in the d-axis magnetic flux using the correlation K in Fig. 2.

[0035] The motor temperature Temp of the motor temperature estimator 280 shows an example of the temperature estimation of the motor magnet. The winding temperature Tcoil is calculated by the function CalcTcoil from the thermal resistance and heat capacity connected to the winding Coil, with the winding loss Pcoil as the input heat quantity. The stator temperature Tsta is calculated by the function CalcTsta from the thermal resistance and heat capacity connected to the stator Sta and the case temperature Tcase, with the stator loss Psta as the input heat quantity, from a table or an approximation formula. The magnet temperature Tmag is calculated by the function CalcTmag_pre from the thermal resistance and heat capacity connected to the magnet Mag (the rotor core and magnet are treated as a magnet collectively), with the loss Prot including the rotor and magnet loss Pmag as the input heat quantity, from a table or an approximation formula, and the refrigerant (oil) temperature Toil.

[0036] In Fig. 4, the change in refrigerant flow rate is modeled by adjusting the thermal time constant between the magnet and refrigerant by multiplying the thermal resistance Rrot-oil between the rotor and refrigerant, which includes the thermal resistance Rmag-oil between the magnet and refrigerant, by a coefficient. Of course, the same result can be achieved by modeling by setting a heat capacity between the magnet and refrigerant and adjusting the thermal time constant between the magnet and refrigerant.

[0037] In this embodiment, a magnet motor has been described as an example, but the same applies to other motors. For example, in a wound field motor, if the voltage applied to the field winding is constant, when the temperature rises, the field winding resistance increases and the field current decreases, which is a similar relationship to that of a magnet motor. In any case, since the motor temperature can be estimated with high accuracy even if the refrigerant flow rate changes, it is possible to reduce the amount of magnets used, improve reliability, and thermally protect the motor.

[0038] Another embodiment in which the refrigerant flow rate is estimated from the motor speed change using the motor temperature estimation logic of Figures 3 and 4 will be described with reference to Figures 5 and 6. Figure 5 is an explanatory diagram of the correlation of the refrigerant flow rate with the motor speed change in another embodiment, and Figure 6 is a block diagram showing the configuration of an inverter control device using the motor speed change in another embodiment.

[0039] In Figures 5 and 6, the same symbols as in Figures 1 and 4 indicate the same operations, and Figure 6 uses the motor speed change to derive the flow rate of the refrigerant that cools the motor. Unlike the magnetic flux estimation block in Figure 1, this can be applied to a motor that cools the motor by spraying refrigerant from the center side of the rotating shaft of the motor rotor, and has the advantage of improving reliability by using the rotation speed measured by a sensor for an inverter control device where repeated acceleration and deceleration of the motor rotation occurs.

[0040] FIG. 5 shows the relationship between rotor speed change (motor speed change) and refrigerant flow rate. When the refrigerant pump is operated at a constant current, the refrigerant flow rate changes due to pressure loss in the refrigerant flow path. If the motor rotation speed ω accelerates and the refrigerant is rapidly sprayed, the refrigerant pressure loss decreases and the refrigerant flow rate increases. Cooling state estimation unit 274 in FIG. 6 estimates the refrigerant flow rate, which changes according to the speed change (acceleration) of the motor rotation speed. When oil is used as the refrigerant, the viscosity changes depending on the oil temperature, so the refrigerant pressure loss also changes depending on the oil temperature. The refrigerant flow rate is calculated using a table or an approximation formula according to the refrigerant temperature. Motor temperature estimation unit 280 using the refrigerant flow rate is the same as in FIG. 4.

[0041] As a result, the inverter control device 200 of this embodiment can accurately estimate the motor temperature from changes in the refrigerant flow rate using changes in the rotational speed ω of the motor spraying the refrigerant, thereby reducing the amount of magnets used, improving reliability, and thermally protecting the motor.

[0042] 7 is a diagram showing an electric vehicle 600 (hybrid vehicle) to which the inverter control device 200 according to one embodiment of the present invention is applied. The electric vehicle 600 has a power train in which the motor 300 is applied as a motor / generator.

[0043] A front wheel axle 601 is rotatably supported at the front of the electric vehicle 600, and front wheels 602, 603 are provided at both ends of the front wheel axle 601. A rear wheel axle 604 is rotatably supported at the rear of the electric vehicle 600, and rear wheels 605, 606 are provided at both ends of the rear wheel axle 604.

[0044] A differential gear 611, which is a power distribution mechanism, is provided in the center of the front axle 601. The power from the engine 610 or the motor 300 is selectively engaged / disengaged via a clutch, and the rotational driving force transmitted via a transmission 612 is distributed to the left and right front axles 601.

[0045] This allows the rotational driving force of motor 300 to be transmitted to differential gear 611, the rotational driving force of engine 610 to motor 300, and the rotational driving force of engine 610 to differential gear 611. In motor 300, three-phase AC power output from inverter 100 under the control of inverter control device 200 is supplied to a stator coil of a stator, whereby the rotor rotates and generates a rotational driving force according to the three-phase AC power.

[0046] That is, the motor 300 is controlled by the inverter control device 200 to operate as an electric motor, and also operates as a generator that generates three-phase AC power by receiving the rotational driving force of the engine 610 and rotating its rotor.

[0047] The inverter 100 is a power conversion device that converts DC power supplied from a high-voltage battery 622, which is a high-voltage (42V or 300V) power source, into three-phase AC power, and controls the three-phase AC current flowing through the stator coil of the motor 300 based on an operation command value and the rotational position of the rotor. The three-phase AC power generated by the motor 300 is converted into DC power by the inverter 100 and charges the high-voltage battery 622.

[0048] Even in the acceleration mode or the high load operation mode, the motor 300 is driven to assist the driving of the engine 610. The motor 300 is cooled by using a motor refrigerant cooling unit 310. The motor refrigerant cooling unit 310 can be configured to cool the gears and clutch in the transmission 612 in addition to the motor 300. The motor 300 shifts the transmission 612 in accordance with the rotation speed of the engine, so that the clutch is engaged / disengaged, and the motor rotation speed also changes in synchronization with the shift timing and the number of stages of the transmission gear, and the change in the refrigerant flow rate Q becomes a disturbance in the motor cooling, resulting in a temperature error in the estimated motor temperature value Temp.

[0049] In acceleration mode or high-load operation mode, a large motor current flows through the motor 300, causing the winding temperature Tcoil and magnet temperature Tmag to rise. When the motor rotation speed is relatively low, the temperature rise of the winding temperature Tcoil is large, and when the motor rotation speed is relatively high, the temperature rise of the magnet temperature Tmag is large. That is, when the electric vehicle 600 is operating at low speed, the motor winding temperature Tcoil ≧ magnet temperature Tmag occurs, and when the electric vehicle 600 is operating at high speed, the motor winding temperature Tcoil ≦ magnet temperature Tmag. For this reason, upper limits are set for each of the winding temperature Tcoil and magnet temperature Tmag to thermally protect the motor. When the motor is a wound field motor, the magnet temperature is estimated as the rotor temperature (field winding temperature).

[0050] The electric vehicle 600 includes an inverter control device 200 for converting a DC voltage to an AC voltage based on a motor output request, an inverter 100 for converting the DC voltage to an AC voltage by a generated PWM pulse to drive a motor 300, and a motor refrigerant cooling unit 310 for cooling the motor. The inverter control device 200 corrects the motor current command of the inverter by the processing of the cooling state estimation unit 270 and the motor temperature estimation unit 280 as described above, so that the winding temperature or rotor temperature of the motor does not exceed a preset temperature in an operating state in which the refrigerant flow rate of the motor refrigerant cooling unit 310 changes. This makes it possible to obtain a desired motor output even when the motor temperature changes depending on the operating state of the electric vehicle.

[0051] The inverter control device according to the embodiment of the present invention described above provides the following advantageous effects.

[0052] (1) The inverter control device 200 of one embodiment of the present invention includes a cooling state estimation unit 270 that estimates the refrigerant flow rate that cools the motor, a motor temperature estimation unit 280 that estimates the motor temperature based on the refrigerant flow rate and the motor loss, and a current command correction unit 290 that corrects the motor current command based on the motor temperature. As a result, the motor temperature can be estimated even if the refrigerant flow rate changes due to an abnormality in the refrigerant pump or the like. As a result, the motor temperature can be estimated with high accuracy even if the refrigerant flow rate changes, which allows for reduced magnet usage, improved reliability, and thermal protection of the motor.

[0053] In other words, the inverter control device 200 controls the inverter 100 that drives the motor 300 cooled by a refrigerant (FIG. 1). The processor of the inverter control device 200 estimates a refrigerant flow rate (e.g., refrigerant flow rate Q or amount of change in refrigerant flow rate ΔQ) indicating the flow rate of the refrigerant (cooling state estimation unit 270). The processor estimates a motor temperature Temp based on the estimated value of the refrigerant flow rate and motor losses (winding loss Pcoil, stator loss Psta, rotor and magnet loss Prot, etc.) (motor temperature estimation unit 280). The processor corrects a current command for the motor 300 so that the estimated value of the motor temperature Temp is equal to or lower than a threshold value (set temperature) (current command correction unit 290). Since the motor temperature Temp is estimated based on an estimated value of the refrigerant flow rate (e.g., refrigerant flow rate Q or amount of change in refrigerant flow rate ΔQ), the motor temperature can be estimated with high accuracy even if the refrigerant flow rate changes. As a result, motor failure due to overheating is suppressed.

[0054] (2) In the inverter control device 200 according to one embodiment of the present invention, the cooling state estimation unit 270 calculates the refrigerant flow rate using logic for estimating the amount of magnetic flux of the motor. In this way, the motor temperature can be accurately estimated from the change in the refrigerant flow rate based on the change in the amount of magnetic flux of the motor, which makes it possible to reduce the amount of magnets used, improve reliability, and thermally protect the motor.

[0055] In detail, as shown in FIG. 4, the processor estimates the magnetic flux amount of the motor from the voltage (e.g., q-axis voltage command), current (e.g., q-axis current Iq), and rotation speed ω of the motor 300 (cooling state estimation unit 270). The processor derives the change amount ΔQ of the refrigerant flow rate based on the estimated value of the magnetic flux amount (e.g., d-axis magnetic flux estimate Φd_est) (cooling state estimation unit 270). The processor estimates the motor temperature using a thermal circuit network model of the motor 300 (motor temperature estimation unit 280). The processor corrects the estimated value of the motor temperature Temp based on the change amount ΔQ of the refrigerant flow rate (motor temperature estimation unit 280). Since the change amount ΔQ (difference) of the refrigerant flow rate cancels the estimation error factor, the motor temperature Temp can be estimated with high accuracy. Note that the processor may determine that the device (e.g., oil pump) in which the motor 300 is incorporated is faulty when the change amount ΔQ of the refrigerant flow rate is equal to or greater than a predetermined value.

[0056] (3) In the inverter control device 200 according to one embodiment of the present invention, the cooling state estimation unit 270 estimates the refrigerant flow rate using the rotation speed measured by a sensor for an inverter control device in which the motor is cooled by spraying refrigerant from the center side of the rotating shaft of the rotor of the motor and the motor rotation is repeatedly accelerated and decelerated. In this way, the motor temperature can be accurately estimated from the change in the refrigerant flow rate using the change in the rotation speed ω of the motor that sprays the refrigerant, thereby reducing the amount of magnets used, improving reliability, and thermally protecting the motor.

[0057] In other words, the processor estimates the refrigerant flow rate based on the rotational acceleration (dω / dt) of the motor 300 (cooling state estimation unit 274, FIG. 6). This makes it possible to accurately estimate the motor temperature even if the motor rotation is accelerated or decelerated.

[0058] (4) In the inverter control device 200 according to one embodiment of the present invention, the motor temperature estimator 280 estimates the motor temperature using a thermal network model of the motor. In this way, the temperature of at least one motor component of the motor can be estimated with high accuracy, which reduces the amount of magnets used, improves reliability, and provides thermal protection for the motor.

[0059] In other words, the processor estimates the motor temperature Temp using a thermal network model of the motor 300 (motor temperature estimation unit 280), as shown in Fig. 4. This makes it possible to easily calculate the motor temperature Temp.

[0060] (5) In the inverter control device 200 according to one embodiment of the present invention, the current command correction unit 290 may compare the estimated temperature of at least one or more components constituting the motor with a preset, predetermined temperature, and reduce the motor current when any of the estimated temperatures of the components constituting the motor exceeds the preset temperature. In this way, reliability can be improved and the motor can be thermally protected even for motor components that have different temperature rises during motor operation.

[0061] In other words, the motor temperature includes the temperatures of one or more components (e.g., windings, rotor, etc.) that make up motor 300. The processor estimates the temperature of each component (motor temperature estimator 280). If any of the estimated temperatures of all the components exceeds its corresponding threshold, the processor reduces the motor current (current command corrector 290). This prevents the components that make up motor 300 from failing due to overheating.

[0062] (6) As shown in Figure 4, the processor estimates the d-axis magnetic flux of the motor based on the change (time derivative) of the q-axis magnetic flux amount Φq (d-axis magnetic flux estimation Φd_est, equation (1)). This makes it possible to accurately estimate the motor temperature even if the q-axis magnetic flux amount changes.

[0063] (7) As shown in Fig. 4, for example, the processor inputs an estimate of the d-axis magnetic flux amount of the motor 300 (d-axis magnetic flux estimate Φd_est) to a first low-pass filter LPF_std having a first time constant and a second low-pass filter LPF_trn having a second time constant shorter than the first time constant. The processor derives the amount of change in the refrigerant flow rate ΔQ from the difference between the output of the first low-pass filter LPF_std and the output of the second low-pass filter LPF_trn. By using two low-pass filters with different time constants, it is possible to easily obtain the amount of change in the d-axis magnetic flux amount ΔΦd_est (the difference between the steady state and the transient state) while removing high-frequency noise.

[0064] (8) The motor 300 includes a rotor having a flow passage through which the refrigerant flows from the inside to the outside in the radial direction, for example. As the rotational acceleration of the motor 300 increases, the centrifugal force increases, and the flow rate of the refrigerant increases.

[0065] (9) As shown in Fig. 7, an electric vehicle 600 includes an inverter control device 200. A motor 300 is mounted on the electric vehicle 600. The motor temperature includes the winding temperature and rotor temperature of the motor 300. The processor corrects the current command of the motor 300 (current command correction unit 290) so that the estimated values ​​of the winding temperature and the rotor temperature are equal to or lower than the respective threshold values. This makes it possible to thermally protect the stator windings and the rotor including the magnets.

[0066] (10) The motor is provided in a transmission unit. The refrigerant for cooling the motor is oil. The inverter control device of the above embodiment suppresses motor failure due to overheating, thereby improving the reliability of the transmission unit. The transmission unit is composed of, for example, a damper, a motor 300, a clutch, a gear box, etc.

[0067] In addition, in the above-described embodiment, the inverter control device alone has been described, but the present invention can also be applied to an inverter device in which an inverter control device and an inverter are integrated, or a motor drive system in which an inverter device and a motor are integrated, so long as the device has the above-described functions.

[0068] The present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the spirit of the present invention.

[0069] The above-mentioned embodiments have been described in detail to clearly explain the present invention, and are not necessarily limited to those having all of the configurations described. In addition, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. In addition, it is possible to add, delete, or replace a part of the configuration of each embodiment with another configuration.

[0070] In addition, the above configurations, functions, etc. may be realized in hardware, partly or in whole, by designing them as integrated circuits, etc. In addition, the above configurations, functions, etc. may be realized in software by a processor interpreting and executing a program that realizes each function. Information such as the program, table, file, etc. that realizes each function can be stored in a memory, a recording device such as a hard disk or SSD (Solid State Drive), or a recording medium such as an IC card, SD card, or DVD.

[0071] The embodiment of the present invention may have the following aspects.

[0072] (A1). An inverter control device that controls the switching operation of a three-phase inverter circuit and drives a motor having a rotor and a stator cooled by a refrigerant, comprising: a current control unit that controls a motor current in response to a motor current command; a cooling state estimation unit that estimates a refrigerant flow rate that cools the motor; a motor temperature estimation unit that estimates the motor temperature based on the estimated refrigerant flow rate and losses in the motor; and a current command correction unit that corrects the motor current command input to the current control unit so that the motor temperature is below a predetermined value.

[0073] (A2). In the inverter control device described in (A1), the cooling state estimation unit estimates a change in a refrigerant flow rate cooling the motor based on a magnetic flux amount calculated from the motor's voltage, current, and rotational speed, and the motor temperature estimation unit corrects the motor temperature of a thermal circuit network model using the change in the estimated value of the refrigerant flow rate.

[0074] (A3) In the inverter control device according to (A1), the cooling state estimation unit estimates a refrigerant flow rate for cooling the motor using a rotation acceleration of the motor, and corrects the refrigerant flow rate of the motor temperature estimation unit. The inverter control device according to the present invention is characterized in that

[0075] (A4). In the inverter control device described in any one of (A1) to (A3), the motor temperature estimation unit estimates the motor temperature from a thermal circuit network model of the motor based on the estimated value of the refrigerant flow rate and losses in the motor.

[0076] (A5). A motor device comprising a current control unit that controls a motor current based on a motor output request, a cooling state estimation unit that estimates a refrigerant flow rate that cools the motor, a motor temperature estimation unit that estimates the temperature of one or more components that constitute the motor based on the estimated refrigerant flow rate and losses in the motor, and a current command correction unit that corrects a motor current command to be input to the current control unit, wherein the current command correction unit compares the estimated temperature of at least one or more components that constitute the motor with a predetermined set temperature that has been set in advance, and reduces the motor current when any of the estimated temperatures of the components that constitute the motor exceed the set temperature.

[0077] (A6). An electric vehicle comprising: a current control unit that controls a motor current that converts the DC voltage of an electric vehicle into AC voltage based on a motor output request; a cooling state estimation unit that estimates a refrigerant flow rate that cools the motor; and a motor temperature estimation unit that estimates a motor winding temperature and a rotor temperature based on the estimated refrigerant flow rate and losses in the motor, wherein the current command correction unit corrects a motor current command so that the motor winding temperature or rotor temperature does not exceed a predetermined temperature.

[0078] According to (A1)-(A6), the motor temperature can be accurately estimated even if the refrigerant flow rate changes, so the amount of magnet used can be reduced to protect the motor from temperature changes, and the desired motor output can be obtained even if the motor temperature changes. [Explanation of symbols]

[0079] 1...Motor device 2. Battery 100...Inverter 200...Inverter control device 210...Current command section 220...Current control unit 230…PWM pulse generator 240...Drive signal generating unit 250…Current detection section 260...Speed ​​calculation section 270...Cooling state estimation unit 280...Motor temperature estimation unit 290...Current command correction section 300…Motor 310...Motor refrigerant cooling section 320...Rotational position sensor 600…Electric vehicle

Claims

1. An inverter control device that controls an inverter that drives a motor cooled by a refrigerant, estimating a refrigerant flow rate indicative of a flow rate of the refrigerant; estimating a motor temperature based on the estimated coolant flow rate and losses in the motor; An inverter control device comprising a processor that corrects a current command for the motor so that the estimated value of the motor temperature is equal to or less than a threshold value.

2. The inverter control device according to claim 1 , The processor, A magnetic flux amount of the motor is estimated from a voltage, a current, and a rotation speed of the motor; deriving a change in the refrigerant flow rate based on the estimated value of the magnetic flux amount; Estimating the motor temperature using a thermal network model of the motor; The estimated value of the motor temperature is corrected based on the amount of change in the refrigerant flow rate. The inverter control device according to the present invention is characterized in that

3. The inverter control device according to claim 1 , The processor, The refrigerant flow rate is estimated based on the rotational acceleration of the motor. The inverter control device according to the present invention is characterized in that

4. The inverter control device according to claim 1 , The processor, The motor temperature is estimated using a thermal network model of the motor. The inverter control device according to the present invention is characterized in that

5. The inverter control device according to claim 1 , the motor temperature includes a temperature of one or more components that configure the motor; The processor, Estimating the temperature of each of said components; If any of the estimated temperatures of all the components exceeds a corresponding threshold, then reduce the current of the motor. The inverter control device according to the present invention is characterized in that

6. The inverter control device according to claim 2, The processor, The amount of d-axis magnetic flux of the motor is estimated based on the amount of change in the amount of q-axis magnetic flux. The inverter control device according to the present invention is characterized in that

7. The inverter control device according to claim 6, The processor, inputting the estimated value of the d-axis magnetic flux amount of the motor to a first low-pass filter having a first time constant and a second low-pass filter having a second time constant shorter than the first time constant; A change amount of the refrigerant flow rate is derived from a difference between an output of the first low-pass filter and an output of the second low-pass filter. The inverter control device according to the present invention is characterized in that

8. The inverter control device according to claim 3, The motor includes a rotor having a flow passage through which the coolant flows from the inside to the outside in the radial direction. The inverter control device according to the present invention is characterized in that

9. An electric vehicle equipped with the inverter control device according to claim 1, The motor is mounted on the electric vehicle, the motor temperature includes a winding temperature and a rotor temperature of the motor; The processor, The motor current command is corrected so that the estimated value of the winding temperature and the estimated value of the rotor temperature are equal to or less than their respective threshold values. An electric vehicle characterized by:

10. The electric vehicle according to claim 9, The motor is provided in a transmission unit, The refrigerant is oil. An electric vehicle characterized by:

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