Inverter control device and electric vehicle

Abstract

An inverter control device (200) controls an inverter (100) that drives a motor (300) cooled by refrigerant. A processor of the inverter control device (200) estimates a refrigerant flow rate (e.g., a refrigerant flow rate Q or a change amount ΔQ of a refrigerant flow rate) indicating the flow rate of the refrigerant (cooling state estimation unit 270). The processor estimates the motor temperature Temp on the basis of the estimated value of the refrigerant flow rate and motor loss (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 less than a threshold value (set temperature) (current command correction unit 290).

Description

Inverter control device and electric vehicle

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

[0002] Inverter control devices that control an inverter to rotate a motor based on motor output requirements use refrigerant cooling to continuously drive the motor while maintaining high motor output. A technique for such inverter control devices is known that estimates the motor temperature and controls the inverter so that the motor temperature does not exceed a predetermined set value.

[0003] Motor components such as the rotor and stator are thermally designed, and exceeding their design temperatures can lead to motor failure. Therefore, motor temperature is detected and the motor current is reduced to prevent the design temperature from being exceeded, thereby providing thermal protection for the motor (motor temperature protection). Furthermore, when a magnet is used in the rotor, the amount of magnetic flux changes depending on the magnet temperature, meaning that the desired motor output cannot be achieved even if the motor current is kept constant. Therefore, there is a demand for technology to detect 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 disclosed 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 using a voltage equation and a second temperature estimation using a thermal circuit model.

[0005] Japanese Patent Publication No. 2022-184581

[0006] The technology of Patent Document 1 does not calculate the temperature using the refrigerant flow rate 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 the motor temperature even when the refrigerant flow rate changes.

[0008] In order to achieve the above 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 the flow rate of the refrigerant, estimates a motor temperature based on the estimated refrigerant flow rate and a loss in the motor, and 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.

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

[0010] A block diagram showing the configuration of a motor device having an inverter control device according to an embodiment of the present invention. An explanatory diagram showing refrigerant flow rate estimation in one embodiment. An explanatory diagram of a thermal network model in one embodiment. A block diagram showing a refrigerant estimation unit and a motor temperature estimation unit in one embodiment. An explanatory diagram showing the correlation between motor speed change and refrigerant flow rate in another embodiment. A block diagram showing the configuration of an inverter control device in another embodiment. A configuration diagram of an electric vehicle to which the motor device is applied.

[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 motor's rotor, stator, etc., and thermally protecting the motor. One embodiment of the present invention will now 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, etc.

[0013] Battery 2 is a DC voltage source for inverter 100. The DC voltage DCV of battery 2 is converted by inverter 100 into a three-phase AC voltage with variable voltage and variable frequency, and is applied to motor 300. To cool the motor, 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 motor 300.

[0014] The motor 300 is a synchronous motor that is driven to rotate by a supply of three-phase AC voltage. A rotational position sensor 320 is attached to the motor 300 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 windings. Alternatively, the rotational position sensor 320 may be configured using 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 d-axis and q-axis current detection values ​​(Id, Iq) by performing a three-phase / two-phase conversion on 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. The current command unit 210 outputs a torque command T ＊ dq axis current command Id ＊ , 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 ＊ is corrected to obtain 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 calculates the current detection value (Id, Iq) detected by the current detection unit 250 and the corrected current command Id input from the current command correction unit 290. ＊＊ , Iq ＊＊ The voltage command (Vd ＊ , Vq ＊ ) is 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] While the above description uses Fig. 1 to illustrate an example of the configuration of motor device 1 when controlling the current of motor 300 in accordance with a current command from a higher-level controller, the configuration of Fig. 1 can also be applied when other control methods are adopted. For example, when controlling the rotational speed of motor 300, the motor rotational speed ω is calculated based on the time change in rotational position θ, and a voltage command or current command is generated so that it matches the speed command from the higher-level controller. Furthermore, when controlling the output torque of motor 300, a relational expression or map between motor current (Id, Iq) and motor torque is used to generate current commands (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 the cooling state estimation unit and the 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 refrigerant flow rate. Using the correlation between the amount of magnetic flux and the refrigerant flow rate, estimating the refrigerant flow rate based on the amount of magnetic flux in one embodiment will be described.

[0023] The relationship between the motor's magnet temperature and magnetic flux amount in Figure 2(a) shows 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 formula for calculating the magnetic flux amount will be described later. Meanwhile, the relationship between the motor's magnet temperature and refrigerant flow rate, as shown in Figure 2(b), shows that the magnet temperature increases as the refrigerant flow rate decreases, and the magnet temperature decreases as the refrigerant flow rate increases. 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] FIG. 3 illustrates the heat transfer of the motor's coolant flow rate in a thermal network model according to one embodiment. The motor's losses are the winding loss Pcoil, the stator iron loss Psta, and the magnet loss Prot, which includes the rotor iron loss, as input heat quantities to the model. The input temperatures from the temperature sensors are the motor housing temperature Tcase and the coolant temperature Toil. While it is possible to increase the input temperature by attaching one or more temperature sensors to the windings, it is preferable to calculate the winding temperature using a thermal network model. Furthermore, when the motor is divided into one or more motor components, the winding temperature Tcoil, the stator temperature Tsta, and the magnet temperature Tmag are used.

[0025] One or more motor components have a thermal capacity as a parameter, which is an element of the thermal network model. Each motor component is connected by thermal resistance. Examples of thermal resistance include 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 refrigerant, Rrot-oil, and the thermal resistance between the winding and 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 calculations performed by a microcomputer. It is also possible to perform calculations using the thermal network method on the cloud, and the input temperature and the motor operating state required for calculating the input heat amount (rotational speed ω, currents Id, Iq, torque command T ＊ ) via communication and receive the motor temperature (one or all of the winding temperature Tcoil, stator temperature Tsta, and magnet temperature Tmag), thereby reducing the calculation load on the microcomputer.

[0027] Regarding the refrigerant oil, by ignoring the heat capacity of the refrigerant (ignoring the temperature time constant), the order of the differential equation, which is equal to the number of heat capacities, can be reduced by giving the refrigerant temperature Toil, thereby reducing the computational load on the microcomputer. Changes in the refrigerant oil flow rate can be treated as changes in the thermal time constant, either as changes in heat capacity or as changes in the thermal resistances connected to the refrigerant oil (thermal resistance Rsta-coil between the stator and winding, and thermal resistance Rsta-rot between the stator and magnet). For example, by setting the thermal resistance using the design refrigerant flow rate as a reference value, and decreasing the thermal resistance when the refrigerant flow rate increases and increasing the thermal resistance when the refrigerant flow rate decreases, the thermal time constants due to changes in refrigerant flow rate can be made equal.

[0028] Furthermore, if motor losses are separated into smaller parts, it is possible to separate and calculate the motor components in the thermal network model as well. The motor can be thermally protected by setting an upper limit on the temperature of each motor component, or the select high temperature of each motor component can be treated as the motor temperature. Preferably, simplifying the thermal network model simplifies the derivation of parameters for the thermal network model and avoids overfitting.

[0029] FIG. 4 is a block diagram illustrating a refrigerant estimation unit and a motor temperature estimation unit in one embodiment of a method for estimating a 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 from the motor voltage equation as shown in Equation (1) by using the q-axis voltage command Vq ＊ , q-axis current command Iq ＊ Alternatively, it can be obtained by the time differentiation of the q-axis current Iq, the winding resistance R, the rotational speed ω, and the q-axis magnetic flux Φq.

[0031]

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

[0033] To estimate the refrigerant flow rate, which indicates 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 operating state of the motor (voltage, current, rotation speed). Factors contributing to the estimation error of the d-axis magnetic flux estimation Φd_est include an error in the q-axis magnetic flux amount Φq, a voltage drop error in inverter 100, a dead time error in inverter 100, and a voltage detection error in 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 estimator 270 in Figure 4 uses the amount of change ΔQ in the refrigerant flow rate, and by using the difference between the first low-pass filter LPF_std, which has a long time constant, and the second low-pass filter LPF_trn, which has a short time constant, the amount of change ΔΦd_est in the d-axis magnetic flux is determined while canceling factors of estimation error in the d-axis magnetic flux estimate Φd_est, and the amount of change ΔΦd_est in the d-axis magnetic flux is output from the amount of change ΔΦd_est in the d-axis magnetic flux using the correlation K in Figure 2.

[0035] The motor temperature Temp of the motor temperature estimator 280 represents an example of the temperature estimation of the motor magnet. The winding temperature Tcoil is calculated using 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 using 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 using the function CalcTmag_pre from the thermal resistance and heat capacity connected to the magnet Mag (the rotor core and magnet are collectively treated as the magnet), 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 Figure 4, changes in refrigerant flow rate are modeled by adjusting the thermal time constant between the magnet and refrigerant by correcting the thermal resistance Rrot-oil between the rotor and refrigerant, which includes the thermal resistance Rmag-oil between the magnet and refrigerant, by multiplying it by a coefficient.Of course, the same result can be achieved by setting a heat capacity between the magnet and refrigerant and modeling it so that the thermal time constant between the magnet and refrigerant is adjusted.

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

[0038] Another embodiment in which the refrigerant flow rate is estimated from motor speed changes 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 motor speed changes in another embodiment, and Figure 6 is a block diagram showing the configuration of an inverter control device using motor speed changes in another embodiment.

[0039] 5 and 6, the same symbols as in Figures 1 and 4 indicate the same operations, and Figure 6 uses changes in motor speed to derive the flow rate of refrigerant that cools the motor. Unlike the magnetic flux estimation block in Figure 1, this can be applied to motors that are cooled by spraying refrigerant from the center 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 inverter control devices where repeated acceleration and deceleration of motor rotation occur.

[0040] Figure 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. The cooling state estimation unit 274 in Figure 6 estimates the refrigerant flow rate, which changes in response to speed changes (acceleration) in the motor rotation speed. When oil is used as the refrigerant, the viscosity changes with oil temperature, so the refrigerant pressure loss also changes with the oil temperature. The refrigerant flow rate is calculated using a table or an approximation formula according to the refrigerant temperature. The motor temperature estimation unit 280 using the refrigerant flow rate is the same as in Figure 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 that sprays the refrigerant, thereby reducing the amount of magnet 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 wheel axle 601, and the power from the engine 610 or the motor 300 is selectively engaged / disengaged via a clutch, and the rotational driving force transmitted via the transmission 612 is distributed to the left and right front wheel 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 is supplied to the stator coil of the stator in accordance with the control of inverter control device 200, causing the rotor to rotate and generating a rotational driving force corresponding 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 when the rotor rotates upon receiving the rotational driving force of the engine 610.

[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 (42 V or 300 V) 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 during acceleration mode or high-load operation mode, motor 300 is driven to assist the driving of engine 610. Motor 300 is cooled using motor refrigerant cooling unit 310. Motor refrigerant cooling unit 310 can also cool the gears and clutches in transmission 612 in addition to motor 300. Motor 300 changes the speed of transmission 612 in accordance with the engine rotation speed, which causes the clutch to engage and disengage, and the motor rotation speed also changes in synchronization with the shift timing and the number of gears, and changes in refrigerant flow rate Q act as a disturbance to motor cooling, resulting in a temperature error in estimated motor temperature value Temp.

[0049] In acceleration mode or high-load operation mode, a large motor current flows through motor 300, causing winding temperature Tcoil and magnet temperature Tmag to rise. When the motor rotation speed is relatively low, the temperature rise in winding temperature Tcoil is large, and when the motor rotation speed is relatively high, the temperature rise in magnet temperature Tmag is large. That is, when electric vehicle 600 is operating at low speed, the motor winding temperature Tcoil ≧ magnet temperature Tmag may occur, and when electric vehicle 600 is operating at high speed, the motor winding temperature Tcoil ≦ magnet temperature Tmag. For this reason, upper limits are set for 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] Electric vehicle 600 includes inverter control device 200 for converting DC voltage to AC voltage based on a motor output request, inverter 100 for converting DC voltage to AC voltage using generated PWM pulses to drive motor 300, and motor refrigerant cooler 310 for cooling the motor. Inverter control device 200 corrects the motor current command of the inverter by processing cooling state estimator 270 and motor temperature estimator 280 as described above, so that the motor winding temperature or rotor temperature does not exceed a preset temperature in an operating state in which the refrigerant flow rate of motor refrigerant cooler 310 changes. This allows a desired motor output to be obtained 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. This configuration makes it possible to estimate the motor temperature even when the refrigerant flow rate changes due to an abnormality in the refrigerant pump or the like. As a result, the motor temperature can be accurately estimated even when the refrigerant flow rate changes, which enables reduction in 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, which is cooled by a refrigerant (see FIG. 1 ). The processor of the inverter control device 200 estimates a refrigerant flow rate (e.g., refrigerant flow rate Q or refrigerant flow rate change ΔQ) indicating the flow rate of the refrigerant (cooling state estimation unit 270). The processor estimates a motor temperature Temp based on 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 a current command for the motor 300 so that the estimated value of the motor temperature Temp is equal to or less than a threshold (set temperature) (current command correction unit 290). Because the motor temperature Temp is estimated based on an estimated value of the refrigerant flow rate (e.g., refrigerant flow rate Q or refrigerant flow rate change ΔQ), the motor temperature can be accurately estimated even when 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. This allows the motor temperature to be accurately estimated from changes in the refrigerant flow rate based on changes in the amount of magnetic flux of the motor, thereby reducing the amount of magnet used, improving reliability, and thermally protecting the motor.

[0055] Specifically, as shown in FIG. 4 , the processor estimates the amount of magnetic flux of the motor from the voltage (e.g., q-axis voltage command), current (e.g., q-axis current Iq), and rotational speed ω of the motor 300 (cooling state estimation unit 270). The processor derives a change in refrigerant flow rate ΔQ based on the estimated value of the amount of magnetic flux (e.g., d-axis magnetic flux estimate Φd_est) (cooling state estimation unit 270). The processor estimates the motor temperature using a thermal 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 in refrigerant flow rate ΔQ (motor temperature estimation unit 280). The change in refrigerant flow rate ΔQ (difference) cancels out factors that contribute to estimation errors, allowing for accurate estimation of the motor temperature Temp. Note that if the change in refrigerant flow rate ΔQ is equal to or greater than a predetermined value, the processor may determine that a device (e.g., an oil pump) incorporating the motor 300 is faulty.

[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 of the rotor shaft of the motor and the motor rotation is repeatedly accelerated and decelerated. This allows the motor temperature to be accurately estimated from changes in the refrigerant flow rate using changes in the rotation speed ω of the motor that sprays refrigerant, thereby reducing the amount of magnet 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 allows the motor temperature to be estimated with high accuracy even when the motor rotation speed 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. This allows the temperature of at least one motor component to be estimated with high accuracy, thereby reducing the amount of magnet used, improving reliability, and providing thermal protection for the motor.

[0059] 4, the processor estimates the motor temperature Temp using a thermal network model of the motor 300 (motor temperature estimation unit 280). 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 corrector 290 may compare the estimated temperature of at least one component of the motor with a predetermined set temperature, and reduce the motor current when any of the estimated temperatures of the components of the motor exceeds the set temperature. This improves reliability and thermally protects the motor even for motor components that experience 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 the 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 breakdowns of the components that make up the motor 300 due to overheating.

[0062] (6) As shown in Figure 4, the processor estimates the d-axis magnetic flux amount 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 allows the motor temperature to be estimated with high accuracy even if the q-axis magnetic flux amount changes.

[0063] (7) As shown in FIG. 4 , the processor inputs an estimated value of the d-axis magnetic flux amount (d-axis magnetic flux estimate Φd_est) of the motor 300 to, for example, 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 ΔQ in the refrigerant flow rate 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 ΔΦd_est in the d-axis magnetic flux amount (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 path through which the refrigerant flows from the inside to the outside in the radial direction. As the rotational acceleration of the motor 300 increases, the centrifugal force increases, and the refrigerant flow rate 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 for the motor 300 (current command corrector 290) so that the estimated values ​​of the winding temperature and the rotor temperature are equal to or lower than their 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 that cools the motor is oil. The inverter control device of the above embodiment can prevent 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 gearbox, etc.

[0067] Furthermore, 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 the inverter control device and the inverter are integrated, or a motor drive system in which the inverter device and the motor are integrated, as long as they have 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-described embodiments have been described in detail to clearly explain the present invention, and are not necessarily limited to those including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, or to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with another configuration.

[0070] Furthermore, some or all of the above-described configurations, functions, etc. may be implemented in hardware, for example, by designing them as integrated circuits. Furthermore, the above-described configurations, functions, etc. may be implemented in software by a processor interpreting and executing a program that implements each function. Information such as the programs, tables, and files that implement 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 the motor current in response to a motor current command; a cooling state estimation unit that estimates the flow rate of refrigerant that cools the motor; a motor temperature estimation unit that estimates the motor temperature based on the estimated value of the 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 equal to or less than a predetermined value.

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

[0074] (A3) In the inverter control device described in (A1), the cooling state estimation unit estimates a refrigerant flow rate that cools the motor using the rotational acceleration of the motor, and corrects the refrigerant flow rate of the motor temperature estimation unit.

[0075] (A4) In the inverter control device according to 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 a loss in the motor.

[0076] (A5) A motor device comprising a current control unit that controls 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 make up 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 input to the current control unit, wherein the current command correction unit compares the estimated temperature of at least one or more components that make up the motor with a predetermined set temperature, and reduces the motor current when any of the estimated temperatures of the components that make up 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 the motor winding temperature and 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 preset temperature.

[0078] According to (A1)-(A6), the motor temperature can be estimated with high accuracy 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.

[0079] DESCRIPTION OF SYMBOLS 1...motor device 2...battery 100...inverter 200...inverter control device 210...current command section 220...current control section 230...PWM pulse generation section 240...drive signal generation section 250...current detection section 260...speed calculation section 270...cooling state estimation section 280...motor temperature estimation section 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, comprising a processor that estimates a refrigerant flow rate indicating 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 motor temperature is below a threshold value.

2. An inverter control device as claimed in claim 1, wherein the processor estimates the amount of magnetic flux of the motor from the voltage, current and rotational speed of the motor, derives the amount of change in the refrigerant flow rate based on the estimated value of the amount of magnetic flux, estimates the motor temperature using a thermal circuit network model of the motor, and corrects the estimated value of the motor temperature based on the amount of change in the refrigerant flow rate.

3. An inverter control device according to claim 1, wherein the processor estimates the refrigerant flow rate based on the rotational acceleration of the motor.

4. An inverter control device according to claim 1, characterized in that the processor estimates the motor temperature using a thermal network model of the motor.

5. An inverter control device as claimed in claim 1, wherein the motor temperature includes the temperatures of one or more components constituting the motor, and the processor estimates the temperature of each of the components, and reduces the current of the motor when any of the estimated temperatures of all of the components exceeds a corresponding threshold value.

6. An inverter control device according to claim 2, characterized in that said processor estimates the amount of d-axis magnetic flux of said motor based on the amount of change in the amount of q-axis magnetic flux.

7. An inverter control device as claimed in claim 6, characterized in that the processor inputs an 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, and derives the amount of change in the refrigerant flow rate from the difference between the output of the first low-pass filter and the output of the second low-pass filter.

8. An inverter control device according to claim 3, wherein the motor is provided with a rotor having a flow path through which the refrigerant flows from the inside to the outside in the radial direction.

9. An electric vehicle equipped with the inverter control device according to claim 1, wherein the motor is mounted on the electric vehicle, the motor temperature includes a winding temperature and a rotor temperature of the motor, and the processor corrects a current command for the motor so that the estimated value of the winding temperature and the estimated value of the rotor temperature are below their respective threshold values.

10. An electric vehicle according to claim 9, wherein the motor is provided in a transmission unit, and the refrigerant is oil.

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