Electric motor control method and electric motor control device

Abstract

To provide a method for controlling an electric motor and a device for controlling an electric motor which suppress a surge generated in a switching element and reduce a burden applied on the switching element, even when a sudden change of a load on an electric motor occurs.SOLUTION: A method for controlling an electric motor, which calculates a voltage command value applied to an electric motor on the basis of a current value supplied to the electric motor, controls a PWM signal transmitted to the pair of switching elements on the basis of the voltage command value, and thereby controls the AC power, when DC power is converted into AC power by at least a pair of switching elements, and the AC power is supplied to an electric motor of an electric vehicle, lowers a switching speed of the switching elements when a sudden change of a load applied on the electric motor is detected.SELECTED DRAWING: Figure 9

Description

[Technical Field]

[0001] The present invention relates to a method for controlling an electric motor and a device for controlling an electric motor. [Background technology]

[0002] Patent Document 1 discloses that the switching speed of a semiconductor switching element is changed depending on the magnitude of the DC power supply voltage; when the DC power supply voltage is high and there is no allowance for the withstand voltage of the semiconductor switching element, the switching speed is slowed down to suppress the surge voltage caused by switching so that the withstand voltage is not exceeded; and when the DC power supply voltage is low and there is allowance for the withstand voltage of the semiconductor switching element and a large surge can be tolerated, the switching speed is increased to suppress losses. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 3052792 Summary of the Invention [Problem to be solved by the invention]

[0004] When the DC power supply voltage is low, a certain level of surge is tolerated in the switching elements. However, in an electric vehicle, if a sudden change in the load on the motor occurs depending on the driving conditions (such as spinning or sudden braking on a slippery road, or continuous slipping / gripping due to driving on a rough road), the current supplied to the motor may momentarily rise beyond the normal operating range, and the magnitude of the surge may exceed the allowable range depending on the current, exceeding the withstand voltage of the switching elements.

[0005] The present invention aims to provide a method for controlling an electric motor and a device for controlling an electric motor that suppresses surges generated in switching elements and reduces the burden on the switching elements even when a sudden change in load on the electric motor occurs. [Means for solving the problem]

[0006] The method for controlling an electric motor according to the present invention is a method for controlling an electric motor, in which DC power is converted into AC power by at least a pair of switching elements and the AC power is supplied to an electric motor of an electric vehicle, by calculating a voltage command value to be applied to the electric motor based on a current value supplied to the electric motor, and controlling a PWM signal to be sent to the pair of switching elements based on the voltage command value. In this control method, when a sudden change in the load applied to the electric motor is detected, the switching speed of the switching elements is reduced, and the detection of the sudden change in the load is determined by whether or not the rate of change in the rotation speed of the electric motor exceeds a predetermined threshold. When a voltage command value is generated based on a torque command value and a current value required by an electric vehicle, a sudden change in load is detected when the ratio of the torque command value, accelerator opening, or brake operation amount to the rate of change of the wheel speed or the rate of change of the rotation speed of the electric vehicle is equal to or greater than a predetermined value. . [Effects of the Invention]

[0007] According to the present invention, even in the event of a sudden change in the load on the motor, for example, a momentary increase in the current flowing through the motor, the switching speed of the switching elements is reduced to suppress surge voltage, thereby reducing the burden on the switching elements. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram showing an example of a block configuration of a control device for an electric motor according to a first embodiment. [Figure 2] FIG. 2 is a diagram showing an example of a block configuration of a control calculation unit that constitutes the control device for the electric motor according to the first embodiment. [Figure 3] FIG. 3 is a diagram showing an example of a block configuration of a current vector control unit that constitutes the motor control device of the first embodiment. [Figure 4] FIG. 4 is a diagram showing an example of a block configuration of a voltage phase control unit that constitutes the motor control device of the first embodiment. [Figure 5] FIG. 5 is a diagram illustrating an example of the relationship between the voltage phase and the torque. [Figure 6]FIG. 6 is a diagram showing an example of a block configuration of an output switch constituting the motor control device of the first embodiment. [Figure 7] FIG. 7 is a diagram showing an example of a block configuration of a sudden load change detection unit that constitutes the motor control device of the first embodiment. [Figure 8] FIG. 8 is a diagram showing an example of a block configuration of an acceleration calculation unit constituting the sudden load change detection unit. [Figure 9] FIG. 9 shows an example of a block configuration of a gate drive circuit that constitutes an inverter. FIG. 9(a) shows a gate drive circuit configured to include a fixed resistor and a switch, and FIG. 9(b) shows a gate drive circuit configured to include a variable resistor. [Figure 10] FIG. 10 is a diagram illustrating the operation of the switching element. [Figure 11] FIG. 11 is a control flow of the motor control device of the first embodiment. [Figure 12] FIG. 12 is a diagram showing an example of a block configuration of a control calculation unit that constitutes the control device for the electric motor according to the second embodiment. [Figure 13] FIG. 13 is a diagram showing an example of a block configuration of a sudden load change detection unit constituting the motor control device of the second embodiment. [Figure 14] FIG. 14 is an overall schematic diagram of a motor control device according to the third embodiment. [Figure 15] FIG. 15 is a diagram showing an example of a block configuration of a control calculation unit that constitutes the control device for an electric motor according to the third embodiment. [Figure 16] FIG. 16 is a diagram showing an example of a block configuration of a sudden load change detection unit constituting the motor control device of the third embodiment. [Figure 17] FIG. 17 is a diagram showing the definition of the sudden load change region. [Figure 18] FIG. 18 is a diagram showing an example of a block configuration of a control calculation unit that constitutes the control device for the electric motor according to the fourth embodiment. [Figure 19] FIG. 19 is a diagram showing the behavior of torque and rotation speed when traveling on a rough road. [Figure 20]FIG. 20 is a time chart showing the operation of the sudden load change detection unit that constitutes the motor control device of the fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] [First embodiment] FIG. 1 is a diagram showing an example of a block configuration of a control device for an electric motor 7 according to a first embodiment. A control method for an electric motor 7 according to the present invention is applied to the control device shown in FIG. 1. The control method for an electric motor 7 according to the present invention is applicable to an electric vehicle equipped with an electric motor 7 that functions as part or all of the vehicle's drive source. Electric vehicles include not only electric vehicles, but also hybrid vehicles and fuel cell vehicles.

[0010] The electric motor 7 to be controlled is, for example, an IPM (Interior Permanent Magnet) type three-phase synchronous motor. The electric motor 7 drives the electric vehicle by receiving three-phase AC power from the inverter 5, and also generates a regenerative current when braking the electric vehicle and outputs this to the inverter 5.

[0011] The control device for the electric motor 7 of this embodiment includes a control calculation unit 1, a first coordinate conversion unit 2 (dq axis → UVW phase conversion unit), a PWM conversion unit 3, a voltage detector 4, an inverter 5, a current detector 6, a rotor position sensor 8, a rotation speed calculation unit 9, and a second coordinate conversion unit 10 (UVW phase → dq axis conversion unit).

[0012] The control calculation unit 1 controls the entire control device. The control calculation unit 1 receives a torque command value T * , the rotation speed N of the electric motor 7, and the dq-axis current i d ,i q Information on the temperature (PM temperature) of the power module 53 (FIG. 9) of the inverter 5, information on the temperature of the cooling water that cools the power module 53, etc., information on a discharge request, etc. are input.

[0013] The control calculation unit 1 controls the motor 7 to generate a desired torque command value T * To achieve this, the dq-axis current i d ,iq and the DC voltage V detected by the voltage detector 4. dc and the rotation speed N calculated (detected) by the rotation speed calculation unit 9, the dq-axis final voltage command value v * d_fin ,v * q_fin Output.

[0014] Furthermore, the control calculation unit 1 outputs a gate resistance control signal to the inverter 5 (switching element 531 (FIG. 9)) based on the state of the electric vehicle, and outputs carrier frequency information to the PWM conversion unit 3.

[0015] The first coordinate transformation unit 2 calculates the dq-axis final voltage command value v * d_fin ,v * q_fin Based on the electrical angle θ of the motor 7, the three-phase voltage command value v is calculated according to the following formula (1). u * ,v v * ,v w * and outputs it to the PWM conversion unit 3. Note that PWM (Pulse Width Modulation) is an abbreviation for Pulse Width Modulation.

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[0016] The PWM converter 3 converts the three-phase voltage command value v u * ,v v * ,v w * and the DC voltage V detected by voltage detector 4. dc This is a high-voltage element drive signal (D * uu ,D * ul ,D * vu ,D *vl ,D * wu ,D * wl ) and output it to inverter 5.

[0017] The inverter 5 generates a three-phase voltage v based on the high-voltage element drive signal. u ,v v ,v w and applies it to the electric motor 7. The inverter 5 includes a power module 53 (FIG. 9) that includes a plurality of high-voltage elements (switching elements 531 such as IGBTs, and a feedback capacitor 532 (FIG. 9)). The inverter 5 is also connected to a smoothing capacitor 51 and a battery 52.

[0018] Furthermore, the inverter 5 switches the switching speed of the switching element 531 by switching the resistance value of the gate drive circuit 54 connected to the switching element 531 (FIG. 9) based on a gate resistance control signal as will be described later.

[0019] The current detector 6 detects the current i of at least two of the three phases. u , i v The second coordinate transformation unit 10 detects i u , i v Based on the electrical angle θ, the dq axis current i d ,i q Convert to.

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[0020] A rotor position sensor 8 detects the electrical angle θ of the rotor of the electric motor 7. A rotation speed calculation unit 9 calculates and outputs the rotation speed N of the electric motor 7 from the amount of change per unit time of the electrical angle θ.

[0021] [Control and calculation section 1] 2 is a diagram showing an example of a block configuration of a control calculation unit 1 constituting the control device for the electric motor 7 of the first embodiment. The control calculation unit 1 includes a current vector control unit 11, a voltage phase control unit 12, an output switch 13, a sudden load change detection unit 14, and a gate resistance setting unit 15.

[0022] [Current vector control unit 11] 3 is a block diagram of a current vector control unit 11 constituting the control device for the electric motor 7 of the first embodiment. The current vector control unit 11 includes a non-interference voltage calculation unit 111, a filter 112, a current target value calculation unit 113, a subtractor 114, a PI compensator 115, and an adder 116. In FIG. 3, the d-axis voltage command value v * di_fin Only the signals related to the calculation of the q-axis voltage command value v * qi_fin The signals related to the calculation of are not shown.

[0023] The current target value calculation unit 113 calculates the torque command value T * and the d-axis current command value i * d , and the q-axis current command value i * q This table stores a table in which the desired torque (torque command value T * ) is most efficiently generated. This table may also take into consideration the temperature characteristics of the motor 7. The current target value calculation unit 113 refers to this table and calculates the torque command value T * , the rotation speed N of the electric motor 7, and the DC voltage V of the battery 52. dc The d-axis current command value i * d and outputs the obtained command value to subtractor 114. Current target value calculation unit 113 can also output the obtained command value to voltage phase control unit 12.

[0024] The subtractor 25 subtracts the d-axis current command value i * d and the d-axis current i dThe deviation between the calculated value and the calculated value is output to the PI compensator 115.

[0025] The PI compensator 115 is a computing unit that performs so-called PI control. More specifically, the PI compensator 115 calculates the d-axis current command value i * d The actual current (d-axis current i d ) to follow the d-axis current command value i * d and the d-axis current i d In order to perform feedback control based on the deviation from the current, the current feedback voltage command value v is calculated using the following equation (3). di ' is calculated. The current feedback voltage command value v di ' is output to the adder 116.

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[0026] The non-interference voltage calculation unit 111 refers to a table stored in advance and calculates the torque command value T * , the rotation speed N of the electric motor 7, and the DC voltage V of the battery 52. dc According to this, the d-axis decoupling voltage command value v * d_dcpl and outputs the obtained command value to the filter 112. The table used here stores interference voltage values ​​corresponding to current values ​​that generate the desired torque most efficiently, which have been obtained in advance through experiments or analysis. More specifically, when currents flow through the d-axis and q-axis, ω·Ld·i d , ω Lq i on the q axis q Therefore, the d-axis non-interfering voltage command value v * d_dcpl , and the q-axis decoupling voltage command value v * q_dcpl is the voltage to cancel these out. Note that Ld is the reactance on the d axis, and Lq is the reactance on the q axis.

[0027] The filter 112 is a so-called low-pass filter. The filter 112 is a low-pass filter that takes into consideration that the interference voltage depends on the current flowing in the d-axis and q-axis, and is set to a time constant that satisfies the target responsiveness of the d-axis current. The filtered d-axis non-interacting voltage command value v d_dcpl_flt is output to adder 116.

[0028] Then, as shown in the following formula (4), the adder 116 calculates the d-axis non-interacting voltage command value v d_dcpl_flt and the current feedback voltage command value v output from the PI compensator 115. di By adding ' and ', the d-axis voltage command value v is obtained, in which the interference voltage generated when the current flows on the d-axis is suppressed. * di_fin is calculated.

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[0029] Although omitted in the figure, the q-axis voltage command value v * qi_fin The d-axis voltage command value v * di_fin The calculated dq-axis voltage command value v * di_fin ,v * qi_fin is output to the output switch 13.

[0030] [Voltage phase control unit 12] 4 is a diagram showing an example of a block configuration of the voltage phase control unit 12 constituting the control device for the electric motor 7 of the first embodiment. The voltage phase control unit 12 controls a voltage phase command value α * The generator includes a modulator 1201, a voltage phase table 1202, a filter 1203, a torque calculator 1204, a subtractor 1205, a PI compensator 1206, an adder 1207, and a voltage phase command value limiter 1208.

[0031] Furthermore, the voltage phase control unit 12 controls the voltage norm command value V * aThe voltage phase control unit 12 includes a current target value calculation unit 1209, a magnetic flux calculation unit 1210, a filter 1211, a magnetic flux calculation unit 1212, a subtractor 1213, a PI controller 1214, an adder 1215, and a voltage norm command value limiting unit 1216. Furthermore, the voltage phase control unit 12 includes a vector conversion unit 1217.

[0032] The modulator 1201 (feedforward voltage norm command value generator) modulates the DC voltage V dc and a reference modulation factor M * Based on this, the feedforward voltage norm command value V is calculated using the following equation (5). * a_ff The calculated feedforward voltage norm command value V * a_ff is output to the voltage phase table 1202 and the adder 1215.

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[0033] The modulation factor here is the phase-to-phase voltage (for example, the voltage between the UV phases v u -v v ) the amplitude of the fundamental component of the DC voltage V dc It is defined as the ratio of the modulation factor to the output voltage. When the modulation factor is 1 or less, it is in the normal modulation region where a quasi-sine wave voltage can be generated by PWM control, and when it exceeds 1, it is in the overmodulation region where there are upper and lower limits to how much a quasi-sine wave can be generated by PWM control. For example, when the modulation factor is about 1.1, even if you try to generate a quasi-sine wave by PWM control, the output voltage will be a so-called square wave voltage.

[0034] The voltage phase table 1202 uses a look-up table previously obtained by experiment or analysis to calculate the torque command value T * , the rotation speed N of the electric motor 7, and the feedforward voltage norm command value V * a_ff The feedforward voltage phase command value α according to ff The feedforward voltage phase command value αff is output to the adder 1207. The lookup table stores voltage phase command values ​​for each operating point of each index in a nominal state, which are measured in advance through experiments.

[0035] The torque calculation unit 1204 stores a lookup table that indicates the relationship between the d-axis and q-axis current values ​​flowing to the electric motor 7, which have been measured in advance through experiments or the like, and the torque generated in the electric motor 7. The torque calculation unit 1204 refers to this lookup table to calculate the dq-axis current i d ,i q From this, the torque estimation value T est and outputs the calculated value to the subtractor 1205.

[0036] The filter 1203 is a low-pass filter similar to the filter 112 constituting the current vector control unit 11, and is used to filter the input torque command value T * The torque reference value T ref and outputs it to the subtractor 1205.

[0037] The subtractor 1205 subtracts the torque reference value T ref and the torque estimate T est Deviation from T err Calculate the deviation T err is output to the PI compensator 1206.

[0038] The PI compensator 1206 is a computing unit that performs so-called PI control. ref and the torque estimate T est Deviation from T err In order to perform feedback control based on the above, the feedback voltage phase command value α fb Calculate.

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[0039] where K αpis the proportional gain, K αi is the integral gain. The calculated feedback voltage phase command value α fb is output to the adder 1207.

[0040] The adder 1207 calculates the feedforward voltage phase command value α ff and the feedback voltage phase command value α fb The value (voltage phase command value) obtained by adding these is output to the voltage phase command value limiting unit 1208.

[0041] The voltage phase command value limiting unit 1208 limits the output value of the adder 1207 within a predetermined range α min From α max The limited value is set to the voltage phase command value α * The vector conversion unit 1217 outputs the vector as a predetermined range α min From α max (hereinafter also referred to as "upper and lower limit values ​​α") will be described with reference to FIG.

[0042] Fig. 5 is a diagram showing an example of the relationship between voltage phase and torque. When the electric motor 7 to be controlled exhibits the characteristics shown in Fig. 5, the upper and lower limit values ​​α are set to ±105°, which is the peak-to-peak value of the curve in the diagram, as a range in which the correlation between voltage phase and torque is maintained.

[0043] Further, while the value (voltage phase command value) output from the adder 1207 exceeds the upper / lower limit value α (while it is stuck to the upper / lower limit value α), the voltage phase command value limiting unit 1208 limits the voltage phase command value α * is limited by the upper and lower limit value α, to the PI compensator 1206. * While it is notified that the integral is limited, the integral value is stopped from being updated for the so-called anti-windup.

[0044] The current target value calculation unit 1209 is the same as the current target value calculation unit 113 constituting the current vector control unit 11. The current target value calculation unit 1209 refers to the table in the same manner as above, and calculates the torque command value T * , the rotation speed N of the electric motor 7, and the DC voltage V of the battery 52. dc The d-axis current command value i * d and q-axis current command value i * q and outputs the obtained command value to the magnetic flux calculation unit 1210.

[0045] The magnetic flux calculation unit 1210 calculates the d-axis current command value i input from the current target value calculation unit 1209. * d , and the q-axis current command value i * q Using the number of winding interlinkage magnetic fluxes Φa, the d-axis inductance Ld, and the q-axis inductance Lq, which are constants of the motor 7, a magnetic flux norm command value Φ0, which is the norm of the composite magnetic flux of the magnet magnetic flux and the current magnetic flux, is calculated as shown in the following formula (7).

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[0046] Similarly, the magnetic flux calculation unit 1212 calculates the d-axis current i d , q-axis current i q and calculate the flux norm estimate Φ based on the following equation (8): 0_est Calculate.

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[0047] The filter 1211 is the same as the filter 1203 and is configured to receive a flux norm reference value Φ 0_ref Calculate.

[0048] The subtractor 1213 subtracts the flux norm reference value Φ 0_ref and the flux norm estimate Φ 0_est The deviation between the calculated value and the calculated value is output to the PI controller 1214.

[0049] The PI controller 1214 controls the flux norm reference value Φ 0_ref and the flux norm estimate Φ 0_est and the feedback voltage norm command value V aー_fb Calculate.

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[0050] where K Φp is the proportional gain, K Φi is the integral gain.

[0051] The adder 1215 calculates the feedforward voltage norm command value V a_ff and the feedback voltage norm command value V a_fb The sum of these is output to the voltage norm command value limiting unit 1216.

[0052] The voltage norm command value limiting unit 1216 limits the feedforward voltage norm command value V a_ff and the feedback voltage norm command value V a_fb The voltage norm command value is the sum of the voltage norm lower limit 0 and the voltage norm upper limit V a_max The voltage norm upper limit V a_max is the maximum allowable setting value M of the modulation factor in voltage phase control * max and DC voltage V dc Based on this, it is always calculated using the following formula (10).

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[0053] Here, while the voltage norm command value is stuck to the upper limit value, the voltage norm is fixed, and the conventional voltage phase control in which the estimated torque is fed back to the voltage phase is performed.

[0054] Furthermore, while the voltage norm command value limiting unit 1216 is sticking to the upper or lower limit value, it sends a notification signal to the PI controller 1214 to notify that the voltage norm command value is being limited. While being notified that the voltage norm command value is being limited, the PI controller 1214 stops integral calculations for anti-windup.

[0055] The vector conversion unit 1217 converts the voltage norm command value V * a and the voltage phase command value α after limit processing * is input, and the d-axis voltage command value v is calculated based on the following equation (11). * dv_fin , and the q-axis voltage command value v * qv_fin and outputs it to the output switch 13.

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[0056] [Output switch 13] 6 is a diagram showing an example of a block configuration of the output switch 13 constituting the control device for the electric motor 7 of the first embodiment. As shown in FIG. 6, the output switch 13 includes a switch 131 and a control mode determination unit 132.

[0057] The switch 131 receives the d-axis voltage command value v from the current vector control unit 11. * di_fin , and the q-axis voltage command value v * qi_fin is input, and the d-axis voltage command value v is output from the voltage phase control unit 12. * dv_fin , and the q-axis voltage command value v * qv_fin is entered.

[0058] Furthermore, the switch 131 selects between the current vector control and the voltage phase control based on the control mode signal input from the control mode determination unit 132, and when the current vector control is selected, the d-axis voltage command value v * di_fin , and the q-axis voltage command value v * qi_finThe final dq-axis voltage command value v * d_fin ,v * q_fin to the first coordinate transformation unit 2, and when voltage phase control is selected, the d-axis voltage command value v * dv_fin , and the q-axis voltage command value v * qv_fin The final dq-axis voltage command value v * d_fin ,v * q_fin to the first coordinate transformation unit 2.

[0059] The control mode determination unit 132 determines the dq-axis final voltage command value v * d_fin ,v * q_fin Then, the DC voltage Vdc is input, and the control mode is determined according to the following formula (12) and Table 1.

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[0060] As shown in Table 1, M ratio When becomes larger than 1.05, it switches to voltage phase control (second control mode), and M ratio When becomes smaller than 1.00, it switches to current vector control (first control mode), and M ratio is 1.00≦M ratio If ≦1.05, the current control mode is maintained.

[0061] The control mode determination unit 132 outputs information about the control mode to the switch 131 and the sudden load change detection unit 14 .

[0062] [Load sudden change detection unit 14] Fig. 7 is a diagram showing an example of a block configuration of the sudden load change detection unit 14 that constitutes the control device for the electric motor 7 of the first embodiment. Fig. 8 is a diagram showing an example of a block configuration of an acceleration calculation unit 151 that constitutes the sudden load change detection unit 14. As shown in Fig. 7, the sudden load change detection unit 14 has an acceleration determination unit 141 and a sudden load change determination unit 142.

[0063] As shown in FIG. 8, the acceleration determination unit 141 includes a rotation speed change rate calculation unit 1411, a phase lead compensation value calculation unit 1412, an adder 1413, and a rotation speed change rate calculation unit 1414.

[0064] The rotation speed change rate calculation unit 1411 approximately differentiates the rotation speed N to calculate the rate of change per unit time of the rotation speed N. The phase lead compensation value calculation unit 1412 applies a gain k N where the gain k N is the delay time in detecting the rotation speed. For example, if the rotation speed calculation unit 9 (Fig. 1) calculates the rotation speed N based on the amount of change in the electrical angle θ over 2 [ms], the delay time is about half of 2 [ms], so the gain k N =0.001 (1 [ms]).

[0065] An adder 1413 adds the rotation speed N and the output of the phase lead compensation value calculation unit 1412, and outputs the rotation speed N' after phase lead compensation.

[0066] The rotation speed change rate calculation unit 1414 approximately differentiates the rotation speed N' to calculate the rate of change of the rotation speed N' per unit time, and outputs this as acceleration to the sudden load change determination unit 142. Note that the time constant τ w is set to a value that is short enough to maintain the properties of the approximate differentiation while taking into consideration the resolution of the rotation speed N and the effects of noise, etc.

[0067] The sudden load change determination unit 142 determines whether or not a sudden change in load has occurred based on, for example, Table 2 shown below, and outputs the result. [Table 2]

[0068] As shown in Table 2, the sudden load change determination unit 142 determines, for example, the torque command value T * If is greater than 200 [Nm], the control mode is current vector control, and the acceleration (threshold) is lower than -200000 [rpm / s] (deceleration) (if the absolute value becomes higher), it is determined that a sudden change has occurred.

[0069] Furthermore, the load sudden change determination unit 142 determines, for example, the torque command value T * is greater than 200 [Nm], the control mode is voltage phase control, and the acceleration (threshold) is lower than −100000 [rpm / s] (deceleration), it is determined that a sudden change has occurred.

[0070] Generally, current vector control is more robust than voltage phase control with respect to sudden changes in load, and therefore the acceleration threshold value is set to a more relaxed value for current vector control.

[0071] In addition, the load sudden change determination unit 142 determines, for example, the torque command value T * is greater than 200 [Nm], the control mode is current vector control, and the acceleration is -200000 [Nm] or greater, the torque command value T * is greater than 200 [Nm], the control mode is voltage phase control, and the acceleration is -100000 [Nm] or greater, the torque command value T * If the load is 200 [Nm] or less (Table 2: other than the above), it is determined that there is no sudden change in the load.

[0072] The sudden load change determination unit 142 determines the torque command value T * For example, if the torque command value T * The smaller the acceleration (threshold value) for detecting a sudden change in the load may be set lower (the absolute value may be higher).

[0073] [Gate resistance setting section 15] The gate resistance setting unit 15 sets the gate resistance control signal based on, for example, Table 3 shown below. [Table 3]

[0074] When it is necessary to discharge the smoothing capacitor 51 connected to the inverter 5 due to a system shutdown or the like, that is, when a discharge request is received from the electric vehicle side as shown in Table 3, the gate resistance setting unit 15 outputs a gate resistance control signal that increases the gate resistance. This increases the loss in the switching element 531, enabling discharge to be performed in a short time.

[0075] When there is no discharge request and the sudden load change determination unit 142 determines that there is no sudden load change, the gate resistance setting unit 15 outputs a gate resistance control signal that reduces the gate resistance when the temperature of the cooling water that cools the power module 53 exceeds, for example, 40° C. or the temperature of the power module 53 exceeds 100° C. This reduces the loss (heat) in the switching element 531 and suppresses the temperature rise of the power module 53.

[0076] When there is no discharge request and the sudden load change determination unit 142 determines that there is no sudden load change, if the temperature of the cooling water that cools the power module 53 is, for example, 40°C or lower and the temperature of the power module 53 is 100°C or lower, the gate resistance setting unit 15 determines that the state is a low temperature state in which the withstand voltage (allowable voltage) of the switching element 531 is reduced, and outputs a gate resistance control signal that increases the gate resistance.

[0077] When there is no discharge request and sudden load change determination unit 142 determines that a sudden load change has occurred, gate resistance setting unit 15 outputs a gate resistance control signal that increases the gate resistance.

[0078] [Gate drive circuit 54 of inverter 5] 9A and 9B are diagrams showing an example of a block configuration of the gate drive circuit 54 constituting the inverter 5, in which FIG. 9A shows a configuration in which the gate drive circuit 54 includes a fixed resistor 544 and a switch 543, and FIG. 9B shows a configuration in which the gate drive circuit 54 includes a variable resistor 545.

[0079] As shown in FIG. 9(a), the power module 53 to which the gate drive circuit 54 is connected has series circuits for the U phase, V phase, and W phase, each of which is provided with a parallel circuit of a switching element 531U and a feedback diode 532U on the upper arm side and a parallel circuit of a switching element 531L and a feedback diode 532L on the lower arm side, and these are connected in parallel.

[0080] In FIG. 9(a), the three-phase voltage v of the U phase of the power module 53 u Only the series circuit outputting the V-phase three-phase voltage v is shown. v and the W-phase three-phase voltage v w 9(b), the switching element 531L on the lower arm side, the feedback diode 532L, and the gate drive circuit 54 connected to the switching element 531L are not shown.

[0081] The gate drive circuit 54 includes a gate drive IC 541 , a fixed resistor 542 , a switch 543 and a fixed resistor 544 , and applies a gate voltage to the power module 53 .

[0082] The gate driver IC 541 generates a high-voltage element drive signal (D * uu ,D * ul ,D * vu ,D * vl ,D * wu ,D * wl) to output a gate voltage based on the gate driving IC 541. A fixed resistor 542 is arranged between the gate driving IC 541 and the switching element 531 (gate terminal). A series circuit of a switch 543 and a fixed resistor 544 is also arranged between the gate driving IC 541 and the switching element 531 (gate terminal) so as to bypass the fixed resistor 542. The resistance value (Rq1) of the fixed resistor 542 and the resistance value (Rq2) of the fixed resistor 544 can each be set to any resistance value.

[0083] When a gate resistance control signal that reduces the gate resistance is input, the switch 543 is turned on, and the fixed resistor 544 is conductive between the gate drive IC 541 and the switching element 531 (gate terminal). At this time, the gate resistance of the gate drive circuit 54 becomes a low resistance (Rq1·Rq2 / (Rq1+Rq2)).

[0084] On the other hand, when a gate resistance control signal that increases the gate resistance is input, the switch 543 is turned off, and the fixed resistor 544 is made non-conductive. At that time, the gate resistance of the gate drive circuit 54 becomes a high resistance (Rq1).

[0085] Note that multiple series circuits each consisting of a switch 543 and a fixed resistor 544 may be connected in parallel. In this case, before a sudden change in load is detected, all of the switches 543 are in the ON state, and the gate resistance of the gate drive circuit 54 is in the lowest state. Then, when a sudden change in load is detected, the switches 543 are turned OFF, and the gate resistance of the gate drive circuit 54 is in the highest state.

[0086] 9(b), as a modified example of the gate drive circuit 54, a variable resistor 545 may be arranged between the gate drive IC 541 and the switching element 531 (gate terminal), and the resistance value of the variable resistor 545 may be changed based on a gate resistance control signal. In this case, for example, when a gate resistance control signal that reduces the gate resistance is input, the resistance value of the variable resistor 545 becomes minimum, and when a gate resistance control signal that increases the gate resistance is input, the resistance value of the variable resistor 545 becomes maximum.

[0087] It is also preferable to set the rate at which the switching speed is reduced when a sudden change in load is detected in the first control mode (current vector control) selected to be lower than the rate at which the switching speed is reduced when a sudden change in load is detected in the second control mode (voltage phase control) selected.

[0088] That is, when a sudden change in load is detected while current vector control is selected as the control mode, the control mode determination unit 132 may output a gate resistance control signal that sets the gate resistance to a medium level (resistance value: minimum<medium<maximum) to the gate drive circuit 54. At this time, the resistance value of the variable resistor 545 becomes a medium resistance value.

[0089] Current vector control is more robust against sudden load changes than voltage phase control, and as with voltage phase control, reducing the switching speed results in a switching speed that is lower than the switching speed necessary to appropriately suppress surge voltages, resulting in unnecessary losses. Therefore, as described above, when a sudden load change occurs in current vector control, by outputting to the gate drive circuit 54 a gate resistance control signal that sets the gate resistance to the medium level as described above, it is possible to appropriately suppress surge voltages while suppressing losses.

[0090] Furthermore, in light of the above, when current vector control is selected as the control mode, the control may be configured so that detection of a sudden change in load is not performed, or even if a sudden change in load is detected, control is performed so that the gate resistance is not changed.

[0091] [Surge voltage generated in switching element 531] 10 is a diagram showing the operation of the switching element 531 (FIG. 9). In FIG. 10, the collector current I c and the collector-emitter voltage V ce The graph shows the change over time.

[0092] As shown in the left diagram of Figure 10, when the gate resistance is small, the gate current becomes large, so the turn-off time (and turn-on time) becomes short. At this time, the collector current Ic falls rapidly and the collector-emitter voltage V ce rises rapidly. Then, the collector-emitter voltage V ce In this case, a large surge voltage (Vs) occurs and the withstand voltage of the switching element 531 may be exceeded.

[0093] On the other hand, as shown in the right diagram of Figure 10, increasing the gate resistance reduces the gate current, lengthening the turn-off time (and turn-on time). At this time, the collector current Ic falls gradually and the collector-emitter voltage V ce This causes the collector-emitter voltage V ce The surge voltage (Vs) is suppressed.

[0094] [Control Flow] 11 shows a control flow of the control device for the electric motor 7 according to the first embodiment. The control flow of the control device (control method) for the electric motor 7 according to the first embodiment will be described.

[0095] In step S101, the rotation speed calculation unit 9 (FIG. 1) acquires the electrical angle θ and executes a rotation speed calculation process, and outputs information on the rotation speed N obtained by the calculation to the control calculation unit 1 (FIG. 1).

[0096] In step S102, the second coordinate conversion unit 10 (FIG. 1) converts the current i detected by the current detector 6 into u ,i v From dq axis current i d ,i q is calculated and output to the control calculation unit 1 (Fig. 1).

[0097] In step S103, the voltage detector 4 (FIG. 1) detects the output voltage of the battery 52 (FIG. 1) and converts it into a DC voltage V dc and outputs it to the control calculation unit 1 (Fig. 1).

[0098] In step S104, the control calculation unit 1 (FIG. 1) calculates the torque command value T * Also, information on discharge request (yes or no) is acquired.

[0099] In step S105, the control calculation unit 1(1) acquires information on the coolant temperature and information on the temperature of the power module 53 (FIG. 9). Note that steps S101 to S105 may be executed in any order.

[0100] In step S106, the control calculation unit 1 (current vector control unit 11) (FIGS. 1 and 2) calculates the torque command value T * , dq-axis current i d ,i q , DC voltage V dc , the dq-axis voltage command value v based on the rotation speed N * di_fin ,v * qi_fin is calculated and output to the output switch 13 (FIG. 2).

[0101] In step S107, the control calculation unit 1 (voltage phase control unit 12) (FIGS. 1 and 2) calculates the torque command value T * , dq-axis current i d ,i q , DC voltage V dc , the dq-axis voltage command value v based on the rotation speed N * dv_fin ,v * qv_fin The result is output to the output switch 13 (FIG. 2). Note that steps S106 and S107 are executed simultaneously.

[0102] In step S108, the control calculation unit 1 (output switch 13) (FIGS. 1 and 2) determines the control mode and sets the d- and q-axis voltage command value v * di_fin ,v * qi_fin , dq-axis voltage command value v * dv_fin ,v * qv_fin The selected command value is used as the dq axis final voltage command value v * d_fin,v * q_fin to the first coordinate transformation unit 2 (FIG. 1).

[0103] In step S109, the control calculation unit 1 (sudden load change detection unit 14) (FIGS. 1 and 2) DC voltage V dc , the rotation speed N, and the control mode, it is determined whether or not a sudden change in the load has occurred, and if a sudden change is detected, it outputs a detection signal to the gate resistance setting unit 15 (FIG. 2).

[0104] In step S110, the control calculation unit 1 (gate resistance setting unit 15) (FIGS. 1 and 2) sets the gate resistance control signal based on the temperature of the power module 53, the temperature of the cooling water, a discharge request (present or absent), and a detection signal indicating a sudden change in the load (present or absent).

[0105] In step S111, the control calculation unit 1 (gate resistance setting unit 15) (FIGS. 1 and 2) outputs the set gate resistance control signal to the gate drive circuit .

[0106] In the control device (control method) for the electric motor 7 of the first embodiment, the series of control steps from step S101 to step S111 are repeatedly executed.

[0107] [Effects of the first embodiment] According to the control method for the electric motor 7 of the first embodiment, DC power is converted into AC power by at least one pair of switching elements 531 (switching element 531U, switching element 531L), and AC power (three-phase voltage v u ,v v ,v w ), the current value (for example, i u ,i v ) to be applied to the motor 7 based on the voltage command value (dq axis final voltage command value v * d_fin ,v * q_fin ) and calculates the voltage command value (dq axis final voltage command value v * d_fin ,v* q_fin ) to be transmitted to the pair of switching elements 531 (switching element 531U, switching element 531L) based on the PWM signal (high-power element drive signal (D * uu ,D * ul ,D * vu ,D * vl ,D * wu ,D * wl )) to control the AC power (three-phase voltage v u ,v v ,v w ) is a control method for the electric motor 7, in which, when a sudden change in the load applied to the electric motor 7 is detected, the switching speed of the switching element 531 (switching element 531U, switching element 531L) is reduced.

[0108] With the above method, even if there is a sudden change in the load on the motor 7, for example, a momentary increase in the current flowing through the motor 7, the switching speed of the switching element 531 (switching element 531U, switching element 531L) is reduced to suppress the surge voltage, thereby reducing the burden on the switching element 531 (switching element 531U, switching element 531L).

[0109] In this embodiment, a sudden change in load is detected based on whether or not the rate of change in the rotation speed N of the electric motor 7 (Table 2: acceleration) exceeds a predetermined threshold value.

[0110] With the above method, since a sudden change in the load is accompanied by a sudden change in the rotation speed N, an increase in surge voltage can be suppressed by making a judgment based on the rate of change in the rotation speed N.

[0111] In this embodiment, phase lead compensation is performed on the rotation speed N (the phase lead component is calculated by the phase lead compensation value calculation unit 1412), and a sudden change in the load is detected based on the rate of change in the rotation speed N' after compensation (FIG. 8).

[0112] By using the above method to perform phase lead compensation on the rotation speed N, it is possible to eliminate the delay time when detecting the rotation speed N, thereby eliminating the delay in detecting a sudden change in load that accompanies this delay time, and to execute control to reduce the switching speed before the surge voltage increases.

[0113] In this embodiment, a sudden change in load is detected only when the rate of change of the rotation speed N is on the deceleration side and its absolute value exceeds a predetermined threshold value (Table 2).

[0114] By using the above method, the current is less likely to rise when the switching speed suddenly changes to the acceleration side, preventing an increase in loss due to an unnecessary decrease in switching speed.

[0115] In this embodiment, the torque command value T * and the current value (e.g., i u ,i v ) based on the voltage command value (dq axis final voltage command value v * d_fin ,v * q_fin ) is generated, the torque command value T * The smaller the threshold (absolute value of acceleration) is, the larger the torque command value T * If the load is below a predetermined value (for example, 200 [Nm] or less), the detection of a sudden change in load is not performed (Table 2).

[0116] With the above method, when the torque generated in the electric motor 7 is low, the absolute value of the peak current value that increases with the change in the rotation speed N is small, and the increase in the surge voltage generated in the switching element 531 (switching element 54U, switching element 531L) is also small, so that an increase in loss due to an unnecessary decrease in the switching speed can be prevented.

[0117] In this embodiment, the voltage command value (dq axis final voltage command value v * d_fin ,v * q_fin) and the voltage command value (dq axis final voltage command value v * d_fin ,v * q_fin When any of the second control modes that calculates the above equation is selected, the absolute value of the threshold value (Table 2: acceleration) of the rate of change of the rotation speed N of the electric motor 7 when detecting a sudden change in the load when the first control mode is selected is set to be larger than the absolute value of the threshold value (Table 2: acceleration) of the rate of change of the rotation speed N of the electric motor 7 when detecting a sudden change in the load when the second control mode is selected.

[0118] Furthermore, the voltage command value (dq axis final voltage command value v) is calculated by current vector control based on the operating state of the electric motor 7. * d_fin ,v * q_fin ) and the voltage command value (dq axis final voltage command value v * d_fin ,v * q_fin When either of the second control modes that calculates ) is selected, the rate of decrease in switching speed when a sudden change in load is detected when the first control mode is selected is set to be lower than the rate of decrease in switching speed when a sudden change in load is detected when the second control mode is selected (Table 2).

[0119] Furthermore, the voltage command value (dq axis final voltage command value v) is calculated by current vector control based on the operating state of the electric motor 7. * d_fin ,v * q_fin ) and the voltage command value (dq axis final voltage command value v * d_fin ,v * q_fin When either of the first and second control modes that calculates the load change amount is selected, the detection of a sudden load change is not performed when the first control mode is selected, and the detection of a sudden load change is performed when the second control mode is selected.

[0120] The above method makes it possible to suppress an increase in loss by suppressing an unnecessary decrease in switching speed in current vector control that is robust against sudden changes in load.

[0121] In this embodiment, when no sudden change in load is detected, the switching speed is set based on at least one of the temperature related to the switching element 531 (PM temperature) and the temperature of the cooling system for the switching element 531 (coolant temperature).

[0122] Furthermore, if no sudden change in the load is detected, the output voltage (DC voltage V dc ) to set the switching speed.

[0123] With the above method, if a sudden change in load occurs, the switching speed is slowed down to suppress the surge voltage; if no sudden change in load occurs and it is determined that the withstand voltage of switching element 531 will be high (temperature is high), the surge voltage is tolerated and the switching speed is increased to suppress losses; and if it is determined that the withstand voltage of switching element 531 will be low (temperature is low), the switching speed is slowed down to suppress the surge voltage, thereby reducing the burden on switching element 531.

[0124] In this embodiment, when performing discharge control of the smoothing capacitor 51 connected to the DC power source (battery 52) that supplies DC power and the switching element 531 (switching element 531U, switching element 531L), the switching speed during the execution of the discharge control is set to be lower than the switching speed before the discharge control is executed.

[0125] By using the above method, the power of the smoothing capacitor 51 can be quickly consumed and discharged during discharge control.

[0126] According to the control device for the electric motor 7 of this embodiment, at least a pair of switching elements 531 (switching elements 531U, 531L) that convert DC power into AC power and supply it to the electric motor 7 of the electric vehicle, and a current value (for example, i u ,i v ) and a current detection means (current detector 6) for detecting a current value (for example, i u ,i v ) to be applied to the motor 7 based on the voltage command value (dq axis final voltage command value v * d_fin ,v * q_fin ) and a voltage command value (dq axis final voltage command value v * d_fin ,v * q_fin ), and a PWM control means (PWM conversion unit 3) that controls AC power by transmitting a PWM signal to the switching element 531 (switching elements 531U, 531L), and a resistance setting means (gate drive circuit 54) that can set a gate resistance is connected to the switching element 531 (switching element 531U, switching element 531L), and the control calculation means (control calculation unit 1) includes a sudden load change detection unit 14 that detects a sudden change in the load applied to the motor 7, and a gate resistance setting unit 15 that, when the sudden load change detection unit 14 detects a sudden change in the load, controls the resistance setting means (gate drive circuit 54) so ​​that the gate resistance becomes higher than before the sudden change in load occurred.

[0127] With the above configuration, even if there is a sudden change in the load on the motor 7, for example, a momentary increase in the current flowing through the motor 7, the switching speed of the switching element 531 (switching element 531U, switching element 531L) is reduced to suppress the surge voltage, thereby reducing the burden on the switching element 531 (switching element 531U, switching element 531L).

[0128] In this embodiment, the resistance setting means (gate drive circuit 54) includes a first resistance element (fixed resistor 542) disposed between the PWM control means (PWM conversion unit 3) and the switching element 531 (switching elements 531U and 531L), and a series circuit of a switch 543 and a second resistance element (fixed resistor 544). The series circuit is disposed between the PWM control means (PWM conversion unit 3) and the switching element 531 (switching elements 531U and 531L) and is disposed so as to bypass the first resistance element (fixed resistor 542). The gate resistance setting unit 15 turns on the switch 543 when there is no sudden change in the load, and turns off the switch 543 when it detects a sudden change in the load. This simple configuration allows for gate resistance control.

[0129] [Second embodiment] Fig. 12 is a diagram showing an example of a block configuration of a control calculation unit 1 constituting the control device for the electric motor 7 of the second embodiment. Fig. 13 is a diagram showing an example of a block configuration of a sudden load change detection unit 14 constituting the control device for the electric motor 7 of the second embodiment.

[0130] In the control device (control method) for the electric motor 7 of the second embodiment, the sudden load change detection unit 14 constituting the control calculation unit 1 detects a torque command value T * and dq axis current i instead of rotation speed N d ,i q Further, the gate resistance setting unit 15 constituting the control calculation unit 1 receives the DC voltage V instead of the temperature (PM temperature) of the power module 53 (FIG. 9) and the cooling water temperature. dc is entered.

[0131] As shown in FIG. 13, the sudden load change detection unit 14 includes a sudden load change determination unit 142 (the same as in the first embodiment) and a current prediction unit 143.

[0132] The current prediction unit 143 predicts the dq-axis current i d ,i qThen, the current prediction unit 143 calculates a current prediction value I, which is the magnitude of the current after a certain time t [s], based on the following formulas (13), (14), and (15). a_est Calculate.

number

number

number

[0133] z in equation (14) -1 is the delay operator, and equation (14) is I From before to now a The amount of change per unit time is calculated.

[0134] The sudden load change determination unit 142 determines whether a sudden change in load has occurred based on Table 4 shown below and outputs the result. In the second embodiment, a sudden change in load is determined based on a predicted current value instead of the acceleration in Table 2 above. [Table 4]

[0135] As shown in Table 4, the load sudden change determination unit 142 determines, for example, the torque command value T * is greater than 200 [Nm], and the control mode is current vector control and the current prediction value I a_est If the current is higher than 1000 [A], it is determined that a sudden change in load has occurred.

[0136] Furthermore, the load sudden change determination unit 142 determines, for example, the torque command value T * is greater than 200 [Nm], and the control mode is voltage phase control and the current prediction value I a_est If the current is higher than 800 [A], it is determined that a sudden change in load has occurred.

[0137] Generally, voltage phase control is based on the premise that the inverter is driven mainly in the overmodulation region, and since there is a tendency for carrier harmonics that cannot be detected by the current detector 6 (Fig. 1) to increase, voltage phase control has a stricter threshold (lower threshold).

[0138] In addition, the load sudden change determination unit 142 determines, for example, the torque command value T * is greater than 200 [Nm] and the control mode is current vector control and the current predicted value I a_est When the torque command value T * is greater than 200 [Nm] and the control mode is voltage phase control and the current prediction value I a_est When the torque command value T * If the load is 200 [Nm] or less, it is determined that there is no sudden change in the load.

[0139] The gate resistance setting unit 15 shown in FIG. 12 outputs a gate resistance control signal based on Table 5 shown below. [Table 5]

[0140] When there is no discharge request and the sudden load change determination unit 142 determines that there is no sudden change in the load, the gate resistance setting unit 15 determines, for example, the DC voltage V dc If the voltage is lower than 350V, the gate resistance is reduced by outputting a gate resistance control signal. dc If the voltage is 350V or higher, a gate resistance control signal is output that increases the gate resistance.

[0141] In normal operation without sudden changes in load, there is a voltage tolerance margin for the temperature fluctuation range, and the DC voltage V of the battery 52 dc If the margin of withstand voltage for the fluctuation range of DC voltage V dc When the voltage exceeds a predetermined value (for example, 350 V), the gate resistance is increased to suppress the surge voltage.

[0142] When there is no discharge request and the sudden load change determination unit 142 detects a sudden change in the load, or when there is a discharge request, the gate resistance setting unit 15 outputs a gate resistance control signal that increases the gate resistance.

[0143] According to the control method of the electric motor 7 of the second embodiment, the current value (dq axis current i d ,i q ) and the current value (dq axis current i d ,i q ) from the rate of change of the magnitude of the current after a certain time (current prediction value I a_est ) and calculate the predicted value (current predicted value I a_est ) exceeds a predetermined threshold. With the above method, a sudden change in load is accompanied by a sudden change in current, so even if the current magnitude remains the same, the switching speed is slowed down to suppress the increase in surge voltage, thereby suppressing unnecessary increases in loss.

[0144] [Third embodiment] Fig. 14 is an overall schematic diagram of a control device for an electric motor 7 according to a third embodiment. Fig. 15 is a diagram showing an example of a block configuration of a control calculation unit 1 constituting the control device for an electric motor 7 according to the third embodiment. Fig. 16 is a diagram showing an example of a block configuration of a sudden load change detection unit 14 constituting the control device for an electric motor 7 according to the third embodiment. Fig. 17 is a diagram showing the definition of a sudden load change region.

[0145] As shown in Fig. 14, information on the amount of brake operation (braking force) associated with the brake operation by the driver of the electric vehicle is input to a control calculation unit 1 constituting a control device (control method) for an electric motor 7 of the third embodiment. Also, as shown in Fig. 15, the control calculation unit 1 includes a normal carrier frequency selection unit 16 that selects a carrier frequency for PWM control when there is no sudden change in the load. Also, information on the normal carrier frequency is input to a gate resistance setting unit 15 from the normal carrier frequency selection unit 16.

[0146] Normally, the carrier frequency selector 16 selects the torque command value T *and the rotation speed N are input. Then, the normal carrier frequency selection unit 16 sets the carrier frequency based on Table 6 shown below. [Table 6]

[0147] As shown in Table 6, the normal carrier frequency selection unit 16 selects the torque command value T * For example, if the absolute value of is greater than 250 [Nm] and the absolute value of the rotation speed N is lower than 100 [rpm], the normal carrier frequency is set to 1.5 [kHz].

[0148] Furthermore, the normal carrier frequency selector 16 selects the torque command value T * For example, if the absolute value of is greater than 250 [Nm] and the absolute value of the rotation speed N is 100 [rpm] or more (Table 6: Other than the above), or if the torque command value T * If the absolute value of is, for example, 250 [Nm] or less (Table 6: other than the above), the carrier frequency is normally set to 10 [kHz].

[0149] As described above, carrier frequency selector 16 normally lowers the carrier frequency to suppress heat generation in switching element 531 at low rotation speeds and high torque, and selects a high-frequency carrier frequency that places importance on control performance at other times.

[0150] As shown in Figure 16, the sudden load change detection unit 14 has an acceleration calculation unit 151 and a sudden load change determination unit 142, as in the first embodiment, but information on the brake operation amount is input to the sudden load change determination unit 142 instead of the control mode.

[0151] Unlike the first embodiment (Table 2), the sudden load change determination unit 142 determines whether or not a sudden change in load has occurred based on the following Table 7. Table 7 lists the braking force corresponding to the amount of brake operation. [Table 7] As shown in Table 7, the sudden load change detection unit 14 calculates the torque command value T * -braking force) is lower than a predetermined threshold value Kth described later, and the torque command value T * For example, if the load is lower than 250 [Nm], it is determined (predicted) that there will be no sudden change in the load.

[0152] Furthermore, the load sudden change detection unit 14 calculates the acceleration / (torque command value T * -braking force) is lower than a predetermined threshold value Kth described later, and the torque command value T * For example, when the braking force is greater than 250 [Nm] (Table 7: Other than the above) and the torque command value T * If the value is greater than twice the value of the load, it is determined that a sudden change in load has occurred, or it is predicted that a sudden change in load will occur.

[0153] Furthermore, the load sudden change detection unit 14 calculates the acceleration / (torque command value T * - braking force) is equal to or greater than a predetermined threshold value Kth (Table 7: other than the above), it is determined that a sudden change in load has occurred or is predicted to occur. * In place of the acceleration, the accelerator opening may be applied, and in the determination (Table 7), the rate of change of the rotation speed N (corresponding to acceleration) or the rate of change of the wheel speed (rotational speed) of the electric vehicle (corresponding to acceleration) may be applied instead of the acceleration.

[0154] In FIG. 17, the horizontal axis represents the torque of the electric motor 7 (torque command value T * ) minus the braking force ([T * In a plane coordinate system with the vertical axis representing acceleration, this line represents the normal maximum acceleration / deceleration line, which is the boundary between the area where a sudden change in load occurs and the area where a sudden change in load does not occur.

[0155] The threshold value Kth shown in Table 7 corresponds to the gradient of the normal maximum acceleration / deceleration line shown in FIG.

[0156] In Figure 17, the normal acceleration region is [T *-braking force] ≥ 0 and the wheels (drive wheels) of the electric vehicle accelerate without slipping. * -braking force]≦0, and the wheels of the electric vehicle decelerate without slipping.

[0157] The area described as "super uphill" is [T * -braking force]≧0, for example, the road surface on which the electric vehicle is traveling has a steep uphill gradient, causing the electric vehicle to decelerate or accelerate in the direction opposite to the traveling direction.

[0158] The area described as "super downslope" is [T * -braking force]<0, for example, in this region, the road surface on which the electric vehicle is traveling has a steep downward gradient, causing the electric vehicle to accelerate in the direction of travel.

[0159] The sudden load change region (slip) is [T * -braking force] ≧ 0, the electric vehicle accelerates in the direction of travel, but the wheels slip on the road surface.

[0160] The sudden load change area (sudden deceleration) is [T * -Braking force] < 0, the electric vehicle decelerates, but the wheels slip on the road surface and eventually lock (stop rotating).

[0161] In the third embodiment, when the electric vehicle enters a sudden load change region (slip, sudden deceleration) shown in FIG. 17, it is determined that a sudden change in load has occurred.

[0162] Also, the torque (torque command value T * ) is larger than a certain level, and at the same time, the braking force (torque command value T * Even if a wheel slippage occurs, the system determines that a sudden change in load equivalent to wheel lock from slippage has occurred, or predicts a sudden change in load.

[0163] The gate resistance setting unit 15 sets the gate resistance control signal and the carrier frequency according to Table 8 below. [Table 8]

[0164] The setting of the gate resistance control signal in the gate resistance setting unit 15 is the same as in the first embodiment (Table 3). When there is no discharge request, the gate resistance setting unit 15 outputs information about the normal carrier frequency set by the normal carrier frequency to the PWM conversion unit 3. Furthermore, when there is a discharge request, the gate resistance setting unit 15 outputs information about a carrier frequency (e.g., 12 [kHz]) that is higher than the highest carrier frequency (e.g., 10 [kHz]) among the normal carrier frequencies set by the normal carrier frequency to the PWM conversion unit 3.

[0165] In the third embodiment, when there is a discharge request, the gate resistance is increased and the carrier frequency is also increased, thereby increasing the switching loss and enabling efficient discharge.

[0166] According to the control method of the electric motor 7 of the third embodiment, the torque command value T * and the current value (e.g., I u ,I v ) based on the voltage command value (dq axis final voltage command value v * d_fin ,v * q_fin ) is generated, the torque command value T * A sudden change in load is detected when the ratio between either the accelerator opening or brake operation amount (braking force) and either the rate of change (acceleration) of the wheel speed of the electric vehicle or the rate of change (acceleration) of the rotation speed N is equal to or greater than a predetermined value.By using the above method, it can be determined that there will be no sudden change in load within a predetermined range of operation of the electric vehicle in response to the operation requested by the driver, so it is possible to suppress an increase in loss due to an unnecessary decrease in switching speed, while also preparing to suppress an increase in surge voltage due to a sudden change in load outside the predetermined range.

[0167] In the third embodiment, the torque command value T * and the current value (e.g., I u ,I v ) based on the voltage command value (dq axis final voltage command value v * d_fin ,v * q_fin ) is generated, the torque command value T * Alternatively, a sudden change in load is detected when the accelerator opening and brake operation amount (braking force) are equal to or greater than a predetermined value. By using the above method, it is possible to prepare for a sudden change in load caused by the wheels slipping and locking on a low μ road surface (slippery road surface) such as an icy road or packed snow road, and to suppress an increase in surge voltage.

[0168] In the third embodiment, when performing discharge control of the smoothing capacitor 51 connected to the DC power supply (battery 52) that supplies DC power and the switching element 531 (switching element 531U, switching element 531L), the switching speed during the execution of the discharge control is set to be lower than the switching speed before the discharge control is executed, and the switching frequency (for example, 12 [kHz]) of the PWM signal during the discharge control is set to be lower than the switching speed before the discharge control is executed. * The frequency is set higher than the highest switching frequency (for example, 10 kHz) among the switching frequencies set based on the rotation speed N of the electric motor 7. By using the above method, the power of the smoothing capacitor 51 can be quickly consumed and discharged during discharge control.

[0169] [Fourth embodiment] Fig. 18 is a diagram showing an example of a block configuration of the control calculation unit 1 constituting the control device for the electric motor 7 of the fourth embodiment. Fig. 19 is a diagram showing the behavior of the torque and the rotation speed N when traveling on a rough road. Fig. 20 is a time chart showing the operation of the sudden load change detection unit 14 constituting the control device for the electric motor 7 of the fourth embodiment.

[0170] In the control device (control method) for the electric motor 7 of the fourth embodiment, the control calculation unit 1 has a vibration suppression control unit 17. The vibration suppression control unit 17 receives a torque command value T * The torque command value T * The ' (first torque command value) is a command value required by the driver's operation (accelerator opening degree, etc.), and does not take into consideration vibration of the electric vehicle due to the torsional vibration system from the output shaft of the electric motor 7 to the wheels.

[0171] The vibration control unit 17 controls the torque command value T so as to suppress the vibration of the vehicle caused by the torsional vibration system from the output end of the electric motor 7 to the wheels, as in the prior art (for example, Patent No. 3508742). * ' is compensated for to obtain the torque command value T * (second torque command value). Then, the vibration suppression control unit 17 calculates the torque command value T * is output to the current vector control unit 11, the voltage phase control unit 12, and the sudden load change detection unit 14.

[0172] The sudden load change detection unit 14 receives the torque command value T * ', torque command value T * The sudden load change detection unit 14 receives the torque command value T * and torque command value T * A counter (not shown) is provided to count the number of times that the absolute value of the difference between the value ' exceeds a predetermined threshold value Tth.

[0173] The sudden load change detection unit 14 detects the occurrence of a sudden change in load as shown in Table 9 below, and executes counter processing. [Table 9]

[0174] As shown in Table 9, the load sudden change detection unit 14 detects the torque command value T * and torque command value T * Absolute value of the difference between |T * '-T *| exceeds a threshold Tth (for example, 10 [Nm]), and the count value of the counter reaches a predetermined count value k max If the number of times is less than 5 (for example), the count is incremented by 1, and in this case it is determined that there is no sudden change in the load.

[0175] On the other hand, the load sudden change detection unit 14 detects the absolute value |T * '-T * | exceeds the threshold Tth, and the count value of the counter reaches a predetermined count value k max When it reaches this value, the counting is stopped and the count number is held, and it is determined that a sudden change in the load has occurred.

[0176] Furthermore, the load sudden change detection unit 14 detects when the count value of the counter reaches a predetermined count value k max If the absolute value |T * '-T * When the state where | is equal to or less than the threshold value Tth has elapsed for a predetermined time tc [s] (for example, 2 [s]), the count value is cleared.

[0177] Similarly, the load sudden change detection unit 14 detects when the count value of the counter reaches a predetermined count value k max If the absolute value |T * '-T * When the state where | is equal to or less than the threshold value Tth has elapsed for a predetermined time tc [s] (for example, 2 [s]), the count value is cleared.

[0178] The upper diagram in Fig. 19 shows the torque command value T * and torque command value T * 19 shows a time chart of rotation speed N, and the bottom diagram of FIG. 19 shows a time chart of rotation speed N. For example, when traveling on a rough, undulating road where the wheels repeatedly spin (slip) and grip (grip), if the frequency of repetition approaches the resonance frequency of the torsional vibration system depending on the traveling speed or the rotation speed N of the electric motor 7, a vibration component may be superimposed on the rotation speed N as shown in the bottom diagram of FIG. 19, causing repeated sudden acceleration and deceleration.

[0179] At this time, the vibration suppression control unit 17 acts to reduce the rotational speed vibration, and the torque command value T required by the accelerator opening etc. * The torque command value T is calculated by superimposing a torque compensation value of the same frequency as the vibration occurring at the rotation speed N on the * is generated.

[0180] Therefore, the torque command value T * vibrates at the same frequency as the rotation speed N, but the two have a relationship in which the vibration components cancel each other out, so the torque generated by the electric motor 7 is * This is almost the same as the ', and can suppress vibrations generated in electric vehicles.

[0181] Figure 20 shows the absolute value |T * '-T * 10 is a time chart showing the count value of the counter of the sudden load change detection unit 14 and the determination of a sudden load change by the sudden load change detection unit 14.

[0182] As shown in FIG. 20, the initial count value of the counter is zero, but the absolute value |T * '-T * Each time | exceeds Tth, the counter count is incremented by 1, and the count value becomes k max The count value remains constant when the absolute value |T * '-T * If the state where | does not exceed the threshold Tth continues for tc [s], the count value is reset.

[0183] The sudden load change detection unit 14 determines that there is no sudden change in the load in the initial state, but when the count value of the counter reaches k max When the count value of the counter is reset, it is determined that the sudden change in load has been resolved.

[0184] According to the control method of the electric motor 7 of the fourth embodiment, the torque command value T * and the current value (e.g., i u ,i v) based on the voltage command value (dq axis final voltage command value v * d_fin ,v * q_fin ) is generated, and the torque command value T * The first torque command value (torque command value T * The second torque command value (torque command value T * ), the second torque command value (torque command value T * ) and the first torque command value (torque command value T * The difference between the count value k and the amplitude of the count value k exceeds a predetermined value. max The above method detects a sudden change in load when the vehicle is traveling on a rough road where the wheels repeatedly spin (slip) and grip the ground (grip), and can suppress an increase in surge voltage.

[0185] Although the embodiments of the present invention have been described above, the above embodiments merely illustrate some of the application examples of the present invention, and the technical scope of the present invention is not intended to be limited to the specific configurations of the above embodiments. Furthermore, the above embodiments can be combined as appropriate. [Explanation of symbols]

[0186] 1 control calculation unit, 14 load sudden change detection unit, 15 gate resistance setting unit, 3 PWM conversion unit, 531 (531U, 531L) switching element, 54 gate drive circuit, 6 current detector, 7 electric motor

Claims

1. A method for controlling an electric motor, in which DC power is converted into AC power by at least a pair of switching elements and the AC power is supplied to an electric motor of an electric vehicle, the method comprising: calculating a voltage command value to be applied to the electric motor based on a current value supplied to the electric motor; and controlling a PWM signal to be transmitted to the pair of switching elements based on the voltage command value, When a sudden change in the load applied to the electric motor is detected, the switching speed of the switching element is reduced. The detection of the sudden change in the load is determined based on whether or not a rate of change in the rotation speed of the electric motor exceeds a predetermined threshold value; When the voltage command value is generated based on a torque command value and the current value required by the electric vehicle, A control method for an electric motor, which detects a sudden change in the load when a ratio between the torque command value, accelerator opening, or brake operation amount and either a rate of change in wheel speed of the electric vehicle or a rate of change in the rotation speed is equal to or greater than a predetermined value.

2. 2. The method for controlling an electric motor according to claim 1, further comprising: performing phase lead compensation on the rotational speed; and detecting a sudden change in the load based on a rate of change in the rotational speed after compensation.

3. 3. The method for controlling an electric motor according to claim 1, wherein a sudden change in the load is detected only when the rate of change of the rotational speed is on the deceleration side and its absolute value exceeds a predetermined threshold value.

4. A method for controlling an electric motor described in any one of claims 1 to 3, wherein the threshold value is increased as the torque command value becomes smaller, or when the torque command value is below a predetermined value, detection of a sudden change in the load is not performed.

5. A method for controlling an electric motor, in which DC power is converted into AC power by at least a pair of switching elements and the AC power is supplied to an electric motor of an electric vehicle, the method comprising: calculating a voltage command value to be applied to the electric motor based on a current value supplied to the electric motor; and controlling a PWM signal to be sent to the pair of switching elements based on the voltage command value, thereby controlling the AC power, When a sudden change in the load applied to the electric motor is detected, the switching speed of the switching element is reduced. The detection of the sudden change in the load is determined based on whether or not a rate of change in the rotation speed of the electric motor exceeds a predetermined threshold value; the voltage command value is generated based on a torque command value and the current value required by the electric vehicle, and the torque command value is a second torque command value obtained by performing vibration suppression calculation processing on a first torque command value required by a driver's operation to suppress torsional vibration from an output shaft of the electric motor to a wheel, A method for controlling an electric motor, the method detecting a sudden change in the load when the difference between the second torque command value and the first torque command value repeatedly increases and decreases with an amplitude exceeding a predetermined magnitude.

6. When either a first control mode in which the voltage command value is calculated by current vector control based on an operating state of the electric motor or a second control mode in which the voltage command value is calculated by voltage phase control is selected, 4. The method for controlling an electric motor according to claim 1, wherein an absolute value of the threshold value for the rate of change of the rotation speed of the electric motor when detecting a sudden change in the load when the first control mode is selected is set to be larger than an absolute value of the threshold value for the rate of change of the rotation speed of the electric motor when detecting a sudden change in the load when the second control mode is selected.

7. When either a first control mode in which the voltage command value is calculated by current vector control based on an operating state of the electric motor or a second control mode in which the voltage command value is calculated by voltage phase control is selected, 4. A method for controlling an electric motor according to claim 1, wherein the rate of reduction in the switching speed when a sudden change in the load is detected when the first control mode is selected is set to be lower than the rate of reduction in the switching speed when a sudden change in the load is detected when the second control mode is selected.

8. When either a first control mode in which the voltage command value is calculated by current vector control based on an operating state of the electric motor or a second control mode in which the voltage command value is calculated by voltage phase control is selected, 4. A method for controlling an electric motor according to claim 1, wherein detection of a sudden change in the load is not performed when the first control mode is selected, and detection of a sudden change in the load is performed when the second control mode is selected.

9. 9. A motor control method according to claim 1, wherein when a sudden change in the load is not detected, the switching speed is set based on at least one of a temperature related to the switching element and a temperature of a cooling system for the switching element.

10. 9. The motor control method according to claim 1, wherein, when a sudden change in the load is not detected, the switching speed is set based on the output voltage of a DC power supply that supplies the DC power.

11. When performing discharge control of a smoothing capacitor connected to a DC power supply that supplies the DC power and the switching element, The switching speed during execution of the discharge control is set to be lower than the switching speed before execution of the discharge control, 5. The method for controlling an electric motor according to claim 4, wherein a switching frequency of the PWM signal during the discharge control is set higher than the highest switching frequency among the switching frequencies set based on the torque command value and the rotation speed of the electric motor when the discharge control is not executed.

12. at least one pair of switching elements that convert DC power into AC power and supply the AC power to an electric motor of an electric vehicle; a current detection means for detecting a current value supplied to the electric motor; a control calculation means for calculating a voltage command value to be applied to the electric motor based on the current value; a PWM control means for controlling the AC power by transmitting a PWM signal to the switching element based on the voltage command value, a resistance setting means capable of setting a gate resistance is connected to the switching element; The control calculation means a sudden load change detection unit that detects a sudden change in the load applied to the electric motor; a gate resistance setting unit that controls the resistance setting means when the sudden load change detection unit detects a sudden change in the load so that the gate resistance becomes higher than that before the sudden change in the load occurs, the sudden load change detection unit determines whether the sudden change in the load has occurred based on whether a rate of change in the rotation speed of the electric motor has exceeded a predetermined threshold value; When the voltage command value is generated based on a torque command value and the current value required by the electric vehicle, a control device for an electric motor that detects a sudden change in the load when a ratio between the torque command value, the accelerator opening, or the brake operation amount and either a rate of change in wheel speed of the electric vehicle or a rate of change in the rotation speed is equal to or greater than a predetermined value.

13. At least one pair of switching elements that convert DC power into AC power and supply it to an electric motor of an electric vehicle; a current detection means for detecting a current value supplied to the electric motor; a control calculation means for calculating a voltage command value to be applied to the electric motor based on the current value; a PWM control means for controlling the AC power by transmitting a PWM signal to the switching element based on the voltage command value, a resistance setting means capable of setting a gate resistance is connected to the switching element; The control calculation means a sudden load change detection unit that detects a sudden change in the load applied to the electric motor; a gate resistance setting unit that controls the resistance setting means when the sudden load change detection unit detects a sudden change in the load so that the gate resistance becomes higher than that before the sudden change in the load occurs, the sudden load change detection unit determines whether the sudden change in the load has occurred based on whether a rate of change in the rotation speed of the electric motor has exceeded a predetermined threshold value; the voltage command value is generated based on a torque command value and the current value required by the electric vehicle, and the torque command value is a second torque command value obtained by performing vibration suppression calculation processing on a first torque command value required by a driver's operation to suppress torsional vibration from an output shaft of the electric motor to a wheel, The motor control device detects a sudden change in the load when the difference between the second torque command value and the first torque command value repeatedly increases and decreases with an amplitude exceeding a predetermined magnitude.

14. The resistance setting means a first resistance element disposed between the PWM control means and the switching element; a series circuit of a switch and a second resistance element, the series circuit being disposed between the PWM control means and the switching element and being disposed so as to bypass the first resistance element; The gate resistance setting unit If there is no sudden change in the load, the switch is turned on.

14. The motor control device according to claim 12, wherein the switch is turned off when a sudden change in the load is detected or when a sudden change in the load is predicted.

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