electric vehicles

Abstract

This allows for more effective suppression of motor torque ripple at frequencies near the vehicle's resonant frequency. [Solution] The electric vehicle comprises a motor, an inverter that drives the motor, and a control device that calculates the current commands for the d and q axes by superimposing harmonic superposition current commands on the basic current commands for the d and q axes based on the torque command of the motor, and controls the inverter using the calculated d and q axis current commands. The control device uses harmonic superposition current commands of a frequency within the frequency range of the resonant frequency plus or minus the compensation frequency among the following 6n (n: natural number) electrical frequencies based on the rotational speed of the motor.

Description

Technical Field

[0001] This disclosure relates to an electric vehicle.

Background Art

[0002] Conventionally, in an electric vehicle including a motor and an inverter that drives the motor by switching a plurality of switching elements, a pulse pattern of a switching pulse for determining a switching timing of the switching elements to suppress a harmonic component of a predetermined order with respect to a fundamental frequency of an output to the motor is calculated, and a gate pulse for driving the switching elements on and off based on the pulse pattern and a magnetic pole position of a rotor of the motor is output (see, for example, Patent Document 1). In this electric vehicle, in a specific rotational speed range, in order to reduce losses generated by the motor, the pulse pattern is calculated so as to suppress a harmonic component having an order within a frequency range that causes an increase in losses generated by the motor.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the above-described electric vehicle, although it is possible to reduce losses generated by the motor in a specific rotational speed range, there is a possibility that torque ripple of the motor at a frequency near the resonance frequency of the vehicle cannot be sufficiently suppressed. The main object of the electric vehicle of this disclosure is to be able to more sufficiently suppress torque ripple of the motor at a frequency near the resonance frequency of the vehicle.

Means for Solving the Problems

[0005] The electric vehicle of this disclosure employs the following means to achieve the main objective described above. The electric vehicle of this disclosure comprises a motor, an inverter for driving the motor, and a control device that calculates the current commands for the d-axis and q-axis by superimposing harmonic superposition current commands on basic current commands for the d-axis and q-axis based on the torque command of the motor, and controls the inverter using the calculated current commands for the d-axis and q-axis. The gist of the control device is that it uses the harmonic superposition current commands of a frequency within the frequency range of the resonant frequency plus or minus the compensation frequency among the following 6n (n: natural number) electrical frequencies based on the rotational speed of the motor.

[0006] In the electric vehicle of this disclosure, the current commands for the d-axis and q-axis are calculated by superimposing harmonic superposition current commands on the basic current commands for the d-axis and q-axis based on the torque command of the motor, and the inverter is controlled using the calculated current commands for the d-axis and q-axis. In this case, harmonic superposition current commands are used for frequencies within the frequency range of the resonant frequency plus or minus the compensation frequency among the 6n (n: natural number) electrical frequencies based on the motor's rotational speed. This makes it possible to more sufficiently suppress the torque ripple of the motor at frequencies near the vehicle's resonant frequency. [Brief explanation of the drawing]

[0007] [Figure 1] This is a schematic diagram of the electric vehicle 10 according to the embodiment of the disclosure. [Figure 2] This is a flowchart showing an example of a processing routine. [Figure 3] This is a flowchart showing an example of a subprocessing step. [Modes for carrying out the invention]

[0008] Embodiments for implementing this disclosure will be described with reference to the drawings. Figure 1 is a schematic diagram of an electric vehicle 10 according to an embodiment of this disclosure. As shown in the figure, the electric vehicle 10 of the embodiment includes a motor 22, an inverter 24, a battery 26, and an electronic control unit (hereinafter referred to as "ECU") 50.

[0009] The motor 22 is configured as a three-phase AC motor and has a rotor with permanent magnets embedded in the rotor core and a stator with three-phase (U-phase, V-phase, W-phase) coils wound around the stator core. The rotor of the motor 22 is connected to a drive shaft 16 which is connected to drive wheels 12a and 12b via a differential gear 14. The inverter 24 is connected to a power line 28 (positive electrode line 28p and negative electrode line 28n) to which the battery 26 is connected. The inverter 24 comprises six switching elements, transistors T11 to T16, and six diodes D11 to D16 which are connected in parallel to each of the six transistors T11 to T16. The transistors T11 to T16 are arranged in pairs, with two on the source side and two on the sink side with respect to the positive electrode line 28p and the negative electrode line 28n. Each connection point of a pair of transistors T11-T16 is connected to the three-phase (U-phase, V-phase, W-phase) coils of the motor 22. Therefore, by adjusting the ratio of the on-times of the pair of transistors T11-T16 by the ECU 50, a rotating magnetic field is formed in the three-phase coils of the motor 22, and the rotor of the motor 22 is driven to rotate. The battery 26 is configured as, for example, a lithium-ion secondary battery or a nickel-metal hydride secondary battery. The positive and negative terminals of the battery 26 are connected to the power line 28. A smoothing capacitor 30 is connected to the power line 28.

[0010] The ECU50 is equipped with a microcomputer, various drive circuits, and various logic ICs. The microcomputer has a CPU, ROM, RAM, flash memory, input / output ports, and communication ports. Signals from various sensors are input to the ECU50. For example, the rotational position θm of the rotor of the motor 22 from the rotational position sensor 22a, and the phase currents Iu, Iv, and Iw of each phase of the motor 22 from the current sensors 22u, 22v, and 22w are input to the ECU50. The voltage Vb of the battery 26 from the voltage sensor 26v, the current Ib of the battery 26 from the current sensor 26i, and the voltage VH of the capacitor 30 (power line 28) from the voltage sensor 30v are also input to the ECU50. The ECU 50 also receives the following inputs: an on / off signal from the power switch 60, the shift position SP from the shift position sensor 62 (which is the operating position of the shift lever 61), the accelerator pedal position Acc from the accelerator pedal position sensor 64 (which is the amount the accelerator pedal 63 is pressed), the brake pedal position BP from the brake pedal position sensor 66 (which is the amount the brake pedal 65 is pressed), and the vehicle speed v from the vehicle speed sensor 67. The ECU 50 outputs switching control signals to the transistors T11 to T16 of the inverter 24. The ECU 50 calculates the electrical angle θe and rotational speed Nm of the motor 22 based on the rotational position θm of the rotor of the motor 22, and uses the electrical angle θe to perform coordinate transformation (3-phase to 2-phase transformation) of the phase currents Iu, Iv, and Iw of each phase to the d-axis and q-axis currents Id and Iq. The ECU 50 also calculates the charge level SOC of the battery 26 based on the integrated value of the current Ib of the battery 26.

[0011] In the electric vehicle 10 of this embodiment, the ECU 50 sets the required torque Td* required for driving (required to the drive shaft 16) based on the accelerator opening Acc and vehicle speed V, sets the torque command Tm* for the motor 22 to drive with the set required torque Td*, and performs switching control of transistors T11 to T16 of the inverter 24 based on the set torque command Tm*. The inverter 24 is basically controlled by pulse width modulation control (PWM control).

[0012] Next, the operation of the electric vehicle 10 of the embodiment, in particular, the control of the inverter 24 by the ECU 50 will be described. Figure 2 is a flowchart of an example of a processing routine that is repeatedly executed by the ECU 50. When this routine is executed, the ECU 50 first inputs the electrical angle θe, rotational speed Nm, and torque command Tm* of the motor 22 (step S100). Subsequently, the sub-process in Figure 3 sets the electrical 6n (n: 1~4) order, i.e., the electrical 6th, 12th, 18th, and 24th harmonic superposition implementation flag F[6n] based on the torque command Tm* and rotational speed Nm of the motor 22 (step S110). Here, the electrical 6n order harmonic superposition implementation flag F[6n] is a flag that indicates whether or not it is necessary to reduce the electrical 6n order torque ripple of the motor 22. The explanation of the processing routine in Figure 2 will be interrupted and the sub-process in Figure 3 will be described.

[0013] In the subprocess shown in Figure 3, the ECU 50 first sets the variable n to a value of 1 (step S300). Next, it determines whether the absolute value of the torque command Tm* of the motor 22 is less than or equal to the threshold Tmref (step S310). If it determines that the absolute value of the torque command Tm* of the motor 22 is greater than the threshold Tmref, it sets the value of the electrical 6n-th harmonic superposition implementation flag F[6n] to 0 (step S360). This is because when the torque command Tm* of the motor 22 is large (when the accelerator opening Acc is large), the driver is less likely to feel the effects of the torque ripple of the motor 22 due to the feeling of vehicle acceleration and road noise.

[0014] If it is determined in step S310 that the absolute value of the torque command Tm* of the motor 22 is less than or equal to the threshold Tmref, the electrical 6th-order frequency f[6n] is calculated using equation (1) with the rotational speed Nm[rpm] of the motor 22 and the number of pole pairs P (step S320). Next, it is determined whether the electrical 6th-order frequency f[6n] is greater than the frequency obtained by subtracting the compensation frequency β from the vehicle's resonant frequency fr (fr-β) (step S330), and whether the electrical 6th-order frequency f[6n] is less than the frequency obtained by adding the compensation frequency β to the vehicle's resonant frequency fr (fr+β) (step S340). That is, it is determined whether the electrical 6th-order frequency f[6n] is within the range of the vehicle's resonant frequency fr plus or minus the compensation frequency β. Here, the resonant frequency fr and the compensation frequency β are predetermined based on the vehicle's specifications, etc.

[0015] f[6n]=Nm·P·6n / 60 (1)

[0016] If, in step S330, it is determined that the 6th harmonic frequency f[6n] is greater than the frequency (fr-β), and in step S340, it is determined that the 6th harmonic frequency f[6n] is less than the frequency (fr+β), then the value of the 6th harmonic superposition implementation flag F[6n] is set to 1 (step S350). On the other hand, if, in step S330, it is determined that the 6th harmonic frequency f[6n] is less than or equal to the frequency (fr-β), or if, in step S340, it is determined that the 6th harmonic frequency f[6n] is greater than or equal to the frequency (fr+β), then the value of the 6th harmonic superposition implementation flag F[6n] is set to 0 (step S360).

[0017] After setting the electrical 6n-th harmonic superposition implementation flag F[6n] in this way, it is determined whether the variable n is valued at 4 (step S370). If it is determined that the variable n is not valued at 4, the variable n is incremented by 1 (step S380), and the process returns to step S310. In this manner, the electrical 6n-th (n: 1 to 4)-th harmonic superposition implementation flag F[6n] is set, i.e., the 6th, 12th, 18th, and 24th harmonics. If it is determined in step S370 that the variable n is valued at 4, the subprocess shown in Figure 3 is terminated.

[0018] Returning to the explanation of the processing routine in Figure 2, if the electrical 6n (n: 1~4) harmonic superposition implementation flag F[6n] is set in step S110, the variable n is set to value 1 (step S120), and it is determined whether the electrical 6n harmonic superposition implementation flag F[6n] is value 1 or value 0 (step S130). If it is determined that the electrical 6n harmonic superposition implementation flag F[6n] is value 1, the electrical 6n harmonic superposition current commands Id[6n], Iq[6n] and harmonic superposition voltage commands Vd[6n], Vq[6n] for the d-axis and q-axis are set based on the electrical angle θe and torque command Tm* of the motor 22 (steps S140, 150). Here, the current commands Id[6n], Iq[6n] and voltage commands Vd[6n], Vq[6n] for superimposing the 6th-order d-axis and q-axis harmonics are for suppressing the 6th-order torque ripple.

[0019] The current commands Id[6n] and Iq[6n] for superimposing 6n-order d-axis and q-axis harmonics are obtained, for example, by applying the electrical angle θe and torque command Tm* to a predetermined harmonic superimposition current command map, which is the relationship between the electrical angle θe and torque command Tm* and the d-axis and q-axis harmonic superimposition current commands Id[6n] and Iq[6n], and deriving the corresponding d-axis and q-axis harmonic superimposition current commands Id[6n] and Iq[6n] from the map. The voltage commands Vd[6n] and Vq[6n] for superimposing 6n-order d-axis and q-axis harmonics are obtained, for example, by applying the electrical angle θe and torque command Tm* to a predetermined harmonic superposition voltage command map, which is defined as the relationship between the electrical angle θe and torque command Tm* and the d-axis and q-axis harmonic superposition current commands Vd[6n] and Vq[6n], and deriving the corresponding d-axis and q-axis harmonic superposition voltage commands Vd[6n] and Vq[6n] from the map.

[0020] If it is determined in step S130 that the flag F[6n] for the implementation of electrical 6th harmonic superposition is 0, the current commands Id[6n], Iq[6n] and the voltage commands Vd[6n], Vq[6n] for the electrical 6th harmonic superposition on the d and q axes are set to 0 (steps S160, S170).

[0021] When the current commands Id[6n] and Iq[6n] for harmonic superposition on the d-axis and q-axis of the 6n-th electrical order and the voltage commands Vd[6n] and Vq[6n] for harmonic superposition on the d-axis and q-axis are set in steps S140 to S170, it is determined whether the variable n is equal to 4 (step S180). When it is determined that the variable n is not equal to 4, the variable n is incremented by 1 (step S190), and the process returns to step S130. In this way, the current commands for harmonic superposition on the d-axis and q-axis of the 6n-th (n: 1 to 4) electrical order, that is, the 6th, 12th, 18th, and 24th electrical orders, and the voltage commands Vd[6n] and Vq[6n] for harmonic superposition on the d-axis and q-axis are set.

[0022] When it is determined in step S180 that the variable n is equal to 4, the basic current commands Id0 and Iq0 on the d-axis and q-axis are set based on the torque command Tm* of the motor 22 (step S200). Here, the basic current commands Id0 and Iq0 on the d-axis and q-axis are obtained, for example, by applying the torque command Tm* to a basic current command map defined in advance as the relationship between the torque command Tm* of the motor 22 and the basic current commands Id0 and Iq0 on the d-axis and q-axis, and deriving the corresponding basic current commands Id0 and Iq0 on the d-axis and q-axis from the map.

[0023] Subsequently, the d-axis and q-axis current commands Id*, Iq* are calculated by equations (2) and (3) using the d-axis and q-axis fundamental current commands Id0, Iq0 and the d-axis and q-axis harmonic superposition current commands Id[6], Iq[6], Id

[12] , Iq

[12] , Id

[18] , Iq

[18] , Id

[24] , Iq

[24] of the 6th, 12th, 18th, and 24th electrical orders (step S210). Then, the d-axis and q-axis voltage commands Vd*, Vq* are calculated by equations (4) and (5) using the d-axis and q-axis current commands Id*, Iq*, the currents Id, Iq, the d-axis and q-axis harmonic superposition voltage commands Vd[6], Vq[6], Vd

[12] , Vq

[12] , Vd

[18] , Vq

[18] , Vd

[24] , Vq

[24] of the 6th, 12th, 18th, and 24th electrical orders, and the rotational speed Nm of the motor 22 (step S220), and the processing routine in FIG. 2 is terminated. In equations (4) and (5), "Vdff" and "Vqff" are the feed-forward terms of the voltage commands Vd*, Vq*, "R" is the line resistance value of the motor 22, "kpd" and "kpq" are the gains of the proportional terms of the feedback control, and "kid" and "kiq" are the gains of the integral terms of the feedback control. These are, for example, predetermined in advance.

[0024] Id* = Id0 + Id[6] + Id

[12] + Id

[18] + Id

[24] (2) Iq* = Iq0 + Iq[6] + Iq

[12] + Iq

[18] + Iq

[24] (3) Vd* = Vdff + R·Id* + Nm·(Vd[6] + Vd

[12] + Vd

[18] + Vd

[24] ) + kpd·(Id* - Id) + kid·∫(Id* - Id)dt (4) Vq* = Vqff + R·Iq* + Nm·(Vq[6] + Vq

[12] + Vq

[18] + Vq

[24] ) + kpq·(Iq* - Iq) + kiq·∫(Iq* - Iq)dt (5)

[0025] After calculating the voltage commands Vd* and Vq* for the d and q axes, the voltage commands Vd* and Vq* for the d and q axes are converted to phase voltage commands Vu*, Vv*, and Vw* for each phase using the electrical angle θe of the motor 22 (2-phase to 3-phase conversion). Next, PWM signals for transistors T11 to T16 of the inverter 24 are generated using the phase voltage commands Vu*, Vv*, and Vw* for each phase and the carrier wave (triangular wave). Then, the switching control of transistors T11 to T16 is performed using the PWM signals for transistors T11 to T16 of the inverter 24.

[0026] In the electric vehicle 10 of the embodiment described above, the current commands Id* and Iq* for the d and q axes are calculated by superimposing the current commands Id[6n] and Iq[6n] for the superposition of 6n-th order d and q axes onto the basic current commands Id0 and Iq0 for the d and q axes based on the torque command Tm* of the motor 22, and the inverter 24 is controlled using the calculated current commands Id* and Iq* for the d and q axes. In this case, for frequencies within the range of the vehicle's resonant frequency fr plus or minus compensation frequency β among the 6n-th order electrical frequencies f[6n], the current commands Id[6n] and Iq[6n] for the superposition of 6n-th order d and q axes are set based on the electrical angle θe of the motor 22 and the torque command Tm*, and for other frequencies, the value of the current commands Id[6n] and Iq[6n] for the superposition of 6n-th order d and q axes is set to 0. This makes it possible to more effectively suppress the torque ripple of the motor 22 at frequencies near the vehicle's resonant frequency.

[0027] In the embodiment described above, the electrical 6n-th (n: 1st to 4th) harmonic superposition implementation flag F[6n] is set by the subprocessing shown in Figure 3. However, the torque command Tm* and rotational speed Nm of the motor 22 may be applied to a predetermined map showing the relationship between the torque command Tm* and rotational speed Nm of the motor 22 and the electrical 6n-th harmonic superposition implementation flag F[6n], and the corresponding electrical 6n-th harmonic superposition implementation flag F[6n] may be derived from the map and set.

[0028] In the embodiments described above, the n of the 6n-th order of electrical energy was set to 1 to 4, but it is not limited to this. For example, n may be set to 1 to 3, 1 to 5, 1 to 6, etc.

[0029] In the embodiment described above, the vehicle is an electric vehicle 10 equipped with a motor 22 and an inverter 24, but it is not limited to this. For example, it may be a hybrid vehicle configuration that further includes an engine in addition to the same hardware configuration as the electric vehicle 10, or a fuel cell vehicle configuration that further includes a fuel cell in addition to the same hardware configuration as the electric vehicle 10.

[0030] Although the embodiments for implementing this disclosure have been described above, this disclosure is not limited in any way to these embodiments, and can of course be implemented in various forms without departing from the gist of this disclosure. [Industrial applicability]

[0031] This disclosure can be used in industries such as electric vehicle manufacturing. [Explanation of Symbols]

[0032] 10 electric vehicles, 22 motors, 24 inverters, 50 ECUs.

Claims

[Claim 1] An electric vehicle comprising: a motor; an inverter for driving the motor; and a control device that calculates current commands for the d-axis and q-axis by superimposing harmonic superposition current commands on basic current commands for the d-axis and q-axis based on the torque command of the motor, and controls the inverter using the calculated current commands for the d-axis and q-axis, The control device uses the harmonic superposition current command for a frequency within the frequency range of the resonant frequency plus or minus the compensation frequency, among the following 6n (n: natural number) electrical frequencies based on the rotational speed of the motor. Electric car.

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