JP7590943B2 - MOTOR DRIVE DEVICE AND ELECTRIC VEHICLE - Google Patents

Description

The present invention relates to a motor drive device and an electric vehicle.

A motor drive device includes a power conversion circuit that converts DC power to AC power, and drives the motor by controlling the output voltage output from the power conversion circuit. When a motor is rotated at high speed, the voltage induced in the stator winding increases. To deal with this, synchronous PWM control is used, in which the switching operation in the power conversion circuit is synchronized with the rotation of the motor. In synchronous PWM control, control is performed so that the number of pulses per cycle of the output voltage is 3 or 1. In this way, the utilization rate of the DC power supply voltage input to the power conversion circuit is improved, and it becomes possible to deal with the increase in induced voltage generated when the motor rotates at high speed.

On the other hand, in a three-phase synchronous motor (hereinafter sometimes referred to as "motor"), current control is performed so that the detected values of the d-axis current and q-axis current match their respective command values on the dq coordinates synchronized with the rotation of the motor. Normally, a design can be based on current control by applying non-interference control that cancels the interference components that occur between the d-axis and q-axis. However, in practice, detection errors and detection delays in current sensors, etc., and calculation delays in the controller affect the d-axis current and q-axis current, resulting in a resonance phenomenon in which the d-axis current and q-axis current oscillate at a certain frequency.

In Patent Document 1, the pulsating component is extracted from the detected value of the d-axis current or q-axis current, and the phase information used in the control is corrected based on the result, thereby taking measures against the resonance phenomenon.

JP 2010-172060 A

The device described in Patent Document 1 suppresses the motor resonance phenomenon based on the pulsating component of the d-axis current or q-axis current, i.e., the signal that is an AC quantity. Therefore, under conditions where the motor rotates at high speed, the calculation delay of the controller becomes significant and the resonance phenomenon cannot be suppressed. In addition, the continuous correction amount generated by the device described in Patent Document 1 is not accurately reflected in synchronous PWM control that operates intermittently with a voltage with a limited number of pulses, and the resonance phenomenon cannot be suppressed.

The motor drive device according to the present invention includes a power conversion circuit that converts DC power to AC power, and drives a motor by controlling the pulse width of the output voltage output from the power conversion circuit. The motor drive device includes a PWM pulse generation unit that generates a switching signal that operates a switching element of the power conversion circuit, and a stabilization signal generation unit that generates a stabilization signal that reduces the DC component contained in the phase current based on information about the phase current flowing through the motor, and the PWM pulse generation unit generates the switching signal based on the stabilization signal to correct the pulse width.

According to the present invention, even in the case of synchronous PWM control where the motor rotates at high speed, the motor resonance phenomenon can be suppressed and the motor can be stably controlled.

FIG. 2 is a configuration diagram of a motor drive device. FIG. 2 is a configuration diagram of a control unit according to the first embodiment. FIG. 2 is a configuration diagram of a stabilization signal generating unit according to the first embodiment. 5A to 5E are diagrams illustrating waveforms of U-phase output voltages generated by the power conversion circuit in response to switching signals according to the first embodiment. FIG. 13 is a configuration diagram of a stabilization signal generating unit according to a modified example. FIG. 11 is a configuration diagram of a control unit according to a second embodiment. 13A and 13B are diagrams illustrating a waveform of a U-phase output voltage generated by a power conversion circuit in response to a switching signal according to a second embodiment. FIG. 13 is a configuration diagram of a stabilization signal generating unit according to a third embodiment. FIG. 13 is a configuration diagram of an electric vehicle according to a fourth embodiment.

Below, an embodiment of the present invention will be described with reference to the drawings. The following description and drawings are examples for explaining the present invention, and appropriate omissions and simplifications have been made to clarify the explanation. The present invention can be implemented in various other forms. Unless otherwise specified, each component may be singular or plural. Note that the same elements in the drawings are given the same reference numerals, and duplicate explanations will be omitted. Also, the drawings show control lines and information lines that are considered necessary for explanation, and do not necessarily show all control lines and information lines. In reality, it can be considered that almost all components are connected to each other.

[First embodiment]
FIG. 1 is a configuration diagram of a motor driving device 100.
The motor drive device 100 uses synchronous PWM control to drive a three-phase synchronous motor 101. The three-phase synchronous motor 101 is, for example, a three-phase permanent magnet synchronous motor, and has a U-phase winding, a V-phase winding, and a W-phase winding.

The motor drive device 100 includes a power conversion circuit 102, a DC power supply 103, a smoothing capacitor 104, and a control unit 105.

The DC power supply 103 supplies DC power to the power conversion circuit 102. The DC power supply 103 is, for example, a lithium ion secondary battery. The smoothing capacitor 104 smoothes the DC voltage VDC supplied to the power conversion circuit 102. The voltage sensor 108 is connected in parallel to the DC power supply 103, and the value of the DC voltage VDC detected by the voltage sensor 108 is input to the control unit 105.

The power conversion circuit 102 comprises semiconductor switching elements SW1 to SW6 that constitute upper and lower arms for three phases. The semiconductor switching elements SW1 to SW6 may be IGBTs, MOSFETs, or other power semiconductor elements. In the power conversion circuit 102, the semiconductor switching elements SW1 to SW6 are operated according to switching signals S1 to S6 described below, and the power conversion circuit 102 converts DC power supplied from the DC power source 103 into AC power to drive the three-phase synchronous motor 101. In this embodiment, synchronous PWM control is performed, and the switching signals S1 to S6 are generated so that the number of pulses within one period of the output voltage from the power conversion circuit 102 is three.

A current sensor 107 is provided between the three-phase synchronous motor 101 and the power conversion circuit 102 to detect the current of each phase, and the values of the U-phase current Iu, V-phase current Iv, and W-phase current Iw detected by the current sensor 107 are input to the control unit 105.

The three-phase synchronous motor 101 is provided with a rotor position sensor 106 that detects the rotor position, and the value of the rotor position θdc detected by the rotor position sensor 106 is input to the control unit 105. The rotor position sensor 106 is, for example, a resolver.

A torque command Tm is input to the control unit 105 from a higher-level control device (not shown). The control unit 105 generates switching signals S1 to S6 by vector control based on the torque command Tm, the U-phase current Iu, the V-phase current Iv, and the W-phase current Iw detected by the current sensor 107, the DC voltage VDC detected by the voltage sensor 108, and the rotor position θdc detected by the rotor position sensor 106. The generated switching signals S1 to S6 drive the semiconductor switching elements SW1 to SW6 of the power conversion circuit 102.

FIG. 2 is a block diagram of the control unit 105.
The control unit 105 includes a current command generating unit 200 , a current control unit 201 , a voltage amplitude and phase calculation unit 202 , a three-phase/dq conversion unit 203 , a rotation speed calculation unit 204 , a PWM pulse generating unit 205 , and a stabilization signal generating unit 206 .

The current command generating unit 200 generates a d-axis current command Id* and a q-axis current command Iq* that realize maximum torque/current control and field-weakening control based on the torque command Tm. Here, maximum torque/current control is control that maximizes the motor torque for the same current. Field-weakening control is control that prevents the motor terminal voltage, which increases with the rotation speed of the three-phase synchronous motor 101, from exceeding the maximum output voltage of the power conversion circuit 102.

The three-phase/dq converter 203 converts the U-phase current Iu, V-phase current Iv, and W-phase current Iw detected by the current sensor 107 into a d-axis detected current Id and a q-axis detected current Iq based on the rotor position θdc detected by the rotor position sensor 106.
The rotation speed calculation unit 204 calculates the rotation angular speed ω based on the rotor position θdc detected by the rotor position sensor 106 .

The current control unit 201 generates a d-axis voltage command Vd* and a q-axis voltage command Vq* based on the d-axis current command Id* and the q-axis current command Iq* from the current command generation unit 200, the d-axis detected current Id and the q-axis detected current Iq from the three-phase/dq conversion unit 203, and the rotational angular velocity ω from the rotational velocity calculation unit 204. The current control unit 201 controls the d-axis current and the q-axis current of the three-phase synchronous motor 101 so that they follow the d-axis current command Id* and the q-axis current command Iq*, respectively.

The voltage amplitude and phase calculation unit 202 calculates a voltage amplitude command Va* and a voltage phase θV based on the d-axis voltage command Vd* and the q-axis voltage command Vq* from the current control unit 201 using the following equations (1) and (2).
Va*=√(Vd*^2+Vq*^2)...(1)
θV=atan(-Vd*/Vq*)...(2)

The PWM pulse generating unit 205 outputs switching signals S1 to S6 based on the DC voltage VDC detected by the voltage sensor 108 and the rotor position θdc detected by the rotor position sensor 106 in response to the voltage amplitude command Va* and voltage phase θV from the voltage amplitude phase calculation unit 202. Here, the PWM pulse generating unit 205 receives the U-phase stabilization signal Δαu, V-phase stabilization signal Δαv, and W-phase stabilization signal Δαw, which will be described in detail later, from the stabilization signal generating unit 206. The PWM pulse generating unit 205 corrects the pulse width of the output voltage output from the power conversion circuit 102 by outputting the switching signals S1 to S6 taking into account the U-phase stabilization signal Δαu, V-phase stabilization signal Δαv, and W-phase stabilization signal Δαw.

The stabilization signal generating unit 206 outputs a U-phase stabilization signal Δαu, a V-phase stabilization signal Δαv, and a W-phase stabilization signal Δαw, which will be described in detail later, based on the d-axis current command Id* and the q-axis current command Iq* from the current command generating unit 200, the d-axis detected current Id and the q-axis detected current Iq from the three-phase/dq conversion unit 203, the rotor position θdc detected by the rotor position sensor 106, and the DC voltage VDC detected by the voltage sensor 108.

FIG. 3 is a diagram showing the configuration of the stabilization signal generator 206. As shown in FIG.
The stabilization signal generator 206 includes a subtractor 300a, a subtractor 300b, a dq/three-phase converter 301, a U-phase stabilization signal generator 302a, a V-phase stabilization signal generator 302b, and a W-phase stabilization signal generator 302c.

The subtractor 300a calculates the difference between the d-axis detection current Id from the three-phase/dq conversion unit 203 and the d-axis current command Id* from the current command generation unit 200, and outputs the d-axis current deviation ΔId. This calculation is performed to extract the pulsating component contained in the d-axis detection current Id.

The subtractor 300b calculates the difference between the q-axis detected current Iq from the three-phase/dq conversion unit 203 and the q-axis current command Iq* from the current command generation unit 200, and outputs the q-axis current deviation ΔIq. This calculation is performed to extract the pulsating component contained in the q-axis detected current Iq.

The dq/3-phase conversion unit 301 converts the d-axis current deviation ΔId from the subtractor 300a and the q-axis current deviation ΔIq from the subtractor 300b into a U-phase current deviation ΔIu, a V-phase current deviation ΔIv, and a W-phase current deviation ΔIw based on the rotor position θdc detected by the rotor position sensor 106.

The U-phase stabilization signal generating unit 302a includes a PI control unit 303 and a voltage/angle conversion unit 308. The PI control unit 303 includes a proportional control gain 304, an integral control gain 305, an integrator 306, and an adder 307. The PI control unit 303 performs proportional-integral control based on the input U-phase current deviation ΔIu, and outputs a correction voltage ΔVu. The voltage/angle conversion unit 308, which will be described in detail later, converts the correction voltage ΔVu into a U-phase stabilization signal Δαu.

That is, the U-phase stabilization signal generating unit 302a generates a correction voltage ΔVu using the PI control unit 303 so that the U-phase current deviation ΔIu from the dq/three-phase conversion unit 301 converges to zero, and converts the correction voltage ΔVu into a U-phase stabilization signal Δαu.

The V-phase stabilization signal generating unit 302b and the W-phase stabilization signal generating unit 302c have the same configuration as the U-phase stabilization signal generating unit 302a, and generate correction voltages by the PI control unit 303 so that the current deviation of each phase converges to zero, and convert the correction voltages into stabilization signals for each phase.

Here, when the pulsating component contained in the d-axis current deviation ΔId or the q-axis current deviation ΔIq is generated by the resonance phenomenon of the three-phase synchronous motor 101, the fluctuation period of the pulsating component corresponds to the fundamental frequency of the three-phase synchronous motor 101. Then, when the d-axis current deviation ΔId and the q-axis current deviation ΔIq are converted by the dq/three-phase conversion unit 301 into the U-phase current deviation ΔIu, the V-phase current deviation ΔIv, and the W-phase current deviation ΔIw, the pulsating component contained in the d-axis current deviation ΔId or the q-axis current deviation ΔIq is converted into the DC component of each phase current. In other words, the pulsating component of the d-axis current or the q-axis current generated by the resonance phenomenon of the three-phase synchronous motor 101 corresponds to the DC component in the U-phase current, the V-phase current, and the W-phase current. Therefore, the U-phase correction voltage ΔVu generated by the PI control unit 303 is expressed as a DC amount.

A voltage/angle converter 308 performs a calculation on the U-phase correction voltage ΔVu based on the DC voltage VDC detected by the voltage sensor 108, as shown in the following equation (3), and converts it into a U-phase stabilization signal Δαu corresponding to an angle.
Δαu=(π/2)・(-ΔVu/VDC)...(3)
The U-phase stabilization signal Δαu is calculated from the U-phase correction voltage ΔVu, which is a DC amount, and is therefore also a DC amount.

Similarly, the V-phase stabilization signal generating unit 302b generates a V-phase correction voltage ΔVu from the V-phase current deviation ΔIv by PI control, and further converts the V-phase correction voltage ΔVu into a V-phase stabilization signal Δαv corresponding to the angle according to the following equation (4).
Δαv=(π/2)・(-ΔVv/VDC)...(4)

Similarly, the W-phase stabilization signal generating unit 302c generates a W-phase correction voltage ΔVw from the W-phase current deviation ΔIw by PI control, and further converts the W-phase correction voltage ΔVw into a W-phase stabilization signal Δαw corresponding to the angle according to the following equation (5).
Δαw=(π/2)・(-ΔVw/VDC)...(5)

As in the case of the U-phase stabilization signal generating unit 302a, the V-phase correction voltage ΔVv and the V-phase stabilization signal Δαv generated in the V-phase stabilization signal generating unit 302b are DC amounts. Similarly, the W-phase correction voltage ΔVw and the W-phase stabilization signal Δαw generated in the W-phase stabilization signal generating unit 302c are DC amounts.

In this way, the U-phase stabilization signal generating unit 302a, the V-phase stabilization signal generating unit 302b, and the W-phase stabilization signal generating unit 302c include feedback control units such as the PI control unit 303, and generate stabilization signals (Δαu, Δαv, Δαw) to reduce the DC components contained in the phase currents.

The U-phase stabilization signal Δαu, V-phase stabilization signal Δαv, and W-phase stabilization signal Δαw generated by the stabilization signal generation unit 206 are input to the PWM pulse generation unit 205. In this embodiment, synchronous PWM control is performed, and switching signals S1 to S6 are generated so that the number of pulses within one period of the output voltage from the power conversion circuit 102 is 3. Then, the resonance phenomenon of the three-phase synchronous motor 101 is suppressed by correcting the pulse width of the output voltage based on the U-phase stabilization signal Δαu, V-phase stabilization signal Δαv, and W-phase stabilization signal Δαw.

Figures 4(a) to 4(e) are diagrams showing the waveforms of the U-phase output voltage generated by the power conversion circuit 102 using switching signals S1 to S6. The horizontal axis is the phase (angle) and the vertical axis is the voltage, showing one period of the output voltage.

4A shows the waveform of the U-phase output voltage when the U-phase stabilization signal Δαu is set to zero and the resonance phenomenon of the three-phase synchronous motor 101 is not corrected. As shown in the figure, the number of pulses in one period of the output voltage of the three-phase synchronous motor 101 is three. The timing at which the voltage level of the output voltage is switched is set to 0° (or 360°) and near 180°, that is, the timing at which the voltage level of the output voltage is switched is set to near the zero crossing of the fundamental wave component of the output voltage. The pulse width of the output voltage is controlled as an angle α. The angle α is controlled so that the voltage amplitude command Va* from the voltage amplitude phase calculation unit 202 and the fundamental wave amplitude of the U-phase output voltage match. Specifically, the angle α is calculated using the following equations (6) and (7).
α=cos-1((MF+1)/2)...(6)
MF=(π/2)・(Va*/VDC)...(7)

4B shows the waveform of the U-phase output voltage when the U-phase stabilization signal Δαu is reflected to correct the resonance phenomenon of the three-phase synchronous motor 101. Note that the U-phase stabilization signal Δαu is a positive DC amount. The U-phase stabilization signal Δαu is reflected in the section αPu where a negative voltage occurs from 0° to 180° according to the following equation (8), and the U-phase stabilization signal Δαu is reflected in the section αNu where a positive voltage occurs from 180° to 360° according to the following equation (9).
αPu=α−Δαu...(8)
αNu=α+Δαu...(9)

In addition, the U-phase stabilization signal Δαu may be reflected according to equation (9) in the section αPu where a negative voltage occurs from 0° to 180°, and the U-phase stabilization signal Δαu may be reflected according to equation (8) in the section αNu where a positive voltage occurs from 180° to 360°.

In this way, the pulse width of the U-phase output voltage is corrected based on the U-phase stabilization signal Δαu, ie, a U-phase output voltage including a DC amount corresponding to the U-phase stabilization signal Δαu is generated.
As with the U-phase output voltage, the pulse widths of the V-phase output voltage and the W-phase output voltage are corrected based on the V-phase stabilization signal Δαv and the W-phase stabilization signal Δαw, and the phase difference between the phases is controlled to be 120° before being applied to the three-phase synchronous motor 101.

In summary, when the PWM pulse generating unit 205 switches the voltage level near the zero crossing of the fundamental wave component of the output voltage, in the section where the fundamental wave component is positive and the voltage level is negative, it subtracts or adds the pulse width of the output voltage according to the stabilization signal (Δαu, Δαv, Δαw), and in the section where the fundamental wave component is negative and the voltage level is positive, it corrects the pulse width by adding or subtracting the pulse width of the output voltage according to the stabilization signal (Δαu, Δαv, Δαw).

An output voltage including a DC amount corresponding to the stabilization signal (Δαu, Δαv, Δαw) is generated in each phase, and the U-phase current deviation ΔIu, V-phase current deviation ΔIv, and W-phase current deviation ΔIw, which are DC amounts, are suppressed. This corresponds to a reduction in the pulsating components included in the d-axis current deviation ΔId and the q-axis current deviation ΔIq, and as a result, the resonance phenomenon of the three-phase synchronous motor 101 can be corrected.

Figure 4(b) shows an example of the U-phase output voltage waveform that is linearly symmetrical about 90° and 270°. However, if a difference of Δα is provided between the positive and negative sides, it can also be applied to asymmetric output voltage waveforms.

FIG. 4(c) shows the case where the present invention is applied to an asymmetric U-phase output voltage waveform.
In this case, Δαu1 to Δαu4 are set to satisfy the following formula (10) so that a difference of Δα is provided between the positive voltage and the negative voltage.
Δαu1+Δαu2=Δαu3+Δαu4=2Δαu...(10)

When reflecting the U-phase stabilization signal Δαu, the sections αPu1, αPu2 in which negative voltages occur from 0° to 180° and the sections αNu1, αNu2 in which positive voltages occur from 180° to 360° are set according to the following equations (11) to (14).
αPu1=α−Δαu1...(11)
αPu2=α−Δαu2...(12)
αNu1=α+Δαu3...(13)
αNu2=α+Δαu4...(14)

Although an example in which the voltage level of the output voltage is switched at 180° and 360° is shown in FIG. 4(a) to FIG. 4(c), the present invention can also be applied to a case in which no switching occurs at 180° and 360°.
4(d) shows the waveform of the U-phase output voltage where no switching occurs at 180° and 360°. This is the waveform of the U-phase output voltage when the U-phase stabilization signal Δαu is set to zero and the resonance phenomenon of the three-phase synchronous motor 101 is not corrected. The pulse width of the output voltage is controlled as an angle α.

FIG. 4(e) shows the waveform of the U-phase output voltage when the U-phase stabilization signal Δαu is reflected in the waveform of the U-phase output voltage where no switching occurs at 180° and 360°.
In this case, the U-phase stabilization signal Δαu is reflected in the section αPu where a negative voltage occurs from 0° to 180° according to equation (8), and the U-phase stabilization signal Δαu is reflected in the section αNu where a positive voltage occurs from 180° to 360° according to equation (9).

The motor drive device 100 shown in this embodiment can correct the resonance phenomenon of the three-phase synchronous motor 101 based on the DC amount, so that the effect of the calculation delay of the controller can be avoided when the three-phase synchronous motor 101 rotates at high speed. The DC amount does not have to be a completely DC amount. For example, even if the AC component is sufficiently lower than the fundamental wave frequency, it can be regarded as a DC amount, and in this case, the same effect can be achieved. Furthermore, the correction voltage (ΔVu, ΔVv, ΔVw) for correcting the resonance phenomenon of the three-phase synchronous motor 101 is converted into a stabilization signal (Δαu, Δαv, Δαw) based on a formula. Therefore, even in synchronous PWM control that operates intermittently with an output voltage with a limited number of pulses, the signal for correcting the resonance phenomenon of the three-phase synchronous motor 101 can be accurately superimposed on the output voltage. Therefore, even in synchronous PWM control in which the motor rotates at high speed, the resonance phenomenon of the motor can be suppressed and the motor can be stably controlled.

FIG. 5 is a diagram showing the configuration of a stabilization signal generating unit 206A according to a modified example.
3, the differences ΔIu, ΔIv, ΔIw between the current and the current command value are input, and the correction voltages ΔVu, ΔVv, ΔVw are calculated by the PI control unit 303. In this modification, the three-phase currents Iu, Iv, Iw are input, and the correction voltages ΔVu, ΔVv, ΔVw are calculated by the I control unit 303I.

The stabilization signal generating unit 206A includes a U-phase stabilization signal generating unit 302a1, a V-phase stabilization signal generating unit 302b1, and a W-phase stabilization signal generating unit 302c1. The U-phase stabilization signal generating unit 302a receives the U-phase current Iu detected by the current sensor 107 and the DC voltage VDC detected by the voltage sensor 108. The V-phase stabilization signal generating unit 302b receives the V-phase current Iv detected by the current sensor 107 and the DC voltage VDC detected by the voltage sensor 108. The W-phase stabilization signal generating unit 302c receives the W-phase current Iw detected by the current sensor 107 and the DC voltage VDC detected by the voltage sensor 108.

The U-phase stabilization signal generating unit 302a1 includes an I control unit 303I and a voltage/angle conversion unit 308. The I control unit 303I includes an integral control gain 305 and an integrator 306, performs integral control, and outputs a correction voltage ΔVu. The voltage/angle conversion unit 308 converts the correction voltage ΔVu into a U-phase stabilization signal Δαu, as described in the first embodiment. That is, the U-phase stabilization signal generating unit 302a1 generates a correction voltage ΔVu by feedback control so as to reduce the DC component contained in the detected U-phase current Iu, and converts the correction voltage ΔVu into a stabilization signal Δαu.

The V-phase stabilization signal generating unit 302b1 and the W-phase stabilization signal generating unit 302c1 are configured similarly to the U-phase stabilization signal generating unit 302a1, and generate a correction voltage by feedback control to reduce the DC component contained in the detected phase current, and convert the correction voltage into a stabilization signal.

In this modified example, the three-phase currents Iu, Iv, and Iw are input and the I control unit 303I calculates the correction voltages ΔVu, ΔVv, and ΔVw. By using the I control unit 303I to set the cutoff frequency of the integral control gain 305 sufficiently small relative to the fundamental wave frequency, the fundamental wave components contained in the three-phase currents Iu, Iv, and Iw can be regarded as almost zero, and the DC amount corresponding to the pulsating component of the d-axis current or q-axis current caused by the resonance phenomenon of the three-phase synchronous motor 101 can be extracted. This provides the same effect as the first embodiment.

[Second embodiment]
FIG. 6 shows a control unit 105B according to the second embodiment.
In the control unit 105B according to this embodiment, the voltage amplitude and phase calculation unit 202 shown in the first embodiment in Fig. 2 is replaced with a voltage phase calculation unit 500, and the PWM pulse generation unit 205 shown in the first embodiment in Fig. 2 is replaced with a PWM pulse generation unit 501. The other configurations are the same as those in the first embodiment, and the same configurations are denoted by the same reference numerals and the description thereof will be omitted. The configuration diagram of the motor drive device 100 shown in Fig. 1 is also the same in this embodiment.

The voltage phase calculation unit 500 calculates the voltage phase θV using equation (2) based on the d-axis voltage command Vd* and the q-axis voltage command Vq* from the current control unit 201, and outputs the voltage phase θV to the PWM pulse generation unit 501. In this embodiment, synchronous PWM control is also performed, and the PWM pulse generation unit 501 generates switching signals S1 to S6 so that the number of pulses in one period of the output voltage from the power conversion circuit 102 is 1. In this case, if the maximum value of the voltage that the power conversion circuit 102 can output is Vmax, the voltage amplitude command Va* shown in the first embodiment is always Vmax. Therefore, in this embodiment, only the voltage phase θV is controlled so that the d-axis detection current Id and the q-axis detection current Iq from the three-phase/dq conversion unit 203 follow the d-axis current command Id* and the q-axis current command Iq* from the current command generation unit 200, respectively.

The PWM pulse generating unit 501 outputs switching signals S1 to S6 based on the DC voltage VDC detected by the voltage sensor 108 and the rotor position θdc detected by the rotor position sensor 106 in response to the voltage phase θV from the voltage amplitude phase calculation unit 202. The PWM pulse generating unit 501 receives the U-phase stabilization signal Δαu, the V-phase stabilization signal Δαv, and the W-phase stabilization signal Δαw from the stabilization signal generating unit 206 as described in the first embodiment. The PWM pulse generating unit 501 corrects the pulse width of the output voltage output from the power conversion circuit 102 by outputting the switching signals S1 to S6 taking into account the U-phase stabilization signal Δαu, the V-phase stabilization signal Δαv, and the W-phase stabilization signal Δαw.

Figures 7(a) and 7(b) are diagrams showing the waveforms of the U-phase output voltage generated by the power conversion circuit 102 in response to switching signals S1 to S6. The horizontal axis is the phase (angle) and the vertical axis is the voltage, showing one cycle of the output voltage.

Figure 7 (a) shows the waveform of the U-phase output voltage when the U-phase stabilization signal Δαu is set to zero and the resonance phenomenon of the three-phase synchronous motor 101 is not corrected. As shown in the figure, the number of pulses in the fundamental wave period of the three-phase synchronous motor 101 is 1. In addition, the timing at which the voltage level of the output voltage is switched is set to 0° (or 360°) and 180°, that is, the timing at which the voltage level of the output voltage is switched is set near the zero crossing of the fundamental wave component of the output voltage. The output voltage in this embodiment corresponds to the first embodiment in which the angle α is set to zero. In other words, the fundamental wave amplitude of the output voltage is constant, and only the voltage phase θV can be manipulated.

Fig. 7(b) shows the waveform of the U-phase output voltage when the U-phase stabilization signal Δαu is reflected to correct the resonance phenomenon of the three-phase synchronous motor 101. However, the U-phase stabilization signal Δαu is a positive DC amount. As shown in Fig. 7(b), the pulse width of the U-phase output voltage is corrected based on the U-phase stabilization signal Δαu. Specifically, +2Δαu is reflected in the section where a positive voltage was generated from 0° to 180°, and -2Δαu is reflected in the section where a negative voltage was generated from 180° to 360°.
Alternatively, −2Δαu may be reflected in the section where a positive voltage occurs from 0° to 180°, and +2Δαu may be reflected in the section where a negative voltage occurs from 180° to 360°.

As with the U-phase output voltage described above, the pulse widths of the V-phase output voltage and the W-phase output voltage are corrected based on the V-phase stabilization signal Δαv and the W-phase stabilization signal Δαw, and the phase difference between the phases is controlled to be 120° before being applied to the three-phase synchronous motor 101.

In summary, when the PWM pulse generating unit 501 switches the voltage level near the zero crossing of the fundamental wave component of the output voltage, in the section where the fundamental wave component is positive and the voltage level is a positive voltage, it adds or subtracts the pulse width of the output voltage according to the stabilization signal (Δαu, Δαv, Δαw), and in the section where the fundamental wave component is negative and the voltage level is a negative voltage, it subtracts or adds the pulse width of the output voltage according to the stabilization signal (Δαu, Δαv, Δαw), to correct the pulse width.

The motor drive device 100 shown in this embodiment has the same effect as the first embodiment, even when synchronous PWM control is performed and the number of pulses in one period of the output voltage by the power conversion circuit 102 is 1. That is, the motor drive device 100 can correct the resonance phenomenon of the three-phase synchronous motor 101 based on the DC amount, so that the influence of the calculation delay of the controller can be avoided when the three-phase synchronous motor 101 rotates at high speed. And even in synchronous PWM control that operates intermittently with an output voltage with a limited number of pulses, a signal that corrects the resonance phenomenon of the three-phase synchronous motor 101 can be accurately superimposed on the output voltage. Therefore, even in synchronous PWM control where the motor rotates at high speed, the resonance phenomenon of the motor can be suppressed and the motor can be stably controlled.

[Third embodiment]
FIG. 8 is a diagram showing the configuration of a stabilization signal generating unit 206B according to the third embodiment.
In the stabilization signal generator 206B according to this embodiment, the PI control unit 303 in the U-phase stabilization signal generator 302a shown in the first embodiment of Fig. 3 is replaced with a disturbance compensation control unit 700. The other configuration is the same as in the first embodiment, and the same configuration is assigned the same reference numerals and the description thereof will be omitted. The configuration diagram of the motor drive device 100 shown in Fig. 1 is also the same in this embodiment.

The stabilization signal generating unit 206B shown in FIG. 8 includes a subtractor 300a, a subtractor 300b, and a dq/three-phase conversion unit 301, similar to the stabilization signal generating unit 206 shown in the first embodiment of FIG. 3, and also includes a U-phase stabilization signal generating unit 302a2, a V-phase stabilization signal generating unit 302b2, and a W-phase stabilization signal generating unit 302c2. In FIG. 8, the subtractor 300a, the subtractor 300b, and the dq/three-phase conversion unit 301 are omitted from the illustration of the stabilization signal generating unit 206B.

As shown in FIG. 8, the U-phase stabilization signal generating unit 302a2 includes a disturbance compensation control unit 700 and a voltage/angle conversion unit 308.

The disturbance compensation control unit 700 includes a proportional control gain 701, a differential control gain 702, a pseudo differential controller 703, an adder 704, a previous value holder 705, and an adder 706. In the disturbance compensation control unit 700, the value obtained from the U-phase current deviation ΔIu via the proportional control gain 701 and the value obtained from the U-phase current deviation ΔIu via the differential control gain 702 and the pseudo differential controller 703 are added in the adder 704. Then, in the adder 706, the output value from the adder 704 and the output value from the previous value holder 705 are added to generate a correction voltage ΔVu. The correction voltage ΔVu is input to the voltage/angle conversion unit 308 and also to the previous value holder 705, and the value is held until the next calculation.

The pseudo differential controller 703 performs calculations in accordance with the transfer function of the following equation (15).
GD(s)=s/(1+τ・s)...(15)
The time constant τ is set so as to remove high-frequency noise contained in the calculation result of the pseudo differential controller 703. In the disturbance compensation control unit 700, the proportional control gain 701 is preferably set to the winding resistance value of the three-phase synchronous motor 101, and the differential control gain is preferably set to the inductance value of the three-phase synchronous motor 101. In other words, the proportional control and differential control (pseudo differential) are preferably set so as to form an inverse model (simulation model) of the three-phase synchronous motor 101.

The correction voltage ΔVu from the disturbance compensation control unit 700 is input to the voltage/angle conversion unit 308, which generates the U-phase stabilization signal Δαu. The configurations of the V-phase stabilization signal generation unit 302b2 and the W-phase stabilization signal generation unit 302c2 are the same as the configuration of the U-phase stabilization signal generation unit 302a2.

The motor drive device 100 according to this embodiment has the same effects as those described in the first embodiment. Furthermore, according to this embodiment, the stabilization signals (Δαu, Δαv, Δαw) of each phase are generated using a controller (disturbance compensation control unit 700) equivalent to an inverse model of the three-phase synchronous motor 101, instead of the PI control unit 303 of the first embodiment, so that the setting values of the control parameters (proportional control gain 701 and differential control gain 702) can be easily designed according to the parameters of the three-phase synchronous motor 101.

Furthermore, this embodiment can be applied to either the PWM pulse generating unit 205 shown in the first embodiment or the PWM pulse generating unit 501 shown in the second embodiment. In other words, this embodiment can be applied even when synchronous PWM control is performed and the number of pulses within one period of the output voltage from the power conversion circuit 102 is 3 or 1.

[Fourth embodiment]
FIG. 9 is a configuration diagram of an electric vehicle 800 according to the fourth embodiment.
The electric vehicle 800 is an electric vehicle equipped with any one of the motor drive devices 100 described in the first, second, or third embodiment and a three-phase synchronous motor 101 .

As shown in FIG. 9, an electric vehicle 800 has a pair of axles 801a and 801b supported on the vehicle body. Wheels 802a and 802b are fixed to both ends of one axle 801a, and wheels 802c and 802d are fixed to both ends of the other axle 801b. A three-phase synchronous motor 101 is connected to one axle 801a, and the rotational power of the three-phase synchronous motor 101 is transmitted to the wheels 802a and 802b via the axle 801a. The motor drive device 100 receives a torque command Tm from a higher-level control device (not shown) in the electric vehicle and drives the three-phase synchronous motor 101.

In the motor drive device 100 of the electric vehicle 800, synchronous PWM control is performed, and the number of pulses within one period of the output voltage from the power conversion circuit 102 is controlled to be 3 or 1, thereby driving the three-phase synchronous motor 101. At this time, the pulse width of the output voltage output from the power conversion circuit 102 is corrected based on the stabilization signal (Δαu, Δαv, Δαw) from the stabilization signal generation unit 206, thereby realizing stable control of the three-phase synchronous motor 101 with the resonance phenomenon of the three-phase synchronous motor 101 suppressed. Avoiding the resonance phenomenon of the three-phase synchronous motor 101 suppresses the pulsating components contained in the d-axis current Id and the q-axis current Iq, leading to improved quietness and driving efficiency of the electric vehicle 800.

This embodiment describes an example in which the motor drive device 100 is applied to an electric vehicle, but the same effect can be obtained by applying the motor drive device 100 to a railway or the like.

In the first to third embodiments, the motor drive device 100 has been described with reference to its configuration diagram. In these configuration diagrams, a part or all of the configuration except for the power conversion circuit 102 may be realized by a processor (e.g., CPU, GPU) and a program executed by the processor. In this case, the program is executed by the processor to perform a predetermined process using storage resources (e.g., memory) and/or interface devices (e.g., communication ports) as appropriate, so the subject of the process may be the processor. Similarly, the subject of the process performed by executing the program may be a controller, device, system, computer, or node having a processor. The subject of the process performed by executing the program may be a calculation unit, and may include a dedicated circuit (e.g., FPGA or ASIC) that performs a specific process.

The program may be installed in a device such as a computer from a program source. The program source may be, for example, a program distribution server or a computer-readable storage medium. When the program source is a program distribution server, the program distribution server may include a processor and a storage resource that stores the program to be distributed, and the processor of the program distribution server may distribute the program to be distributed to other computers. Also, in the following description, two or more programs may be realized as one program, and one program may be realized as two or more programs.

The present invention is not limited to the above-mentioned embodiment, and other forms that are conceivable within the scope of the technical concept of the present invention are also included in the scope of the present invention as long as they do not impair the features of the present invention. In addition, a configuration may be made by combining the above-mentioned embodiment with a plurality of modified examples. For example, the above-mentioned embodiment has been described in detail to clearly explain the technology of the present disclosure, and is not necessarily limited to those having all of the described configurations. In addition, it is also possible to add, delete, or replace other configurations with respect to a part of the configuration of each embodiment. For example, a configuration may be made in which differential control is added to the PI control unit 303, or integral control is added to the disturbance compensation control unit 700. In addition, in the first to fourth embodiments, the case where the number of pulses in one period of the output voltage by the power conversion circuit 102 is 3 or 1 is described, but it is possible to perform similar control even with other pulse numbers. In short, a similar effect can be obtained by controlling the power conversion circuit to generate an output voltage including a pulsating component as a direct current based on the stabilization signal (Δαu, Δαv, Δαw).
(The same effect can be achieved by controlling the power conversion circuit to generate an output voltage that includes a DC component.)

According to the embodiment described above, the following advantageous effects can be obtained.
(1) The motor drive device 100 includes a power conversion circuit 102 that converts DC power to AC power, and drives a three-phase synchronous motor 101 by controlling the pulse width of the output voltage output from the power conversion circuit 102. The motor drive device 100 includes PWM pulse generation units 205 and 501 that generate switching signals for operating switching elements of the power conversion circuit 102, and stabilization signal generation units 302a, 302a1, 302a2, 302b, 302b1, 302b2, 302c, 302c1, and 302c2 that generate stabilization signals for reducing DC components contained in phase currents based on information on phase currents flowing through the three-phase synchronous motor 101, and the PWM pulse generation units 205 and 501 generate switching signals based on the stabilization signals to correct the pulse width. This makes it possible to suppress the resonance phenomenon of the motor and stably control the motor even in synchronous PWM control in which the motor rotates at high speed.

100: motor drive device, 101: three-phase synchronous motor (motor), 102: power conversion circuit, 103: DC power supply, 104: smoothing capacitor, 105: control unit, 106: rotor position sensor, 107: current sensor, 108: voltage sensor, 200: current command generation unit, 201: current control unit, 202: voltage amplitude and phase calculation unit, 203: three-phase/dq conversion unit, 204: rotational speed calculation unit, 205, 501: PWM pulse generation unit, 206: stabilization signal generation unit, 300a, 300b: subtractor, 301: dq/three-phase conversion unit, 302a, 302a1, 302a 2: U-phase stabilization signal generator, 302b, 302b1, 302b2: V-phase stabilization signal generator, 302c, 302c1, 302c2: W-phase stabilization signal generator, 304: Proportional control gain, 305: Integral control gain, 306: Integrator, 307: Adder, 308: Voltage/angle converter, 700: Disturbance compensation controller, 701: Proportional control gain, 702: Differential control gain, 703: Pseudo differential controller, 704, 706: Adder, 705: Previous value holder, 800: Electric vehicle, 801a, 801b: Axles, 802a, 802b, 802c, 802d: Wheels.

Claims (13)

1. A motor drive device comprising a power conversion circuit that converts DC power into AC power, and drives a motor by controlling a pulse width of an output voltage output from the power conversion circuit,
a PWM pulse generating unit that generates a switching signal for operating a switching element of the power conversion circuit;
a stabilization signal generating unit that generates a stabilization signal for reducing a DC component included in a phase current based on information of the phase current flowing through the motor,
The motor drive device, wherein the PWM pulse generating unit generates the switching signal based on the stabilization signal and corrects the pulse width. 2. The motor drive device according to claim 1,
The stabilization signal generator includes a feedback control unit,
A motor drive device that generates the stabilization signal so as to reduce a DC component contained in the phase current by feedback control of the feedback control unit. 3. The motor drive device according to claim 2,
The stabilization signal generation unit calculates a current deviation, which is the difference between a current command based on a torque command to the motor and a detected current of the phase current, generates a correction voltage using the feedback control unit so that the current deviation converges to zero, and converts the correction voltage into the stabilization signal. 4. The motor drive device according to claim 3,
The feedback control unit is a motor drive device that performs feedback control using proportional-integral control. 4. The motor drive device according to claim 3,
The feedback control unit is a motor drive device that performs feedback control using control including pseudo differential control. 3. The motor drive device according to claim 2,
The motor drive device, wherein the stabilization signal generation unit generates a correction voltage using the feedback control unit so as to reduce a DC component contained in the detected current of the phase current, and converts the correction voltage into the stabilization signal. 7. The motor drive device according to claim 6,
The feedback control unit is a motor drive device that performs feedback control using integral control. In the motor drive device according to any one of claims 3 to 6,
A motor drive device, wherein the stabilization signal generation unit includes a voltage angle conversion unit that converts the correction voltage into the stabilization signal based on the following equations (3), (4), and (5).
Δαu=(π/2)・(-ΔVu/VDC)...(3)
Δαv=(π/2)・(-ΔVv/VDC)...(4)
Δαw=(π/2)・(-ΔVw/VDC)...(5)
Here, ΔVu represents the U-phase correction voltage, ΔVv represents the V-phase correction voltage, ΔVw represents the W-phase correction voltage, Δαu represents the U-phase stabilization signal, Δαv represents the V-phase stabilization signal, Δαw represents the W-phase stabilization signal, and VDC represents the DC voltage supplied to the power conversion circuit. The motor drive device according to any one of claims 1 to 7,
The motor drive device, wherein the PWM pulse generating unit generates the switching signal so that the number of pulses within one period of the output voltage is 3. 10. The motor drive device according to claim 9,
The motor drive device, when switching the voltage level near the zero crossing of the fundamental wave component of the output voltage, the PWM pulse generating unit subtracts or adds to the pulse width of the output voltage in response to the stabilization signal in a section where the fundamental wave component is positive and the voltage level is negative voltage, and adds or subtracts the pulse width of the output voltage in response to the stabilization signal in a section where the fundamental wave component is negative and the voltage level is positive voltage, to correct the pulse width. The motor drive device according to any one of claims 1 to 7,
The motor drive device, wherein the PWM pulse generating unit generates the switching signal so that the number of pulses within one period of the output voltage is 1. 12. The motor drive device according to claim 11,
when switching a voltage level near a zero crossing of a fundamental wave component of the output voltage, the PWM pulse generating unit adds or subtracts the pulse width of the output voltage in a section where the fundamental wave component is positive and the voltage level is a positive voltage in response to the stabilization signal;
A motor drive device that corrects the pulse width by subtracting or adding to the pulse width of the output voltage in accordance with the stabilization signal in a section where the fundamental wave component is negative and the voltage level is a negative voltage. A motor drive device according to any one of claims 1 to 7,
The motor driven by the motor drive device;
an axle coupled to the motor;
and a wheel fixed to the axle.

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