JP3580133B2 - Motor control device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a motor control device, and more particularly to a technique for driving an AC motor with a rectangular wave voltage.
[0002]
[Prior art]
When an AC motor is driven by using a DC power supply, an inverter is used. The inverter is controlled by an inverter drive circuit, and generally, a pulse width modulation (PWM) waveform voltage is applied to the AC motor.
[0003]
However, if the PWM waveform voltage is applied to the AC motor, the voltage utilization rate is limited, and there is a problem that a sufficiently high output cannot be obtained. On the other hand, when a large amount of field weakening current flows, copper loss occurs. In this regard, JP-A-55-49996, JP-A-58-119791, and JP-A-3-143289 disclose that both a PWM waveform voltage and a rectangular wave voltage are applied to a motor as required. In addition, a technique for improving the output of an electric motor has been disclosed.
[0004]
[Problems to be solved by the invention]
However, according to the techniques disclosed in JP-A-55-49996 and JP-A-58-119791, a complete rectangular wave voltage is not applied to the electric motor until the peak value of the fundamental wave exceeds a certain value. At an intermediate peak value, only the section centered on the phase timing of π / 2, 3π / 2 is rectangular, and a comb-like waveform remains around it. For this reason, the switching by the inverter is still continued in that portion, and energy loss occurs.
[0005]
Further, according to the technique disclosed in Japanese Patent Application Laid-Open No. 3-143289, the PWM circuit and the rectangular wave generating circuit have different configurations, and it is not possible to implement both the PWM control and the rectangular wave control with a simple configuration. It is difficult to smoothly connect the PWM control and the rectangular wave control without generating a shock of the motor.
[0006]
The present invention has been made in view of the above problems, and a first object is to provide a simple configuration capable of shifting from a state of supplying a pulse width modulation waveform voltage to an AC motor to a state of supplying a rectangular wave voltage. Another object of the present invention is to provide an electric motor control device.
[0007]
A second object is to provide a motor control device that can smoothly transition from a state in which a pulse width modulation waveform voltage is supplied to an AC motor to a state in which a rectangular wave voltage is supplied.
[0008]
A third object is to provide a motor control device that can supply an AC motor with a waveform voltage that has a relatively small inverter loss while supporting an AC voltage having an arbitrary peak value.
[0009]
A fourth object is to provide a motor control device that can suppress inverter heat generation by supplying a waveform voltage with a small inverter loss to an AC motor.
[0010]
[Means for Solving the Problems]
(1) In order to solve the above problems, a first invention is a motor control device including an inverter for driving an AC motor and inverter control means for performing switching control on the inverter, wherein the inverter control means includes: The voltage of each phase applied to the AC motor sequentially becomes a first reference voltage in a first period, becomes a second reference voltage higher than the first reference voltage in a second period, and becomes the first reference voltage in a third period. Rectangular wave control means for performing switching control on the inverter so that the inverter becomes a reference voltage, becomes a third reference voltage lower than the first reference voltage in a fourth period, and becomes the first reference voltage in a fifth period. It is characterized by. By doing so, switching loss in the inverter can be reduced, heat generation of the inverter can be suppressed, and the AC motor can be driven with high efficiency.
[0011]
(2) In one aspect of the present invention, the inverter control unit includes a unit that expands and contracts the width of the second period and the fourth period while maintaining a center position. In this way, the effective value of the power supplied to the AC motor can be changed without changing the phase.
[0012]
(3) In one aspect of the present invention, the inverter control means includes a pulse width modulation wave control means for performing switching control on the inverter by using a pulse width modulation method; Control switching means for switching between the rectangular wave control means and the rectangular wave control means, wherein the control switching means includes a voltage applied to the AC motor when switching from the pulse width modulation wave control means to the rectangular wave control means. The width of the second period and the fourth period is set so that the peak value of the fundamental wave of the waveform changes continuously. This makes it possible to smoothly shift from the pulse width modulation wave control to the rectangular wave control, and reduce the shock generated in the AC motor.
[0013]
(4) Further, according to one aspect of the present invention, a temperature detecting means for detecting a temperature of the inverter, and switching by the pulse width modulated wave control means when the temperature detected by the temperature detecting means exceeds a predetermined temperature. Switching from control to switching control by the rectangular wave control means further includes switching means for switching control of the inverter by the control switching means. In this way, when the temperature of the inverter rises, the switching is switched to the switching control by the rectangular wave control means that generates less heat, and further temperature rise of the inverter can be suppressed.
[0014]
(5) In one aspect of the present invention, the rectangular wave control means includes means for determining a predetermined threshold value, means for supplying a reference sine wave value, and a voltage applied to each phase of the AC motor. Is defined as the second reference voltage when the value of the reference sine wave is equal to or greater than the predetermined threshold, and the value of the basic sine voltage is less than the predetermined threshold and the predetermined threshold is signed. When the value is equal to or greater than the inverted value, the first reference voltage is set, and when the value of the reference sine wave is less than the value obtained by inverting the sign of the predetermined threshold, the third reference voltage is set. Means for controlling the switching of the inverter. With this configuration, the switching timing of the inverter can be obtained in real time.
[0015]
(6) Further, in the second invention, a voltage command value for commanding a voltage of each phase of the AC motor is inputted, and a pulse width modulation waveform voltage corresponding to the voltage command value is applied to the AC motor. A modulating wave control unit, and when any one of the voltage command values is equal to or greater than a predetermined maximum value, the voltage command value of each phase input to the pulse width modulation wave controlling unit is converted into a sign of the voltage command value. And a rectangular wave control means for correcting the predetermined maximum value or a value obtained by inverting the sign to a predetermined value and inputting the corrected value to the pulse width modulation wave control means. With this configuration, it is possible to easily shift to the rectangular wave control only by correcting the voltage command value while using the existing inverter and the pulse width modulation wave control means.
[0016]
(7) Further, in one aspect of the present invention, when any one of the voltage command values becomes equal to or more than the predetermined maximum value, the rectangular wave control means may input each of the square wave control values to the pulse width modulation wave control means. The phase voltage command value is gradually approached to a predetermined maximum value or a value obtained by inverting the sign of the predetermined maximum value in a predetermined cycle. By doing so, it is possible to prevent an overcurrent due to a sudden change in the voltage command, and it is possible to stably control the AC motor.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0018]
Embodiment 1 FIG.
FIG. 1 is a diagram illustrating a configuration of a motor control device according to Embodiment 1 of the present invention. The motor control device 10 shown in FIG. 1 is mounted on an electric vehicle, and includes an inverter 14 to which a DC voltage is applied by a battery 12 and an AC motor 16 to which a three-phase AC voltage is applied by the inverter 14. And further includes a voltage command value Vu^*, Vv^*, Vw^*Is input, and a PWM control unit 18 that performs switching control of the inverter 14 based on the value is input to the PWM control unit 18.^*, Vv^*, Vw^*And a control unit 20 for supplying
[0019]
In such a configuration, the current value of each phase is detected from the output from the inverter 14, and the value is input to the control unit 20. Further, the control unit 20 receives a torque command determined by other control devices (not shown) in consideration of the accelerator opening, the capacity of the battery 12, and the like. Then, the control unit 20 determines the voltage command value Vu in real time based on these values.^*, Vv^*, Vw^*Is calculated and supplied to the PWM control unit 18.
[0020]
Further, the PWM control unit 18 outputs the voltage command value Vu^*, Vv^*, Vw^*And a triangular wave, and on / off commands are given to a plurality of switching elements included in the inverter 14 based on the comparison result. Thereby, the voltage command value Vu^*, Vv^*, Vw^*Is a sine wave, the inverter 14 applies a PWM waveform voltage (pseudo sine wave voltage) to the AC motor 16. On the other hand, voltage command value Vu^*, Vv^*, Vw^*Is in the form of a rectangular wave, the inverter 14 applies a rectangular wave voltage corresponding to the rectangular wave to the AC motor 16.
[0021]
FIG. 2 is a flowchart illustrating the operation of motor control device 10 according to Embodiment 1 of the present invention having the above configuration. As shown in the figure, first, in the electric motor control device 10, the control unit 20 controls the voltage command value Vu based on the current values Iu, Iv, Iw supplied to the AC motor 16 and the torque command value.^*, Vv^*, Vw^*Is generated (S101). Next, a peak value Vac is calculated based on the voltage command value (S102). That is, the normal voltage command value Vu^*, Vv^*, Vw^*Has a sinusoidal waveform, and the peak value Vac of the sine wave is calculated in this process. That is, assuming that the current rotor position of the AC motor 16 is θ and the phase difference between the rotor origin and the zero point of the energizing current is α, for example, the voltage command value Vu^*, Vv^*Is determined as follows.
[0022]
(Equation 1)
Vu^*= Vac × sin (θ + α) (1)
Vv^*= Vac × sin (θ + α−2 / 3π) (2)
When θ + α is eliminated from these equations, the peak value Vac is obtained as follows.
[0023]
(Equation 2)
Vac = 2 / √3 × (Vu^*2 + Vu^*× Vv^*+ Vv^{* 2})^1/2          (3)
That is, the voltage command value Vu^*, Vv^*, Vw^*The peak value Vac can be calculated using any two of the values. Then, the motor control device 10 determines whether or not the peak value Vac satisfies the following expression (S103).
[0024]
(Equation 3)
Vac> Vdc / 2 (4)
Here, Vdc is the voltage of the battery 12. That is, here, the voltage command value Vu given from the control unit 20 is used.^*, Vv^*, Vw^*Is determined to change over the supply voltage of the battery 12. If the peak value Vac exceeds a value obtained by dividing the battery voltage Vdc by 2, the process shifts to a rectangular wave voltage control mode, which is one of the features of the present invention. On the other hand, if the peak value Vac is equal to or smaller than the value obtained by dividing the battery voltage Vdc by 2, the AC motor 16 is driven in the PWM control mode based on the triangular wave comparison as in the related art.
[0025]
FIG. 3 is a flowchart illustrating a process of the electric motor control device 10 in the rectangular wave voltage control mode. As shown in the figure, when the motor control device 10 is in the rectangular wave voltage control mode, first, the voltage threshold value Vth is calculated according to the following equation (S201).
[0026]
(Equation 4)
Vth = Vac × sin [cos^-1{ΠVac / (2Vdc)}] (5)
FIG. 4 is a diagram showing the relationship between the voltage waveform applied to AC motor 16 in the rectangular wave control mode and voltage threshold Vth. In the figure, a waveform 22 is a voltage command value Vu given to the PWM control unit 18 in the rectangular wave control mode.^*, Vv^*, Vw^*Is represented. On the other hand, the waveform 24 is the voltage command value Vu originally output from the control unit 20 in the PWM control mode.^*, Vv^*, Vw^*That is, the voltage command value Vu calculated in S101.^*, Vv^*, Vw^*It is. Then, the fundamental wave obtained when the waveform 22 is inversely Fourier-transformed matches the waveform 24. In the rectangular wave control mode of motor control device 10 according to the present embodiment, voltage command value Vu^*, Vv^*, Vw^*Is the voltage command value Vu related to the waveform 22 in real time.^*, Vv^*, Vw^*The voltage of the waveform 22 is applied to the AC motor 16. By doing so, even when the control mode is shifted, the effective value of the fundamental wave, which is considered to have a large effect on the torque of the AC motor 16, does not change. The drive feeling of the electric vehicle equipped with the device 10 can be maintained at a favorable level.
[0027]
In order to generate the waveform 22, it is necessary to obtain timings of the electrical angles α, 180 ° −α, 180 ° + α, and 360 ° −α shown in FIG. Here, this timing is obtained by calculating a voltage threshold value Vth, which is a potential difference from the horizontal axis in the figure to the point where the waveforms 22 and 24 intersect. First, the peak value Vrec of the fundamental wave of the waveform 22 is calculated using α.
(Equation 5)
Vrec = 2Vdc / π × cosα (6)
It is expressed as This is obtained by performing an inverse Fourier transform on the waveform 22. Then, under the condition that the peak value Vrec is equal to the peak value Vac,
(Equation 6)
α = cos^-1{ΠVac / (2Vdc)} (7)
Is required. By the way, the voltage threshold Vth is calculated using the electrical angle α,
(Equation 7)
Vth = Vac × sinα (8)
Expression (5) is derived by substituting Expression (7) into this.
[0028]
Thus, in motor control device 10, voltage command value Vu output from control unit 20 is provided.^*, Vv^*, Vw^*By monitoring whether or not the value exceeds the voltage threshold value Vth, the timings of the electrical angles α, 180 ° −α, 180 ° + α, 360 ° −α can be easily obtained, and the waveform 22 is generated. can do. That is, in S202 of FIG. 3, the u-phase voltage command value Vu^*, It is determined whether or not the absolute value exceeds the voltage threshold value Vth. And, if it exceeds, the voltage command value Vu^*Of Vu to Vdc / 2^*(S203), while the voltage command value Vu is corrected.^*Is less than voltage threshold Vth, voltage command value Vu^*Is set to zero (S204). Similar processing is applied to the v-phase voltage command value Vv * and the w-phase voltage command value Vw * (S205 to S210). Then, the corrected voltage command value Vu^*, Vv^*, Vw^*Is supplied to the PWM control unit 18 (S211).
[0029]
In this case, 0 potential (first reference voltage) in the first period of electrical angles 0 to α, Vdc / 2 (second reference voltage) in the second period of electrical angles α to 180 ° −α, and electrical angles α to 0 potential (first reference voltage) in the third period of 180 ° −α to 180 ° + α, electrical angle −Vdc / 2 (third reference voltage) in the fourth period of 180 ° + α to 360 ° −α, electrical angle A voltage that changes like 0 potential (first reference voltage) can be applied to the AC motor 16 during a fifth period of 360 ° -α to 360 °.
[0030]
By doing so, the number of times of switching in the inverter 14 can be reduced. For example, in the normal triangular wave comparison PWM control, if the motor energizing current cycle is Tcu and the PWM carrier cycle is Tca, the number of times of switching in the inverter 14 is Tcu / Tca times. In the control mode, the number of times of switching is only two per cycle, and the number of times of switching can be reduced to 2Tca / Tcu. As a result, the switching loss in the inverter 14 can be reduced to 2Tca / Tcu.
[0031]
Further, the maximum output voltage in the triangular wave comparison PWM control is theoretically √3 Vdc / 2, but in the rectangular wave control mode, the maximum output voltage is given by the above equation (6).
(Equation 8)
Vrecmax = 2√3Vdc / π (9)
And the maximum output voltage can be made 4 / π times. As a result, the field weakening current can be reduced, and the motor efficiency can be improved.
[0032]
In the above description, the mode shifts to the rectangular wave control mode when a voltage command value exceeding the limit voltage of the PWM control is issued. However, as described above, the advantage that the switching loss can be reduced in the rectangular wave control mode. In other cases, the AC motor 16 may be driven in the rectangular wave control mode.
[0033]
Embodiment 2 FIG.
Next, an electric motor control device according to Embodiment 2 of the present invention will be described. The motor control device according to the present embodiment focuses on the fact that the switching loss of the inverter 14 can be reduced according to the rectangular wave control mode of the motor control device 10 according to the first embodiment. The above-mentioned rectangular wave control mode is used to prevent the rise.
[0034]
FIG. 5 is a diagram showing a configuration of a motor control device according to Embodiment 2 of the present invention. The motor control device 10a shown in the figure has substantially the same configuration as the motor control device 10 according to the first embodiment, except for the control unit 20a and the temperature sensor 21. Other configurations are the same as those of the motor control device 10 according to the first embodiment.
[0035]
First, a temperature sensor 21 is attached to the inverter 14 in the motor control device 10a shown in FIG. Further, the control unit 20a receives the temperature of the inverter 14 detected by the temperature sensor 21, that is, the inverter temperature Tnow, and when the temperature exceeds the temperature threshold value Tinv, shifts to the rectangular wave control mode under a certain condition. ing. That is, conventionally, when the temperature of the inverter 14 rises above a certain level, measures have been taken by restricting the output of the inverter 14 or the like, but the motor control device 10a according to the second embodiment immediately reduces the output in such a case. Instead, the control is temporarily shifted to the rectangular wave control mode in which the switching loss is small and the heat generation is small.
[0036]
FIG. 6 is a flowchart illustrating the operation of the electric motor control device 10a according to Embodiment 2 of the present invention. As shown in the figure, the control unit 20a of the motor control device 10a first determines whether the inverter temperature Tnow output from the temperature sensor 21 exceeds the temperature threshold value Tinv (S301). If so, it is determined whether the AC motor 16 can be driven in the rectangular wave control mode (S302). This is because if the electric frequency is significantly smaller than the time constant of the AC motor 16, the AC motor 16 cannot be controlled in the rectangular wave control mode. The motor control device 10 according to the first embodiment shifts to the rectangular wave control mode when the peak value Vac exceeds Vdc / 2. In such a case, the electric frequency is set to be sufficiently large. Since it is conceivable, the determination in S302 is omitted.
[0037]
If it is determined in S302 that the rectangular wave control is possible, the control unit 20a drives the AC motor 16 with the rectangular wave voltage according to the flowchart shown in FIG. 3 (S303). If it is determined in step S302 that rectangular wave voltage control is impossible, the control unit 20a performs triangular wave comparison PWM control as in the related art. At this time, protection of the inverter 14 is achieved by limiting the output as in the related art.
[0038]
If it is determined in S301 that the inverter temperature Tnow is equal to or lower than the temperature threshold value Tinv, then the control unit 20a determines whether the peak value Vac exceeds Vdc / 2 (S304). If the peak value Vac exceeds Vdc / 2, it is determined whether rectangular wave control is possible (S302). If possible, the process proceeds to S303, where a rectangular wave voltage is applied to the AC motor 16, and If it is impossible, the process proceeds to S305 to apply a sine wave voltage (pseudo sine wave voltage) to the AC motor 16. If the peak value Vac does not exceed Vdc / 2, the process also proceeds to S305 to apply a sine wave voltage (pseudo sine wave voltage) to the AC motor 16. Even if the mode is shifted to the rectangular wave control mode by the above control, if the inverter temperature Tnow still rises, the inverter 14 is protected by the output limitation as usual.
[0039]
By doing so, it is possible to reduce the case where the output limitation is imposed on the inverter 14 as compared with the system in which the output is limited immediately when the temperature of the inverter 14 rises.
[0040]
Embodiment 3 FIG.
FIG. 7 is a diagram illustrating a configuration of a motor control device according to Embodiment 3 of the present invention. As shown in the figure, the motor control device 30 includes a current map 32, a PI control unit 34, a dq-3 phase conversion unit 36, a rectangular wave voltage command generation unit 38, a PWM inverter 40, It is configured to include a −dq conversion unit 42 and an AC motor 44, and is for performing vector control of the AC motor 44.
[0041]
In the figure, a torque command generated based on an accelerator opening or the like is input from a control unit (not shown) to a current map 32. Here, a current command value Id is determined based on the current map.^*, Iq^*Is output. Also, the currents Iu, Iv, Iw supplied from the PWM inverter 40 to the AC motor 44 are input to the three-phase-dq converter 42, where the values are AD-converted and further converted into two-phase. As a result, currents Id and Iq are generated. Then, the PI control unit 34 sets the current command value Id^*, Iq^*Vd based on the differences between the currents Id and Iq^*, Vq^*Which are converted into three phases by the dq-3 phase converter 36 and the voltage command value Vu^*, Vv^*, Vw^*Is generated. The rectangular wave voltage command generation unit 38 outputs the voltage command value Vu^*, Vv^*, Vw^*Is normally set as it is in the PWM inverter 40, and especially when high output is required in the AC motor 44, the voltage command values Vu^*, Vv^*, Vw^*To correct the square wave voltage command value Vu^{* *}, Vv^**, Vw^**Is generated, and the value is set in the PWM inverter 40.
[0042]
In addition, in the control units 20 and 20a included in the motor control devices 10 and 10a according to the first and second embodiments, the voltage command value Vu is also set.^*, Vv^*, Vw^*Is similarly determined.
[0043]
FIG. 8 is a flowchart illustrating the operation of motor control device 30 according to the embodiment of the present invention. As shown in the figure, first, in the motor control device 30, the current map 32, the PI control unit 34, the dq-three-phase conversion unit 36, and the three-phase-dq conversion unit 42 use the voltage command value Vu.^*, Vv^*, Vw^*Is generated (S401). Then, it is determined whether or not any one of the absolute values of the voltage command values exceeds the PWM counter maximum value Cmax (S402). As described above, the voltage command value Vu can be calculated without calculating the peak value.^*, Vv^*, Vw^*If the transition of the rectangular wave control is simply determined using only the absolute value of, the processing load on the rectangular wave voltage command generation unit 38 can be reduced.
[0044]
Then, the voltage command value Vu^*, Vv^*, Vw^*If any one of them exceeds the PWM counter maximum value Cmax, it is set to the value of the PWM counter maximum value Cmax or its opposite sign according to the sign of each value. Then, the corrected voltage command value is changed to a rectangular wave voltage command value Vu.^**, Vv^**, Vw^**The value is set in the PWM inverter 40 (S412). Thus, the voltage command value Vu^*, Vv^*, Vw^*, The rectangular wave voltage command value Vu^**, Vv^**, Vw^**Is set, the processing load on the rectangular wave voltage command generation unit 38 can be further reduced.
[0045]
Specifically, first, the rectangular wave voltage command generation unit 38 outputs the voltage command value Vu^*Is determined to be 0 or more (S403). If it is 0 or more, the rectangular wave voltage command value Vu is determined.^**Is set to the value of the PWM counter maximum value Cmax (S404). On the other hand, voltage command value Vu^*Is less than 0, the maximum value of the PWM counter with a minus sign is the square wave voltage command value Vu.^**Is set (S405). Subsequently, the voltage command value Vv^*, Vw^*(S406 to S411). On the other hand, the rectangular wave voltage command generation unit 38 outputs the voltage command value Vu^*, Vv^*, Vw^*If none of them exceeds the PWM counter maximum value Cmax, the voltage command values Vu^*, Vv^*, Vw^*Is set in the PWM inverter 40 as it is (S412).
[0046]
By doing so, it is possible to output up to a higher speed range without changing the voltage of the power supply that supplies power to the PWM inverter 40. FIG. 9 is a diagram comparing the output when the AC motor 44 is driven by the motor control device 30 and the output when the processing of the rectangular wave voltage command generation unit 38 is not performed. As shown in the figure, according to the present motor control device 30, the rectangular wave voltage command generation unit 38 causes the PWM inverter 40 to output the rectangular wave voltage command value Vu.^**, Vv^**, Vw^**Is set, it is possible to improve the torque particularly in the high speed rotation range. Therefore, for example, the AC motor 44 can be downsized. In addition, if the operation region of the AC motor 44 is sufficient as it is, the power source can be downsized.
[0047]
In the above description, the voltage command value Vu^*, Vv^*, Vw^*When any one of the absolute values of the above exceeds the PWM counter maximum value Cmax, the square wave voltage command generation unit 38 immediately switches the voltage command value between Cmax and -Cmax. Vu^**, Vv^**, Vw^**However, as shown by the transition line 46 in FIG. 10, the rectangular wave voltage command value Vu^**, Vv^**, Vw^**May gradually approach the PWM counter maximum value Cmax from the current voltage command value. By doing so, it is possible to prevent an overcurrent or the like due to a sudden change in the voltage command during the transition from PWM control to rectangular wave control in a comparative process, and to stabilize the control of the AC motor 44. Further, if the electric motor control device 30 is applied to a vehicle, it is possible to maintain a suitable drive feeling at the time of control switching.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a motor control device according to a first embodiment of the present invention.
FIG. 2 is a flowchart illustrating an operation of the electric motor control device according to the first embodiment of the present invention.
FIG. 3 is a flowchart illustrating an operation of the electric motor control device according to the first embodiment of the present invention.
FIG. 4 is a diagram showing a time transition of a voltage command value given to a PWM control unit in the electric motor control device according to the first embodiment of the present invention.
FIG. 5 is a diagram showing a configuration of a motor control device according to a second embodiment of the present invention.
FIG. 6 is a flowchart illustrating an operation of the electric motor control device according to the second embodiment of the present invention.
FIG. 7 is a diagram showing a configuration of a motor control device according to a third embodiment of the present invention.
FIG. 8 is a flowchart illustrating an operation of the electric motor control device according to the third embodiment of the present invention.
FIG. 9 is a diagram showing motor output by a motor control device according to Embodiment 3 of the present invention.
FIG. 10 is a diagram illustrating a modification of the motor control device according to Embodiment 3 of the present invention.
[Explanation of symbols]
10, 10a, 30 motor control unit, 12 battery, 14 inverter, 16, 44 AC motor, 18 PWM control unit, 20, 20a control unit, 21 temperature sensor, 22, 24 (voltage command value) waveform, 32 current map , 34 PI control unit, 36 dq-three phase conversion unit, 38 square wave voltage command generation unit, 40 PWM inverter, 42 three-phase-dq conversion unit, 46 transition line (of rectangular wave upper and lower values).

Claims (6)

An inverter that drives an AC motor, and an inverter control unit that performs switching control on the inverter,
The inverter control means may be configured such that the voltage of each phase applied to the AC motor sequentially becomes a first reference voltage in a first period, becomes a second reference voltage higher than the first reference voltage in a second period, A rectangle that performs switching control on the inverter so that the first reference voltage is obtained in three periods, the third reference voltage is lower than the first reference voltage in a fourth period, and the first reference voltage is obtained in a fifth period. Including wave control means,
The rectangular wave control means,
Means for determining a predetermined threshold;
Means for providing a value of the reference sine wave;
The voltage applied to each phase of the AC motor is the second reference voltage when the value of the reference sine wave is equal to or greater than the predetermined threshold, and the value of the reference sine wave is less than the predetermined threshold. And the first reference voltage when the predetermined threshold value is equal to or greater than the value obtained by inverting the sign, and when the value of the reference sine wave is less than the value obtained by inverting the sign of the predetermined threshold value. Means for performing switching control of the inverter so as to set the third reference voltage;
Including
The predetermined threshold value includes a peak value Vac obtained from any two values of voltage command values for instructing voltages of the respective phases of the AC motor, and a voltage Vdc of a battery for driving the AC motor. Vth calculated based on the following equation:
Vth = Vac × sin [cos ^-1 {πVac / (2Vdc)}]
An electric motor control device, characterized in that: The motor control device according to claim 1,
The rectangular wave control means performs the switching control when any one of the voltage command values for commanding the voltage of each phase of the AC motor is equal to or greater than a predetermined maximum value.
An electric motor control device, characterized in that: The motor control device according to claim 1 or 2,
The motor control device, wherein the inverter control unit includes a unit that expands and contracts the width of the second period and the fourth period while maintaining a center position . The motor control device according to claim 3,
The inverter control means includes a pulse width modulation wave control means for performing switching control on the inverter using a pulse width modulation method, a control switching means for switching between the pulse width modulation wave control means and the rectangular wave control means, , Further comprising
The control switching means, when switching from the pulse width modulation wave control means to the rectangular wave control means, so that the peak value of the fundamental wave of the voltage waveform applied to the AC motor continuously changes. A motor control device, wherein the widths of two periods and the fourth period are set. The motor control device according to claim 4,
Temperature detection means for detecting the temperature of the inverter,
When the temperature detected by the temperature detecting means exceeds a predetermined temperature, switching of the control of the inverter by the control switching means from switching control by the pulse width modulated wave control means to switching control by the rectangular wave control means. Means,
A motor control device, further comprising: The motor control device according to any one of claims 2 to 5,
The rectangular wave control means, when any one of the voltage command values is equal to or greater than the predetermined maximum value , gradually changes the voltage command value for commanding the voltage of each phase of the AC motor at a predetermined cycle, the second Performing switching control on the inverter so as to approach the reference voltage or the third reference voltage;
An electric motor control device, characterized in that:

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