JP2014113048A - Vector control device for electric motor, and vehicle drive system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vector control device for an electric motor that reduces a harmonic loss.SOLUTION: The vector control device for controlling a power converter for converting DC power to AC power and supplying the AC power to an electric motor includes: a vector control section 3 for computing an output voltage to be output from the power converter by vector control on the basis of a torque command and a flux command input thereinto, and generating a PWM signal to control the power converter on the basis of the output voltage; and a first flux command generation section 11a for generating a flux command for an asynchronous PWM mode, and controllingly decreasing a field flux and increasing a rotational frequency in the electric motor when a modulation rate becomes equal to or higher than a first threshold. The flux command generated by the first flux command generation section 11a is input into the vector control section 3 when an output frequency of the power converter is lower than a predetermined value higher than an output frequency bringing the modulation rate to the first threshold.

Description

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

  A technique of performing vector control of an electric motor using an inverter is widely used (see, for example, Patent Document 1 below). This vector control of an electric motor is a technique for managing and controlling a magnetic flux component and a torque component separately in a rotating coordinate system, and is also used in recent electric vehicle control.

  In an inverter for driving an electric vehicle, an asynchronous PWM mode in which the carrier frequency does not depend on the frequency of the AC output voltage command is used in the low speed range. Thereafter, when the upper limit of the modulation rate by the asynchronous PWM control is exceeded, a synchronous PWM mode (for example, synchronous three-pulse mode) in which the carrier frequency is an integral multiple of the frequency of the AC voltage command is used, and the output voltage is saturated to the maximum value. One pulse mode is used in the fixed high speed range.

Japanese Patent No. 4065903

  However, according to the above conventional technique, in the asynchronous PWM mode, for example, control is performed to increase the output voltage by using constant magnetic flux command control, and when the upper limit of the modulation rate of the asynchronous PWM mode is exceeded, the mode is switched to the synchronous PWM mode. . On the other hand, in the synchronous PWM mode (especially the 1 pulse mode), the harmonic loss due to the ripple is larger than in the asynchronous PWM mode. Accordingly, if the synchronous PWM mode area can be reduced and the asynchronous PWM mode area can be increased, the harmonic loss due to ripple can be reduced. When the output voltage is increased and the modulation rate reaches the upper limit, the operation mode of the asynchronous PWM mode is limited because the mode is switched to the synchronous PWM mode. For this reason, there was a problem that harmonic loss due to ripples could not be reduced.

  The present invention has been made in view of the above, and an object thereof is to obtain a vector control device and a vehicle drive system for an electric motor that can reduce harmonic loss.

  In order to solve the above-described problems and achieve the object, the present invention is a vector control device for controlling a power converter that converts direct current power into alternating current power and supplies the alternating current power to the motor. A vector control unit that calculates an output voltage to be output by the power converter by vector control based on a torque command and a magnetic flux command, and generates a PWM signal for controlling the power converter based on the output voltage; A magnetic flux command generator for generating a magnetic flux command for PWM mode, and performing control to reduce the field magnetic flux in the electric motor and increase the rotational speed when the modulation rate is equal to or greater than a first threshold value, When the output frequency of the converter is less than a predetermined value larger than the output frequency when the modulation factor becomes the first threshold value, the magnetic field generated by the magnetic flux command generation unit is generated. Characterized by inputting an instruction to the vector control unit.

  According to the present invention, there is an effect that harmonic loss can be reduced.

FIG. 1 is a diagram illustrating a configuration example of a vector control apparatus for an electric motor according to a first embodiment. FIG. 2 is a diagram illustrating a configuration example of the first magnetic flux command generation unit. FIG. 3 is a diagram illustrating an example of the modulation factor and the pulse mode according to the first embodiment. FIG. 4 is a diagram illustrating an example of a magnetic flux command according to the first embodiment. FIG. 5 is a diagram illustrating an example of a modulation rate and a pulse mode according to the conventional technique. FIG. 6 is a diagram illustrating an example of a magnetic flux command according to the prior art. FIG. 7 is a diagram showing an example of the effect of the first embodiment in comparison with the prior art. FIG. 8 is a diagram illustrating a configuration example of a first magnetic flux command generation unit of the vector control apparatus for the electric motor according to the second embodiment. FIG. 9 is a diagram illustrating a configuration example of the vehicle drive system according to the third embodiment.

  Embodiments of a vector control device for an electric motor and a vehicle drive system according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
FIG. 1 is a diagram illustrating a configuration example of a first embodiment of a vector control apparatus for an electric motor according to the present invention. The electric motor vector control apparatus according to the present embodiment controls a power converter 2 that drives and controls an AC electric motor (electric motor) 1. As shown in FIG. 1, the vector control apparatus for an electric motor according to the present embodiment includes a vector control unit 3, a DC voltage detection unit 4, a speed detection unit 5, a current detection unit 6, and a torque command generation unit 10. The 1st magnetic flux command generation part 11a, the 2nd magnetic flux command generation part 11b, the magnetic flux command selection part 11c, and the pulse mode selection part 12 are provided.

  The power converter 2 includes a switching element, converts a DC voltage into an AC voltage based on a switching signal input from the vector control unit 3, and supplies the AC voltage to the AC motor 1. The DC voltage detection unit 4 detects a DC voltage applied to the power converter 2, and the current detection unit 6 detects a current of each phase output from the power converter 2. Note that the DC voltage detection unit 4 may detect the current of each of the three phases, but only needs to detect a current of at least two phases, and the current of the remaining one phase can be calculated. The speed detector 5 detects the rotational speed of the AC motor 1. In addition, when the speed sensorless vector control system which calculates the rotational speed of the AC motor 1 by calculation without using the speed detection unit 5 is adopted, the speed detection unit 5 may not be provided.

  The torque command generator 10 generates a torque command and inputs it to the vector controller 3. The vector control unit 3 detects the magnetic flux command input from the magnetic flux command selection unit 11 c, the torque command input from the torque command generation unit 10, the current detected by the DC voltage detection unit 4, and the speed detection unit 5. Based on the rotation speed and the motor constant of the AC motor 1, a vector control calculation is performed to control the power converter 2 so that the torque generated by the AC motor 1 matches the input torque command. The vector control unit 3 calculates an AC output voltage command and an AC output voltage amplitude command as calculation results of the vector control calculation, and based on the calculated AC output voltage command and the pulse mode command input by the pulse mode selection unit 12. A switching signal is generated by PWM control and output to the power converter 2. The AC converter 1 is driven by the power converter 2 performing a power conversion operation by the switching element based on the switching signal (PWM signal). The vector control unit 3 also outputs the frequency of the AC output voltage command (inverter output frequency) to the pulse mode selection unit 12.

  There are no particular restrictions on the control methods of vector control and PWM control in the vector control unit 3, and commonly used control methods can be used. Here, the vector control unit 3 generates the switching signal. However, the present invention is not limited to this, and a switching signal generation unit is provided separately, and the vector control unit 3 outputs an AC output voltage command to the switching signal generation unit. Then, the switching signal generator may generate a switching signal based on the AC output voltage command and the pulse mode command and output the switching signal to the power converter 2.

  The pulse mode selection unit 12 determines the pulse mode based on the output voltage amplitude command that is the calculation result of the vector control unit 3, the DC voltage detected by the DC voltage detection unit 4, and the inverter output frequency, and the determined pulse mode As a pulse mode command to the vector control unit 3 and the magnetic flux command selection unit 11c. A method for determining the pulse mode according to the present embodiment will be described later.

  In the present embodiment, as the pulse mode, in PWM control, the asynchronous PWM mode that does not depend on the inverter output frequency, and the carrier frequency and the inverter output frequency are synchronized to set the carrier frequency to an integral multiple of the inverter output frequency. The synchronous PWM mode to be performed is defined. Further, for the synchronous PWM mode, the pulse mode is classified according to how many times the carrier frequency is the inverter output frequency, and the pulse mode whose carrier frequency is N times the inverter output frequency (N is an integer of 1 or more) is synchronized N. It is called a pulse mode, and the synchronous 1 pulse mode is called a 1 pulse mode as generally called.

  The first magnetic flux command generator 11a calculates a magnetic flux command value for the asynchronous PWM mode and outputs it to the magnetic flux command selector 11c. The second magnetic flux command generator 11b calculates a magnetic flux command value for the synchronous PWM mode and outputs it to the magnetic flux command selector 11c. The magnetic flux command selection unit 11c is input from the first magnetic flux command generation unit 11a and the second magnetic flux command generation unit 11b based on the pulse mode command output from the pulse mode selection unit 12. The selected magnetic flux command is output to the vector control unit 3. Specifically, the magnetic flux command selection unit 11c selects the output of the second magnetic flux command generation unit 11b and outputs it to the vector control unit 3 when the pulse mode command is the synchronous PWM mode. In the asynchronous PWM mode, the output of the first magnetic flux command generator 11a is selected and output to the vector controller 3.

  FIG. 2 is a diagram illustrating a configuration example of the first magnetic flux command generator 11a of the present embodiment. As shown in FIG. 2, the first magnetic flux command generation unit 11 a of the present embodiment includes a constant magnetic flux command generation unit 111, a weakening magnetic flux control unit 112, and a low order selection unit 113.

  The constant magnetic flux command generator 111 outputs a constant rated secondary magnetic flux as a magnetic flux command. The rated secondary magnetic flux is generally secured as large as possible under the condition that the iron core of the AC motor 1 is not magnetically saturated, but the value of the rated secondary magnetic flux is not particularly limited.

  The weakening magnetic flux control unit 112 generates a magnetic flux command by so-called weakening magnetic flux control that increases the rotational speed by reducing the field magnetic flux, and outputs the magnetic flux command to the low order selection unit 113. In the flux weakening control, the AC output voltage is constant (that is, the modulation factor is constant), and the magnetic flux is reduced. Conventionally, this flux-weakening control is generally performed after the AC output voltage is close to the maximum value and the mode is shifted to the 1-pulse mode. In this embodiment, in the asynchronous PWM mode, the modulation rate is equal to or higher than the first threshold value. If this happens, the flux-weakening control is performed. That is, the magnetic flux weakening control unit 112 performs the magnetic flux weakening control so that the modulation factor becomes the first threshold value, and generates a magnetic flux command. As this 1st threshold value, the value smaller than the 2nd threshold value which is a threshold value of the modulation factor in the 2nd magnetic flux command production | generation part 11b mentioned later is set.

  As the first threshold value, for example, when a value less than or equal to the boundary value 78.5% (0.785) that causes overmodulation in the asynchronous PWM mode is set, even when the rated secondary magnetic flux is set to a value similar to the conventional value, overmodulation As a result, the region of the asynchronous PWM mode can be expanded as compared with the conventional case. Although a value exceeding 78.5% may be set as the first threshold value, in this case, control corresponding to overmodulation is performed. For example, the control method described in “Actual and Design of AC Servo System”, General Electronic Publishing 1990 p39-46 can be applied.

  The lower selection unit 113 selects the lower one of the magnetic flux command output from the constant magnetic flux command generation unit 111 and the magnetic flux command output from the weakening magnetic flux control unit 112 and outputs the selected one to the magnetic flux command selection unit 11c. .

  By the above operation, the first magnetic flux command generation unit 11a outputs a magnetic flux command by constant magnetic flux control when the modulation factor is less than the first threshold, and the magnetic flux by weakening magnetic flux control when the modulation factor is greater than or equal to the first threshold. Commands can be output.

  The second magnetic flux command generation unit 11b includes a constant magnetic flux command generation unit 111, a weak magnetic flux control unit 112, and a low-order selection unit 113, like the first magnetic flux command generation unit 11a. The constant magnetic flux command generator 111 in the second magnetic flux command generator 11b outputs a constant magnetic flux as a magnetic flux command in the same manner as the constant magnetic flux command generator 111 in the first magnetic flux command generator 11a. However, the constant magnetic flux command generation unit 111 in the second magnetic flux command generation unit 11b outputs the magnetic flux command at the time of switching from the asynchronous PWM mode to the synchronous PWM mode as a constant value instead of the above-described rated secondary magnetic flux. For example, the magnetic flux command selection unit 11c holds the output magnetic flux command, and the magnetic flux command input from the first magnetic flux command generation unit 11a when the asynchronous PWM mode is switched to the synchronous PWM mode is used as the second magnetic flux. The command generation unit 11b is notified. The constant value of the magnetic flux command output from the constant magnetic flux command generator 111 is not limited to this, and may be a predetermined value, for example.

  The weak flux control unit 112 of the second magnetic flux command generator 11b performs the weak flux control so that the modulation factor becomes the second threshold value, and generates a magnetic flux command. The second threshold value may be 100%, but here it is set to a value less than 100%, for example, 95%. Moreover, the low-order selection part 113 of the 2nd magnetic flux command generation part 11b is the weakness of the magnetic flux command output from the constant magnetic flux command generation part 111 of the 2nd magnetic flux command generation part 11b, and the 2nd magnetic flux command generation part 11b. Of the magnetic flux commands output from the magnetic flux controller 112, the lower one (smaller one) is selected and output to the magnetic flux command selector 11c.

  In addition, the second magnetic flux command generation unit 11b uses the constant magnetic flux control and the weakening magnetic flux control to control the modulation rate to be less than the first threshold. However, the second magnetic flux command generation unit 11b uses the magnetic flux control method. Is not limited to these control methods as long as the modulation rate is controlled to be less than the first threshold.

  FIG. 3 is a diagram illustrating an example of a modulation rate (voltage modulation rate) and a pulse mode according to the present embodiment. FIG. 4 is a diagram illustrating an example of a magnetic flux command according to the present embodiment. 3 and 4, the horizontal axis indicates the inverter output frequency. A method for determining the pulse mode according to the present embodiment will be described with reference to FIGS. FIG. 4 shows a magnetic flux command input to the vector control unit 3 when the control shown in FIG. 3 is performed. The magnetic flux command output from the first magnetic flux command generation unit 11a is used as the first magnetic flux command, and the magnetic flux command output from the second magnetic flux command generation unit 11b is used as the second magnetic flux command.

  FIG. 3A shows the inverter output frequency at which the modulation rate reaches 100% when the conventional technique (for example, the technique described in Patent Document 1 above) is used. In the prior art, the modulation rate is increased by constant magnetic flux control until the modulation rate reaches 100%. FIG. 3B shows the inverter output frequency at which switching from the asynchronous PWM mode to the synchronous PWM mode in the present embodiment is performed.

  In the present embodiment, the asynchronous PWM mode is switched to the synchronous PWM mode based on the inverter output frequency. Specifically, for example, the asynchronous PWM mode is set in a region below fc / X, and the synchronous PWM mode is set in a region where the inverter output frequency is fc / X or more. Here, fc represents the carrier frequency in the asynchronous PWM mode, and is set independently of the inverter output frequency (for example, set to 1 kHz or the like). X indicates “carrier frequency fc / inverter output frequency” at the switching point from the asynchronous PWM mode to the synchronous PWM mode. The value of X is the lowest frequency of the synchronous PWM mode. In (B), the inductance characteristic of the AC motor 1 and the inverter are set such that the current ripple due to switching, that is, the low-order harmonic component of the current is not more than a predetermined allowable value. Determine the output frequency.

  The carrier frequency fc of asynchronous PWM is set so that the switching loss in the power converter 2 is less than or equal to the allowable value. That is, the lowest frequency (mode switching frequency) in the synchronous PWM mode shown in FIG. 3B is determined from the carrier frequency fc, the allowable current ripple value in the synchronous PWM mode, and the inductance characteristics of the motor. Note that the method for defining the inverter output frequency (mode switching frequency) that is a condition for switching from the asynchronous PWM mode to the synchronous PWM mode is not limited to the form of fc / X.

  As shown in FIGS. 3 and 4, constant magnetic flux control using the magnetic flux command generated by the constant magnetic flux command generating unit 111 of the first magnetic flux command generating unit 11 a is performed in the region where the modulation factor is smaller than the first threshold, When the modulation rate is equal to or higher than the first threshold value, the weakening magnetic flux control using the magnetic flux command generated by the weakening magnetic flux control unit 112 of the first magnetic flux command generation unit 11a is performed.

  When the inverter output frequency becomes equal to or higher than fc / X, switching to the synchronous PWM mode is performed. Thereafter, in the region smaller than the second threshold, the constant magnetic flux command generation unit 111 of the second magnetic flux command generation unit 11b generates the frequency. The constant magnetic flux control using the magnetic flux command is performed, and when the modulation rate becomes equal to or greater than the second threshold value, the weak magnetic flux control using the magnetic flux command generated by the weak magnetic flux control unit 112 of the second magnetic flux command generation unit 11b is performed. .

  In the synchronous PWM mode, as in Patent Document 1, when the modulation rate is less than a certain value (the above-described second threshold), the synchronous three-pulse mode is selected, and when the modulation rate is greater than or equal to a certain value, 1 is set. The pulse mode may be changed in the synchronous PWM mode, such as the pulse mode, but there is no restriction on the pulse mode in the synchronous PWM mode.

  In this embodiment, the asynchronous PWM mode and the synchronous WM mode are switched based on the inverter output frequency. However, the asynchronous PWM mode and the synchronous PWM mode are similarly switched based on the rotation speed detected by the speed detection unit 5. You may make it switch.

  FIG. 5 is a diagram illustrating an example of a modulation rate (voltage modulation rate) and a pulse mode according to a conventional technique (the technique described in Patent Document 1). The modulation rate 31 in FIG. 5 indicates the modulation rate according to the prior art, and the dotted modulation rate 32 indicates the modulation rate of the present embodiment (the modulation rate shown in FIG. 3). FIG. 6 is a diagram illustrating an example of a magnetic flux command according to a conventional technique (the technique described in Patent Document 1). A magnetic flux command 33 in FIG. 6 indicates a magnetic flux command according to the prior art, and a dotted magnetic flux command 34 indicates a modulation factor (the magnetic flux command shown in FIG. 4) of the present embodiment.

  In the control method of the prior art, as shown in FIG. 5, constant magnetic flux control is performed until the modulation rate reaches a certain value (for example, 78.5%), and when the modulation rate exceeds the certain value, synchronous PWM mode (synchronous 3 pulses) is performed. Mode). Thereafter, when the modulation rate reaches 100%, the mode shifts to the 1-pulse mode, and the flux weakening control is performed. For this reason, in the conventional technique, the region of the asynchronous PWM mode is limited until the modulation rate increases to a constant value by constant magnetic flux control.

  On the other hand, in this embodiment, as described later, switching from the asynchronous PWM mode to the synchronous PWM mode is determined by the inverter output frequency, and until the inverter output frequency satisfies the switching condition to the synchronous PWM mode. Asynchronous PWM mode. Therefore, if the mode switching frequency (fc / X) is set larger than the inverter output frequency (FIG. 5 and FIG. 3A) at which the modulation factor shown in FIG. Compared to technology, the area of asynchronous PWM mode can be expanded. In the present embodiment, the mode switching frequency is set larger than the inverter output frequency at which the modulation factor shown in FIG. 3 is 100%, and the asynchronous PWM mode is expanded as compared with the prior art.

  FIG. 7 is a diagram showing an example of the effect of the present embodiment in comparison with the prior art. In FIG. 7, the loss in the prior art (the technique described in Patent Document 1) is shown on the left side, and the loss in the present invention is shown on the right side. The loss shown in FIG. 7 indicates the loss of the entire system when the inverter is operated from the position where the inverter output frequency is 0 to the inverter output frequency at the position shown in FIG.

  In the low frequency region, the harmonic loss of the AC motor 1 can be reduced in the asynchronous PWM mode having a sufficient number of switching times than in the case of driving in the synchronous PWM mode. Therefore, in the present embodiment, in the low frequency region, the harmonic loss of the AC motor 1 can be reduced as compared with the prior art by expanding the region for driving the AC motor 1 in the asynchronous PWM mode. Although the loss of the power converter 2 (converter loss) increases as the switching speed increases, the loss of the entire system can be reduced under operating conditions where the effect of reducing the motor loss is dominant.

  Moreover, since the high frequency current of the AC motor 1 decreases due to the increase in impedance of the AC motor 1 as the frequency increases, the high frequency loss also decreases. Therefore, in the higher speed region than FIG. 3B, the motor loss does not increase even if the synchronous PWM mode with a small number of switchings is adopted, and the converter switching loss reduction effect can be obtained. To increase the modulation rate.

  As described above, by applying the vector control device of the present embodiment, the high frequency loss of the motor is reduced, and the total loss with the fundamental wave loss is minimized, so that the loss of the entire motor can be reduced and the cooling performance is suppressed. be able to. Therefore, the motor can be reduced in size and weight by reviewing the cooling fin shape and cooling air passage of the motor.

  Note that any element may be used as the switching element and the diode element of the power converter 2, but, for example, a wide band gap semiconductor can be used. Examples of wide band gap semiconductors include those formed of silicon carbide, gallium nitride-based materials, diamond, or the like. Switching elements and diode elements formed by such wide band gap semiconductors have high voltage resistance and high allowable current density, so that switching elements and diode elements can be miniaturized. By using elements and diode elements, it is possible to reduce the size of a semiconductor module incorporating these elements.

  In addition, since the wide band gap semiconductor has high heat resistance, it is possible to reduce the size of the heat dissipating fins of the heat sink and the air cooling of the water cooling portion, thereby further reducing the size of the semiconductor module. Furthermore, since the power loss is low, it is possible to increase the efficiency of the switching element and the diode element, and further increase the efficiency of the semiconductor module.

  Thus, in the present embodiment, the first magnetic flux command generator 11a that generates a magnetic flux command for asynchronous PWM mode, the second magnetic flux command generator 11b that generates a magnetic flux command for synchronous PWM mode, The first magnetic flux command generation unit 11a generates a magnetic flux command so as to suppress the modulation rate below the first threshold corresponding to the asynchronous PWM mode. Then, switching from the asynchronous PWM mode to the synchronous PWM mode is performed based on the inverter output frequency. For this reason, the region of the asynchronous PWM mode can be expanded as compared with the conventional case, and the overall loss can be reduced.

Embodiment 2. FIG.
FIG. 8 is a diagram illustrating a configuration example of the first magnetic flux command generation unit 11d according to the second embodiment of the vector control device for the electric motor according to the present invention. The motor vector control device of the present embodiment is the same as that of the first embodiment except that the first magnetic flux command generation unit 11d is provided instead of the first magnetic flux command generation unit 11a of the motor vector control device of the first embodiment. This is the same as the vector control device of the motor. The first magnetic flux command generation unit 11d of the present embodiment includes an optimum magnetic flux command generation unit 21, an allowable maximum magnetic flux command generation unit 22, and a low order selection unit 23.

  The optimum magnetic flux command generation unit 21 generates a magnetic flux command that satisfies the minimum loss condition (maximum efficiency condition) as shown in FIG. 2 of International Publication No. 2008/107992 and the description thereof, for example. The magnetic flux value that satisfies the maximum efficiency condition can be obtained for each torque command as described in International Publication No. 2008/107992. Therefore, the optimum magnetic flux command generating unit 21 retains the magnetic flux that is the minimum loss condition for each torque command as a characteristic in the form of a function or a table, and the maximum efficiency condition based on the torque command and the retained characteristic. Find a magnetic flux command that satisfies

  The allowable maximum magnetic flux command generation unit 22 generates the maximum magnetic flux command that can be output according to the inverter output frequency. For example, the maximum magnetic flux command that can be output can be generated by the calculation method of the maximum voltage secondary magnetic flux command described in claim 3 of Patent Document 1.

  The low level selection unit 23 selects the lower one of the magnetic flux command generated by the optimum magnetic flux command generation unit 21 and the allowable maximum magnetic flux command generation unit 22 and inputs it to the magnetic flux command selection unit 11c. The operations of the present embodiment other than those described above are the same as those of the first embodiment.

  Similarly, a second magnetic flux command generator 11e (not shown) having the same configuration as the first magnetic flux command generator 11d may be provided instead of the second magnetic flux command generator 11b. In this case, the allowable maximum magnetic flux command generation unit 22 of the second magnetic flux command generation unit 11e generates a magnetic flux having a higher modulation rate than the allowable maximum magnetic flux command generation unit 22 of the first magnetic flux command generation unit 11d.

  Further, the configurations of the first magnetic flux command generation unit and the second magnetic flux command generation unit are not limited to the configurations described in the first embodiment and the second embodiment. The configuration described in claim 1 of International Publication No. 2008/107992 may be used.

  The first magnetic flux command generation unit 11a of the first embodiment and the first magnetic flux command generation unit 11d of the present embodiment are both provided, and the magnetic flux command generated by the first magnetic flux command generation unit 11a and the first Of the magnetic flux commands generated by one magnetic flux command generation unit 11d, the lower one may be input to the magnetic flux command selection unit 11c.

  As described above, the first magnetic flux command generator 11d that performs optimal magnetic flux control is provided. For this reason, the same effects as those of the first embodiment can be obtained, and the loss can be further reduced as compared with the first embodiment.

Embodiment 3 FIG.
In the present embodiment, a vehicle drive system to which the vector control device described in the first embodiment and the second embodiment is applied will be described.

  FIG. 9 is a diagram illustrating a configuration example applied to a railway vehicle as a vehicle drive system. The vehicle drive system includes an AC motor 1, a power converter 2, an input circuit 105, and a vector control device 106. The AC motor 1 is the same as the AC motor 1 shown in FIG. 1 and is mounted on a railway vehicle. The power converter 2 is the same as the power converter 2 shown in FIG. 1, converts the DC power supplied from the input circuit 105 into AC power, and drives the AC motor 1. The vector control device 106 corresponds to the vector control device described in the first and second embodiments.

  Although not shown, the input circuit 105 includes a switch, a filter capacitor, a filter reactor, and the like, and one end of the input circuit 105 is connected to the overhead line 101 via the current collector 102. The other end is connected to a rail 104 that is a ground potential via a wheel 103. The input circuit 105 receives supply of DC power or AC power from the overhead line 101 and generates DC power to be supplied to the power converter 2.

  As described above, by applying the vector control apparatus of the present embodiment to a vehicle drive system, it is possible to realize loss reduction and downsizing as the entire system.

  As described above, the electric motor vector control device and the vehicle drive system according to the present invention are useful for a vector control device that controls an AC motor, and are particularly suitable for a vector control device that controls an AC motor in an electric vehicle. .

  DESCRIPTION OF SYMBOLS 1 AC motor, 2 Power converter, 3 Vector control part, 4 DC voltage detection part, 5 Speed detection part, 6 Current detection part, 10 Torque command generation part, 11a, 11d 1st magnetic flux command generation part, 11b 2nd Magnetic flux command generation unit, 11c magnetic flux command selection unit, 12 pulse mode selection unit, 21 optimum magnetic flux command generation unit, 22 allowable maximum magnetic flux command generation unit, 100 vehicle drive system, 105 input circuit, 106 vector control device, 111 constant magnetic flux Command generation unit, 112 Weak magnetic flux control unit, 113, 23 Low order selection unit.

Claims (6)

A vector control device that controls a power converter that converts DC power into AC power and supplies AC power to the motor,
A vector control unit that calculates an output voltage to be output from the power converter by vector control based on the input torque command and magnetic flux command, and generates a PWM signal for controlling the power converter based on the output voltage When,
A magnetic flux command generator for generating a magnetic flux command for asynchronous PWM mode, and performing control to increase the rotational speed by reducing the field magnetic flux in the electric motor when the modulation rate is equal to or higher than the first threshold;
With
When the output frequency of the power converter is less than a predetermined value greater than the output frequency when the modulation factor becomes the first threshold value, the vector control is performed on the magnetic flux command generated by the magnetic flux command generation unit. A vector control device for an electric motor characterized by being input to a motor.   2. The electric motor vector control device according to claim 1, wherein the predetermined value is a value larger than an output frequency of the power converter when the modulation factor is 78.5%. 3. The magnetic flux command generator is
The electric motor vector control device according to claim 1, wherein constant magnetic flux control is performed when the modulation factor is less than the first threshold. The magnetic flux command generator is
The smaller one of the magnetic flux command generated by the constant magnetic flux control and the magnetic flux command generated by the control for reducing the field magnetic flux in the electric motor and increasing the rotation speed so that the modulation factor becomes the first threshold value. The vector control apparatus for an electric motor according to claim 3, wherein A vehicle drive system for driving an electric vehicle,
A vector control device for an electric motor according to any one of claims 1 to 4,
A power converter controlled by the vector controller;
An input circuit for generating DC power to be input to the power converter;
An electric motor driven by the power converter;
A vehicle drive system comprising:   The vehicle drive system according to claim 5, wherein at least one of a switching element and a diode element provided in the power converter is formed of a wide band gap semiconductor.

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