JP6499405B2 - Motor control device and air conditioner equipped with the motor control device - Google Patents

Description

  The present invention relates to a motor control device and an air conditioner including the motor control device.

  Motor control devices used in air conditioners and the like have strong demands for downsizing, a reduction in the number of parts, high efficiency, and high output, and many technologies have been developed to realize these demands.

  In order to reduce the size and increase the efficiency of the motor, if an embedded magnet type motor (IPM: Interior Permanent Magnet motor) in which the motor stator side is concentrated and the permanent magnet is embedded inside the motor rotor is used, the motor winding The waveform of the induced electromotive force induced in the waveform from an ideal sine wave shape to a distorted waveform including harmonics.

  When a sinusoidal voltage waveform is output from the motor control device to a motor having such a distorted induced electromotive force waveform, a harmonic component is generated in the motor current waveform due to the distortion of the induced electromotive force waveform. Due to the harmonic components of the motor current waveform, the motor increases the iron loss and decreases the efficiency.

  In order to reduce iron loss caused by such harmonic components of the current waveform, Patent Document 1 discloses that an induced electromotive force is provided by providing a slit in the rotor core or a step in the outer diameter of the rotor. Disclosing the sinusoidal waveform. Patent Document 2 holds in advance harmonic component data of the induced electromotive force waveform as a table in order to reduce distortion of the motor current waveform, and reduces harmonics of the motor current waveform based on these data. To disclose.

JP 2013-255328 A Japanese Patent Laid-Open No. 2004-64909

  In the method of converting the induced electromotive force waveform into a sine wave according to the motor shape described in Patent Document 1, if the motor current has a magnitude that does not affect the permeability distribution created by the induced electromotive force, the current waveform is a sine wave. It becomes. However, when the motor current increases and the magnetic flux generated by the motor current has a magnitude that affects the permeability distribution created by the induced electromotive force, higher harmonic components such as a third-order component are generated in the motor current.

  Similarly, in the method of controlling the voltage command value so that the current waveform is sinusoidal by the current controller described in Patent Document 2, the motor current does not affect the permeability distribution created by the induced electromotive force. If it is large, the current waveform is a sine wave. However, when the motor current increases and the magnetic flux generated by the motor current has a magnitude that affects the permeability distribution created by the induced electromotive force, the permeability distribution at the time of acquiring the pre-stored induced electromotive force waveform, that is, external drive Since the magnetic permeability distribution at the time and the magnetic permeability distribution during the load operation are different, the sine wave effect of the motor current is reduced.

  An object of the present invention is to provide a motor control device that can suppress distortion of a current waveform that occurs during load operation.

In order to solve the above problems, a motor control device of the present invention includes a power converter that supplies three-phase AC power to a permanent magnet motor, a control device that controls the output voltage of the power converter, A voltage high-order component calculation unit that calculates the voltage phase and amplitude of a voltage high-order component that generates a current having a phase opposite to that of the generated fifth-order and seventh-order high-order current components; the voltage phase and the voltage high order components consisting of the amplitude is, and a voltage adder for adding the voltage command values of the control device.

  ADVANTAGE OF THE INVENTION According to this invention, the motor control apparatus which can suppress the distortion of the current waveform generate | occur | produced at the time of load operation can be provided.

Block diagram showing the overall configuration of the motor controller Phase and composition rate of current 5th and 7th components at the same rotation speed and the same fundamental wave current amplitude value FIG. 1 is a block diagram illustrating an overall configuration diagram of a motor control device according to a first embodiment. Detail of voltage higher-order component calculation unit and addition unit of Example 1 (rotating coordinates and fixed coordinates) Phase difference characteristics of current 5th and 7th order components FFT result of current waveform when driving a real machine by conventional method FFT result of current waveform when the actual machine is driven by the method of Example 1 Current waveform when driving a real machine FIG. 3 is a block diagram illustrating an overall configuration diagram of a motor control device according to a second embodiment. Detail of voltage higher-order component calculation unit and addition unit of Example 2 (rotating coordinates and fixed coordinates) Example of setting high-order voltage components in Example 2 Example of switching setting for high-order voltage output of Example 2 PWM frequency switching setting example Overall configuration diagram of air conditioner of Example 3 Schematic of rotation speed-torque characteristics of compressor motor of Example 3

  The motor control device of the present invention has a power converter that supplies power to a permanent magnet motor, a control device that controls the output voltage of the power converter, and a phase opposite to a higher-order current component that is generated when a sine wave voltage is energized. A voltage high-order component calculation unit that calculates the voltage phase and amplitude of a voltage high-order component that generates current, and a voltage addition that adds the voltage phase and amplitude calculated by the voltage high-order component calculation unit to the voltage command value of the control device A section. According to the present invention as described above, even when the motor current is distorted, it is possible to suppress the distortion of the current waveform by generating the current advanced by 180 degrees with respect to the higher-order component of the motor current. Moreover, by suppressing the high-order component of the motor current, it is possible to suppress an increase in the high-order component of the output power of the power converter and improve the high efficiency. Further, the sine wave of the current waveform can reduce torque pulsation and vibration.

  A first embodiment of the present invention will be described with reference to FIGS. In this embodiment, the control method of the present invention is applied to a motor control device 2 that drives a permanent magnet synchronous motor 1 (hereinafter referred to as “motor”) by PWM control. An example of adding a higher voltage component to the command value will be described.

  As shown in FIG. 1, the motor control device 2 that drives the motor 1 detects the current output from the DC power source 3, the power conversion circuit 4 that converts DC power generated by the DC power source into AC power, and the power conversion circuit 4 And a control device 6 that performs vector control based on the output current information 5A detected by the current detector 5 and the output current information 5A detected by the current detector 5.

  The control device 6 includes a vector controller 7 that calculates an applied voltage command 7A to the motor 1 based on the current information 5A detected by the current detector 5, and a PWM pulse based on the applied voltage command 7A and the carrier signal. It comprises a PWM pulse generator 8 that converts the signal 8A. In addition, the power conversion circuit 4 generates a gate signal to the IGBT of the main circuit based on the power conversion main circuit 4A composed of a semiconductor switching element such as an IGBT and a diode, and the PWM pulse signal 8A from the PWM pulse generation unit 8. It consists of a generated gate driver 4B.

  Here, the vector control unit 7 is "examination of a new vector control method for a permanent magnet synchronous motor for high speed" (Electrology D, Vol.129 (2009) No.1 pp.36-45) Realized by using general vector control such as the method proposed in "Simple Vector Control of Permanent Magnet Synchronous Motor with Position Sensor" (Decology D, Vol.124 (2004) No.11 pp.1133-1140) Yes, it does not specify the control method.

  The relationship between the current value and the higher-order current component will be described with reference to FIG. 2 (a) and 2 (b) show the current fifth-order component and seventh-order component when the phase β of the current fundamental wave component having the same rotation speed and the same fundamental wave current effective value is 31 degrees, 42 degrees, and 53 degrees. It is the result of extracting only. As the phase β increases, a magnetic flux that cancels the magnetic flux of the magnet is generated. For this reason, the magnetic permeability distribution varies depending on the phase β of the current. In this case, the vertical axis represents the current fifth-order component, the phase β of the seventh-order component, and the horizontal axis represents the current amplitude values of the fifth-order component and the seventh-order component when the fundamental wave is 100. As shown in FIG. 2, the amplitude and phase of the current fifth-order component and seventh-order component change as the phase increases. Thus, when trying to make the current waveform sinusoidal based on the original induced electromotive force waveform, an error occurs as the magnetic flux generated at the time of winding energization increases, and depending on the conditions, the distortion of the motor current increases and vibration occurs.・ Noise is generated and efficiency is reduced.

  Therefore, in the present invention, as shown in FIG. 3, a voltage high-order component calculation unit 9 for calculating a voltage high-order component that cancels the current high-order component with the operating condition of the motor as an input is provided to suppress the current high-order component. .

  Hereinafter, a method for calculating the phase and amplitude of the voltage higher-order component using the table will be described with reference to FIGS.

  The voltage high-order component calculation unit 9 is shown in FIG. FIG. 4A is a block diagram of a method using rotating coordinates, and FIG. 4B is a block diagram of a method using fixed coordinates. The high-order voltage component calculation unit receives the rotation speed command value and the torque command value 5B given as the rotation speed and torque or the command value. The voltage high-order component calculation unit 9 is preliminarily given as a table the phase and amplitude of the voltage high-order component that cancels out the current high-order component, receives each operating condition value (rotation speed and torque) as input, and the phase at each order And amplitudes 9A_d and 9A_q (or 9A_U, 9A_V, and 9A_W) are output. Thereafter, the amplitude and phase of the voltage high-order component are added to the voltage command value by the voltage adding unit 10.

  Note that the amplitude and phase of the voltage higher-order component under each operating condition may be obtained from actual measurement results, or may be obtained by magnetic field analysis or the like. Moreover, you may use the voltage equation mentioned later.

  FIG. 5 shows the amplitude values of the current fifth-order component and seventh-order component when the amplitude value of the voltage fifth-order component is constant and the phase is swung from 0 to 360 degrees. From Fig. 5, not only the 5th-order component whose phase has been changed but also the 7th-order component, the higher-order component of the motor when added to the applied voltage also affects other higher-order components. By canceling, the amplitude value of the seventh-order component also changes. The phase and amplitude of the voltage higher-order component for canceling the current higher-order component can be obtained by the above-described method. However, depending on the motor, when trying to eliminate the higher-order harmonic component, other higher-order harmonic components May increase.

  6 and 7 show the current FFT results, and FIGS. 8 and 9 show the current waveforms. FIGS. 6 and 8 show the results in the case of the conventional control method in which the voltage higher-order component is not added, and FIGS. 7 and 9 show the results in the present embodiment in which the voltage force higher-order component is added. From FIG. 6 and FIG. 8, it can be confirmed that when the voltage high-order component is not added, the fifth and seventh current high-order components are largely generated. On the other hand, in FIG. 7 and FIG. 9, when the voltage higher-order component is added to the command voltage by the method of this embodiment, the distortion of the motor current waveform is suppressed, and the fifth and seventh current higher-order components can be reduced. I can confirm.

  As shown in FIG. 4, by using the voltage higher-order component calculation unit 10, it is possible to suppress higher-order components of the motor current. In other words, by using the configuration of the present embodiment, it is possible to suppress higher order components of the motor current even when the motor induced electromotive force is distorted. Further, by suppressing the high-order motor current component, it is possible to suppress the high-order output power component of the power converter caused by the high-order current component, and to realize high efficiency of the motor control device.

  In this embodiment, a 2: 3 concentrated winding IPM motor increases the effect, but it can be a fractional slot, distributed winding machine, surface magnet motor, induction machine, switched reluctance motor, or synchronous motor. It is valid.

  A method of solving a voltage equation from a current waveform will be described with reference to FIG. 10 as an example of a method of adding the voltage high-order component 9A to the fundamental wave applied voltage command. Since the configuration is the same as that of the motor control device 1 shown in FIG. 3, the description thereof is omitted.

In the first embodiment, the high-order voltage component is obtained from the rotation speed and torque information 5B. In this embodiment, for example, current information 5A obtained by a current waveform acquisition method using one shunt resistor is used as an input. The obtained current waveform is FFTed by the FFT unit 11 to obtain the phase and amplitude of the current higher-order component under the current operating conditions, and the current having the same amplitude as the current phase advanced by 180 degrees with respect to this current phase. An n-th order voltage waveform that generates a waveform is generated. At this time, the FFT unit 11 receives the current waveform, outputs the amplitude value and phase for each order, and inputs them to the voltage high-order component calculation unit. Equation (1) shows an expression for obtaining the voltage V _n necessary to cancel the obtained n-th order current value i _n sinn (· t). If such a method is used, it becomes possible to automatically calculate the phase and amplitude regardless of which motor is attached.
V _n (t, θ) = R * i _n * sinn (・ t + ・) + di _n / dt * sinn (・ t + ・) * L… (1)
Ideally, it is possible to suppress the current high-order component by outputting all the high-order components included in the motor current with the amplitude and phase of the voltage high-order component set to 9A. However, when this method is used, the number of PWM pulses included in one cycle of voltage / current is reduced when the motor rotation speed is in a high speed range with a constant PWM pulse number, compared to the low speed range. The accuracy of the detection is reduced, and it is difficult to output a high-order component.

  Therefore, FIG. 11 shows an example of a method of stopping the output of the component having a large order from the induced electromotive force high-order component generation unit 9 depending on the motor rotational speed. Here, the case where the current high-order component: the third, fifth and seventh order components are switched by the motor speed is shown. As shown in FIG. 11, when the motor rotation speed is accelerated and becomes equal to or higher than the rotation speed N1, the amplitude value of the current seventh-order component is set to 0 and the output from the voltage higher-order component calculation unit 9 is stopped. Similarly, when the rotation speed is N2 or more, the amplitude value of the current fifth-order component is set to 0, and the output from the voltage higher-order component calculation unit 9 is stopped.

  Note that switching the voltage high-order component amplitude value rotates the voltage high-order component amplitude value from the rotation speed N4 as shown in FIG. 12 (b) in order to suppress fluctuations in the current, rotation speed, and torque at the time of switching. A method of changing at a constant rate up to several N5 may be used. In order to make the switching even smoother, as shown in FIG. 12 (c), a method of changing the voltage higher-order component amplitude value from the rotation speed N4 to the rotation speed N5 while changing the ratio like a curve may be used. Further, the amplitude value may be switched by using a motor output torque or DC bus current information 5A.

  As described above, when the number of PWM pulses is constant and the motor rotation speed is in the high speed range, the number of PWM pulses included in one cycle of voltage / current is smaller than that in the low speed range. It becomes difficult to output a large component from the power converter 4. FIG. 13 shows an example of a method for changing the PWM frequency according to the motor rotation speed. FIG. 13 shows a case where the PWM frequency is switched between f1 and f2 depending on the rotational speed. As shown in FIG. 13 (a), when the motor rotation speed is accelerated and becomes equal to or higher than the rotation speed N6, the PWM frequency is switched from f2 to f1. FIGS. 13B and 13C are modified examples of the frequency changing method.

  In this way, by making the PWM frequency variable according to the number of rotations, the PWM frequency is increased in the high speed range to maintain the number of PWM pulses included in one cycle of voltage / current, and the order of the higher voltage component is A large component can be output. Further, by reducing the PWM frequency in the low speed region, it is possible to reduce the switching loss and drive the motor control device 1 with high efficiency.

  In this embodiment, a method using one shunt resistor was introduced as a current detection method, but a three shunt resistor may be used, or a motor current sensor may be used. Note that the detection method using a shunt resistor greatly depends on the PWM frequency, but this is not the case when a current sensor is used. In addition, the impedance changes from proportional to saturation as the frequency increases. At this time, it is necessary to correct the inductance component of the voltage equation (1) depending on the order. A table or the like may be used for this correction. The use of a 2: 3 concentrated winding IPM motor is very effective, but it is also effective for fractional slots and distributed winding machines. It is also effective for surface magnet motors, induction machines, switched reluctance motors and synchronous motors. is there.

  A third embodiment in which the motor control device 1 of the first and second embodiments is applied to the compressor drive of the air conditioner 100 will be described with reference to FIG.

  As shown in FIG. 14, the air conditioner 100 according to the present embodiment includes an outdoor unit 101 that exchanges heat with the outside air, an indoor unit 102 that exchanges heat with the room, and a pipe 103 that connects the outdoor unit 101 and the indoor unit 102. The The outdoor unit 101 includes a compressor 104 that compresses refrigerant, a compressor drive motor 105 that drives the compressor 104, a motor drive device 106 that controls the compressor, and a heat exchanger 107 that exchanges heat with the outside air using the compressed refrigerant. The The motor control device 1 of the first and second embodiments is applied to the motor driving device 106. The indoor unit 102 includes a heat exchanger 108 that exchanges heat with the room, and a blower 109 that blows air into the room.

  FIG. 18 plots the operating points of the compressor driving motor. In FIG. 18, the horizontal axis represents the rotational speed and the vertical axis represents the torque. Here, since the efficiency of the air conditioner is largely due to the low speed and low load region, the efficiency of the compressor driving motor needs to be improved in the low speed and low load region.

  Since the compressor drive motor contributes to as few as four points, using the method of Example 1 with these operating conditions (rotation speed and torque) as input, the number of necessary tables is reduced and the motor is reduced. This leads to improved efficiency and, in turn, improved air conditioner performance. Further, when the method of the second embodiment is used, a sufficient effect can be obtained by applying only the low speed side because the number of PWM pulses is sufficiently secured on the low speed side where the contribution of efficiency is high.

  In particular, on the high speed side, as described above, it becomes difficult to generate higher-order components when the number of times of switching decreases, so it is necessary to increase the number of times of switching of the inverter, that is, the carrier frequency. However, since the switching loss increases by raising the carrier frequency, the efficiency of the system decreases. Therefore, the efficiency of the system is improved by not generating a high-order voltage component on the high speed side.

  As described above, according to the third embodiment, in the case of an air conditioner system that requires few operating points and efficiency at low-speed rotation, the power high-order component of the power conversion circuit is reduced with the same power conversion circuit configuration as the conventional motor control device Therefore, the efficiency of the air conditioner can be improved without adding parts.

  In addition, since the air conditioner is a home appliance, the input voltage is limited to 100V or 200V, and depending on the motor specifications, the upper limit voltage value is reached under rated conditions. In such a case, as described above, in addition to the method of increasing the PWM frequency, a similar effect can be obtained by providing a booster circuit on the converter side to increase the upper limit voltage value.

  In this example, the air conditioner system was taken as an example, but Example 1 was implemented for systems with few operating points, such as automobile main motors and elevator motors, and systems that required efficiency at low speeds. The same effect can be obtained by applying or using Example 2 together.

  In addition, this invention is not limited to Example 1-3, Various modifications are included. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. Further, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Further, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment. Each of the above-described configurations, functions, processing units, processing means, and the like may be realized by hardware by designing a part or all of them with, for example, an integrated circuit. Further, the control lines and information lines indicate what is considered necessary for the explanation, and not all the control lines and information lines on the product are necessarily shown.

DESCRIPTION OF SYMBOLS 1 ... Permanent magnet synchronous machine (motor), 2 ... Motor controller, 3 ... DC power supply, 4 ... Power converter, 4A ... Power conversion main circuit, 4B ... Gate driver, 5 ... Power converter output current detection part, 6 ... Control device, 7 ... Vector control unit, 8 ... Pulse creation unit, 9 ... Voltage high-order component calculation unit, 10 ... Voltage addition unit, 10 ... FFT unit

Claims (3)

A power converter for supplying three-phase AC power to the permanent magnet motor;
A control device for controlling the output voltage of the power converter;
A voltage high-order component calculation unit for calculating the voltage phase and amplitude of the voltage high-order component that generates a current having a phase opposite to that of the fifth-order and seventh-order high-order current components generated when the sine wave voltage is energized;
A voltage adder for adding the voltage high order components consisting of the voltage phase and the amplitude calculated by the voltage higher component calculation unit, the pressure command value collector of the control device,
A motor control device comprising: A compressor,
The motor control device according to claim 1, which controls a motor of the compressor;
With
The motor control device according to claim 1, wherein when the rotational speed of the permanent magnet motor is equal to or greater than a predetermined value, the high-order voltage component composed of the voltage phase and the amplitude is not added to the voltage command value.   An air conditioner comprising the motor control device according to claim 2.