JP2008263692A - Motor drive device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To sinusoidally drive a motor by V/f control without a sensor. <P>SOLUTION: DC power of a DC power supply 2 is converted into AC power by an invertor circuit 3, the motor 4 is driven and a motor load 5 is rotationally driven. A current detecting means 6 detects a peak value of motor current or a motor current corresponding to a rotating field, and a control means 7 performs V/f-control to the invertor circuit 3. An output frequency is corrected so that the motor peak current becomes a setting value. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a motor drive device, and more particularly to a motor control means by V / f control of a permanent magnet motor.

Conventionally, this type of motor drive device detects an inverter circuit output current, performs coordinate conversion of the motor current according to a motor applied voltage phase, and performs V / f control so that the motor current after the coordinate conversion becomes a predetermined value. (For example, refer to Patent Document 1).
JP 2000-236694 A

  However, since the conventional motor drive device instantaneously detects the motor current corresponding to the motor applied voltage phase, and converts the coordinate to a DC component, the high-speed A / D conversion means or the high-speed current detection means and the high-speed coordinates are converted. Conversion means is required, and there is a problem that a processor such as a microcomputer for controlling the inverter circuit is high speed and high price. Further, since the control is performed by the effective current vector after the coordinate conversion, there is a problem that current setting becomes complicated in control of a no-load or a fan or a pump whose load changes according to the rotation speed.

  Further, when the lead angle control is required at a high speed rotation such as a saliency motor (IPMSM), there is a problem that the lead angle control becomes difficult.

  The present invention solves the above-described conventional problems, and basically sensorless sine wave drive is possible with an inexpensive current sensor without coordinate conversion, and the torque varies depending on the load with large torque fluctuation and the rotational speed. The purpose is to realize a motor drive device that can drive a sensorless sine wave with a low-speed and low-cost processor and a simple control program, even for saliency motors that require variable load and lead angle control. It is.

  In order to solve the above-described conventional problems, the motor driving device of the present invention drives a permanent magnet motor with a sensorless sine wave by an inverter circuit that converts DC power into AC power, and corresponds to a peak value of motor current or a rotating magnetic field. The inverter circuit output frequency is controlled so that the motor current is detected and becomes a set value, and a frequency component such as frequency or phase is corrected by an error signal between the motor current set value and the detected motor current.

  The motor drive device of the present invention detects the motor current corresponding to the peak value of the motor current or the rotating magnetic field and controls the inverter circuit output frequency so as to be a set value. Regardless of the saliency motor, stable control can be performed without turbulence, and also stable control can be easily performed in lead angle control, and control can be performed without high-speed A / D conversion means and high-speed calculation means. A motor drive device capable of sensorless sine wave drive can be realized with a simple control program. In addition, a simple and inexpensive current sensor can be used, and the control program can be simplified, so that an inexpensive and highly reliable motor drive device can be realized. Furthermore, since the processor is lightly loaded, a single processor can control multiple motors simultaneously. And a system capable of simultaneously driving a plurality of motors can be easily configured.

  A first invention is a DC power supply, an inverter circuit that converts DC power of the DC power supply into AC power, a permanent magnet motor driven by the inverter circuit, a load driven by the motor, It comprises current detection means for detecting a drive current and control means for controlling the inverter circuit by an output signal of the current detection means to drive the motor in a sine wave. The control means sets the output frequency of the inverter circuit. Frequency setting means, a current setting means for setting a driving current corresponding to the peak current of the motor or the rotating magnetic field, a driving current signal corresponding to the motor peak current or the rotating magnetic field detected by the current detecting means, and the The current comparison means for comparing the setting signal of the current setting means and the output frequency from the output signal of the current comparison means Is provided with frequency component correction control means for correcting the output voltage phase, can prevent turbulence in the V / f control, can operate from the maximum load to no load, and can control the lead angle. As a result, the motor control program is simplified, and an inexpensive and highly reliable motor drive device can be realized.

  In the second invention, the frequency component correction means for correcting the output frequency or the output voltage phase of the inverter circuit in the first invention is such that the control gain increases as the inverter circuit output frequency increases, and the rotation speed Since the control gain can be increased as the value becomes higher, irregularity in the high speed region can be prevented, and stable rotation control can be performed even at high speed. In particular, this is effective for stabilization control during high-speed operation of the salient pole permanent magnet motor (IPMSM).

  According to a third aspect of the invention, the frequency component correction means for correcting the output frequency or the output voltage phase of the inverter circuit according to the first aspect of the invention is such that the control gain is set to zero or not corrected when the motor is started. Since V / f control is performed without frequency correction at the time of start-up, there is no frequency fluctuation at the time of motor start-up, so that a sine wave current flows through the motor and stable start-up is possible.

  According to a fourth aspect of the invention, the current setting means in the first aspect of the invention changes the set value in accordance with the output signal of the frequency setting means for setting the output frequency of the inverter circuit. When the voltage is saturated and the advance angle is increased as in the case of a dehydrating motor of a washing machine, a motor drive device that can increase the output torque and can rotate at high speed can be realized.

(Embodiment 1)
FIG. 1 shows a block diagram of a motor drive apparatus according to Embodiment 1 of the present invention.

  In FIG. 1, a DC power source 2 is constructed by applying AC power from an AC power source 1 to a DC power source circuit composed of a rectifier circuit, and DC power is converted into three-phase AC power by a three-phase full-bridge inverter circuit 3. 4 is driven. In the DC power supply 2, capacitors 21a and 21b are connected in series to the DC output terminal of the full-wave rectifier circuit 20, and the connection point of the capacitors 21a and 21b is connected to one terminal of the AC power supply input to constitute a voltage doubler rectifier circuit. The voltage applied to the inverter circuit 3 is increased to reduce the current, thereby reducing the inverter circuit loss. The motor 4 drives a motor load 5 such as a compressor of an air conditioner or a dewatering drum of a washing machine. By connecting the current detection means 6 to the negative voltage side of the inverter circuit 3 and detecting the current flowing through the inverter circuit 3, it corresponds to the output current of the inverter circuit 3, that is, the peak current Ip of the motor 4 or the rotating magnetic field. Drive current is detected.

  The current detection means 6 is a so-called one-shunt method current detection method, and is a shunt resistor 60 connected to the emitter terminal side of the lower arm transistor of the inverter circuit 3 and a current detection circuit that detects a current flowing through the shunt resistor 60. 61. The current detection circuit 61 includes a signal level conversion amplifier circuit and a peak current detection circuit for A / D conversion and current detection by a processor such as a microcomputer. Details will be described later.

  In the 1 shunt method, when the carrier frequency is high or the modulation degree becomes large, a current undetectable region appears. Therefore, the 3 shunt method is more suitable for detecting an instantaneous current corresponding to each phase. Although excellent, in the present invention, since the peak value of the motor sine wave current or the current corresponding to the rotating magnetic field is detected, the circuit configuration is simpler and the current detection is easier in the one-shunt method. In particular, when the PWM control of the inverter circuit is two-phase modulation, peak current detection is facilitated. Of course, there is no problem with the three-shunt method.

  The control means 7 V / f controls the output voltage of the inverter circuit 3 so that the peak current Ip of the motor 4 or the drive current corresponding to the rotating magnetic field becomes a set value, and sets the inverter circuit output frequency. Frequency setting means 70, current setting means 71 for setting the motor drive current peak value Ip, current comparison means 72 for comparing the output signal ips of the current setting means 71 and the output signal ip of the current detection means 6, and current comparison means Frequency component correction means 73 for correcting the output signal f of the frequency setting means 70 in accordance with the output signal Δi of 72, and V / f control for calculating the motor applied voltage signal Vδ from the frequency f1 after frequency correction and the motor induced voltage constant. It comprises means 74, PWM control means 75, and phase signal generation means 76. The PWM control means 75 performs PWM control of the inverter circuit 3 in accordance with the voltage signal Vδ and the DC bus voltage Vp of the inverter circuit 3, and usually uses two-phase modulation. When the two-phase modulation is used, not only the motor phase voltage can be increased, but also the switching loss of the inverter circuit 3 can be reduced, and the peak current detection accuracy of the motor 4 can be improved. The phase signal generating means 76 integrates the angular frequency ω with time to obtain the electrical angle θ corresponding to the carrier signal, and multiplies the time t from the zero phase of the period signal f1 by the angular frequency ω to obtain the electrical angle ωt. You may ask for it.

  The frequency setting means 70 sets a motor driving frequency, and is set to a driving frequency f corresponding to the number of poles p and the number of rotations n of the rotor. The applied voltage Va of the motor 4 may be approximately equal to the motor induced voltage Em or a voltage slightly higher than the motor induced voltage Em. Therefore, the V / f control means 74 causes the motor rotation speed n, that is, the inverter to be applied. An output voltage control signal Vδ is applied to the PWM control means 75 so that a voltage Va obtained by multiplying the circuit drive frequency f1 by an induced voltage constant is applied to the motor 4. Vδ is obtained from Equation 1.

  Here, Vs is an applied voltage at startup.

  The motor phase control signal is obtained from Equation 2 from the voltage signal Vδ and the electrical angle θ.

  The frequency component correction means 73 performs a correction control by correcting and changing the inverter frequency in proportion to the current error signal Δi, and performs a turbulence prevention operation and a lead angle control. That is, according to Equation 3, when the motor current ip increases from the set value ips (because Δi becomes negative), the drive frequency is decreased, and when the motor current ip decreases from the set value ips (because Δi becomes positive), the reverse occurs. Increase the drive frequency.

  The frequency component correction unit 73 includes a proportional integration unit and an addition unit (both not shown). The proportional integration unit obtains a product of the current error signal Δi and the proportionality constant Kf. The inverter drive frequency f1 is obtained by adding the output signal of the proportional integration unit to the output signal f. Kf shown in Equation 3 is obtained from the product (Kf = f · k) of the output signal f of the frequency setting means 70 and the proportionality constant k. That is, it means that the frequency control gain Kf increases in proportion to the set frequency f. At low frequencies, the proportionality constant Kf is lowered to reduce frequency change or phase change, and at high frequencies the proportionality constant Kf is increased. Control is performed so that the motor peak current becomes the set value Ips. Proportional integral control may be used instead of proportional control, and the proportionality and integral gain may be changed according to the drive frequency.

  FIG. 2 is a control vector diagram of the non-saliency motor (SPMSM) showing the present invention, and shows the relationship between the rotor magnet axis dq coordinate of the motor and the motor applied voltage γ-δ coordinate. The motor applied voltage coordinate (γ-δ coordinate) is advanced by the load angle δ from the dq coordinate, the motor applied voltage Va is equal to the δ-axis voltage, and only the δ-axis is controlled, so Va = Vδ and Vγ = 0. Therefore, the reverse coordinate transformation is unnecessary. The motor induced voltage Em is on the q axis, and the vector of the motor current I is set to be substantially equal to the q axis current Iq at the rated load. In FIG. 2, the motor current vector I is displayed with a phase γ delay from the q axis. The phase of the motor applied voltage Va and the current I is indicated by φ.

  The present invention controls the angular velocity of the motor applied voltage coordinate (γ-δ coordinate) by controlling the frequency so that the motor current vector I becomes a set value. As a result, the motor angle is controlled by controlling the load angle δ. This means that the peak values of the currents Iu, Iv, and Iw are controlled. Further, since the magnetic flux Ψ of the rotating magnetic field is a product of the inductance L and the current I, that is, Ψ = L · I, controlling the current I means controlling the rotating magnetic flux Ψ constant. It is obvious that the effective value is the same as the peak value of the motor phase currents Iu, Iv, Iw.

  In the conventional method, that is, when the δ-axis current Iδ is controlled to a predetermined value, the δ-axis current Iδ fluctuates due to load fluctuations, so it is necessary to change the Iδ setting value according to the load state. When the motor current (or the motor peak current Ip) is controlled to be constant, the load angle δ and the phase φ change automatically according to the load, so there is a feature that it is not necessary to change the current value.

  In the conventional Iδ constant control or Iγ constant control, the advance angle control is difficult. However, in the present invention for controlling the current vector I or the current peak value Ip, the influence of torque fluctuation or load angle fluctuation is the current vector. Since it directly appears as fluctuations in I or peak current Ip, it is excellent in detecting load fluctuations, and has an advantage in that it is excellent in stabilization against load fluctuations. In particular, in the advance angle control in which the current vector I is advanced from the q axis, the I control is more advantageous than the Iδ control and the Iγ control because the torque fluctuation becomes more remarkable.

  If the current setting value ips is set according to the load, high-efficiency operation can be performed. Therefore, it may be changed according to the load torque and the rotational speed. However, according to the present invention, if the set value of the current setting means 71 is made constant from the time of start-up, the start-up torque can be increased, and further, stable operation can be achieved even if the motor current is controlled constant up to the advance angle control region.

  To further explain the frequency correction operation, if the motor current ip increases from the set value ips, the error signal Δi becomes a negative value, and the frequency correction signal Δf (Δf = Kf × Δi) also becomes a negative value. = F + Δf, the corrected frequency f1 decreases, the γ-δ axis approaches the dq axis, the load angle δ decreases, and the motor current I decreases, so that the constant current control operation is performed. Turbulence occurs when there is torque fluctuation in V / f control, but by adding frequency control, the disturbance is suppressed and the rotational speed fluctuation is extremely reduced. Is done. Furthermore, since the frequency correction gain increases in proportion to the set frequency f, the higher the frequency, the larger the constant current action and the lower the turbulence. Since the motor coil voltage vector ωLI in the vector diagram of FIG. 2 is proportional to the frequency, it is considered that the present invention corrects the motor drive frequency in proportion to the motor coil voltage vector. In other words, the motor coil voltage vector ωLI increases as the drive frequency increases, and the motor coil voltage vector ωLI and the load angle δ are correlated, so that the load angle fluctuation, that is, the turbulence phenomenon is also proportional to the motor coil voltage vector ωLI. . Therefore, it can be seen that the turbulence can be reduced by correcting the frequency in proportion to the motor coil voltage vector ωLI.

  FIG. 3 shows a startup control method of the motor applied voltage and frequency and the frequency correction gain.

  So-called V / f control is performed to linearly increase the applied voltage and drive frequency from the start of operation to the target rotational speed, and the frequency correction gain Kf is also increased in proportion to the drive frequency. The motor current set value may be constant. In the case of a fan or pump load, high-efficiency operation control can be performed by changing the current set value according to the drive frequency. Further, since the reluctance torque increases when the saliency motor advances the current more than the q axis, the set current ips may be increased in proportion to the frequency in order to control the advance angle.

  Further, the startup time ts until the target rotational speed is reached can be reduced by changing the start time ts according to the moment of inertia of the load. That is, as the moment of inertia increases, the turbulence can be reduced by increasing the startup time ts.

  By changing the frequency correction gain Kf in accordance with the drive frequency, the motor rotation speed fluctuation at the low start-up speed can be reduced, and the start-up current can be increased by bringing the motor current close to a sine wave. As shown in Kfa of FIG. 3, the control gain is not increased linearly in proportion to the time, the control gain in the initial stage of startup is set to almost zero, and the control gain is increased during the startup as shown in Kfb. Good. Note that if the proportional control gain is increased, oscillation easily occurs and noise is weakened. Therefore, a low-pass filter and a limiter may be appropriately provided.

  FIG. 4 shows a vector diagram of a saliency motor (IPMSM).

  Since the saliency motor uses reluctance torque, it is necessary to control the advance angle. Generally, when the advance angle is advanced by 30 degrees, the maximum efficiency operation is assumed. In order to increase the advance angle β, it is necessary to increase the load angle δ (δ = φ + β). By setting the current I to be large, the load angle δ can be increased. Since the induced voltage Em increases as the operation speed increases, the voltage saturation becomes such that the induced voltage Em becomes higher than the DC bus voltage Vp. Therefore, when the motor applied voltage Va is saturated, it is necessary to advance the current. The set value ips should be increased. Although the set current value ips may be increased as the frequency increases, motor efficiency can be improved by changing the current set value after detecting voltage saturation. In the detection of voltage saturation (Em> Va), the motor induced voltage Em is proportional to the drive frequency (Em = Ke × f), and the motor applied voltage peak value Vap is obtained from the DC bus voltage Vp and the modulation factor m (Vap = m). XVp), voltage saturation can be determined by simply comparing the drive frequency, the DC bus voltage Vp, and the modulation factor.

  5 and 6 show the shunt resistance voltage waveform and current detection timing during two-phase modulation.

  5 and 6, c represents a triangular wave carrier signal, and vu and vv represent u-phase and v-phase modulated signals, respectively. Since the w-phase lower arm transistor is forced to conduct, the w-phase modulation signal is not shown.

  There are two types of patterns in which the motor peak current appears in the two-phase modulation, as shown in FIGS. 5 and 6, and at least one peak current corresponding to each UVW phase can be detected at least three times in one cycle. As the peak detection method, the shunt resistor terminal voltage is amplified and detected by the A / D conversion means built in the processor at the current peak timing, and the maximum value is obtained by software, and the output terminal of the voltage amplification means is a diode and capacitor. The peak current is detected by a peak hold circuit composed of a discharge resistor, and the motor phase current is detected for each carrier signal and converted to γ-δ coordinates to obtain Iγ and Iδ. There are three possible methods for obtaining

  The above-described method 1 configured by a one-shunt method using a voltage amplifier and a peak hold circuit has the advantage that the processor software has the least burden and is simple. However, when a diode or the like is used for the peak hold circuit, temperature characteristics and diode variations become problems.

  Next, a method for detecting the peak value with the software of the processor will be described.

  In FIG. 5, since the motor current peak value appears at the peak timing (zero vector) t3 of the carrier signal c, the peak current can be detected at time t3. Therefore, it is preferable to compare the current signals after A / D conversion at the carrier signal peak time t3 during one cycle of the motor driving frequency and set the maximum value as the motor current peak value. However, since the carrier signal peak detection method can obtain data only once in one cycle, there is a problem that the reliability of data is lowered when the carrier frequency is low or low.

  If not only the carrier signal timing t3 but also the peak value of the current pattern shown in FIG. 6 is detected, the current peak value detection accuracy is improved. That is, after the carrier signal peak time t3, the current is detected at a timing t5 between t4 and t6 when the PWM control level comparator operates, and the peak is detected by determining the magnitude by software.

  As described above, the present invention controls the motor current corresponding to the motor peak current or the rotating magnetic flux to a predetermined value in order to drive the permanent magnet motor by sensorless sine wave by V / f control. The constant drive current is controlled by controlling the motor drive frequency with the error signal and the relationship between the rotor magnet coordinate (dq coordinate) and the applied voltage coordinate (γ-δ coordinate) is a constant load angle δ. , There is no turbulence in the V / f control, and stable operation can be achieved even with advance control. According to the present invention, stabilization control is possible regardless of a saliency motor or a non-saliency motor, and advance angle control is also facilitated. Regardless of the non-saliency motor or saliency motor, even if the output current setting value is constant from the start-up, stable operation is possible from start-up to the rated value. There is a feature that works.

  In the first embodiment, the motor voltage is V / f controlled by the signal f1 after frequency correction, but the effect is the same even if the V / f control is performed by the signal f before correction.

  Hereinafter, a second embodiment of the present invention will be described with reference to FIG.

(Embodiment 2)
FIG. 7 shows a block diagram of the control means of the motor drive apparatus in Embodiment 2 of the present invention.

  The block diagram of the control means shown in FIG. 7 is a partial modification of the control means 7 shown in FIG. 1, and the output signal Δi of the current comparison means 72 is connected between the phase signal generation means 76 and the PWM control means 75. In addition to the frequency component correction means 73a that performs this, the phase θ is directly changed. In addition to the V / f control means 74 and the phase signal generation means 76, the output signal f of the frequency setting means 70 controls the load angle δ by directly correcting the electrical angle θ without correcting the frequency, and the motor current peak value is obtained. Constant control. That is, when the error signal Δi increases, it is determined that the current I increases and the load angle δ increases, and the phase θ is decreased. When the error signal Δi decreases, the current I decreases and the load angle δ decreases. And the phase θ is increased. The basic operation is the same as in the first embodiment. In the first embodiment, the frequency is changed in order to change and correct the phase ωt, and in the second embodiment, there is a difference in that the electrical angle is directly changed. However, basically, changing the angular velocity is the same.

  As described above, according to the present invention, since the motor drive frequency is controlled so that the motor peak current or the motor drive current corresponding to the motor rotating magnetic field becomes the set value, the γ-δ axis and d The phase relationship of the -q axis becomes a predetermined value corresponding to the load, and the phase relationship between the rotating magnetic field and the rotor magnetic flux can be kept constant, so that sensorless sine wave driving is possible. In particular, even if the motor load fluctuates greatly from no load to the rated load, it is possible to operate with only constant current control, so the control is very simple. In addition, by changing the frequency correction gain for correcting the drive frequency by the current error signal according to the drive frequency, the high-speed region irregularity is suppressed, and the rotational speed variation becomes extremely small. In addition, since there is no need to perform coordinate conversion or vector decomposition of the motor current, there is a feature that the control program is simplified and the motor control is easy even with an 8-bit microcomputer because almost no calculation is required.

  The present invention uses V / f control that does not estimate the rotor position and uses almost no motor parameters. Furthermore, since the rotation speed is open loop control, fluctuations in the rotation speed are very small, the control method is simple, and current detection is simple and low. Noise, low cost, high reliability motor drive device can be realized. In particular, control is possible regardless of saliency motors and non-saliency motors, the advance angle control is easy, the motor control program and current detection are simplified, and the burden on the processor is reduced. It can be applied to a compressor motor, a washing motor, and a drying fan motor simultaneous sine wave drive system, and an inexpensive and highly reliable multiple motor simultaneous drive device can be realized.

  As described above, the motor drive device of the present invention detects the motor current corresponding to the peak value of the motor current or the rotating magnetic field by driving the permanent magnet motor with the inverter circuit that converts the DC power into the AC power. The inverter circuit output voltage and the motor drive frequency are controlled so as to be set to the set value, so that it can be applied to most motor drive devices that drive permanent magnet motors. The present invention can be applied to a motor driving device for a vacuum cleaner, a motor driving device for a vacuum cleaner, a fan motor driving device such as a ventilation fan or a combustor, and a compressor motor driving device for an air conditioner or a refrigerator. Furthermore, the present invention can also be applied to a multiple motor simultaneous drive system such as a heat pump washer / dryer or an air conditioner.

1 is a block diagram of a motor drive device according to Embodiment 1 of the present invention. Motor control vector diagram of the motor drive device Start-up control diagram of the motor drive device Vector of the same saliency motor Shunt resistance voltage waveform and current detection timing diagram Shunt resistance voltage waveform and current detection timing diagram Block diagram of control means in embodiment 2 of the present invention

Explanation of symbols

2 DC power supply 3 Inverter circuit 4 Motor 5 Motor load 6 Current detection means 7 Control means 70 Frequency setting means 71 Current setting means 72 Current comparison means 73 Frequency component correction means

Claims (4)

DC power source, inverter circuit for converting DC power of the DC power source into AC power, a permanent magnet motor driven by the inverter circuit, a load driven by the motor, and a current for detecting a driving current of the motor Detection means; and control means for controlling the inverter circuit by an output signal of the current detection means to drive the motor in a sine wave, the control means is a frequency setting means for setting an output frequency of the inverter circuit; Current setting means for setting a driving current corresponding to the peak current or rotating magnetic field of the motor, a driving current signal corresponding to the motor peak current or rotating magnetic field detected by the current detecting means, and a setting signal for the current setting means Current comparison means for comparing the output frequency or output voltage level from the output signal of the current comparison means. A motor drive device having the frequency component correction control means for correcting the. 2. The motor driving apparatus according to claim 1, wherein the frequency component correcting means for correcting the output frequency or the output voltage phase of the inverter circuit increases the control gain as the inverter circuit output frequency increases. 2. The motor driving apparatus according to claim 1, wherein the frequency component correcting means for correcting the output frequency or the output voltage phase of the inverter circuit sets the control gain to zero or does not correct it when the motor is started. 2. The motor drive apparatus according to claim 1, wherein the current setting means changes the set value in accordance with an output signal of the frequency setting means for setting the output frequency of the inverter circuit.

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