JP4798066B2 - Motor drive device - Google Patents

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 the inverter circuit DC current using a shunt resistor, estimates the motor effective current Iδ from the DC current, and performs V / f control so that the motor current becomes a predetermined value. (For example, see Patent Document 1).
JP 2005-218273 A

  However, the conventional motor drive device uses a filter circuit and an integration circuit (average circuit) to detect the DC average current from the shunt resistance voltage that changes according to the switching state of the inverter circuit, so that the circuit becomes complicated and the current detection accuracy When the value is increased, there is a problem that current detection responsiveness deteriorates. Furthermore, because the V / f control of the permanent magnet motor is a sensorless control method that does not calculate and estimate the rotor position, turbulence is likely to occur, and if control responsiveness is poor, turbulence is likely to occur, so detection accuracy and control responsiveness are traded. There was an issue that turned off.

  Further, since the conventional method is a method in which the motor effective current Iδ is estimated and calculated to change the drive frequency, there is a problem that when the load torque increases, the rotational speed decreases and the target rotational speed cannot be controlled.

  The present invention solves the above-mentioned conventional problems, detects a DC peak current corresponding to a motor peak current, controls it to a predetermined value, and drives a sensorless sine wave, and has excellent current detection accuracy and detection response. Therefore, the control responsiveness is good, and the object is to detect the torque current and perform the maximum efficiency operation by simple vector control.

In order to solve the above-described conventional problems, a motor driving device of the present invention includes 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; current detection means for detecting a direct current of the inverter circuit; 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 a frequency setting means for setting an output frequency of the inverter circuit, a voltage control means for controlling the inverter circuit output voltage according to an output signal of the frequency setting means, and sets a peak value of the inverter circuit DC current Current setting means, a DC current peak value detected from the output signal of the current detection means and the current setting means Current comparison means for comparing the setting signals of the current, correction means for correcting the output frequency or output voltage from the output signal of the current comparison means, and the DC current peak value detected by the current detection means and the inverter output setting The torque calculation means calculates and estimates the torque current from the signal and the motor constant, and the DC current peak value and the torque current are substantially equal .

  The motor drive device of the present invention detects the peak value of the inverter circuit DC current and controls the ratio of the inverter circuit output frequency to the voltage so that it becomes a set value to drive the sensorless sine wave. Since the control can be performed without conversion, the control program is simple and can be configured with an inexpensive processor and current detection means that do not require high-speed computation, and an inexpensive and highly reliable motor drive device can be realized. In addition, the motor torque is estimated and calculated from the detected peak current, inverter output frequency, and output voltage for optimal operation control. The motor efficiency is maximized to reduce motor heat generation and inverter circuit loss, and operation according to the load torque. Control becomes possible.

The 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, and the inverter circuit Current detecting means for detecting the direct current of the current and control means for controlling the inverter circuit by the output signal of the current detecting means to drive the motor in a sine wave. The control means determines the output frequency of the inverter circuit. Frequency setting means for setting, voltage control means for controlling the output voltage of the inverter circuit according to an output signal of the frequency setting means, current setting means for setting a peak value of the inverter circuit DC current, and output of the current detection means A current comparing means for comparing a DC current peak value detected from the signal with a setting signal of the current setting means; A correcting means adapted to correct the output frequency or the output voltage from the output signal of the comparator means, said current DC current peak value detected by the detection means and the inverter output setting signal and torque calculation for calculating the estimated torque current from the motor constant The DC current peak value and the torque current are almost equal to each other, and the load on the processor is light and optimal current control according to the motor load can be performed. A highly reliable motor drive device can be realized.

Further , the maximum efficiency operation can be performed as in the vector control, the loss of the motor and the inverter circuit can be reduced, and the motor and the inverter circuit can be downsized and reduced in price.

(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 and reduce the inverter circuit and motor loss. The motor 4 drives a motor load 5 such as a compressor of an air conditioner, a washing and dewatering drum of a washing machine, or a fan / pump. By connecting the current detection means 6 to the negative voltage side of the inverter circuit 3 and detecting the direct 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. The drive current to be detected is detected.

  The current detection means 6 is a so-called one-shunt current detection method, and is a shunt resistor 60 commonly 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 circuit and a high-speed operational amplifier circuit for detecting current by an A / D conversion circuit built in a processor such as a microcomputer.

  In the 1-shunt current detection method, when the carrier frequency is high or the modulation degree becomes large, a current undetectable region appears. Therefore, when detecting an instantaneous current corresponding to each phase, 3-shunt current detection Although the method is superior, since the peak value of the motor current is detected in the present invention, the one-shunt current detection method has a simpler circuit configuration, facilitates current detection, and is inexpensive. Further, when the PWM control of the inverter circuit is set to two-phase modulation, the pulse width in which the peak current appears increases, so that the peak current can be easily detected. Of course, there is no problem with three-phase modulation.

  The control means 7 comprises a processor such as a microcomputer, detects the shunt resistance peak current Ip corresponding to the peak current of the motor 4, and outputs the output frequency and output voltage of the inverter circuit 3 so that the detected current becomes a set value. The frequency setting means 70 for setting the inverter circuit output frequency, the voltage control means 71 for controlling the inverter output voltage ratio according to the output signal ω of the frequency setting means 70, and the DC current peak value Ip are set. Current setting means 72 for comparing, peak current detecting means 73 for detecting the peak value from the output signal of the current detecting means 6, and comparing the output setting signal ips of the current setting means 72 with the output signal ip of the peak current detecting means 73 to obtain an error. A current comparator 74 that generates a signal Δip (Δip = ips−ip), and an output signal Δip of the current comparator 74 Correction means 75 for correcting the output signal ω of the frequency setting means 70 or correcting the inverter circuit output voltage phase, and inverter control means 76 for PWM control of the inverter circuit 3 in a sine wave form in accordance with the output signal Vδ of the voltage control means 71. And an output angular frequency signal ω1 of the correction means 75 to generate a phase signal θ and add a phase signal θ to the inverter control means 76. The torque calculation means 78 calculates and estimates the q-axis current Iq, that is, the torque current, from the inverter output voltage and output frequency ω and the output signal ip of the peak current detection means 73 so that the motor efficiency is maximized. The set value of the current setting means 72 is changed and controlled. Further, since the load torque can be determined by detecting the torque current, it is easy to detect the air engagement of the pump load or the load state such as the closed state of the fan. The DC voltage detecting means 79 detects the DC voltage Vdc of the DC power supply 2 and is necessary for accurately controlling the inverter circuit output voltage Va. In other words, by controlling the modulation degree of the PWM inverter circuit according to the DC power supply voltage Vdc, it is possible to improve the control accuracy of the V / f control that controls the ratio of the drive frequency and the output voltage to a constant level, and the fluctuation of the DC power supply voltage Regardless, the inverter output voltage can be controlled constant.

  The correcting means 75 amplifies the current error signal Δip at a constant ratio Kf and converts it into a frequency component, a adding means 75b for adding the output signal Δω to the output signal ω of the frequency setting means 70, a current The voltage correction means 75c converts the error signal Δip into a voltage correction signal ΔVδ by proportional integration. The output signal ω1 of the adding means 75b is applied to the phase signal generating means 77 to prevent turbulence by frequency correction, and the output signal ΔVδ of the voltage correcting means 75c is applied to the voltage control means 71 so that the detected peak current Ip becomes the set value Ips. Feedback control. The voltage control means 71 is an inverter control means 75 so that a voltage corresponding to a control voltage Vδ obtained by adding the correction voltage ΔVδ and the starting voltage Vs to the voltage obtained by multiplying the inverter circuit drive frequency ω by the induced voltage constant Ke is applied to the motor 4. To control. Vδ is obtained from Equation 1.

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

  By the frequency correction means 75a of the correction means 75, the inverter frequency is corrected and changed in proportion to the current error signal Δip, and the stabilization control is performed, so that turbulence can be prevented. That is, according to Equation 3, when the motor current ip increases from the set value ips (because Δip becomes negative), the drive frequency is decreased, and when the motor current ip decreases below the set value ips (because Δip becomes positive), the reverse Increase the drive frequency.

  Kf shown in Equation 3 is obtained from the product (Kf = ω · k) of the output signal ω of the frequency setting means 70 and the proportionality constant k (not shown). That is, it means that the frequency control gain Kf increases in proportion to the set frequency ω. At a low frequency, the proportionality constant Kf is lowered to reduce frequency change or phase change, and at a high frequency, the proportionality constant Kf is increased. Control is performed so that the motor peak current becomes the set value Ips. In fan / pump loads, torque is proportional to the square of the rotational speed, so damping is caused by torque fluctuations and can be stabilized by V / f control alone. However, in constant torque loads, turbulence occurs only by V / f control. It cannot be stabilized. However, negative feedback control of the frequency can stabilize and suppress turbulence.

  FIG. 2 is a control vector diagram of the non-salience motor (SPMSM) according to the present invention, showing the relationship between the rotor magnet axis coordinates (dq coordinates) of the motor and the motor applied voltage axis coordinates (γ-δ coordinates). Yes. The motor applied voltage axis coordinate (γ-δ coordinate) is advanced by the load angle δ from the dq coordinate, the motor applied voltage (= inverter circuit output voltage) Va is equal to the δ axis voltage, and only the voltage vector of the δ axis is controlled. Therefore, since Va = Vδ and Vγ = 0, it is not necessary to perform coordinate inverse transformation, and the inverter three-phase output voltage can be calculated from Equation 2. Since the motor induced voltage Em is on the q axis, the q axis current vector Iq of the motor current I is referred to as a torque current, and the set value Ips of the inverter DC current peak value Ip that is equal to the motor peak current is substantially equal to the torque current Iq. With this setting, simple vector control is possible.

  The motor current vector I is displayed with a phase γ delay from the q axis, and the motor applied voltage Va is set to 1.1 times or more of the motor induced voltage Vm. The phase φ indicates the phase (power factor angle) between the motor applied voltage Va and the current I. If the load torque is constant, Iq is constant, so the motor coil voltage vector ωLI from the induced voltage Em is on the one-dot chain line (ωLIq), and the maximum efficiency operation is performed with a vector relationship (I = Iq) perpendicular to the q axis ( If the motor applied voltage at that time is Va0, the advance angle is obtained when the motor applied voltage Va is smaller than Va0, and the delay angle is produced when the motor applied voltage Va is larger than Va0.

  The present invention performs simple vector control so that the current phase γ from the q axis is zero, in other words, the current peak value Ip is equal to the torque current Iq. Since the voltage drop due to the motor resistance can be ignored, the load angle δ (or sin δ) is calculated from the motor applied voltage Va, the motor induced voltage Em, and the motor peak current Ip, and the torque current Iq is calculated and estimated.

  In the conventional single shunt current detection method, there is a problem that the detection accuracy is poor in the method of estimating Iδ from the direct current, and the method of detecting the current according to the switching vector of the inverter circuit and reproducing the sine wave increases the carrier frequency. There was a problem that it was difficult to reproduce the current. However, the method for detecting the current peak value Ip is characterized in that the circuit is simple, the detection accuracy is high, and coordinate conversion is not required, so the burden on the processor is reduced. In the present invention for controlling the current peak value Ip, the influence of torque fluctuation or load angle fluctuation appears directly as fluctuations in the current vector I or peak current Ip, so that it is excellent in detecting load fluctuations and is stable against load fluctuations. There are excellent features. The Ip control according to the present invention has a more remarkable torque fluctuation than the Iδ control and the Iγ control, and is advantageous as a current control method because coordinate conversion is unnecessary.

  FIG. 3 shows a PWM signal and a shunt resistance voltage waveform during two-phase modulation.

  In FIG. 3, vc is a triangular wave carrier signal, vu and vv are u-phase and v-phase modulation signals, up, vp and wp are upper arm control signals for each phase of UVW, and Vsh is a shunt resistance voltage waveform. Since the w-phase lower arm transistor is forced to conduct, the w-phase modulation signal is not shown.

  As shown in FIG. 3, the pattern in which the motor peak current appears in two-phase modulation is a section where only the upper arm of one phase is on (t0 to t2, t4 to t5), or the upper arm of the two phases is turned on. Appear in a certain section (t5 to t7). Unlike the three-phase modulation, the two-phase modulation is PWM-controlled only for the two phases, so that the section where the peak current appears is widened, so that the peak current can be easily detected.

  FIG. 4 shows a phase in which the two modulation signal waveforms of each phase of UVW and each phase current appear in the shunt resistor. The interval from 0 to 1 / 3π is the W phase current Iw and the V phase current Iv, the interval from 1 / 3π to 2 / 3π is the U phase current Iu and the V phase current Iv, and the interval from 2 / 3π to π is the U phase. A phase current Iu, a W-phase current Iw, and each phase current appear sequentially. As shown by the arrows in the figure, the section in which the current peak value appears is usually about 30 degrees behind the phase at which the voltage from the neutral point of each phase reaches its peak, so it is positive near the two peaks of the two-phase modulation. The peak value of each negative phase current appears. That is, the interval 0 to 1 / 3π is the peak value of Iw, the interval 1 / 3π to 2 / 3π is the peak value of Iv, the interval 2 / 3π to π is the peak value of Iu, and the peak value is 6 times in one period. Appears. When the current phase is delayed by about 30 degrees from the voltage phase, it is easy to detect the peak current. However, when the current phase is delayed by 60 degrees, the pulse width becomes narrow and current detection becomes difficult. However, in the case of IPMSM, since the power factor angle φ of the voltage phase and the current phase is small, detection of the current peak value is easy, and in the case of SPMSM, the degree of advance is small, so the power factor angle φ is large. This is very rare and causes little problem in practice.

  The one-shunt current detection method and the method constituted by the voltage amplifier and the peak hold circuit have the feature that not only the hardware configuration is simple, but also the processor software is light and simple. Further, the A / D conversion timing for detecting the current may be the valley or peak (t0, t3, t6 in FIG. 3) of the carrier signal in which all the switching transistors of the inverter circuit are on or off, and the current detection is simple. In addition, it has a strong feature against noise.

  FIG. 5 shows a flowchart of motor current control, and FIG. 6 shows a flowchart of a torque current calculation subroutine.

  In FIG. 5, the motor rotation control starts from step 100, and then the process proceeds to step 101 to set the start-up current Ip, and then proceeds to step 102 to execute the start-up control subroutine. In the start-up control subroutine, the drive frequency ω is increased linearly from substantially zero to the set frequency with time until the steady rotational speed, and the motor applied voltage Va is also increased with time at a constant ratio with respect to the drive frequency ω. At this time, the motor applied voltage Va is corrected by the error signal Δip so that the shunt resistance current peak value Ip becomes a value set at the start-up, and the drive frequency ω is not corrected by the error signal Δip. Next, the routine proceeds to step 103, where it is determined whether or not the predetermined rotational speed has been reached. If the predetermined rotational speed has been reached, the routine proceeds to step 104 where a torque current calculation subroutine is executed.

  FIG. 6 is a detailed flowchart of the torque current calculation subroutine. The subroutine starts from step 200, the peak current of the shunt resistor is detected in step 201, and then the process proceeds to step 202 to detect the DC voltage Vdc of the DC power supply 2. Next, the routine proceeds to step 203, where the inverter output voltage Va is calculated from the DC voltage Vdc, the output voltage command value Vδ and the PWM modulation degree. In step 204, the motor induced voltage Em is obtained from the drive frequency ω and the motor induced voltage constant. In step 205, the cosine cos δ and the sine sin δ of the load angle δ are obtained from the cosine theorem shown in equation 4.

  The control method according to the present invention is basically V / f control, and the voltage ratio k between the motor induced voltage and the motor applied voltage is controlled to be substantially constant. If the voltage k is known, Expression 4 can be expressed by a simpler expression. This reduces the burden on the processor. Formula 5 is used to obtain the ratio k between the motor induced voltage and the motor applied voltage, and is expressed as a value obtained by adding the voltage correction value ΔVa, the induced voltage constant Ke, and the correction value of the driving frequency ω to the V / f control ratio k0.

  If the processor has insufficient computing power, it can be obtained from ω and ΔVδ using a lookup table Fk.

  Equation 6 determines cos δ from the voltage ratio k and the current peak value Ip. The constant kL shown here is the ratio of the induced voltage constant Ke to the motor coil inductance L (Ke / L), which is a motor constant indicating the excitation capability of the motor. It is. If the processor is not capable of computing, cos δ can be obtained from the k and Ip look-up tables Fδ calculated in advance.

  If cos δ is known, sin δ can be obtained from the correspondence table. Therefore, the process proceeds to step 206, and the torque current Iq is obtained from Equation 7. Similarly, Equation 7 represents that the torque current Iq can be obtained from the look-up table Fi of the voltage ratio k and the peak value Ip. Next, the routine proceeds to step 207, where the current peak value set value Ips is changed to Iq or a value with a little margin in Iq, and the routine proceeds to step 208 where the subroutine is returned to return to the main routine shown in FIG.

  Step 105 and subsequent steps show current control for controlling the shunt resistance current peak value Ip to the set value Ips. The step 105 detects the current peak value Ip, and the step 106 calculates the error signal Δip from the set value. Then, the process proceeds to step 107 to control the motor control voltage Vδ so that the error signal Δip is within a predetermined value, and then proceeds to step 108 to control the drive frequency ω1 in proportion to the error signal Δip to stabilize the control. I do. Next, the routine proceeds to step 109, where the PWM control of the inverter circuit 3 is performed, the output voltage and drive frequency of the inverter circuit 3 are controlled, and the routine proceeds to step 110, where it is determined whether the motor control operation has been completed. Is stopped and the process proceeds to the next process. If not completed, the process returns to step 104 to perform motor current control.

  As described above, since the torque current corresponding to the motor load torque is periodically obtained and the set current is periodically changed, the set value is changed so that the torque current always corresponds to the load torque and the maximum efficiency operation is performed. Done.

  As described above, the present invention controls the DC current peak current to a predetermined value in order to drive the permanent magnet motor by sensorless sine wave by V / f control, and further calculates the torque current according to the motor load. Since the torque current Iq and the DC current peak value Ip are controlled to be equal to each other, the motor peak current is almost equal to the torque current, and the current is controlled to the minimum. Become.

  In the present invention, since it is not necessary to reproduce the sine wave current of the motor, the current detection is very simple, and sensorless sine wave driving can be performed only by constant current control without complicated calculation such as coordinate conversion. The sensorless sine wave drive can be realized with an inexpensive processor, and a motor drive device with high efficiency, low noise, and low price can be realized with an inexpensive motor and inexpensive control means.

  In the present embodiment, the motor voltage is V / f controlled by the signal ω before frequency correction, but the effect is the same even if V / f control is performed by the signal ω1 after correction.

  Further, if the inverter output voltage Va is set to be substantially equal to the motor induced voltage Em and the frequency is controlled so that the current Ip becomes a predetermined value, the predetermined advance angle can be set. Is also possible.

  Since the V / f control does not estimate the rotor position, the present invention uses almost no motor parameters. Further, since the rotation speed is open loop control, the fluctuation in the rotation speed is very small, the control method is simple, and the current detection is also easy. Control program development and tuning man-hours can be reduced, and can be realized with an inexpensive processor or semiconductor integrated circuit. Therefore, it is easy to realize a power module in which the control system and the inverter circuit are integrated.

  In particular, control is possible regardless of saliency motors and non-saliency motors, and lead angle control is easy, so the field control field can be expanded to a high speed range by field weakening, and the motor control program and current detection are simplified. The burden on the processor is lightened, and it can be applied to the compressor motor, washing motor, drying fan motor simultaneous sine wave drive system such as heat pump washer / dryer, and low-cost and highly reliable multi-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 Shunt resistance voltage waveform and current detection timing diagram of the motor drive device Current detection timing chart during two-phase modulation of the motor drive device Flow chart of motor control of the motor drive device Flow chart of torque current calculation of the motor drive device

2 DC power supply 3 Inverter circuit 4 Motor 5 Motor load 6 Current detection means 7 Control means 70 Frequency setting means 71 Voltage control means 72 Current setting means 74 Current comparison means 75 Correction means 78 Torque calculation means

Claims (1)

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, and a DC current of the inverter circuit are detected. Current detection means; and control means for controlling the inverter circuit according to an output signal of the current detection means to drive the motor in a sine wave. The control means includes frequency setting means for setting an output frequency of the inverter circuit; A voltage control means for controlling the output voltage of the inverter circuit according to an output signal of the frequency setting means; a current setting means for setting a peak value of the inverter circuit DC current; and a DC current detected from the output signal of the current detection means A current comparing means for comparing a peak value with a setting signal of the current setting means; and an output of the current comparing means. A correcting means adapted to correct than the output frequency or the output voltage signal consists of a torque calculating means for calculating estimated from the torque current DC current peak value and the inverter output setting signal and a motor constant detected by said current detecting means, A motor driving device in which the DC current peak value and the torque current are substantially equal .

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