JP3458539B2 - Inverter control device for motor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor control device ,
In regard to the inverter control, the characteristic at the time of starting is improved. [0002] A conventional motor control device will be described below. FIG. 3 is a block diagram of a conventional motor control device. In FIG. 3, 1 is an AC power supply, 2 is an AC power supply 1
Converter for converting the output of the DC to DC, 3 is the converter 2
, An inverter for converting DC to AC, 5 for a motor driven by the output of the inverter 4, 6 for current detection means for detecting the output current of the inverter 4, and 7 for calculating the output voltage Voltage calculating means, 8 is a frequency calculating means for calculating an output frequency, 9 is a phase calculating means, which obtains a frequency from the frequency calculating means 8 and rotates a phase in a designated rotation direction to calculate a sine wave phase; Is a three-phase sine wave generating means for generating a three-phase sine wave from the voltage calculating means 7 and the phase command means 9, and 11 is a PWM signal for controlling the inverter 4 by PWM modulating the means of the three-phase sine wave generating means 10.
M generating means, 12 is a zero-cross detecting means for detecting a zero-cross from the output of the current detecting means 6, and 13 is a correcting means for correcting a voltage error due to a dead time of a power switching element constituting the inverter 4 from an output of the zero-cross detecting means 12. is there. In accordance with the frequency calculated by the frequency calculation means 8 and the rotation direction specified in advance, the phase command means 9
Calculates the phase data of the three-phase sine wave.
The three-phase sine wave generating means 10 generates a three-phase sine wave according to the voltage calculated in step (1). Further, the correction means 13 performs + correction if the current of the corresponding phase flows from the zero-cross detection means 12 into the motor, and performs-correction if the current flows out of the motor. The PWM generation means 11 modulates the PWM signal into a PWM signal. The inverter 4 is controlled to drive the motor 5. [0005] However, in the above-mentioned method, when the motor is started, the zero-cross detecting means 1 is used.
2, the correction means 13 cannot perform an appropriate correction, and this result further impedes the normal operation of the zero-cross detection means, thereby causing a vicious cycle and deteriorating the starting characteristics of the motor. Was. In particular, in a motor control device in which the modulation frequency of a PWM signal is set high to achieve low noise, the voltage error due to the dead time of the power switching element tends to have a large effect on motor control, and the motor control at the time of motor startup. Has become a level that cannot be ignored. [0007] It is an object of the present invention to solve the above-mentioned problems and to provide a motor control device having good motor starting characteristics. [0008] In order to solve the above-mentioned problems, the present invention provides a sine wave from a designated frequency and rotation direction.
Phase command means for commanding the phase data of
Three-phase from the phase data obtained from the means and the specified applied voltage
Sine wave generating means for generating a sine wave;
Inverter that PWM-modulates the output of the stage and applies it to the motor
And two-phase current detection using the output current of the inverter
Detecting means for calculating the remaining one-phase current from the output of the detector
And the current detection means as an input, and
Current polarity detecting means for outputting a valued signal;
The power switch of the inverter is obtained from the output of the polarity detection means.
Corrects voltage error due to dead time of switching element
Voltage for the motor and the current of the corresponding phase is supplied to the motor.
If the flow direction is positive, the correction voltage is +. If the flow direction is negative, the correction voltage is-.
The correction voltage of the above to the output of the sine wave generating means
Correction means . With this configuration, the current polarity detecting means can be used after starting.
Until the first polarity reversal occurs, the correction means
The correction voltage is synchronized with the switching timing of each phase voltage polarity.
Create a voltage command with the voltage polarity switched, and
After driving the inverter and detecting the current reversal,
On the other hand, when the current polarity is reversed,
The correction voltage according to the polarity binary signal for three phases
Since the output is added to the steps, a motor control device that realizes a smooth start even at the time of start can be provided. An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a motor control device according to an embodiment of the present invention. Current output of the current detecting means 6
The input to the polarity detector 12 is different from the conventional current detector in that the current detector 6a provided in two of the three phases
And a current calculating means 6b for calculating the remaining one-phase current from the output of the current detector 6a. Since the sum of the currents flowing into the motor is 0, it is clear that if a two-phase current can be obtained, the remaining one-phase current can be obtained. A CT or an insulating IC or the like is usually used for the current detector, but all of them are expensive and require a mounting area and a volume. Reducing these numbers is one means for realizing an inexpensive and compact motor control device. However, by using two current detectors, the detection error of the remaining two phases is added to the current value calculated by the current calculation means.
It will include a double error. Therefore, in the present embodiment, only one phase of the two phases provided with the current detector is used for zero-cross detection, and further, from positive to negative and from negative to positive every half cycle of the three-phase sine wave. It is assumed that only the change to is detected. Hereinafter, a case where the motor is started in the normal rotation direction using the W phase for zero-cross detection will be described with reference to FIG. From FIG. 2, the W phase is between π / 3 and 4π / 3.
It outputs a negative voltage, and outputs a positive voltage between 4π / 3 and 7π / 3. Therefore, in the case of the forward rotation direction, only the change in the direction of the W phase current from negative to positive is detected between 2π / 3 and 5π / 3, and the change from positive to negative is detected between 5π / 3 and 8π / 3. Only detect. In addition, the width of zero cross detection is set to 4π /
From 3 to 5π / 3, negative to positive, 7π / 3 to 8π / 3
During the period, it may be set from positive to negative. [0017] The one period as shown in FIG. 2 6 divided to the collector
It can be seen that a zero cross exists in one of the three phases at every 60 ° of the air angle . The phase point at the time of starting is (π / 3 × n +
θ) (n is an integer). Now, when the motor is started from the phase point of (2π / 3 + θ), the output voltage is V _u > 0 V _v > 0 V _w <0. Therefore, the output current is estimated to be i _u > 0 _iv > 0 i _w <0.
The current direction is U-phase positive, V-phase positive, W
The phase is fixed to be negative, and a voltage error due to the dead time of the power switching element is corrected. When the phase is between π and 4π / 3, the V-phase current is positive, the W-phase current is negative, and the U-phase current has a zero cross. In FIG. 2, it is detected in the W phase.
The point at which the polarity of the current first reverses is 4π / 3 + θ
Up to this point, the correction voltage polarity addition
The rule is that the correction voltage is applied according to the applied voltage polarity.
Drive the inverter up to. That is, pay attention to Vu
And polarity inversion at the timing of π.
Since inversion occurs at the timing of 4π / 3,
Will also switch the correction voltage polarities of the u-phase and w-phase.
You. On the other hand, after exceeding 4π / 3 + θ, it is detected.
Signal polarity for dead time correction according to the current polarity signal
Sex will be switched. When the phase data is between 5π / 3 and 2π, U
The phase current is negative, the W phase current is positive, and the V phase current has a zero cross. In this case, (5π /
Up to 3 + θ1), the polarity of the V-phase current is positive.
The means performs positive voltage correction and exceeds (5π / 3 + θ1)
The negative voltage correction because the polarity of the V-phase current becomes negative
You. As described above, the current detected first after the start-up
Until the time of polarity reversal (4π / 3 + θ in this example),
The switching point of the polarity of the positive signal is the switching point of the phase voltage.
After that, the binary signal of the current polarity detection means
It is decided that the correction means operates in the cage. The same applies to 1
A W-phase zero cross is detected every / 2 cycle, and this phase is used as a U-phase and V-phase zero cross. Although the operation in the normal rotation direction has been described above as an example, the same processing is performed in the reverse rotation direction only by reversing the phase relationship. The above embodiment can be realized by software using a microcomputer, which has made remarkable progress in recent years, or by a logic circuit such as an ASIC or a gate array. As described above, the present invention provides a current polarity detecting method.
From the stage until the first polarity reversal occurs,
Is corrected in synchronization with the switching timing of each phase voltage polarity
Create a voltage command with the voltage polarity also switched and
Since the inverter is driven , a motor control device having good starting characteristics can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of a motor control device according to an embodiment of the present invention. FIG. 2 is a voltage and current waveform diagram for explaining an operation according to the embodiment of the present invention. Block diagram of control device [Description of symbols] 1 AC power supply 2 Converter 3 Smoothing capacitor 4 Inverter 5 Motor 6 Current detection means 6a Current detector 6b Current calculation means 7 Voltage calculation means 8 Frequency calculation means 9 Phase command means 10 Three-phase Sine wave generator 11 PWM generator 12 Current polarity detector 13 Corrector

Claims (1)

(57) [Claim 1] Phase command means for commanding sine wave phase data from a designated frequency and rotation direction, and phase data obtained from the phase command means and designation Sine wave generation means for generating a three-phase sine wave from the applied voltage, an inverter for PWM-modulating the output of the sine wave generation means and applying the output to a motor, and two-phase current detection using the output current of the inverter
Current detection means for calculating the remaining one-phase current from the output of the detector, and the current detection means as an input,
A current polarity detection means for outputting a digitized signal, said collector
A correction voltage for correcting a voltage error due to a dead time of the power switching element of the inverter is selected from an output of the flow polarity detection means, and a current of a corresponding phase is supplied to the motor.
If the flow direction is positive, the correction voltage is +. If the flow direction is negative, the correction voltage is-.
The compensation voltage and a <br/> correcting means summing the outputs of the sine wave generating unit, from the beginning after activation current polarity detection means
Until the polarity reversal occurs, the correction means
The polarity of the correction voltage is synchronized with the switching timing of the voltage polarity.
Voltage command is created with the characteristics switched, and the inverter is
After the first current polarity reversal is detected,
Also, when the current polarity is reversed, the three phases are detected from the current polarity detection means.
The correction voltage according to the binary signal of the
Inverter system for motors that is output together
Control device.