KR100877599B1 - Compensation method of Zero-Current-Clamping Effect in Pulsating Carrier-Signal Injection-Based Sensorless Drives - Google Patents

Abstract

The present invention relates to a method of compensating zero-current clamping of an AC motor without position and velocity sensors, in which high-frequency current data are collected from an off-line test on a high-frequency injection sensorless AC motor to obtain a dq axis inductance, The compensated voltage calculated by the on-line compensator is used for the switching of the PWM inverter. In this case, the compensating voltage obtained by the on- And the output is limited to the maximum distortion voltage caused by the device.

Motor, Zero current clamping, Error, Stop coordinate, Synchronization coordinate, Pulse

Description

BACKGROUND OF THE INVENTION Field of the Invention [0001] The present invention relates to a zero-current clamping compensation method for an AC motor without a position sensor and a speed sensor,

1 is a block diagram showing a synchronous injection method of a sensorless AC motor;

Fig. 2 is a block diagram showing a pulsation injection method of a sensorless AC motor

3 is a graph showing the relationship between the position of the fundamental wave current and the current in the stationary coordinate system according to the zero current clamping effect

4 is a graph showing a distortion voltage value according to the magnitude of the phase current

5 is a graph showing time, current, and rotor positional relationships according to the zero current clamping effect

6 is a graph showing the phase current and the high-frequency current according to the position of the rotor at no-

7 is a graph showing the effect of zero current clamping under a load condition

8A is a block diagram illustrating a zero-current clamping compensation apparatus according to the present invention.

8B is a view showing the structure of the compensator of FIG.

9 is a graph showing a no-load experiment waveform when the zero-current clamping effect is not compensated

 10 is a graph showing a no-load experiment waveform for compensating for the zero current clamping effect

11 is a view showing a waveform before compensation when a load is applied;

12 is a view showing a waveform after compensation at the time of application of a load;

13 is a diagram showing a compensation voltage and a phase current

The present invention relates to a zero-current clamping compensation method for an AC motor without a position and velocity sensor, and more particularly, to compensate a zero-current clamping effect in a method of injecting sinusoidal high- And a method of compensating zero current clamping of an AC motor without a position sensor and a velocity sensor that can achieve an error in angle or an improvement in acceleration / deceleration performance.

A major advantage of the AC drive system is that there is no maintenance or maintenance problem due to mechanical wear of the brushes and commutator elements in conventional DC motor drive systems. Due to the robust structure and economical advantages, the drive of AC motors using inverters is increasingly increasing in various industrial fields requiring high performance control.

The basic conditions for high-performance control are the independent control of torque current and flux and that these two components are spatially orthogonal. To do this, you must know the position of the flux. The position of the magnetic flux can be measured directly through the magnetic flux position detector or by estimating the magnetic flux position by measuring the rotational speed of the rotor. However, such position and velocity detectors have the following problems.

First, the cost for the position detector of the rotor and its attachment increases the cost of the motor drive system. Then, the signals received from the detector are converted into signals usable for control through various methods. The electronic circuit for this causes the control system to become complicated. The signal from the detector is often vulnerable to electromagnetic noise and may give false information, which lowers the stability of the drive system. The cause of the mechanical structure or the environment in which the drive system is installed may make it difficult to attach the position detector to the rotating shaft of the motor.

In this way, there have been various problems in finding the position of the rotor speed or flux for high performance control of the AC motor. Recently, studies have been conducted to obtain the position of the magnetic flux without the position and velocity detector or flux detector. The control method is called sensorless control method.

Examples of such a sensorless control method are disclosed in US Pat. Nos. 5,864,898 and 5,606,967, US Pat. No. 5,864,698 discloses a pulsation injection method, and US 6069467 discloses a synchronous injection method.

This synchronous injection method is a method of injecting a high-frequency voltage in a stationary coordinate system as shown in FIG. 1, and uses a negative-sequence component of a high-frequency current, Is very small, and when there is a zero-current clamping phenomenon, a very serious distortion occurs.

As shown in FIG. 2, the pulsating injection method injects a high-frequency voltage of a predetermined magnitude in an estimated synchronous coordinate system, injects a high-frequency voltage, extracts an error from the high-frequency current inside the motor, This method has the advantages that it is strong against zero current clamping and can operate at zero speed - full load operation which is impossible in sensorless control technique of existing voltage integration method and does not need motor constant.

The precise control in the above-described AC motor is directly proportional to the accuracy of the position and velocity information. In the case of the sensorless control described above, since the actual position and velocity controller are removed, A precise estimated position and speed must be obtained.

However, due to the dead time of the pulse width modulation inverter and the parasitic capacitance of the switching device for driving the motor, the Zero Current Clamping Effect occurs at the time when the phase current passes the zero point as shown in FIG.

As shown in FIG. 4, this effect has a nonlinear property that the distortion voltage value (nonlinearly inversely proportional to the equivalent transient time) differs according to the magnitude of the current, and the equivalent transient time is greatest near the zero current and decreases when the current increases.

Such a zero-current clamping effect distorts the high-frequency current including the rotor position information, resulting in distortion of the position signal synchronized every zero point of the current as shown in FIG. Such positional errors not only cause deterioration of the performance of the motor but also cause the system to diverge. Also, the estimated speed required for the speed control is obtained by differentiating the estimated position. The position error shown in FIG. 5 causes a ripple of the estimated speed, resulting in a trip of the drive system due to the overcurrent.

In order to solve this problem temporarily, the bandwidth of the estimation angle measuring device and the speed control device should be lowered. This causes the acceleration / deceleration performance of the motor drive device to be significantly lowered, which causes a decrease in productivity and precision. Another method is a look-up table method, which is a combination of expert experience with data obtained from a long time test. This method requires a lot of development time and requires an additional memory device for data storage The disadvantage is that there are many restrictions to apply directly to actual industrial sites.

The present invention solves the above-mentioned problems, and it is an object of the present invention to provide an apparatus and a method for performing the off-line test and the on-line compensation for compensation in a stationary coordinate system by injecting a voltage in an estimated synchronous coordinate system, Therefore, we can improve the stability and performance of the sensorless system by reducing the estimation angle or the estimated speed ripple for sensorless by compensating the zero current clamping effect after simple offline test using the load condition simulation technique simulating the load condition. I have to.

In order to achieve the above object, the zero current clamping compensation method of an AC motor without position and velocity sensors according to the present invention collects high frequency current data from an off-line test for a high frequency injection sensorless AC motor, The axial inductance is obtained, and the distortion coefficient by zero current clamping is obtained. The obtained distortion coefficient is multiplied by the actual high frequency current to compensate for the influence of the zero current clamping in the actual operating condition through the on-line compensator. The compensation voltage calculated by the on-line compensator is limited to the maximum distortion voltage by the switching element of the inverter .

Embodiments of the present invention having the above features will be described in more detail below. In the following embodiment, the up / down subscript s represents the stationary coordinate system, and r and e represent the synchronous coordinate system, and both r and e are used in the embodiment of the present invention.

1. Modeling in stationary coordinate system

When the phase current passes zero, the inverter output voltage is distorted by the parasitic capacitance of the IGBT (Insulated Gate Bipolar Transistor) and this phenomenon is called zero current clamping.

The voltage error (V _d ) due to the zero current clamping is expressed by Equation (1).

Where Tcn is the effective dead time, Ttr is the equivalent trailing time due to the parasitic capacitance near the zero point of the current, Ts is the sampling time, and Vdc is the DC link voltage.

에 의한 왜곡전압

는 수학식 3과 같이 근사화된다.Figure 4 above shows an example of a typical Ttr curve. This nonlinear curve is approximated by the following equation (2) in which the equation (2) can be approximated by a = Tcn and b = 1, and since the magnitude of the current is very small, When the equations 1 and 2 are combined, high-frequency current

The distortion voltage

Is approximated as shown in Equation (3).

는 고주파 전류에 비례하는 형태임을 알 수 있다. 여기서, α는 영전류클램핑에 의한 왜곡계수를 나타내며, 그 값은 펄스 폭 변조 방식 인버터마다 다른 값을 가진다. From equation (3)

Is proportional to the high-frequency current. Where α represents the distortion coefficient due to zero current clamping, and the value has a different value for each pulse width modulation type inverter.

If the frequency? _C of the injected high-frequency voltage is sufficiently high, the relationship between the high-frequency current and the voltage can be expressed by Equation (4).

는 수학식 5와 같고, V_h는 주입전압, ω_c는 주입전압의 주파수,

는 대상 전동기의 인덕턴스 행렬을 나타낸다. 한편, 상기한 수학식 4는 상전류가 영점을 지날 때마다 성립하는 식이다.Here,

V _h is the injection voltage,? _C is the frequency of the injection voltage,

Represents the inductance matrix of the target motor. Equation (4) is established every time the phase current passes the zero point.

For example, every time the A-phase current passes the zero point, the high-frequency voltage matrix in the stationary coordinate system can be expressed as Equation (6) using Equation (4).

In the above Equation 6 s is a Laplace operator, θ _r is the rotor angle, _S L and ΔL _S are each an average inductance and a difference inductance in the still coordinate system.

2. Off-line test in stationary coordinate system

Accurate estimation of the distortion coefficient [alpha], as revealed in modeling in the above stationary coordinate system, is key to zero current clamping compensation. However, when no load is applied, it is very difficult to find a distortion coefficient since distortion is hardly generated in the zero point of the current as shown in FIG.

For this, as shown in FIG. 7, when no load is applied, a position error (? / 6 in the present invention) is forcedly added to the estimated angle to move the zero point of the phase current and the distribution of the high frequency current. At this time, the estimated angle and the actual angle are shown as the third and fourth waveforms in FIG. 7, and the actual angle is identical to the phase current angle, so that the present invention is advantageous in that the actual angle can be known without an encoder (position sensor).

은 회전자좌표계에서 추정된 q축 고주파 전류 를 나타낸다. 그리고, 도 7에서 θ_r은 회전자(rotor)의 실제각을 나타내고,

은 회전자의 추정각을 나타낸다.6, i _as represents a-phase current in the stationary coordinate system, i _dh ^s represents d-axis high-frequency current in the stationary coordinate system,

Represents the q-axis high-frequency current estimated in the rotor coordinate system. In Fig. 7, &thetas; _r represents the actual angle of the rotor,

Represents the estimated angle of the rotor.

For the off-line test, the inductance Ls and the differential inductance ΔLs in the stationary coordinate system must first be found on the stationary coordinate system. For this purpose, the injection voltage command is expressed as shown in Equation (7).

Since no distortion occurs at the peak portion of the phase current, the high-frequency current at this portion is expressed by Equation (8).

Here, in the case of θ _r = 0 ° (peak region), the dq axis high-frequency current in the stationary coordinate system in Equation (8) is obtained by Equations (9) and (10), respectively.

In Equations (9) and (10), the maximum value occurs at ω _c t = 0 °, in which case Equations (9) and (10) are changed as shown in Equations (11) and (12).

When the equations (11) and (12) are combined, the two inductances can be obtained as shown in equations (13) and (14).

The denominator of Equation (5) is expressed by Equation (15).

Hence, the high-frequency current is rewritten in the stationary coordinate system in Equation (4) as shown in Equations (16) and (17).

Then, the d-axis high-frequency current of Equation (16) is measured at? _R = 90 占 (zero point).

The maximum value is ω _c t = 0 < / RTI > so that Equation (18) becomes Equation (19).

From Equation (19), the distortion coefficient is uniquely determined as in Equation (20).

3. Real-time compensation method

From Equation (3), the compensation voltage should be determined according to the following Equation (21).

8A is a block diagram illustrating a compensation apparatus for realizing the compensation method of the present invention, wherein each controller is a bang-bang type estimator or a PI estimator or a tracking observer, (tracking observer) can be used.

)를 대역차단필터(12)를 통과시킨 후 좌표변환기(14)를 통과시킨 전류(i_dq ^r)를 감산기(16)에서 감산하고, 감산된 전류지령은 전류제어기(18)로 입력되어 설정된 전류로 제어되도록 전압지령(V_dq ^r*)이 출력되고, 출력되는 전압지령령(V_dq ^r*)에 고주파전류(V_dh ^r*)를 가산기(22)를 통해서 가산시킨 후 이를 좌표변환기(24)를 통해서 정지좌표계로 변환시킨 후 보상기(30)로부터 출력되는 보상전압(

)을 가산기(42)에서 가산하고, 가산된 접압지령(

)은 PWM인버 터(44)를 통해서 전동기(46)로 출력되도록 한다.In FIG. 8A, the zero-current clamping compensation apparatus compares the input basic current command (i _dq ^{r *} ) with the electric current of the motor in the stationary coordinate system

(I _dq ^r ) that has passed through the band-pass filter 12 and then passed through the coordinate converter 14 is subtracted by the subtracter 16, and the subtracted current command is inputted to the current controller 18, a voltage control value to be controlled (V _dq ^{r *)} is output, the output command voltage command (V _dq ^{r *)} to the high-frequency current (V _dh ^{r *)} and then was added via the adder 22, this coordinate converter (24 ), And then outputs the compensation voltage ("

) Is added by the adder 42, and the added contact command (

Is output to the electric motor 46 through the PWM inverter 44. [

)은 도 8b에 나타내는 바와 같이 오프라인 시험을 통해서 고주파 전류 데이터를 수집하여 d-q축 인덕턴스를 구하고, 이를 바탕으로 영전류 클램핑에 의한 왜곡 계수(α)를 구하여, 구해진 왜곡 계수(α)에 실제 측정된 전동기(46)의 고주파 전류(

)를 대역통과필터(52)를 통과시켜 곱한 값에 의하여 결정되는 주입된 고주파 전압에 대한 보상전압(

)과 유효전동기의 출력 전류를 대역차단필터(12)를 통과시킨 전류값(

)에 의하여 결정되는 기본파 전압에 대한 보상전압을 가산기(32)를 통하여 가산한 값이 된다. 최종적으로 이는 제한기(34)를 통해서 PWM인버터의 스위칭 소자에 의한 최대 왜곡 전압으로 제한되어 출력되는 (

) 특징을 갖는다.On the other hand, in the above configuration, the compensation voltage (

), As shown in FIG. 8B, the high frequency current data is collected through an off-line test to obtain a dq axis inductance, and a distortion coefficient (?) By zero current clamping is obtained on the basis of the inductance, The high-frequency current (

) To the band-pass filter (52) and a compensation voltage for the injected high-frequency voltage determined by the value

) And the output current of the effective electric motor through the band cut filter 12

) Of the fundamental wave voltage, which is determined by the adder (32). Finally, this is limited to the maximum distortion voltage by the switching element of the PWM inverter through the limiter 34

).

4. Test results

The method of the present invention was conducted on a 600-W permanent magnet synchronous motor. The PWM inverter has 10kHz switching and the dead time is 2μs. The magnitude and frequency of the injection voltage was given as 10V-850Hz.

First, the inductance is obtained by measuring the high frequency current in the off-line test. At this time, the motor speed is 30r / min and the d-axis phase current is 2A. Then, the distortion coefficient is obtained using Equation (18).

9 is a no-load experiment waveform for the case where the zero current clamping effect is not compensated. The A-phase current from the top, the q-axis high-frequency current in the estimated synchronous coordinate system, the actual position, and the estimator input signal sin. Although the magnitude of the high-frequency current is almost zero at the zero point of the phase current, this experiment still shows some distortion. Of course, when the load is applied, larger distortion occurs.

In Fig. 10, experiments were carried out under the same conditions under which the experiment was compensated. The compensation voltage is added to the final output voltage as shown in FIG. Compared with FIG. 9, it can be seen that the compensation effect is clearly exhibited.

Fig. 11 shows waveforms before compensation when a load is applied. 12 is a waveform when compensation is performed. By comparing the two waveforms, we can see that the ripple or distortion after float is remarkably reduced. In both cases, the load was applied in about two seconds.

13 shows the compensation voltage and the phase current. When the phase current deviates from the zero-current clamping region, it maintains a constant value. In the region where the phase current passes through zero, the waveform having the same frequency and phase as the high- .

According to the present invention configured as described above, stability and performance of the sensorless system can be improved by reducing the estimated angle or the estimated speed ripple for sensorless by compensating the zero current clamping effect in real time after simple offline test without a separate device There is an effect that can be made.

Claims (2)

The compensator 30 collects the high frequency current data from the off-line test for the AC motor without position and velocity sensors in the stationary coordinate system to calculate the dq axis average inductance L _S and the differential inductance L _S ,

,

, And based on this, the distortion coefficient (?) By the zero current clamping is calculated by using the equation

Frequency current of the motor 46 actually measured at the obtained distortion coefficient?

) To the band-pass filter (52) and a compensation voltage for the injected high-frequency voltage determined by the value

), A current value obtained by passing the output current of the motor through the band cut filter 12 (

), Which is a value obtained by adding the compensation voltage for the fundamental wave voltage determined by the compensation voltage

), And the output of the compensation voltage is limited to the maximum distortion voltage by the switching element of the inverter through the limiter 34, Adding the pulsating high frequency current (V _dh ^{r *} ) to the voltage command (V _dq ^{r *} ) output from the current controller (18) in the synchronous coordinate system through the adder (22) The voltage command that has passed through the adder 22 is converted into a stationary coordinate system through the coordinate transformer 24 and then a compensation voltage limited by the maximum distortion voltage output from the compensator 30 by the switching element of the inverter

Added by the adder 42 and output to the electric motor 46 through the inverter 44. In this case, And ω _c is the frequency of the injection voltage in the, V _h is the voltage injected, i ^s _qh is a q-axis high frequency current rotating coordinates, i ^s _dh is a high-frequency current is still coordinate system d axis,

Wherein the zero-current clamping compensation method of the AC motor has no position and velocity sensor indicating the estimated angle of the rotor. The position and velocity sensor according to claim 1, characterized in that the position error is forcibly added to the estimated angle of the motor rotor under the no-load condition before the inductance is obtained in the compensator (30), and the zero point of the phase current and the distribution of the high- Zero current clamping compensation method for an alternating current motor without a current limiter.

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