A Method for Estimating Stator Flux Linkage of Permanent Magnet Synchronous Motor Based on Direct Torque Control

Abstract

The invention discloses a closed loop flux linkage estimation method which is applied to a direct torque control system of a permanent magnet synchronous motor. Calculation is conducted through voltage signals and current signals measured in a real-time sampling mode according to a voltage method flux linkage calculation formula so that initial estimation flux linkage can be obtained, then, the initial estimation flux linkage and target control flux linkage are used as input quantity, a PI regulator is used for conducting dynamic state closed loop correction, and accordingly the target control flux linkage can be tracked ultimately. The given control flux linage controlled by direct torque is used as the amplitude of the target control flux linkage in a flux linkage estimator, the rotor position angle is obtained through a position sensor, and the angle information is dynamically compensated to be used as the angle information of the target control flux linkage. Through closed loop regulation to the voltage method flux linkage estimator, flux linkage calculation deviation caused by direct current bias and initial integration in an integration element can be effectively eliminated, the real flux linkage can be accurately estimated, and good rapidity and robustness are achieved in the actual direct torque control system.

Description

technical field [0001] The invention relates to a method for estimating flux linkage of a permanent magnet synchronous motor, in particular to a method for estimating stator flux linkage of a permanent magnet synchronous motor based on direct torque control. Background technique [0002] In the field of motor dynamic control, direct torque control technology is more and more applied to permanent magnet synchronous motors, asynchronous machines and other new motors because of its fast and accurate control performance. In direct torque dynamic control, the two direct control objects are torque and flux linkage, both of which are calculated from changes in voltage, current, position information, and motor parameters, because torque is determined by flux linkage and other parameters Therefore, the calculation of the two control objects is essentially the accurate calculation of the flux linkage of the motor. [0003] Flux linkage calculation methods can generally be divided int...

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Problems solved by technology

The theoretical model of the voltage method is simple, but in practical applications, there are some problems, such as the influence of the stator resistance change at low speed, the initial value of the integral, and the DC bias in the sampling signal.

The current calculation method also has shortcomings. The current method relies more on the motor parameters, and during the operation of the motor, with the change of temperature and speed, the motor parameters will also change to a certain extent. In addition, it is affected by the time constant of the rotor at high speed, resulting in Current method flux calculation is not as accurate as voltage method

According to the characteristics of the voltage method and the current method, the calculation methods of the low-speed current method and the high-speed voltage method can be used, and the conversion between the two can be realized through a filter, but this method is more complicated and can be performed within the working area of ​​the two methods. , on the premise of realizing accurate calculation

Many scholars have made many improvement methods according to the characteristics of voltage method and current method, such as adding low-pass filter method, high-low pass filter matching method, closed-loop correction method, Kalman filter method, etc., these methods have improved to a certain extent. The accuracy of the flux linkage estimation is improved, but it also brings some problems. The method of adding a filter can eliminate the initial integral error and attenuate the DC offset, but it will bring a phase amplitude offset. The combination of high and low pass filters can make the low pass On the basis of the filter, the effect of flux linkage estimation is improved to a certain extent, but more parameters are introduced. The closed-loop correction method has a good effect in steady state, but in the actual direct torque control system, the effect of direct torque control in dynamic state It will interact with the calculation effect of the flux linkage. The result of the double influence makes the entire control system easily lose stability. The calculation method of the flux linkage with the filter also has the problem of poor dynamic effect. The Kalman filter alleviates it to a certain extent. The shortcomings of the current method are eliminated, but the dependence on the motor parameters in the calculation of the flux linkage cannot be avoided. For motors with large changes in motor parameters under different working conditions, there will still be large calculation errors. Adding the Kalman filter also requires relatively complex calculation

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