Method for estimating stator flux of motor in vector converter

Abstract

The invention discloses a method for estimating a stator flux of a motor in a vector converter, and relates to the method for calculating the stator flux of the motor. The method comprises the following steps of: calculating a back electromotive force of a rotor according to the stator current and stator voltage of the motor; synthesizing a given value of a rotor flux of the motor and the position information of the rotor flux to form a given value of a rotor flux vector; and calculating a pre-estimated value of the rotor flux vector under a two-phase stationary coordinate system (alpha-beta) by adopting a closed loop integration scheme, and calculating a pre-estimated value of a stator flux vector according to relationships between the stator flux vector and rotor flux vector of the motor and the pre-estimated value of the rotor flux vector. The method is applied to a relatively wider speed regulation range; a system is ensured to have relatively higher dynamic performance at low speed, and the influence of an incorrect initial flux value can be eliminated; and the rotating speed of the rotor of the motor can be calculated according to the calculated stator flux and the calculated rotor flux without any speed sensor, so the structure of the motor is simplified and cost is decreased.

Description

technical field [0001] The invention relates to a method for calculating the flux linkage of a motor stator, in detail it is a method for estimating the flux linkage of a motor stator in a vector frequency converter based on a DTC algorithm. Background technique [0002] The direct torque control (DTC) technology of asynchronous motors has attracted more and more attention of researchers because of its simple structure, quick response, and little dependence on motor parameters, and it has begun to be applied to frequency converters. In the DTC algorithm, the information of the motor stator flux linkage needs to be known. Usually, the easiest way to calculate the stator flux linkage is to integrate the induced electromotive force, and the pure integration link usually has the problem of DC drift and initial value, with large errors and low accuracy. , The torque ripple of the motor running at low speed. [0003] Solving this problem usually starts from two aspects: one metho...

AI Technical Summary

Problems solved by technology

In the DTC algorithm, the information of the motor stator flux linkage needs to be known. Usually, the easiest way to calculate the stator flux linkage is to integrate the induced electromotive force, and the pure integration link usually has the problem of DC drift and initial value, with large errors and low accuracy. , the torque ripple of the motor running at low speed

[0003] Solving this problem usually starts from two aspects: one method is to use filters to improve the pure integral link, a very natural idea is to add a high-pass filter after the pure integral link, and they are equivalent to a low-pass filter , scholars Yongchang Zhang and Jianguo Zhu in literature 1. "Direct Torque Control of Permanent Magnet Synchronous Motor With Reduced Torque Ripple and Commutation Frequency" (IEEE TRANSACTIONS ON POWER ELECTRONICS, VOL.26, NO.1, JANUARY 2011, pp:235– 248) studied such a method, and studied the method of compensating the magnitude and phase errors caused by the introduction of the high-pass filter. However, although the compensation method for the low-pass filter is relatively simple in calculation, the dynamic performance of the system is low

Another method is to use the current model to calculate the flux linkage of the motor. The current model in the static coordinate system has higher calculation accuracy when the motor is running at low speed, and it is not applicable when the motor is running at medium and high speeds. It is usually transformed into a rotating coordinate system. And it is necessary to obtain the motor rotor parameters and rotor speed information, which increases the amount of calculation. In addition, some researchers have proposed a method to calculate the motor flux linkage from the control theory, such as literature 2. "Novel Direct Torque Control Based on Space Vector Modulation With Adaptive Stator Flux Observer for Induction Motors" (IEEE Transactions on Magnetics VOL. 46, NO.8 , AUGUST 2010 , pp: 3133-3136), Document 3. "On the stator flux linkage estimation of an PMSM with extended kalman filters" ( 5th IET International Conference on Power Electronics, Machines and Drives (PEMD 2010) 2010 ,pp:1–6), Document 4. "Direct torque control of permanent magnet synchronous machines using stator flux full order state observer" (2004 IEEE International Symposium on Industrial Electronics, 2004, VOL 2, pp:913-916) used adaptive flux linkage observer, extended Kalman filter, flux linkage full-order observer, etc., but these methods are more complicated, and the DTC scheme is simple Sexually contradictory

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