Research On A PI Estimator With Parameters Updated In Direct Torque Control Of Permanent Magnet Synchronous Motor

In 1985, M.Depenbrock proposed the Direct Torque Control (DTC) method of asynchronous motor.DTC is very simple and has high control performance. After the successful application of DTC into servosystem of asynchronous motor, DTC has become one of the pop research point of AC servo systems. Butmost researches of DTC are focused on asynchronous motors and until recent years some researches areimplemented on the application of DTC into PMSM. For the research is still in its primary stage, manyquestions need to be solved. In this paper, the application of DTC into PMSM is discussed first, and thensimulation of PMSM DTC is implemented using MATLAB software. Influence of stator resistance variationon the performance of permanent magnet synchronous motor in direct torque control(DTC) system isanalyzed, followed by a technique for stator resistance estimation using a proportional-integral (PI) estimatorwith parameters updated, and is simulated through MATLAB software. The simulation results demonstratethat this estimator is very effective in tracking the stator resistance, and is robust and has short response time,high accuracy. It is also seen that the compensator based on the PI estimator can overcome the probleminstability caused by a large mismatch between the stator resistance in control algorithm and the actual statorresistance. The foundation on the above method, another similar one is put forward. This scheme mainly usesa PI estimator which is based on the error between the actual torque and the estimated torque. It is seenthrough simulation results that the estimator may minish the influence of the stator resistance change, reducethe ripple of the flux and the torque, and improve the performance of the control system. At the end of thispaper, a DTC scheme based on flux error vector estimation (FEVE-DTC) was proposed to reduce torque andflux ripples. Model results shows that the torque and flux ripples were significantly reduced, currentdistortion is also reduced with a lower sample frequency compared that of basic DTC,So it is of superiorrunning performance.