Research Of Performance At Low Speed In DTC Of Permanent Magnet Synchronous Motor

DTC(direct torque control) has simple structure,direct control means,and high stable/transient performance.DTC are focused on asynchronous motors, until recent years some researches begin to study the application of DTC into Permanent Magnet Synchronous Motor. For the research is still in its primary stage,many questions need to be solved.One of central problems is that how to improve the proformance at low speed in direct torque control.The paper is based on the trait of Permanent Magnet Synchronous Motor,and studies the cause of torque and speed ripple of direct torque control system,when Permanent Magnet Synchronous Motor runs at low speed.The paper proposes amended methods.The nuclear work and innovation of the paper is as follows:1. Based on the physical model of Permanent Magnet Synchronous Motor,the paper establishes the simulation model of direct torque control,and studies the effect of zero-voltage vector to the torque and magnetic flux linkage.2. Based on the deadtime model,the paper studies the effect of the deadtime effect to the torque and magnetic flux linkage. The conclusion of theory verifies that the deadtime effect can reduce the torque and impacts on the performance of the system.The paper proposes voltage compensation formula of deadtime effect. Simulation results indicate that the formula is good.3. Based on PI estimator model for the stator resistance,the paper analyses the changing value of stator resistance to the effect of the torque and speed,and proposes adaptive coefficient amended method of fuzzy control theory to improve the veracity of the stator resistance estimator. Simulation results are presented to verify that amended method can improve the dynamic performance of system.4. Based on the whole framework of direct torque control system of Permanent Magnet Synchronous Motor,the paper proposes the hardware and software methods of direct torque control system with TMS320F2812 as controller,and discusses that DSP design methods of direct torque controller.