Reseach On Dead-beat Direct Torque Control Of PMSM System

Permanent magnetic synchronous machine (PMSM), possessing the advantages such as small size, high power density and efficiency, and fast response, has been widely applied in the ac speed adjustment system. The research on the control of PMSM has significant economical and practical benefits. The essential of the AC speed adjustment system is to control the machine’s torque. The direct torque control (DTC) considers the inverter and the machine as the integrated one to directly control the machine torque using the voltage vector technology. PMSM DTC was developed in1997and was well suited for handling the nonlinear dynamics issue brought by the coupling between torque and flux linkages in a motor. Without using speed sensor and rotor parameters, it has many advantages, such as a simple control, fast dynamic response and strong robustness. This paper addressed several key issues associated with PMSM based DTC through the simulation and experimental verification.Firstly, the research background as well as the current research status of the control strategy for PMSM is introduced. It’s shown that DTC for PMSM is featured as high-performance. Three important research topics, i.e., the ripple suppression, the sensorless technology and the stator flux observation are covered in this paper.Secondly, the configuration of PMSM is depicted and the mathematical models under different coordinate frame are given. Based on the discretizing equations of PMSM, a dead-beat direct torque and flux control (DB-DTFC) is proposed and is intended to control the torque and the flux linkage directly under the constant switching frequency. The detailed deduction has been approached for this method. It enables the torque and flux linkage components following the reference one and shows good transient and steady-state responses. Compared to the conventional DTC, DB-DTFC presents favorable control performance, which has been confirmed by the simulation and experiment. Moreover, the robustness of the method is analyzed as the parameters vary.The third part explores the sliding-mode control theory, based on which the sliding mode observer is established to achieve the operation of PMSM without sensor. Aiming to the problems related with the cumbersome calculation, the speed observer is designed according to the active flux concept. Simulation and experimental results have proven that the observer is suitable for a wide speed rang and is simple to be realized.In part four, due to the fact that the performance of the flux observer is easily affected by the machine parameters, the stator flux observer is developed. It could estimate the stator flux precisely and is less sensitive to the induction variation. In addition, it could realize the on-line parameter identification of the resistor, and mitigate the impact of variable resistor on the flux observation. Simulation and experiment have been carried out to verify the observer proposed.Finally, the detailed design of the hardware and software of the PMSM control system is illustrated. The important hardware parts,such as sampling circuit, signal adjust circuit, drive circuit, are described in details, and program flow chart is shown in this part.