Research And Design On Pmsm Dtc System

The attention has been paid to PMSM widely because of its high performance, high torque to inertia ratio and high energy density. In recent years, the rapid development of permanent magnetic material makes it possible for the applications of permanent magnet motor have been developing quickly. After VC, DTC is another speed control technology of AC drive with high performance. It is received increasing attentions, because it is provided with advantages of direct torque control, rapid dynamic response, simple arithmetic, etc. DTC has been applied on asynchronous motor successfully, however, the application on PMSM is proposed in recent years. The control strategy needs to be further researched to improve the control performance on PMSM.In this paper, mathematical models in different coordinate systems are presented. On the basis of the models, the principle of DTC on PMSM is analyzed, and the influence of space voltage vectors on torque and flux is analyzed in particular. Bang-Bang control strategy is adopted to acquire fast torque response, but ripples of the flux and torque are obvious, which is because that the conventional DTC system has only eight optional space voltage vectors, and stator windings acquire the action by only one space voltage vector during a control period. SVPWM is bought into DTC system, and continuous adjustment of space voltage vector is realized. The obvious ripples in the conventional DTC system are reduced effectively.Models of conventional DTC and DTC based on SVPWM are respectively built in MATLAB/Simulink. A variety of motor running states are simulated, which verifies the validity and the correctness of the control strategy.Finally, hardware circuits are designed with the ST7FMC which is a dedicated motor control chip of ST Company, mainly including main circuit, phase current and bus voltage sampling circuit, speed signal detection circuit, keyboard and display circuit, protection circuit and switching power supply circuit. Software design introduces the function and the overall structure of the control system, mainly including main programs, keyboard and display programs and interrupt handling programs.