Exploring and modeling on constant speed control strategy of permanent magnet synchronous motor for direct drive system

In the railway system, in order to realize that locomotives can run stably. According to characteristics of traction and brake of locomotives, constant-speed controller on the base of double-hysteresis regulation is designed in this paper. Via smooth transition among traction, constant-speed and brake control, fluctuations of torque, flux and current are avoided during switches between different control methods. Traction characteristics are reappeared by simulation on direct torque control (DTC) of permanent magnet synchronous motor (PMSM) through MatlabSimulink. Simulation results prove that the control system possesses good dynamic and steady performance, which is also useful for the research on the direct drive system in the railway system.