Closed-loop control of PMSM based on optimal synchronous pulse patterns

Permanent magnet synchronous motor (PMSM) are favored in traction drives of rail vehicles for their high efficiency of operation. Traction inverters always operate at reduced switching frequency to minimize the losses in semiconductor devices. To restrain the motor current harmonics, off-lined calculated optimal synchronous pulse patterns can be used. This paper presents a closed-loop control of permanent magnet synchronous motor traction drives operated with optimal synchronous pulse patterns. The optimization problem was stated based on the minimization of the rms value of the phase current harmonics. And the optimum solutions of the problem were given. Then the relationships between the optimum pulse patterns and their corresponding optimum stator flux linkage trajectory were analyzed. By forcing the stator flux linkage vector to follow this optimum trajectory, a closed-loop vector control of PMSM was proposed. Using the simulation and experimental results, this paper elaborates on the steady-state operating modes for employing various pulse patterns and the transition of different pulse patterns during the dynamic operations. The results validate the proposed control strategy.