Elimination Strategy of Position Error for High Power Permanent Magnet Motor Drive

Permanent magnet synchronous machine (PMSM) becomes more and more popular in railway traction systems. Due to non-ideal factors of position sensor, obtained rotor position exists nonlinear error, which makes a bad influence to control performance of PMSM. In this paper, the effect of position error on current harmonics from the perspective of pulse width modulation is studied by detailed mathematical derivations. Severe dc offset and current harmonics problems caused by position error brings torque ripples and extra switching losses, which is unacceptable in railway traction systems. To solve the problem, an algorithm of reconstructing rotor position considering the characteristics of high power motor is proposed, which is consisted of low-pass filter (LPF) and phase-locked loop (PLL). The reconstruction is implemented on DSP chip, which is simple and reliable. The current harmonics problem can be well improved using the proposed scheme. Simulations have been carried out to verify the effectiveness of proposed rotor position reconstruction strategy.