Strategy and Implementation of Harmonic-Reduced Synchronous Optimal PWM for High Speed PMSM

High speed permanent magnet synchronous motors (PMSMs) are evolving rapidly. However, the ratio of switching frequency over high speed PMSM operating frequency is relatively low and even as low as 5, which causes serious harmonic problems. Since synchronous optimal pulse width modulation (SOP) has the best harmonic performance, combining SOP with commonly used field-oriented control (FOC) is attractive. In this paper, the SOP strategy for high speed PMSM based on sampling period compensation is proposed, which eliminates the synchronization error between SOP and FOC. Besides, a smooth SOP pulse pattern transition strategy utilizing a common sampled phase is proposed as well. The experimental results using a 380V, 14krpm high speed PMSM demonstrate that the proposed method has low current harmonic distortion, fast dynamic response and smooth transition.