Zero-sequence Current Suppressing Strategy for Dual Three-phase Permanent Magnet Synchronous Machines Connected with Single Neutral Point

Abstract

Dual three-phase permanent-magnet synchronous machines (DTP-PMSM) connected with a single neutral point provide a loop for zero-sequence current (ZSC). This paper proposes a novel space vector pulse width modulation (SVPWM) strategy to suppress the ZSC. Five vectors are selected as basic voltage vectors in one switching period. The fundamental and harmonic planes and the zero-sequence plane are taken into consideration to synthesis the reference voltage vector. To suppress the ZSC, a non-zero zero-sequence voltage (ZSV) is generated to compensate the third harmonic back-EMF. Rather than triangular carrier modulation, the sawtooth carrier modulation strategy is used to generate asymmetric PWM signals. The modulation range is investigated to explore the variation of modulation range caused by considering the zero-sequence plane. With the proposed method, the ZSC can be considerably reduced. The simulated and experimental results are presented to validate the effectiveness of the proposed modulation strategy.

Keywords

• zero-sequence current
• a single neutral point
• dual three-phase
• permanent-magnet synchronous machine
• third harmonic back-emf