Adaptive suppression method for DC-link voltage offset in three-phase four-switch inverter-fed PMSM drives

The DC-link voltage offset in three-phase four-switch (TPFS) inverter-fed permanent magnet synchronous motor (PMSM) drives deteriorates the linear modulation range severely, restricting the performance and adjustable speed range of the PMSM. An adaptive control method is proposed in this Letter to suppress the DC-link voltage offset in TPFS inverter-fed PMSM drives. By investigating the effects of four basic voltage vectors on the voltage offset, the proper compensating vectors, whose duration times are obtained by the closed-loop control, are added in each control period. Moreover, an adaptive notch filter is proposed to extract the offset component, providing excellent dynamic and steady performances even at extremely low rotor speed. Experimental results demonstrate the superiority of the proposed adaptive suppression method compared with previous methods.