Expanding Limit of Minimum Sampling Time Using Auxiliary Vectors for PMSM Drives with Single DC-Link Current Sensor

Phase current reconstruction (PCR) strategy can improve the fault tolerance of permanent magnet synchronous motor (PMSM) drives. The PCR precision is largely affected by the unmeasurable zones and time-sharing sampling errors. The upper limit (Tlimit) of PCR allowable range can reflect the requirement of different PCR methods for the minimum sampling time (Tmin). With a longer Tlimit, there is sufficient time for sampling, even if Tlimit is halved due to the symmetrical waveform. Therefore, the extension of Tlimit is the key to eliminate the unmeasurable zones and time-sharing sampling errors. In this paper, a method to increase Tlimit is proposed, which introduces the suitable auxiliary vectors (AVs) in different regions to extend the duration time of the sampling vectors. With the help of a longer Tlimit (12.5%Ts), its possible to eliminate all the unmeasurable zones and time-sharing sampling errors, relieve the pressure on the hardware of current loop, improve the sampling accuracy, and facilitate the reliable operation of the drive. Besides, the switching action times of IGBTs can be reduced by about one-third in the high modulation area. The proposed method is finally proved to accurately reconstruct the phase currents by the experimental results on the PMSM prototype.