Asymmetric Space Vector Pulse Width Modulation for the Phase Current Reconstruction in Three-Phase Inverters

The DC bus single current sensor technique (SCST) has attracted widespread attention in the motor drive system because it reduces cost and volume. However, when DC bus SCST is used with the conventional space vector pulse width modulation (SVPWM) strategy, the current reconstruction of the unobservable area in the sector boundary and low modulation area will degrade the accuracy of sampling data. This paper proposes a novel asymmetric SVPWM (ASVPWM) method for three-phase two-level voltage source inverters, characterized by low computational overhead, accurate current reconstruction, and a constant sampling frequency. The ASVPWM is applied to achieve complete current reconstruction by randomly shifting the switching state pulses of the inverter in the unobservable area. Moreover, the conventional SVPWM is utilized for the proposed method to reduce the current harmonic content in the observable area. The effectiveness of the ASVPWM method was verified by experimental results obtained from a permanent-magnet synchronous motor. It has been demonstrated that by using ASVPWM, the three-phase current signals can be reconstructed while providing low current harmonic distortion (4.60%).