Switching-state phase shift method for three-phase-current reconstruction with a single dc-link current sensor

Instead of directly sampling the phase currents, a technique that adopts a single current sensor in the dc link to reconstruct three-phase currents has arisen. Through this approach, the cost of servo systems can be reduced and the reliability can be improved. However, the duration of an effective vector may be so short that the phase current cannot be measured reliably by the conventional space-vector pulsewidth modulation (PWM) algorithm. In this paper, a new phase-current reconstruction method, switching-state phase shift (SSPS), is proposed based on the PWM pattern modification. The modification is performed by applying phase shifts to the switching-state waveforms of the inverter. The algorithm can realize high-quality reconstruction to the phase current with less impacts on the output current ripples and switching losses. Moreover, it can maximize the linear-modulation region by saturation handling. Measurements on the permanent-magnet synchronous motor servo drives show that the SSPS can offer an attractive performance during both steady-state and dynamic operations in the phase-current reconstruction and regulation.