A Novel Phase Current Reconstruction Method Using a Single DC-Link Current Sensor

Instantaneous phase currents are required for successful operation of three-phase current controllers. The technique for reconstructing motor phase currents using information from a single current sensor in the dc-link of an inverter has been applied to reduce the cost, weight and volume of system. However, the duration of an active switching state may be so short that the dc-link current cannot be measured reliably. This paper presents an improved PWM modulation strategy named switching state axial translation (SSAT) to overcome this problem. The new SSAT method modifies the PWM voltage vectors by moving the switching state waveforms along the axis when the phase currents cannot be measured. A combination of analytical and experimental results shows that this method offers an attractive phase current reconstruction performance.