Single current sensor operation with fixed sampling points using a common-mode voltage reduction PWM technique

A method is proposed for reconstructing AC currents with a single DC side current sensor in three-phase AC motor drive system. The method is based on a common-mode voltage (CMV) reduction PWM technique called LuPWM, which eliminates most of the invalid regions for current reconstruction both around zero voltage and near active-vectors. It realizes fixed-point sampling which is favorable for implementation. And the current prediction is also easier than traditional methods. Furthermore, it remains the good property of LuPWM that the peak-to-peak value of CMV, which leads to the premature deterioration of motor bearings, is reduced to 1/3 of the traditional three-phase PWM method in each sector. The additional computation load is minimal, and it can be widely applied. Experimental results are presented to fully support the above-mentioned claims.