Estimation of Phase Currents from a DC-Link Current Sensor Using Space Vector PWM Method

The single-current sensor technique obtaining three phase currents from only a DC-link current sensor has been applied to reduce the cost and increase the reliability for various voltage-fed PWM inverters; however, in this technique there are some practical problems, such as unreliable detection of phase currents andphase shift. A new method that overcomes these problems by employing the estimation scheme with identified system parameters is proposed. The Space Vector PWM (SVPWM) strategy is modified to generate the switching pattern adequate for the proposed method. To obtain a good detection in spite of parameter uncertainties, system parameters used in the estimation method are identified using a recursive least square method (RLSM). Experimental results show that the proposed scheme not only provides a very good detection method for three phase currents without current sensors, but also identifies system parameters very well. This proposed method is very simple, has a small detection error, and gives the information on system parameters.