Three phase current reconstruction method using predictive current in three shunt sensing PWM inverter

When the vector control is performed using PWM three phase inverter in AC motor drive system, three phase current are obtained by measuring voltage between shunt resistors. The PWM inverter obtaining three phase current by shunt resistor is comparatively cheaper than the method that measures three phase current by Current Sensor. And it reduces the size of AC motor drive system. However, the method sensing the phase current using shunt resistor cannot perform the vector control in high motor speed since there is the area that cannot measure three phase current. In this paper, the boundary where phase currents cannot be obtained is defined and the method reconstructing the phase current is proposed by predicting phase current through load modeling in the area which phase current measurement is impossible. The proposed method can restore phase current up to maximum output voltage of SVPWM inverter in linear area and validity of proposed method is proved through simulation.