AC Voltage and Current Sensorless Control Method for Three-Phase PWM Converter

Abstract

We present a three-phase PWM converter without ac voltage and ac current sensors. The phase angle used in the control system is adjusted by using a PLL controller without sensing ac voltage. To prevent over-current at startup, the initial phase angle of the source voltage is estimated from the shunt current using a novel strategy. Furthermore, the phase currents can be reconstructed from the shunt current without any modification of PWM pattern. To reduce the effect of current ripple, the shunt current is sampled twice for every phase in one PWM period and the sample timings are carefully adjusted. All of the proposed control schemes can be implemented using a single chip microprocessor (SH7046, Renesas Tech.). Simulation and experimental results with a 5-kW prototype confirmed that the schemes worked well.