State Observer-based Current Sensor-less Hysteresis Current Control for Stand-alone Inverters

This paper proposes a current sensor-less hysteresis current control for stand-alone inverter using state observer. Comparing with the popular sine-triangle Pulse Width Modulation (PWM), hysteresis current control has many advantages in a simple implementation, fast response, and robustness. In this hysteresis current control technique, current sensors play an important role. However, the use of current sensors has drawbacks in cost and accuracy. In this paper, a state observer is designed to estimate the current values using mathematical state equations modelling the inverter circuit. The digital controller then uses the estimated current values to implement the adaptive hysteresis current control and calculate the control signal for the switch devices. The simulation results show that the proposed observer-based hysteresis controller give good performance for both cases of AC and DC output reference voltages.