Current Estimation and Sensorless Current Control of Cuk DC-DC Converter using Extended Kalman Filter

Current sensorless control methods, which eliminate the current sensor by using a current observer, can bring cost effective and reliable solutions to digital control of DC-DC converters. Since any inaccuracy in the model of the converter can deviate the observed current from the actual inductor current and consequently result in the steady state error of the output voltage, an accurate model is derived, incorporating the parasitic resistances of the switch, inductors and capacitors and the forward voltage of the diode. According to this model, Cuk converter is a nonlinear system. Therefore an extended Kalman filter (EKF) is used for inductor current estimation and output voltage filtering. In this paper, an accurate current observer is presented for Cuk converters by considering the influential parasitic parameters in the converter model. The estimated current from the observer, is used for current control of the converter. Simulation results of the system show the accuracy and favorable efficiency of the observer and controller.