SEPIC DC/DC converter control by observed-state feedback

DC-DC converters are used in photovoltaic inverters to step-up the solar plant voltage to the DC bus specification value. The single-ended primary inductor converter (SEPIC) is a DC-DC converter, and its modeling is performed in this work using the averaged switch and the small signals approach. On the SEPIC, there are four energy storage elements which hinder its control design. In this paper, the state feedback technique is applied to design the SEPIC controller without order reduction. An advantage of this approach is that no model order reduction is required, but the knowledge of inductors currents and capacitors voltages are necessary, which may be not feasible in practical applications. Therefore, a state observer provides estimated values of the states used in the feedback control. Output feedback with integral action is applied to reduce the steady-state errors. Tests were carried out to track the output signal reference by applying step and ramp variations and also load disturbances. The simulation results highlight that through the application of the observed-state feedback controller was possible to obtain the desired dynamics within the established control goals.