Robust digital controller for fourth-order bidirectional charger/discharger

A 4^th order bidirectional converter for charger/discharger (BCDR) applications is proposed and then robust controller is designed. The advantages and limitations of the proposed converter are compared with the conventional charger/dischargers. Discrete-time modeling and the expressions for small-signal transfer functions of the proposed BCDR are derived using statespace analysis. Based on the discrete-time models controllers for both the charging and discharging modes are designed. Then the robustness of the designed controllers is verified and necessary and sufficient conditions on nominal performance, robust stability and the robust performance conditions are obtained. Robustness of the designed controllers is verified through time-domain simulations and then compared with experimental results.