Digital controller for fourth-order bi-directional DC-DC converter

A 4th order charger/ discharger for dc-grid load leveling applications is proposed and then digital controller is designed. Its salient features and limitations are discussed and then compared with the existing charger/discharger topologies. State-space analysis is used to establish discrete-time modeling and other small-signal transfer functions expressions of the proposed bidirectional topology. These models are subsequently used for controllers design, which are capable of ensuring reliable charging and discharging operations. 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. Charging and discharging features of the proposed topology is verified through timedomain simulations and then compared with experimentally measured results.