Robust Nonlinear State Feedback Control of Bidirectional Interlink Power Converters in Grid-Connected Hybrid Microgrids

In this paper, a new scheme based on state feedback control concept is presented for robust control of bidirectional interlink power converters (BILPCs) in hybrid microgrids (HMGs). The studied grid-connected HMG contains one dc and one ac microgrid, interconnected by BILPCs. To consider uncertainties, the nonlinear uncertain model of the BILPC is derived and linearized based on Lie derivative concept. As a new point of view for dynamic modeling of BILPC, it is indicated that each nonlinear uncertain BILPC model can be represented by two decoupled subsystems. Then, a virtual robust state feedback controller is designed to independently control each of these subsystems with disturbance rejection capability. The gains of the state feedback controllers are obtained using Ackerman pole placement method. To approximate the unknown inputs/unmodeled dynamics, which are needed in the design process of the state feedback controllers, a high-gain proportional-integral (PI) observer is designed. The high gains of this PI observer are determined using linear quadratic regulation method. Simulation results and comparative studies support the efficacy of the proposed control approach.