Robust decentralized control for islanded operation of two radially connected DG systems

A decentralized servomechanism controller for islanded (autonomous) operation of radial connection of two distributed generation (DG) units is proposed in this paper. Each DG unit utilizes a voltage-sourced converter (VSC) for interface to its dedicated load. The DG units and the loads are to operate in the islanded mode of operation. Each DG unit regulates the voltage of its dedicated load in a decentralized manner. In this paper, it is first shown that the radial connection of two DG units in the islanded mode constitutes an interconnected composite system consisting of two subsystems. Moreover, the paper shows that the overall islanded system can be controlled by the local controllers, i.e., there is a solution to the decentralized servomechanism problem for the composite system. The H_∞ robust control method is used to design the voltage controller for each DG unit. Performance of the designed control strategy, based on the simulation case studies in MATLAB/SimPowerSystems, is also presented in this paper.