H∞ structured design of a cascaded voltage/current controller for electronically interfaced distributed energy resources

In this paper a new controller design method for inverter-based distributed energy resources in standalone microgrids is proposed. The objective of the design is to exploit the flexibility and fast dynamics of the voltage inverter. The proposed control method is composed of droop, voltage and current controllers. The droop controller is based on V-I droop characteristics, and exhibits significantly faster dynamics compared to the conventional droop method. The voltage and current controllers utilize the structured H∞ PI regulation strategy to track the reference voltage and current. The PI controller parameters are tuned using Hinfstruct optimization function from the MATLAB® Robust Control Toolbox. The performance of the closed-loop system is analyzed to illustrate the capabilities of the new technique. Simulation results are presented to prove validity and verify the efficiency of the proposed control.