Decentralized Robust Control Design for Direct Current Mirogrids with Structural Constraints

This paper focuses on improving system robustness and enhancing transient performance in a DC (Direct Current) microgrid with constant power loads (CPLs). It is well known that CPLs have a negative impedance effect that may cause instability and excessive oscillations. Most of the existing research on decentralized control for CPLs tends to be ad hoc and offers limited control flexibility. In contrast to many previous approaches, we propose a systematic method for decentralized control design, which allows for a controller with greater control freedom. The problem is framed as a robust control design challenge with structural constraints, ensuring that the cost function decreases while also satisfying the necessary constraints. The proposed method is validated in a one-bus DC microgrid test case. Specifically, the system supports larger CPLs (up to 20kW) without voltage collapse and exhibits a reduced voltage dip and faster recovery time during sudden load changes. Simulation results demonstrate that the designed controller significantly improves voltage stability and transient performance.