Safety-Constrained Stagewise Optimization of Droop Control Parameters for Isolated Microgrids

To improve the primary droop control performance under variable load conditions in the isolated microgrid, this paper proposes a safety-constrained stagewise optimization method for P/f and Q/V droop control parameters. In the first stage, these parameters are determined through look-ahead distributionally robust optimization so that they are robust against general uncertain and variable load conditions. To avoid the excessive pursuit of robustness at the expense of economic benefits, the second and third stages are responsible for addressing accidental extreme disturbances that lead to unacceptable droop control deviations, where the parameters determined in the first stage are modified adaptively according to the contemporary system state. Specifically, the second and third stages are pertinent to Q/V and P/f droop control parameter adaptations, respectively, considering different requirements for voltage and frequency regulation. This design also contributes to simplifying the parameter modification problem. A measurement-driven decentralized method is utilized to quickly accomplish the two adaptation stages, yielding a quick remedy of the frequency and voltage violations. Case studies show that our proposed method can maintain microgrid security and is robust to uncertain load variations without sacrificing economic benefits.