A Modified Newton-Raphson Method for Hybrid AC/DC Microgrids Power Flow Analysis

A hybrid ac/dc microgrid combines advantages of both subgrids. This paper proposes a sequence component based power flow algorithm for a hybrid ac/dc microgrid. In the modeling section, sequence component models of the system components are established considering their unbalanced features. Droop control is applied to distributed generation units to maintain frequency and voltage of an islanded microgrid. In the algorithm section, our proposed approach decomposes the power flow problem into two subproblems which are easy to solve sequentially. First, ac subgrid power flow is solved through a modified Newton-Raphson method. Next, dc subgrid power flow is calculated considering the interlinking converter. The process repeats until the mismatches are smaller than the thresholds of accuracy. Lastly, the result is transformed back to phase coordinates for the final power flow result. The accuracy of the proposed approach is validated by comparing its results with MATLAB/Simulink, and advantage is confirmed compared with a practical equivalencing approach. Finally, the influence of system loading is studied.