Power Flow Analysis of Islanded AC Microgrids

This paper presents a methodology for the steady-state analysis, i.e., power flow analysis, of islanded AC microgrids (MGs), operated under the droop control scheme. In the proposed framework, the power flow is computed using conventional power flow methods. For this purpose, a slack bus is considered to be connected to a random node of the examined MG. Subsequently, an iterative procedure is applied to determine the operational conditions, i.e., voltage level, frequency, active and reactive power absorption/injection, of this slack bus as well as of the rest MG nodes. The objective of the proposed iterative procedure is to force active and reactive power, flowing through the slack bus, to zero, emulating this way the islanded operation of the MG. To evaluate the performance of the proposed methodology, time-domain simulations are conducted on a low-voltage MG, using detailed models for all system components. The corresponding results are compared with those derived using the proposed methodology. In all cases, trivial differences are observed, validating the accuracy and the robustness of the proposed approach.