Three-Phase Distribution Power Flow Calculation for Loop-Based Microgrids

Abstract

This paper introduces an efficient method for calculating the three-phase power flow in a loop-based microgrid. The proposed method incorporates the conventional Newton-Raphson (NR) iterative approach in a backward/forward sweep (BFS) algorithm for power distribution network analyses. Conventional compensation-based approaches are commonly used to account for loop breakpoints (LBPs) and PV nodes. However, the efficiency and the convergence of traditional solutions deteriorate as the number of loops and PV nodes increases. In this paper, we convert microgrid loops into radial structures by breaking up LBPs, when PV nodes connected to distributed generators (DGs) are regulated with scheduled constant voltage magnitudes. Then, we apply a three-phase BFS-based power flow method with an acceptable convergence for radial distribution networks. Next, we use the NR method for power mismatch corrections at LBPs and PV nodes. Finally, the proposed method is extended to islanded microgrids by introducing the system frequency as a variable. We label the proposed loop-based method an NR-BFS power flow calculation scheme, which combines NR and BFS methods for microgrid solutions. The solution of the proposed algorithm, which signifies the application of the improved BFS method, is applicable to active distribution systems with several loops and DGs. The simulation results demonstrate the efficiency of the proposed method in the loop-based microgrid applications.