Nested backward/forward sweep algorithm for power flow analysis of droop regulated islanded microgrids

摘要

In this study, nested backward/forward sweep (NBFS) algorithm, is proposed to solve the load flow problem of islanded microgrids. The proposed algorithm is designed in such a way that the voltage magnitude of the angle reference bus and the system frequency become additional variables in the power flow analysis. In the absence of the slack bus, new loops and equations are introduced in the proposed backward/forward sweep (BFS) method to fulfil the requirement of droop characteristics in the power flow analysis. In each loop of the proposed algorithm, modified equations of BFS are employed to update the voltages of every bus except angle reference bus (slack bus). The voltage of angle reference bus and the system frequency are updated at the end of each loop operation. The proposed NBFS method is applied on several test systems including IEEE 22-bus, 38-bus, 69-bus, and 160-bus and the obtained results are compared with the result obtained from other BFS-based algorithms including direct BFS and modified BFS, Jacobian-based algorithms including Newton trust region (NTR) algorithm and modified Newton -Raphson (MNR) algorithm, and time-domain simulation in PSCAD/EMTDC. The proposed algorithm for droop-regulated AC microgrid exhibits faster convergence with better accuracy as compare to other algorithms.