An improved three-phase unbalanced power flow calculation algorithm of microgrids based on the enhanced loop incidence matrix

Most distributed generation sources (DGs) are connected to the microgrid in the form of power electronics. The line parameters and loads are asymmetrical, and single phase of DGs, which cause the power flow distribution of the system has the characteristics of three-phase imbalance. According to the operation characteristics of DGs and their interfaces with microgrid system, distributed load flow calculation models of DGs and electric vehicle (EV) charging loads are established in this paper. In order to solve the problem of three-phase unbalance in power flow calculation of the microgrid, the reactance matrix of the power flow calculation node containing the self-impedance and mutual impedance of each line is established by using the method of enhanced loop incidence matrix. To solve the problem of weak processing capability of regulated-voltage (PV) nodes in power flow calculation using the forward backward sweep method, the reactive power is compensated and corrected by using voltage deviation of PV nodes in the iterative process. Finally, the method proposed in this paper is verified by IEEE13 test system and a microgrid system, and the results verify the effectiveness of the proposed method.