A Novel Direct Load Flow Algorithm for Unbalanced Micro-grids Considering the Droop Characteristics of DG and Load

Considering that traditional power flow algorithms are not suitable for isolated island and unbalanced micro-grids, in this paper, a new method of power flow calculation is presented. The problem of unbalanced load flow calculation of remote island micro-grids with droop control is divided into two steps: the first step is to conduct normal load flow based on the direct load flow approach while the second step is to update the droop bus. Specifically, the system angular frequency obtained by the direct load flow method is corrected, and then the slack bus voltage amplitude and the remaining droop based DGs and loads feed the generations and loads back to the direct load flow calculation. The final load flow solution is obtained by repeating the two-step above iteratively. The time-consuming LU decomposition and iterative updates of the Jacobian matrix or admittance matrix are no longer needed in the proposed novel direct load flow algorithm for unbalanced microgrids. Therefore, this method is robust and efficient. Through detailed MATLAB simulation analyses on a real Australian micro-grid, the correctness and feasibility of this method is verified.