A modified backward and forward sweep method for microgrid load flow analysis under different electric vehicle load mathematical models

Abstract

A power flow analysis under different electric vehicle (EV) load models based on the modified backward and forward sweep method is presented. Voltage-dependent loads (VDLs) were used to analyze the total power loss and load voltage deviation (LVD) under different EV load models and the general load of the electrical power system. The VDL was defined in the backward stage where the voltage ratio was between bus voltages per nominal voltage. The IEEE 33 bus radial distribution system was selected to be the test system. The EV penetration level was defined as 26.88% compared to the base case of constant power (P). The simulation results showed the impact levels from EV load models to the grid based on the traditional method, with impact levels from high to low being for polynomial load (EVI), constant current load (EVIII), and VDL (EVII) models, respectively. In particular, the highest impact for EVI was in scenario 4 (D), where the total active power loss, total reactive power loss, and LVD were 3.45%, 3.47%, and 3.36%, respectively. Therefore, the EV load model was one important factor to select for solving the power flow of the grid. Moreover, the position and size of the EV load could be considered in the optimal condition for reducing the impact to the grid. However, energy management will become a key challenge for supporting the high penetration of EVs in the near future.