Power imbalance-based droop control for vehicle to grid in primary frequency regulation

Abstract

As demand for electric vehicles (EV) grows, interest in vehicle-to-grid (V2G) is increasing. Although V2G provides additional flexibility for power systems, it can be an inconvenience for the EV owner and shorten the cycle life of EV batteries. In this paper, we propose a power-imbalance-based droop control (PIDC) for V2G, which uses estimated active power imbalance between supply and demand, without any communications or dispatch signal from the automatic generation control (AGC). Unlike the existing frequency droop control, the proposed method controls V2G based on the estimated imbalance. The Imbalance between electricity supply and demand was estimated using the swing equation, frequency deviation, and rate of change of frequency (RoCoF). Conventional frequency droop control has a slow response speed because it only considers the frequency deviation. Using the PIDC, the critical frequency drop was discerned faster and the V2G could react more quickly in critical frequency drop situations. Additionally, battery cycle life was preserved in ordinary frequency fluctuations where V2G is unnecessary. This study used MATLAB R2020a to show the effectiveness and performance of PIDC. The case study results showed that PIDC has a faster response speed and preserves EV battery cycle life compared to frequency droop control.