System frequency control using multi-step smart charging of electric vehicles

In recent years, there has been a rise in the penetration of renewable energy. However, intermittency of renewable energy has resulted in several problems faced by the power systems such as system frequency fluctuation. In order to suppress the system frequency fluctuation, a battery inside an electric vehicle (EV) is expected to be used as a control device for Load Frequency Control (LFC). This paper proposes a new EV multi-step smart charging scheme with two charging sequences: first come first serve schedule and sequence with the ratio of ASOC to remaining grid connecting time. The total controllable capacity of the EVs is estimated based on the lumped EV model. The result shows the effectiveness of the proposed control by multi-step charging on EV which can suppress the frequency fluctuation. In addition, the customer´s convenience is taken into consideration by using the satisfaction index defined as the ratio of charged energy to the required energy.