Reducing Energy Storage Demand with ES-2: Principles Analysis and Control Design

The increasing installation of renewable energy sources (RES) has led to a growing energy storage demand in the grid. The high cost of batteries and the potential environmental impact of used batteries cannot be ignored. Electric spring (ES), as a demand side management (DSM) technique, can effectively reduce the energy storage demand by utilizing the allowable power fluctuation range of non-critical load (NCL). Among the existing ESs, the second version ES (ES-2) can compensate both active and reactive power and has received the most attention. However, the existing researches on ES-2 basically do not consider the power limitation of the NCL, which may result in the NCL voltage exceeding the allowable range and the insufficient reduction of the energy storage demand. To solve this problem, a load voltage angle control strategy for ES-2 is proposed in this paper. This control strategy ensures the power fluctuation of NCL within the allowable range by controlling the angle between the critical load (CL) voltage and the NCL voltage in real time. Meanwhile, the allowable power fluctuation range of NCL is fully utilized to minimize the battery capacity. Finally, the effectiveness of the proposed control strategy is verified by simulation and experiment.