Collaborative Control Framework of Multiple Electric Springs for Frequency Stabilization and Distribution Loss Reduction in Microgrids

Electric springs with capacitive energy storage (ES-1) have been proposed as a continuous demand-side management (DSM) technology to address the intermittency of renewables in power systems. The enabled smart load technology distinguishes itself from other DSM technologies with the unique function of achieving active power manipulation via reactive power control. However, the embedded coupled relationship between the active and reactive powers of the smart load usually results in the contradiction between grid frequency regulation and economic power flow with the conventional control scheme. To address this issue, a centralized control framework is proposed in this paper to achieve the collaborative operation of multiple ES-1s for frequency stabilization and economic power flow in microgrids. The proposed control framework exploits the power variations of the deferrable loads and enables the minimum reactive power flows in the microgrids, which leads to reduced storage requirement and minimum distribution loss. It is the first control framework to address the active and reactive power coupling issue of the ES-1 based smart loads, leading to the independent control of system frequency and optimal reactive power reallocation. The generalized and practical steady-state model of the ES-1 based smart load is investigated. The formulation for achieving the dual-objective optimization is established. Case studies based on experiments and simulations of a 110 V AC microgrid are performed to verify the effectiveness of the proposed control framework.