Identification and Control of Electric Elasticity Limit for Electric-Spring-Based Flexible Loads

By comprehensively analyzing the effective working voltage range of electric springs (ESs), this paper proposes a new control strategy to improve the absorption capacity of ES-based flexible loads for mains voltage fluctuations; thus, enhancing the stability of the microgrid fed by intermittent renewables. Analogous to a mechanical spring, the effective working voltage range of ESs is also restricted by the electric elasticity limit (EEL). In specific circumstances, the ES-based flexible load is incapable of dealing with excessive fluctuations of mains voltage caused by intermittent renewable energy sources. Accordingly, this paper investigates the impact of key parameters on the EEL of ESs, such as the distribution line, the voltage reference, and the loads. Besides, by adjusting the proportion between the critical and the noncritical loads, this paper proposes and implements an EEL controller to regulate the absorption capacity of ES-based flexible loads for mains voltage fluctuations; thus, effectively ensuring the voltage stability of critical loads. Finally, the simulated and experimental results are both given to verify the theoretical analysis for ES-based flexible loads and the feasibility of the proposed EEL controller.