Dynamic Behavior Analysis and Control of Reactive Electric Springs

Electric Spring (ES) technology is an innovative user-level solution developed to stabilize the supply voltage of the loads against variations of the grid voltage. Two basic ES versions exist: reactive and active, whereas the former operates by exchanging only reactive power with the non-critical user loads whilst the latter exchanges both reactive and active power with them. Several strategies have been developed for the ES control, mainly considering loads of R type and focusing on the arrangement of the ES command. This paper deals with a user of RL type equipped with a reactive ES, and pursues the twofold objective of analyzing the dynamic behavior of the user quantities and designing an effective ES control system. The analysis reveals the slightly damped behavior of the user supply voltage in response to an ES command. The designed control system provides a fast and smooth voltage stabilization; to this end, a nested scheme is proposed and the individual controllers are properly synthesized. The performance of the ES control system is validated by Matlab/Simulink simulations.