Adaptive control of energy storage for voltage regulation in distribution system

With the increasing penetration of renewables, the traditional distribution system design philosophy is being challenged. One well-known concern is the voltage rise problem caused by the reverse power flow, when the PV generation substantially exceeds the load demand. Existing solutions of these voltage issues include either restricting PV output or tripping it with over-voltage/under-voltage relays, both of which are disruptive. This paper proposes a novel framework for distribution network voltage regulation by integrating PV system with distributed energy storage system (ESS) and adaptively dispatching the ESS. In the proposed framework, the voltage and current phasors at the point of common coupling (PCC) are continuously monitored to establish a real-time Thevenin equivalent of the distribution grid. Based on this equivalent, the maximum and minimum power injections allowed at PCC are continuously tracked. The voltage violation margins at PCC are calculated and the ESS is controlled adaptively to prevent the occurrence of voltage violation. The proposed method can also be used to mitigate the detrimental effects of sudden change in PV output. The proposed scheme is tested on a typical US distribution system and its effectiveness is demonstrated through simulations.