Design of Regulation Strategy for Voltage Level at Common Coupling Node in Distributed PV System with Energy Storages Devices

With the increased penetration of photovoltaic (PV) power in distribution network, the influence of distributed PV on voltage quality and stability of distribution network keeps increasing. Mechanism of PCC (point of common coupling) voltage variations caused by grid connected PV system is analyzed, and active/reactive power voltage regulation strategy is proposed based on a typical structure of distributed PV systems with energy storage devices. Dead zone with Schmitt circuit characteristics is set in active power and voltage control loop to ensure the priority of reactive power control. Dead zone control may cause frequent voltage shake near the threshold voltage value due to high sensitivity of active power regulation. Then different positive/negative threshold voltage in Schmitt circuit can effectively eliminate voltage shaking phenomenon. Simulation results show that the proposed scheme can effectively deal with voltage problems caused by sudden changes in solar power output, high capacity load switching and distribution network disturbances.