Increasing photovoltaic penetration with local energy storage and soft normally-open points

This paper considers the use of energy storage to mitigate the effects of power output transients associated with photovoltaic systems due to fast-moving cloud cover. In particular, the combination of energy storage with `soft' normally-open points (SNOPs), referring to an AC/AC power electronic conversion device in place of switchgear, is considered. This paper will demonstrate the use of SNOPs with energy storage for providing this damping functionality simultaneous to its other functions. A formula to estimate the level of energy storage required to handle worst-case transient conditions, as well as two high-level control schemes for the SNOP are proposed then tested experimentally through simulation on typical distribution systems with measured historical insolation data.