A Dynamic Operational Scheme for Residential PV Smart Inverters

This paper presents an operational scheme for photovoltaic (PV) inverter reactive power control to accommodate higher levels and leverage efficient use of rooftop PV penetration in distribution systems. The scheme proposes three states of operation with specific operational goals for the PV inverter based on weather conditions and voltage at the interconnection point, and adapts the reactive power control strategy accordingly. In normal state with slowly changing solar irradiance, the control modulates reactive power to reduce power losses. In fluctuating state with rapidly varying solar irradiance due to intermittent passing clouds, the control dynamically changes the reactive power in order to mitigate voltage fluctuations. In contingency state in which the PV terminal voltage violates the nominal operating range, the control adjusts the PV inverter as reactive power sink or source in order to push the voltage back within the range. This paper also proposes a coordination strategy in order to switch control between the states and manage interaction between the fast PV inverter controllers, and the slow on-load tap-changer for voltage regulation. A large-scale distribution network based on the IEEE 37-node test feeder was developed in order to investigate performance of the proposed algorithm.