Optimal parameters of volt-var functions for photovoltaic smart inverters in distribution networks

This paper considers two basic smart inverter functions, volt-var and volt-watt control of photovoltaic (PV) generations, as options for power utilities to improve the system performance. Using forecast solar irradiance and load demand, parameters of the volt-var function are optimally adjusted to reduce the active power curtailment resulting from a preset volt-watt function. This adjustment is performed in coordination with a step voltage regulator to minimize the social cost derived from daily energy loss and solar generation curtailment. On the day of operation, an adaptive control is applied to each PV system to deal with the potential difference between the predicted and the actual solar irradiance. Effectiveness of the proposed method is well illustrated through time-series simulations of a tested system containing a 6.6-kV feeder, which accommodates large-scale PVs and low-voltage networks with many rooftop solar panels. Results show that appropriate volt-var settings can remedy the high-voltage issue caused by high PV generation and that the conflicts between loss reduction and solar energy exploitation efforts can be solved successfully for a given scenario of electricity prices.