Voltage regulation performance of smart inverters: Power factor versus volt-VAR control

Abstract

Due to the insignificant share of inverter-based Renewable Energy Resources (RER) as well as the uncertainty concerning their integration impacts, the capability of RERs to regulate voltage or frequency has not been widely used. However, inverter-based voltage/frequency regulation is of interest due to the fast growth of distributed RERs, especially solar Photovoltaic (PV) resources. The IEEE 1547a standard relaxed some of the restrictions on utilization of Distributed Energy Resources (DER) in voltage/frequency regulation. Smart inverters may employ different control strategies, such as Fixed Power Factor, Volt-VAR, Volt-Watt, and Frequency-Watt. In this study, a comparison between fixed power factor and Volt-VAR control strategies is performed in terms of voltage regulation capability. One hour of quasi-steady-state simulation with one-second time steps is performed, where fast and frequent irradiance variations are occurring. Parametric studies involving controller settings are used to compare voltage regulation performance. The IEEE 13-bus test feeder, modified by adding two PV generators, is used as the case study. Simulation results show that the Volt-VAR control out performs the fixed power factor control when it comes to voltage regulation.