A novel reactive power control strategy for distribution grids with large scale rooftop PV systems

The tendency to deploy large scale PV systems in residential areas nonstop continues all around the world. Especially, installations on single-phase lines are possessing more technical challenges to distribution system operators in terms of voltage unbalance and decreased power quality. Even though node voltages, line, and transformer loadings may be inside the safe limits for primary distribution lines due to aggregation effects, severe voltage fluctuations and equipment overloading may be seen in single-phase secondaries. To identify these problems, it is necessary to model the distribution grid from bottom to top as realistic as possible. In this study, based on such a detailed modelling approach, technical impacts of PV systems are analyzed more accurately by taking individual phases into account. Additionally, a novel reactive power control strategy is proposed benefitting from instantaneous imbalance of load and generation where their weekly changing patterns are considered to update the control parameters dynamically. It is verified that in dealing with voltage fluctuation problem, the proposed method 0.65% and 1.89% is more efficient than its traditional reactive power control method competitors, namely cosφ(P) and Q(V), respectively.