Improvement of imbalance and FRT capacity in distribution voltage deteriorated by integration of renewable power generations by use of STATCOM technology

This paper presents a method to deal with the voltage problems that are caused by the increasing integration of renewable power generations into the distribution system. Some serious problems may occur to the distribution system in case with large amount of power penetration from the renewable sources, such as degradation in voltage quality (fluctuation, rise and imbalance), surplus power at light-load time and increased possibility of voltage instability. The object of this study aims at improving the voltage quality by mitigating the imbalance in the distribution voltage caused by unbalanced loads and further deteriorated by renewable power generations, and meanwhile, leading to the improvement of FRT (Fault Ride Through) capacity so as to ensure power system security at higher penetration levels. For this purpose, this paper suggests to introduce a STATCOM (Static Synchronous Compensator) device into a distribution system that has large numbers of renewable generators. In this study a STATCOM model with relatively lower cost and simple structure was completed based on the existing technologies, and the control systems for improving the imbalance in distribution voltage and for obtaining FRT capacity were proposed. Digital simulations were conducted using a typical detailed distribution system integrated by large numbers of photovoltaic power generators that is estimated probably to appear in the near future. The simulation results have illustrated the validity of the introduction of the proposed STATCOM.