Experimental verification of advanced voltage control for penetration of PV in distribution system with IT sectionalizing switches

In Japan, penetration of photovoltaic generation (PV) systems has been strongly promoted and the accumulated amount of the installation by 2009 is approximately 2.6 GW. Further, the national target of PV installation capacity is 28 GW in 2020 and 53 GW in 2030, respectively. Although most of PV systems are connected into low voltage distribution networks, it brings power flow with greater uncertainty and causes some operational and control problems. In particular, the voltage control problem is one of the foremost concerns and the dominant constraint of the penetration of PV systems into distribution networks. In order to mitigate the impact of future large PV penetration on distribution network voltages, we have proposed a distribution voltage control method that combines a centralized voltage control by tap change transformers (LRT: load ratio control transformer, SVR: step voltage regulator) and a coordinated voltage control by reactive power compensators (STATCOM: static synchronous compensator). The proposed voltage control has been verified by computer simulations. Meanwhile, we have constructed an analog type distribution system simulator for solving various control and operational problems that environmental changes such as an increase of distributed generations cause in 6.6kV distribution system. The simulator named "ANSWER (Active Network Simulator With Energy Resources)" is a 200V experiment system that is designed by three-phase, three-wire, and non-grounded as well as 6.6kV distribution system in Japan. This paper describes the experimental results on the analog type simulator in order to verify the feasibility and availability of the proposed voltage control. The demonstration experiments on a simple test models were conducted and the voltage control behavior with LRT, SVR, and STATCOM was evaluated. As the experimental results, it was verified that the proposed voltage control is effective and implementable to maintain line voltages in distribution networks with high penetration of PV systems. Moreover, it was confirmed that the coordinated voltage control with STATCOM have effects of reducing the voltage fluctuations and avoiding frequent tap changes of LRT and SVR.