Development of New islanding detectors & Voltage control systems by experimental studies supported by NEDO

We are now entering a global era where many more photovoltaic (PV) generation systems will be installed. The fact that these dispersed power sources play an important role in suppressing greenhouse gases is well recognized. Conversely, there are concerns over the positive and negative impacts of too many PV systems on existing electric power systems. Even in case of a high penetration rate for decentralized generation, the distribution system is expected to maintain reliability and those PV generation systems can also contribute the proper ancillary service to the distribution system using battery control, centralized voltage control and islanding protection. This paper describes experimental studies concerning the interconnection technologies used for the high penetration of photovoltaic generation, as obtained from research conducted as part of two contracted projects: "Development of Islanding Prevention Methods under Clustered PV Conditions and Improvement of Electricity Quality" in Thailand and "Demonstrative Project on Grid-interconnection of Clustered Photovoltaic Power Generation Systems" in Ota-city, Japan. This paper outlines the methods described below and covers the proof examination of the following items: - New islanding passive and active detection methods - Voltage suppression control method using storage batteries - Centralized voltage suppression control method In particular, we will show that the unique results obtained by the proposed centralized voltage controller help to maintain a regulated voltage, while equalizing the availability in each residential PV system and maximizing total PV generation output at the same time.