Investigation of protection schemes for high penetration rooftop photovoltaic system

As a clean and renewable source of energy and can be used easily and widely in the future, photovoltaic is one of the most important distributed generations in micro-grid. The deployment of high penetration rooftop photovoltaic (PV) system is becoming a reality in micro-grid. Developing high penetration rooftop PV system in an effective manner is a great challenge. The paper analyzes the characteristics of high penetration rooftop PV system and proposes protection schemes according to the requirements. As the operation of micro-grid is flexible, micro-grid could operate not only in radial or open loop configurations, but also in closed loop configurations according to the security and the reliability requirements. This paper investigates the protection requirements of high penetration rooftop PV system and analyzes the characteristics of conventional protection schemes applied to high penetration rooftop PV system. Obviously, the pilot protection can fulfill the requirements of high penetration rooftop PV system. Taking the fault clearance speeds and the requirement of directional element into account, the paper proposes protection scheme based on overcurrent coordination for high penetration rooftop PV system. The proposed protection schemes show that it can clear the fault instantaneously and significantly improve the reliability and security of high penetration PV system.