Passive anti-Islanding protection for Three-Phase Grid-Connected photovoltaic power systems

•This paper proposes a new passive anti-islanding strategy for photovoltaic systems.•The proposed strategy reduces the voltage stress of photovoltaic inverters.•The performance of the proposed strategy in fault ride-through operation is proved. This paper presents the performances of a new passive anti-islanding protection with minimal switching losses for three-phase grid-connected photovoltaic power systems. The novelty of the proposed strategy consists of five conventional passive relays, which are as follows: over/under current, over/under voltage, over/under frequency, rate of change of frequency, and dc-link voltage-based anti-islanding methods. Integrating these methods in a synergistic way reduces the limitations of each method, while combining the strengths and benefits of each method in islanding detection. As such, the dc-link voltage-based method consists in supervising the dc-link voltage in voltage source converters to reduce the voltage stress and increase performance. The performance in islanding prevention is determined by the detection time of islanding operation mode. The proposed anti-islanding protection was simulated under complete disconnection of the photovoltaic inverter from the electrical power system, as well as under grid faults as required by new grid codes.