DC islanding detection algorithm using injection current perturbation technique for photovoltaic converters in DC distribution

This paper proposes a new islanding detection algorithm for photovoltaic (PV) converters interfaced with a DC distribution system. Islanding detection is a key requirement for electrical safety and equipment protection. Because DC distribution systems lack frequency and phase, which have been utilized in islanding detection algorithms in AC systems, new methods are required for system reliability. The proposed algorithm consists of an active detection method with positive feedback which not only ensures fast detection response but is also more effective at detecting islanding compared to passive methods. The operating principle and mathematical analysis of the proposed algorithm are detailed. A prototype converter employing the designed algorithm is implemented. Experimental results verify the performance of the algorithm. The proposed algorithm shows fast response; less than 0.2 s to detect the islanding condition. In addition, the experimental result shows the average MPPT accuracy is 99.7% in normal conditions, and is minimally affected by the islanding detection method.