Active Converter Injection-based Protection for a Photovoltaic DC Distribution System

Due to the complex muti-branch structure of photovoltaic DC distribution systems, single-ended measurement based protection cannot work well. The DC line-to-line faults are also difficult to locate due to a short time span with fault characteristics that are affected by various converter structures and control algorithms. To resolve these issues, a new DC line protection based on active converter injection is proposed. This method uses communication cooperation to realize the coordination of protection and converter control, then the converter becomes a characteristic signal injection source, that can build a clear protection boundary. The proposed method can complete fast fault detection and precise fault location. Moreover, compared with current DC protection techniques, it does not require additional injection equipment and high sampling frequency. Hardware tests are carried out, illustrating that the proposed approach is effective to achieve line protection through active control of power electronics.