Coordination Control and Protection for Photovoltaic DC Distribution System

Multi-terminal distributed photovoltaic are integrated into the flexible DC distribution system for higher energy conversion efficiency. However, the special fault characteristics of DC system bring challenges to protection such as: 1) Due the complex structure of flexible DC distribution system with multi-terminal distributed photovoltaic, the protection cannot set a clear boundary using single-ended measurement. 2) The DC faults last about several milliseconds and its fault characteristics controlled by power converters’ variable control algorithms, thus causing the difficulty in fault location. Therefore, a novel fault detection and location method-based protection scheme is proposed to deal with these issues. The proposed method utilizes the coordinated control between local protection and the converters in the system, eventually, the problem of unclear protection boundary was solved. Meanwhile, the proposed protection method can distinguish the correct faulted area by calculating harmonic impedance of these characteristic signals. Simulation results show that it is effective to achieve the combination of control and protection through the well controllability of power electronics. The principle is simple and reliable.