Research on the Impact of Distributed Photovoltaics on Traditional Protection of Distribution Networks under Different Grid-Connection Conditions and Optimization Strategies

With the continuous growth of distributed generation (DG) grid-connected capacity, the proportion of distributed photovoltaic (PV) is gradually increasing. Its impact on the safe and stable operation of the distribution network is becoming more and more significant. The traditional distribution network was originally a unidirectional power flow with a single-source radiation structure, but the connection of distributed PV power sources has transformed the distribution network into a complex multi-source system with bidirectional power flow characteristics. This has led to an increase in the uncertainty of the direction and magnitude of current during a fault, making it difficult for the original overcurrent protection scheme to adapt. To address this challenge, this study uses the PSCAD/EMTDC simulation platform to establish an equivalent photovoltaic model with low voltage ride-through (LVRT) capability. By simulating scenarios with different fault locations and types, the impact of distributed photovoltaic grid-connected capacity on the short-circuit current of protection devices is analysed in depth, and the impact on the performance of protection actions is assessed. Finally, this paper proposes a new criterion for coordinating three-stage current protection with grid-connected capacity based on the output characteristics of reactive current, to ensure that distribution networks with distributed photovoltaics can maintain safe and stable operation.