The offline accident of the large-scale wind generator system and its protection & control scheme

There were many accidents of large-scale wind turbines disconnecting from power grid in 2011. Single-phase-to-ground fault cannot be correctly detected. Single-phase-to-ground evolved to phase-to-phase fault. Phase-to-phase fault was isolated slowly, which led to low voltage. And wind turbines without enough low voltage ride-through capacity disconnected from the grid. After some wind turbines disconnected from the grid, over-voltage caused by reactive power surplus made more wind turbines disconnect from the grid. Based on the accident analysis, this paper presents solutions to above problems, including travelling waves based single-phase-to-ground protection, adaptive low voltage protection, integrated protection and control, and high impedance fault detection. The solutions lay foundations in theory and technology to prevent large-scale wind turbines from disconnecting from the operating power grid.