A Low Voltage Ride-Through Segmentation Control Strategy for Variable-Speed Hydropower Plants

Different from the voltage source characteristics of conventional hydropower units, the transient characteristics of large-scale variable-speed hydroelectric units during faults of power grid are unclear. It is urgent to present suitable transient support control strategies for large-scale variable-speed hydroelectric units with high proportion of renewable energy. This paper proposes an improved low-voltage ride through control strategy with a dynamic reactive current scale factor for variable-speed hydropower plants. The strategy calculates the dynamic reactive current scale factor of the hydropower plant under different levels of grid faults in real time considering the grid code requirements for wind power, the operating conditions of the hydropower plants prior to the fault, and the current limit value of the converter. The method can maximize the voltage active support capability of the grid-connected hydropower system while satisfying the constraints and ensuring safe and stable operation of the grid-connected hydropower system during voltage faults. Finally, case study based on MATLAB/Simulink was performed to verify the feasibility and effectiveness of the proposed control strategy.