Stability on variable-speed pumped storage plant with full-size converter under fast power control mode in turbine condition: influence laws, deviation recognition, and quantitative evaluation

• Reveal matching laws between time constants and governor parameters for stability. • Use stability margin to recognize the deviation of simplified and detailed model. • Propose a method for stability performance evaluation. The variable-speed pumped storage plant with full-size converter under fast power control mode is characterized by exceptional power regulation performance. However, its rotational speed and grid frequency decoupling will cause speed instability during small power disturbances under grid-connected operation, which is absent in fixed-speed units. Therefore, this paper investigates the stability of VSPSP with FSC. (1) Influence laws: Analyze influence laws of time constants on stability regions through the state matrix. (2) Deviation recognition: Recognize stability region deviation of simplified and detailed models through the stability margin. (3) Quantitative evaluation: Propose a method considering hydraulic-mechanical-electrical to evaluate the stability performance. This study applies a pumped storage plant as the engineering case, and the following conclusions demonstrate: (1) Reveal the matching laws of time constants to the stability region. (2) The critical stability margin value ( m ) is calculated to ensure that parameters of the simplified model derived theoretically maintain detailed model stability. In this case, the critical value ( m ) is 0.21. (3) Achieve favorable selection of governor parameters based on the evaluation method. These conclusions provide recommendations for matching the parameters between the controller and the controlled system for the VSPSP with FSC under the fast power control mode for stability.