A Novel Method to Analyze the Reactive Power Characteristic of Doubly Fed Adjustable-Speed Pumped Storage Unit

This paper introduces a method to analyze the reactive power characteristics and regulation mechanism on the stator side of a doubly fed induction machine (DFIM) based on adjustable-speed pumped storage (ASPS) unit. The mathematical model and the relationship of the electrical vectors of DFIM are adopted to derive the relation curve of stator current and rotor voltage, which is called V-curve. Based on the V-curve, the reactive power characteristic under the over-excitation, under-excitation and unity-power factor (UPF) of the adjustable-speed DFIM is analyzed. Additionally, the influence of different slip on reactive power output, such as super-synchronous speed, sub-synchronous speed and synchronous speed, is also discussed. Dynamic simulation is carried out to present that the adjustable speed DFIM has better voltage support based on the MATLAB/Simulink platform. Moreover, steady state simulation results prove that the correctness and effectiveness of the proposed V-curve method for the analysis of ASPS unit reactive power characteristics.