Research On Power Control For Variable Speed Pumped Storage With Full-Size Converter

The large-scale development of renewable energy generation such as wind energy and solar energy has brought enormous pressure to the safety and stability of the power system. Power system is in urgent need to configure large capacity energy storage system, compensate the power change, and adapt to the large-scale development of new energy sources. More importantly, in recent years, the demand for the load adjustment is very urgent because of the low power load rate and the fast power fluctuation. Variable speed pumped storage (VSPS) with full-size converter (FSC) can be an effective measure to control the power grid load frequency effectively, restrain the renewable power generation fluctuation, and solve the problem of energy storage and power fluctuation in power grid.Firstly, this paper introduces the structure of VSPS with three level FSC, and analyzes the mathematical model and control strategy of the three-phase machine-side and grid-side PWM converter. Based on the model of machine-side converter, grid-side converter, and pumped storage power unit, the inner and outer rings of the decoupling control strategy of the dq decoupling and synchronous rotating coordinate system are studied. The effectiveness of the model and control strategy are illustrated and analyzed by simulation.Secondly, on a basis of the given reference power generated by the need of grid operation, the relationship of power balance and the characteristic of power regulation of the VSPS with FSC are analyzed. The control strategy and power regulation method in generator mode and pump mode are put forward. The response to the fluctuation of voltage command and the fluctuation of power command in generator mode and pump mode of the VSPS with FSC are studied. It is proved that the VSPS system with FSC can quickly compensate the power fluctuation.Finally, the spectral characteristics of the unit model of VSPS with FSC are presented, using the Fourier transform method based on impulse response. Compared with the spectrum characteristics analysis of wind/solar energy, the effectiveness of control effect of the VSPS system with FSC to the power fluctuation caused by renewable energy is revealed. The effect of VSPS units with FSC on the restrain action of the wind power output fluctuation is simulated and verified based on the example of specific power grid.