An Overall Control of Doubly fed Variable Speed Pumped Storage Unit in Pumping Mode

Doubly fed induction machine(DFIM) has excellent speed regulation performance, which can meet the demand of frequency and voltage regulation of power grid and solve the problem of efficiency reduction of pump-turbine resulting from the change of hydraulic head when applied to pumped storage. To omit the drainage process of runner chamber before DFIM start-up, a control method of soft-starting with slight load is proposed which ensures that the speed of DFIM increases smoothly from zero to the required for gridconnection. The field current compensator and rotor position angle compensator are designed to improve the control accuracy for grid-connection. The operation characteristic curve of pump-turbine and the output of grid frequency controller are considered comprehensively to achieve the load optimal regulative. With the methods mentioned above, an overall control strategy of doubly fed variable speed pumped storage unit in pumping mode is proposed, as well as the control flow. The control strategy is simulated in MATLAB and implemented on a towing unit platform. Results of simulation and experiment verified the effectiveness of the proposed strategy, including soft-start with light-load, grid-connection with no inrush current and speed regulation.