Stability and control of a grid integrated DFIM based variable speed pumped storage system

This paper presents stability and control of a grid integrated doubly-fed induction machine (DFIM) based variable speed pumped storage (VSPS) system. The paper aims to verify whether the VSPS unit can support the grid frequency stability. Models of the converters with control units and the mechanical and electrical machines for the VSPS are developed based on phasor representation technique. Based on the dq-frame control theory, the direct power control strategy is designed. Steady-state and transient stability responses of the proposed system are analyzed in MATLAB/Simulink platform. Frequency stability responses are particularly evaluated by comparing between a grid with VSPS and without it. Frequency droop control is also proposed and validated. The results show that the VSPS improves the steady state operations and dynamic stability of the power system. The droop controller ensures that the frequency dynamic stability is highly improved. Hence, the VSPS system is effective in supporting the frequency stability, and adopting droop control in the power grid.