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This paper proposes to employ an energy storage device (ESD) to assist a doubly fed induction generator (DFIG) in providing the required reactive power to the grid during severe grid faults. The energy storage side converter (ESC) that connects the ESD to the rotor circuit is placed in parallel and coordinated with the normally sized rotor-side converter (RSC) to provide the rotor demagnetizing and reactive currents. Moreover, by appropriate distribution of these two rotor current components between the ESC and the RSC, the required current rating of the ESC and the energy capacity of the ESD are optimized. In particular, this paper proposes to utilize the ESD for the above control objective in an auxiliary control manner, where the primary objective of the ESD is also for steady-state active power regulation for the DFIG. This improves the overall performance/cost ratio of the ESD. The proposed use of the ESD for the transient reactive power control of the DFIG is not only a technically advanced but also economically feasible and promising alternative to the existing control methods for enhancing the transient performance of DFIGs. Numerical simulations are performed to validate the proposed control method.
Shen et al. (Wed,) studied this question.