Virtual Shaft Control of DFIG-Based Wind Turbine for Efficient Transient Energy Capture

In power systems with high penetration of wind power generation, efficient transient energy capture is critical for wind turbines to suppress the power oscillations. In this paper, a novel virtual shaft is applied to the virtual synchronous generator (VSG) and the shaft coupling relationship between doubly fed induction generator (DFIG) based wind turbine and synchronous generator (SG) is analysed. By establishing the state space of parallel generators coupled with a virtual shaft, the effect of parameters in the VSG on the system's transient stability is estimated. Using the Hamilton energy function, the transient energy capture process of VSG with a virtual shaft is presented, and the corresponding requirement of virtual shaft coupling for complete energy transfer from SG to wind turbine is obtained. Furthermore, a novel virtual shaft control strategy of DFIG-based wind turbines is proposed to maximise the transient energy capture. Finally, a typical 9-node power system with high penetration of wind power generation is simulated on a controller hardware-in-the-loop platform. The test results demonstrate that the transient energy of SGs can be captured by wind turbines efficiently, thus suppressing the system frequency variation and rotor angle oscillation.