Cooperative strategy of SMES device and modified control for cost-effective fault ride-through enhancement and power smoothing of 10 MW class superconducting wind turbine

Superconducting wind turbine generators (SWTGs) are an effective option of 10 MW class WTG units integrated into offshore wind farms, owing to their potential advantage of reduced size and weight compared with conventional generators. Reliable grid-connection of SWTGs faces two main challenges including fault ride through (FRT) and wind power smoothing. Traditional solutions consist mainly of device-based and control-based schemes. However, the device-based scheme causes a high-cost burden due to the introduction of additional devices, while the control-based scheme is not suitable for FRT enhancement under serious grid faults. To solve these problems, this paper presents a cooperative strategy integrated with one cost-effective superconducting magnetic energy storage (SMES) device and two modified WTG controls. The utilization of SMES devices can achieve a favorable wind power smoothing effect during normal operations and overvoltage suppressing effect in dc-link of WTG during grid faults. Moreover, two modified WTG controls of power decreasing control method and reactive power control provide effective assistance for suppressing dc overvoltage, offering adequate reactive current support and reducing the capital cost of SMES devices simultaneously. Several test cases are conducted to demonstrate the feasibility of the proposed strategy.