基于变结构准Z源的双馈风电机组强励变换器

当电网电压发生深度跌落时,需要风力发电系统不脱网且向电网提供动态无功支撑,采用传统励磁变换器的双馈风电机组往往需要通过外加装置才能实现这一要求.外加装置使系统变得复杂,可靠性和效率降低.针对这一问题,文中分析了双馈风电机组低电压穿越的瓶颈,提出了构建坚强励磁系统的思想,并设计了一种基于变结构准Z源的新型双馈风电机组强励变换器.将传统的电容型母线替换为准Z源网络,当电网正常时该变换器运行于可调电压的单电容型母线状态,当电网电压发生深度跌落时,该变换器可以迅速升高直流链电压,从而保证转子侧变换器在故障期间始终可控.搭建了双馈风电机组低电压穿越仿真与实验系统,仿真与实验结果表明所提强励变换器拓扑具有良好的稳态与动态性能,在电压深度跌落时能够有效控制转子电流,实现双馈风电机组的低电压穿越和无功支撑.

Forced Excitation Converter for DFIG-based Wind Turbine Based on Variable-Structure Quasi-Z-source

When a severe voltage sag occurs in the power grid, the wind power generation system should keep connected to the power grid and provide dynamic reactive power support to the power grid. The doubly-fed induction generator (DFIG) based wind turbines using the traditional excitation converter usually require additional devices to meet this requirement, which leads to complicated systems with low reliability and efficiency. Aiming at this problem, this paper analyzes the bottleneck of low voltage ride-through (LVRT) of DFIG-based wind turbines, and proposes the idea of building a forced excitation system. A new type of forced excitation converter based on variable structure quasi-Z-source is designed for DFIG-based wind turbines. The traditional capacitive bus is replaced by a quasi-Z source network. When the power grid is normal, the proposed converter operates in the state of single capacitive bus with adjustable voltage. When the power grid voltage drops deeply, the proposed converter can raise the DC-link voltage quickly, ensuring the rotor side converter (RSC) remain controllable during the fault. The simulation and experimental systems for LVRT of DFIG-based wind turbines are constructed. The simulation and experimental results indicate that the proposed forced excitation converter topology has good steady-state and dynamic performances, and it can effectively control the rotor current when the voltage drops deeply and realize the LVRT and reactive power support of DFIG-based wind turbines.