双馈感应式风力发电系统低电压运行特性研究

双馈感应发电机（DFIG）具有有功、无功功率独立调节能力及励磁变频器所需容量小等优点，在风力发电系统中得到越来越广泛的应用。但正是励磁变频器的过流能力限制使得其对电网故障非常敏感，电网故障下DFIG风电机组的控制能力受到限制。当前国外大多数风电并网标准都要求风力发电机在电网电压跌落的情况下不能从电网中解列，以便在故障后电网恢复过程中提供功率支持，避免发生后续更为严重的电网故障，这即是对风电机组低电压穿越能力的要求。为了保护变流器和对电网提供支撑，需要研制一种能够在电网故障发生时为故障电流进行旁路的设备——Crowbar电路。针对Crowbar的电流旁路装置进行了研究，说明Crowbar电路具有抑制转子浪涌电流和保护直流母线的作用，并在小功率平台上进行了试验，证明了这种设备对于提高DFIG系统的LVRT能力具有重要的作用。

Research on Low Voltage Ride through Characteristics of Doubly-Fed Induction Generator Based on Wind Power System

Doubly-fed induction generator is widely used in the wind power generation system due to its advantage of controlling active and reactive power independently, and only a percentage of the power produced by the generator has to pass through the AC excitation converter. However, the converter is quite sensitive to grid disturbance because of its limited partial capacity compared with the generator rating. Nowadays the grid code demands that the wind power generator possesses the ability of riding through the grid voltage dips, in order to prevent the more severe successive grid faults. To protect the converter and to support the grid, it is needed to limit the high inrush rotor current and provide a bypass for it via a crowbar, which is connected to the rotor windings. In this paper, a novel crowbar control strategy is proposed to limit the over current in the rotor, the over voltage of the DC bus. Experiment results prove that crowbar circuit is able to improve the LVRT of DFIG system.