无差拍控制提高变速异步风力发电系统的故障承受能力

变速风力发电机对于电网扰动、故障以及电网电压跌落非常敏感,当上述情况发生时风力发电机将从电网切除,直到电网恢复正常才能重新投入运行.如何在电网发生扰动时保持风力发电机的正常运行是一个有挑战性的课题.未来的电网规范甚至要求在电网发生故障时风力机组仍能保持运行,这就要求必须安装保证风电机组低电压运行的控制装置.文中针对采用全载换流器与电网进行连接的异步风力发电机组提出了相应的风电机组低电压控制器及控制策略,无须进行硬件改造即可实现电网故障情况下风电机组不退出运行.其中,风电机组电气子系统控制器基于无差拍控制策略进行设计.算例给出了300 kW的风电机组在30%电压跌落情况下的暂态过程,没有加入控制器之前风电机组将停机,加入之后则可以保持运行,验证了所提方法的正确性.

Dead-beat Control Strategies for Fault Ride-through Capability Enhancement of Variable Speed Asynchronous Machine Wind Energy Conversion Systems

Variable speed wind turbines are very sensitive to any disturbance, faults and grid voltage sags. They are disconnected from the grid whenever these conditions arise and reconnected once the grid is healthy. Maintaining the wind turbine connected to grid during disturbances is a real challenge. Future grid codes will require wind turbines (WTs) to be connected to the host grid even during the fault condition and to have voltage sag ride-through (VSRT) feature installed. VSRT feature is not available in most of the present WT and few do with hardware modification,thus increasing the cost of the system. In this paper, a control strategy and VSRT for WTs equipped with full-load converter connected asynchronous generators is presented to maintain the turbine connected to grid during fault and post fault condition without hardware modification. The controller of the electric subsystem of the WT is designed following the strategy of "predictive" deadbeat control. The transient behavior of a 300 kW WT during and after a 30% voltage sag, at which WTs are normally programmed to trip, has been simulated and the fault ride-through performances of the controller demonstrated.