电网对称故障时双馈感应发电机不脱网运行的系统仿真研究

System Simulation of a Doubly Fed Induction Generator Ride-through Control for Symmetrical Grid Fault

利用经实验验证的时域仿真模型对一典型的2MW双馈感应风力发电系统在电网对称故障时的控制和响应进行仿真研究。与在电网故障时将转子端部直接短接的保护方案相比较,采用所提出的电网故障励磁控制与正常运行时的风能跟踪控制相结合,可以保证发电机迅速恢复有功输出,从而提高整个电力系统在故障切除后的运行稳定性。针对电网对称故障时发电机不脱网运行的可控范围进行仿真计算的结果表明:典型双馈感应风力发电机可在电网故障引起发电机变压器系统侧电压最低下降到30％额定电压时仍可保持不脱网运行。对影响电网故障励磁控制性能的各种因素,包括发电机故障前初始运行点及电机参数进行了研究,发现适当增加发电机漏感或定予侧电阻有助于进一步提高电网故障时励磁控制的效果。

Using the time domain simulation model which is experimentally verified, a series of case studies on a representative 2MW DFIG wind turbine system is described. In contrast to the scheme of crowbar protection on the rotor side,integration of the proposed grid fault ride-through control with the normal wind power tracking control allows the DFIG to pick up load immediately after fault clearance and hence improves the post-fault stability of the overall power system.The feasibility region of successful ride-through for symmetrical grid faults is obtained by simulation. The result shows that using the proposed control, a typical DFIG system can successfully ride through a symmetrical fault which brings the system side voltage of the generator transformer down to 0.3 pu, at any operating speed. The effects of pre-fault operation point and machine parameters on the effectiveness of the proposed ride-through control strategy are analyzed. Increasing either the leakage inductance or stator side resistance of the DFIG tends to aid grid fault ride-through control.