大型DFIG风电场的LCC-HVDC并网及控制

Modeling and control for DFIG-based wind farm with LCC-HVDC connection

针对大型双馈感应发电机(DFIG)风电场的相控换流器高压直流输电(LCC-HVDC)并网,分析了一种新型拓扑结构,其特点为由STATCOM稳定整流侧交流母线电压,为风电场中的DFIG提供定子励磁并保证整流器正常换向;由整流器跟踪风电场发出的有功功率,并将其送至高压直流母线。给出了该系统在同步旋转坐标系下动态数学模型,通过模型分析可知STATCOM具有非线性强耦合特性而整流器具有非仿射非线性特性。根据这2个方面特点,提出了系统控制策略:针对STATCOM模块,采用反馈线性化方法设计了动态解耦矢量控制器,完成整流侧交流母线电压和频率的控制。针对整流器模块,采用逆系统控制方法完成电流内环设计;以STATCOM直流侧电压为风电场与负载功率平衡指示,基于近似功率平衡动态模型完成电压外环的设计。经Matlab/Simulink仿真验证,系统能够顺利完成黑启动,且具有精确的功率跟踪和快速的功率响应能力。

For the large DFIG-based（Doubly Fed Induction Generator-based） wind farms with LCC-HVDC （Line-Commutated Converter-High-Voltage DC） connection,a topology is analyzed. A STATCOM（Static Synehronous Compensator） is used to regulate the AC voltage at the rectifier side for DFIG stator excitation and rectifier commutation. The rectifier forwards the output active power of wind farm to the HVDC-link. The system dynamic model on dq reference frame is presented and the model analysis indicates that the STATCOM has nonlinear and deep coupling characteristics and the rectifier has non-affine and nonlinear characteristies. The control strategies are proposed accordingly：for STATCOM,a dynamic decoupling vector controller with feedback linearization is designed to implement the voltage and frequency control of AC bus at rectifier side; for rectifier,an inverse-system controller is applied as the inner current loop;and a pseudo -power-balance dynamic model with STATCOM dc-link voltage as its power balance reference is applied as the outer voltage loop. Simulation results show that,the proposed topology can successfully realize the black start,accurately follow up and quickly respond to the power.