海上风电场经VSC-HVDC并网的次同步振荡与抑制

基于电压源换流器的柔性直流(VSC-HVDC)输电技术已经成为远距离海上风电场接入系统的理想解决方案,由于海上风电机组采用大型风力涡轮机,导致轴系各质块的弹性系数相比传统内陆风电机组有所增大,当海上风电场经VSC-HVDC并网时,将引发两种次同步振荡:风电机组轴系扭振、风电机组与VSC-HVDC换流器控制装置之间相互作用引发的次同步振荡。针对此问题,文中建立海上双馈风电场经VSC-HVDC并网的小信号模型,利用参与因子辨识出轴系扭振和装置间相互作用两种振荡模式以及与之相对应的强相关状态变量;在此基础上,通过特征值分析法绘制根轨迹曲线,进一步分析强相关状态变量参数变化对系统电气阻尼特性的影响;基于信号测试法提出了一种附加阻尼控制的双馈风电机组附加励磁阻尼控制器与柔性直流输电系统次同步阻尼控制器协同抑制措施,并通过DIgSILENT/PowerFactory仿真验证了协同抑制方法的有效性。

Subsynchronous Oscillation Caused by Grid-connection of Offshore Wind Farm Through VSC-HVDC and Its Mitigation

The voltage-source-converter based high-voltage direct current(VSC-HVDC)transmission technology has become an ideal solution for grid-connection of remote offshore wind farms. As the offshore wind generation unit using large-scale wind turbines, the elastic coefficient of each mass of the shaft is larger than that of conventional inland wind generation unit. When the offshore wind farms integrated to the power grid through VSC-HVDC, two subsynchronous oscillations are triggered, i. e. , the torsional vibration of the turbine shaft and the subsynchronous oscillation caused by the interaction between the wind turbine and the VSC-HVDC converter. This paper developes a small signal model for grid-connection of offshore wind farm through VSC-HVDC. Then the two oscillation modes and the corresponding strong correlation state variables are analyzed by the participant factor analysis. On this basis, the root locus curve of the strong correlation state parameter is plotted by the eigenvalue analysis method, and its influence on the electrical damping characteristics of the system is analyzed. Based on the signal test method, this paper proposes a co-suppression method of supplementary excitation damping controllers for DFIG-based wind turbines and VSC-HVDC system with supplementary damping control. The co-suppression method is verified by the simulation on DIgSILENT/PowerFactory.