经柔性直流接入的大规模直驱风电场等效建模与小干扰稳定性分析

Equivalent modeling and small-signal stability analysis on PMSG-based large-scale wind farm connected to power system via VSC-HVDC

含多台风机的大规模风电场经柔性直流接入交流系统的详细模型阶数过高,对小干扰稳定性分析和失稳机理研究提出了挑战。为此,建立了风电场经柔性直流接入交流系统的开环、闭环线性化状态空间模型。基于风电场开环状态空间模型及风电场节点电压电流关系,将全阶风电场模型通过单台风机动态及交流拓扑信息矩阵进行等效,并分析了风机输出功率、风机接入位置、风电场拓扑结构和风机数增加对风电场振荡模式阻尼的影响。基于风电场降阶模型构建了风电-柔性直流系统的闭环互联模型,并分析了当风机数增加时两子系统间可能存在的强动态交互作用对闭环系统小干扰稳定性的影响。研究表明当接入风机数增加时,风电场主导振荡模式阻尼降低,当接近于柔性直流整流器的一个开环振荡模式,此时模式谐振诱发强动态交互作用的发生可能导致系统失稳。

The order of the detailed model for large-scale wind farm with wind turbines integrated to AC system via VSC-HVDC(Voltage Source Converter-based High Voltage Direct Current) is too high,which brings challenges to the small-signal stability analysis and instability mechanism research. For that,the open-loop and closed-loop linear state space models of wind farm integrated to AC system via VSC-HVDC are built. Based on the open-loop state space model of wind farm and the relationship between the nodal voltage and current of wind farm,the full-order wind farm model is equivalent through the single wind turbine dynamic and the information matrix of AC topology,meanwhile the impacts of output power of wind turbine,interconnected location of wind turbine,topological structure of wind farm and number increase of wind turbines on oscillation mode damping of wind farm are analyzed. The closed-loop interconnected model of wind farm and VSC-HVDC system is derived based on the reduced-order model of wind farm,and the influences of possible strong dynamic interaction between two subsystems on the small-signal stability are analyzed when the number of wind turbines increases. The research shows that when the number of wind turbines increases,the damping of dominated oscillation mode decreases. When it is closed to an open-loop oscillation mode of VSC-HVDC converter,the strong dynamic interaction induced by modal resonance may cause the system instability.