直驱风电场与LCC-HVDC次同步交互作用的扰动传递路径及阻尼特性分析

当直驱风电场距离电网换相型高压直流输电(line-commutated-converter based high voltage direct current,LCC-HVDC)的整流站较近时,两者间的次同步交互作用机理及特性尚不明确,现有分析方法难以揭示扰动传递过程及子系统间的耦合关系。针对上述问题,该文首先建立直驱风电场经LCC-HVDC送出系统的线性化模型,并基于系统闭环互联传递函数框图揭示次同步频率扰动在直驱风电场与LCC-HVDC之间的传递路径。然后,通过阻尼重构分离出次同步交互作用对次同步振荡(sub-synchronous oscillation,SSO)模式阻尼的影响,并分析控制器参数对SSO模式阻尼的影响。结果表明,直驱风电机组直流电容主导的SSO模式存在不稳定风险;直驱风电场与LCC-HVDC之间的扰动传递路径呈现"8"字型耦合关系,导致两者间存在次同步交互作用;直驱风电机组外环、LCC-HVDC定电流控制器的比例系数增大或积分系数减小时,SSO模式阻尼增大。

Analysis on Disturbance Transfer Path and Damping Characteristics of Sub-synchronous Interaction Between D-PMSG-based Wind Farm and LCC-HVDC

When the direct-drive permanent magnet synchronous generator(D-PMSG)-based wind farm is close to the rectifier station of line-commutated-converter based high voltage direct current(LCC-HVDC), the mechanism and characteristic of sub-synchronous interaction between them are not clear. With the existing analysis methods, it is difficult to reveal the disturbances transfer process and coupling relationship between subsystems. To solve the above problems, the linearization model of the D-PMSG-based wind farm integrated with LCC-HVDC system was established. Based on the closed-loop transfer function diagram of the system, the transfer path of sub-synchronous frequency disturbance between D-PMSG-based wind farm and LCC-HVDC was shown. Then, the influence of sub-synchronous interaction on sub-synchronous oscillation(SSO) mode damping was separated by damping reconstruction, and the influence of controller parameters on SSO mode damping was analyzed. The results show that the SSO mode dominated by DC capacitor of D-PMSG has instability risk. The disturbance transfer path between D-PMSG-based wind farm and LCC-HVDC presents an "8" type coupling relationship, which leads to a sub-synchronous interaction between them. When the proportional coefficient of the D-PMSG outer loop or LCC-HVDC constant current controller increases or their integral coefficient reduces, the SSO mode damping increases.