匹配控制构网型直驱风电场经LCC-HVDC 送出 系统的次同步振荡特性及机理分析

Sub-synchronous Oscillation Characteristics and Mechanism Analysis of Matching-control-based Grid-forming Direct Drive Wind Farm Transmitted Through LCC-HVDC System

在“沙戈荒”地区风电经电网换相高压直流输电(line-commutated-converter based high voltage direct current,LCC-HVDC)外送系统中,采用基于匹配控制的构网型直驱风机(matching control permanent magnet synchronous generator,MC-PMSG)可以提升送端电网的稳定性。然而,当MC-PMSG位于LCC-HVDC整流站近区时,系统的次同步振荡(sub-synchronous oscillation,SSO)特性尚未明确。针对上述问题,该文采用模块化建模法建立MC-PMSG经LCC-HVDC送出系统的小信号模型,通过特征值法研究MC-PMSG与LCC-HVDC对系统各SSO模态的参与情况与系统运行方式变化对次同步振荡阻尼特性的影响,通过阻尼重构法分析LCC-HVDC并网对系统振荡风险的影响机理。研究结果表明,系统存在匹配控制型风机主导、LCC-HVDC参与的SSO模态,MC-PMSG与LCC-HVDC间的次同步交互作用为SSO提供负阻尼;当混合型风电场中的MC-PMSG占比增大、MC-PMSG风电场容量增大或短路比减小、LCC-HVDC定电流控制器的比例系数增大、风机网侧换流控制器外环积分系数减小、直流电容增大时,SSO阻尼增大。通过PSCAD/EMTDC电磁暂态仿真证明理论分析结果的有效性。

The matching-control-based grid-forming permanent magnet synchronous generator(MC-PMSG)can improve the voltage stability of the sending-end power grid in the line-commutated-converter based high voltage direct current(LCC-HVDC)transmission system of wind power in desert and Gobi regions.However,when the MC-PMSG is situated in the vicinity of LCC-HVDC rectifier station,the SSO features are indeterminacy.Aiming at above-mentioned problems,a small-signal model of MC-PMSG through the LCC-HVDC transmission system is erected by using the modularization modeling technique.The eigenvalues are used to study the participation of the MC-PMSG and LCC-HVDC in each SSO mode of the system and the consequence of system parameter changes on SSO damping characteristics.The mechanism of LCC-HVDC grid connection consequence on the SSO damping is analyzed by the damping reconstruction method.The results indicate that an SSO mode in the system is dominated by MC-PMSG,synchronously participated by LCC-HVDC.LCC-HVDC provides negative damping for this SSO mode.When the proportion of the MC-PMSG in the hybrid wind farm increases,the capacity of MC-PMSG increases or the short circuit ratio decreases,the proportional coefficient of the LCC-HVDC constant current controller increases,the integral coefficient of the wind turbine GSC outer loop decreases,or the DC capacitance increases,and the SSO damping increases.The PSCAD/EMTDC electromagnetic transient simulation is used to validate the validity of the theoretical analysis.