直驱风电场经VSC-HVDC并网的次同步振荡特性分析

Subsynchronous Oscillation Characteristic Analysis of Grid-connected DDWFs Via VSC-HVDC System

针对直驱风电场经柔性直流输电(voltage source converter based high voltage direct current,VSC-HVDC)并网引发的次同步振荡(subsynchronous oscillation,SSO)问题,建立了并网系统的动态数学模型。利用特征值法分析了系统中存在的振荡模式,通过参与因子分析可知SSO模式是由直驱永磁风力发电系统和VSC-HVDC共同参与的,分析了直驱永磁风力发电系统直流侧电容、VSC-HVDC交流侧相电抗器、VSC-HVDC直流侧电容和电抗、风电场并网阻抗X/R的大小、等值风机台数对SSO阻尼特性和频率特性的影响。同时,建立了聚合等值风电场经VSC-HVDC并网的动态模型,利用特征值法分析了风电场的聚合特性对系统稳定性的影响。此外,将VSC-HVDC的接入分成源-网-控3部分,在3种不同的运行场景下利用特征值法分析得出VSCHVDC的控制特性和交流侧网络特性对系统SSO特性的影响。通过在PSCAD/EMTDC中搭建了直驱风电场经VSCHVDC并网的仿真模型,验证了理论分析的正确性。

In view of the subsynchronous oscillation(SSO)caused by interconnection of direct-drive wind farms(DDWFs)via voltage source converter based high voltage direct current(VSC-HVDC)transmission system,a dynamic mathematical model of the grid-connected system was established.The oscillation modes in the system were analyzed with eigenvalue method.Participation factor analysis revealed that the SSO mode was mainly influenced by direct-drive permanent magnet(DDPM)wind power generation system and VSC-HVDC.The influence of DC-side capacitance of DDPM wind power generation system,AC-side phase reactor of VSC-HVDC,DC-side capacitance and reactance of VSC-HVDC,X/R of wind farm grid-connected impedance and turbine number on damping and frequency characteristics of the SSO were analyzed.Meanwhile,a dynamic model of aggregated equivalent wind farm via VSC-HVDC system was established,and the influence of wind farm aggregation characteristics on system stability was analyzed with eigenvalue method.Besides,the connection of VSC-HVDC was divided into three parts:source,network and control.Then the influence of control characteristics and AC-side network characteristics of VSC-HVDC on SSO characteristics were analyzed under three different operation conditions.A model of grid-connected DDWFs via VSC-HVDC system was built in PSCAD/EMTDC to verify above theoretical analysis.