基于SISO序阻抗的直驱风场经柔直输电系统中频振荡机理分析及抑制

Mechanism Analysis and Suppression of Medium-frequency Oscillation Based on the SISO Impedance in a PMSG-based Wind Farm When Connected to a VSC-HVDC

直驱风场可通过柔性直流实现大容量、远距离输电。目前已有诸多研究表明直驱风场经柔直输电系统面临着次同步或高频振荡问题。然而,也可能存在一种频段介于两者之间的中频振荡现象,值得进一步研究。为此,该文基于直驱风场经柔直输电系统的单输入单输出(singleinputsingle output,SISO)等效序阻抗模型研究该互联系统的中频振荡机理。然后,据此分析直驱风场和柔直换流站参数对该中频振荡特性的影响,分析结果得到了仿真验证。最后,该文还提出基于虚拟阻抗的阻抗重塑控制,并通过仿真验证所提控制策略对抑制直驱风场经柔直输电系统中频振荡的有效性,对于实际工程具有参考意义。

A permanent magnet synchronous generator(PMSG)-based wind farm can be used to realize the high-capacity and long-distance transmission of the wind power through a voltage source converter based HVDC(VSC-HVDC).They may face sub-synchronous oscillation(SSO)or high frequency oscillation(HFO)issue,which has been well studied recently.However,the medium frequency oscillation(MFO)whose frequency between SSO and HFO may also exist in a PMSG-based wind farm when connected to a VSC-HVDC,which is worthy of researches.In this paper,the mechanism and characteristics of MFO are explored based on the single input single output(SISO)equivalent sequence impedance model of the interconnected system.In addition,the influence of parameters from both PMSG and VSC-HVDC on the MFO characteristics is analyzed as well.And the analysis is validated by simulation.Last but not least,a virtual impedance based impedance reshaping control in the wind farm VSC(WFVSC)station is proposed.With the method,MFO of the interconnected system can be suppressed effectively,which is also validated by simulation,and thus provides important reference for practical engineering.