新能源基地经LCC-HVDC送出系统振荡机理分析与抑制策略(二):阻抗特性与振荡机理分析OA北大核心CSTPCD

Based on the line commutated converter-based high voltage direct current(LCC-HVDC)impedance model established in Part I of the work,this paper analyzes the impedance characteristics and oscillation mechanism of the renewable energy base connected into LCC-HVDC.First,the composition relationship between LCC-HVDC AC port impedance at the sending end with the AC filter impedance and the AC impedance of the valve body is studied.The dominant influence of DC transmission line,receiving-end converter station and power grid strength on the AC port impedance of the valve body at the sending-end converter station is analyzed.Next,the overlapping effect of DC current loop control on the AC impedance of the valve body at the sending-end converter station is studied,and the formation mechanism of the negative damping characteristics of AC port impedance at the sending-end converter station in sub-/super-synchronous frequency band is analyzed.The coupling effects of the converter station and power grid strength at the receiving end on the AC port impedance characteristics at the sending end are discussed.Then,the equivalent model of the renewable energy base connected into LCC-HVDC is established to study the oscillation boundary conditions of the sending-end system.The influence law of LCC-HVDC on impedance characteristics of the renewable energy grid connection point is expounded,and the sub-/super-synchronous oscillation mechanism of different types of renewable energy bases,including permanent magnet synchronous generator(PMSG),doubly-fed induction generator(DFIG)and photovoltaic(PV),connected into LCC-HVDC is revealed.Finally,the simulation results of different types of renewable energy bases connected into LCC-HVDC verify the correctness and versatility of the proposed sub-/super-synchronous oscillation mechanism.