新能源基地经LCC-HVDC送出系统振荡机理分析与抑制策略(三):振荡抑制策略

Oscillation Mechanism Analysis and Suppression Strategy of Renewable Energy Base Connected Into LCC-HVDC(Part Ⅲ):Oscillation Suppression Strategy

针对新能源基地经电网换相换流器型高压直流(line commutated converter-based high voltage direct current,LCC-HVDC)送出系统次/超同步振荡问题,现有研究主要通过新能源侧阻抗重塑设计实现振荡抑制,考虑到实际系统并网台数多、机型繁杂、故障穿越性能等因素制约,其设计裕度受到限制。该文通过LCC-HVDC阻抗重塑实现系统次/超同步振荡抑制。首先,提出送端换流站定触发角控制、受端换流站定直流电流控制的LCC-HVDC阻抗重塑控制策略,建立计及阻抗重塑的LCC-HVDC阻抗解析模型,并验证阻抗模型的准确性。然后,对比分析重塑前后阻抗特性变化,阐述阻抗重塑控制策略的作用机理,消除原有送端换流站直流电流环与功率电路重叠效应所产生的负阻尼。进一步,基于LCC-HVDC阻抗重塑,优化新能源并网点系统阻抗特性,提升直驱风机(permanent magnet synchronous generator,PMSG)、双馈风机(doubly-fed induction generator,DFIG)以及光伏(photovoltaic,PV)不同类型新能源基地经LCC-HVDC送出系统稳定裕度,消除系统次/超同步振荡风险。最后,不同类型新能源基地经LCC-HVDC送出系统仿真结果验证了该文提出的基于LCC-HVDC阻抗重塑振荡抑制策略的有效性。

For sub-/super-synchronous oscillation of renewable energy generation connected into line commutated converter-based high voltage direct current transmission(LCC-HVDC),the existing research mainly adopts the impedance reshaping method of renewable energy to achieve oscillation suppression.Considering the constraints of a large number of grid-connected units,multiple unit types,and fault ride-through performance in the actual system,the design margin is limited.LCC-HVDC impedance reshaping is utilized in this paper to achieve sub-/super-synchronous oscillation suppression.First,the LCC-HVDC impedance reshaping control strategy is proposed,with the fixed trigger angle control adopted at the sending-end converter station and dc current control adopted at the receiving-end converter station.Subsequently,an analytical impedance model of LCC-HVDC considering impedance reshaping is established,and the accuracy of the impedance model is verified.Next,the changes of impedance characteristics between before and after impedance reshaping are compared,and the mechanism of the impedance reshaping control strategy is expounded to eliminate the negative damping caused by the overlapping effect between the original dc current loop and the power circuit at the sending-end converter station.Furthermore,with the LCC-HVDC impedance reshaping control,the system impedance characteristics at the interconnect point of renewable energy units is optimized,and the stability margin 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 can be improved.Finally,simulation results of different types of renewable energy bases connected into LCC-HVDC verify the effectiveness of the proposed LCC-HVDC impedance reshaping-based oscillation suppression strategy.