文中提出一种直流电缆的两层简化结构,以减少应用有限元方法计算直流电缆稳态载流量的计算量,增强其计算效率。将直流电缆结构等效为两层:将除线芯外的各层等效为一层,与线芯构成两层简化结构。等效层的等效导热系数由除线芯外其余各层...文中提出一种直流电缆的两层简化结构,以减少应用有限元方法计算直流电缆稳态载流量的计算量,增强其计算效率。将直流电缆结构等效为两层:将除线芯外的各层等效为一层,与线芯构成两层简化结构。等效层的等效导热系数由除线芯外其余各层的导热系数的调和平均数算得。在算例验证中,针对DC 200 k V YJQ41 1×1000+2×12型号直流电缆,分别用有限元方法计算了该电缆原始结构和两层简化结构不同敷设条件下的给定电流时的线芯温度,并与厂商给出的该型号电缆的技术数据参照对比,证明了应用等效导热系数简化电缆结构以进行有限元求解的结果是准确的。之后文中比较了上述计算过程中两种结构下有限元方法的计算量,比较结果表明,两层简化结构的计算量较原始结构的计算量有显著的减少。展开更多
Given the“carbon neutralization and carbon peak”policy,enhancing the low voltage ride-through(LVRT)capability of wind farms has become a current demand to ensure the safe and stable operation of power systems in the...Given the“carbon neutralization and carbon peak”policy,enhancing the low voltage ride-through(LVRT)capability of wind farms has become a current demand to ensure the safe and stable operation of power systems in the context of a possible severe threat of large-scale disconnection caused by wind farms.Currently,research on the LVRT of wind farms mainly focuses on suppressing rotor current and providing reactive current support,while the impact of active current output on LVRT performance has not been thoroughly discussed.This paper studies and reveals the relation-ship between the limit of reactive current output and the depth of voltage drop during LVRT for doubly-fed induction generator(DFIG)based wind farms.Specifically,the reactive current output limit of the grid-side converter is inde-pendent of the depth of voltage drop,and its limit is the maximum current allowed by the converter,while the reac-tive current output limit of the DFIG stator is a linear function of the depth of voltage drop.An optimized scheme for allocating reactive current among the STATCOM,DFIG stator,and grid-side converter is proposed.The scheme maximizes the output of active current while satisfying the standard requirements for reactive current output.Com-pared to traditional schemes,the proposed LVRT optimization strategy can output more active power during the LVRT period,effectively suppressing the rate of rotor speed increase,and improving the LVRT performance and fault recov-ery capability of wind farms.Simulation results verify the effectiveness of the proposed scheme.展开更多
文摘文中提出一种直流电缆的两层简化结构,以减少应用有限元方法计算直流电缆稳态载流量的计算量,增强其计算效率。将直流电缆结构等效为两层:将除线芯外的各层等效为一层,与线芯构成两层简化结构。等效层的等效导热系数由除线芯外其余各层的导热系数的调和平均数算得。在算例验证中,针对DC 200 k V YJQ41 1×1000+2×12型号直流电缆,分别用有限元方法计算了该电缆原始结构和两层简化结构不同敷设条件下的给定电流时的线芯温度,并与厂商给出的该型号电缆的技术数据参照对比,证明了应用等效导热系数简化电缆结构以进行有限元求解的结果是准确的。之后文中比较了上述计算过程中两种结构下有限元方法的计算量,比较结果表明,两层简化结构的计算量较原始结构的计算量有显著的减少。
基金supported by the National Natural Science Foundation of China 52177108。
文摘Given the“carbon neutralization and carbon peak”policy,enhancing the low voltage ride-through(LVRT)capability of wind farms has become a current demand to ensure the safe and stable operation of power systems in the context of a possible severe threat of large-scale disconnection caused by wind farms.Currently,research on the LVRT of wind farms mainly focuses on suppressing rotor current and providing reactive current support,while the impact of active current output on LVRT performance has not been thoroughly discussed.This paper studies and reveals the relation-ship between the limit of reactive current output and the depth of voltage drop during LVRT for doubly-fed induction generator(DFIG)based wind farms.Specifically,the reactive current output limit of the grid-side converter is inde-pendent of the depth of voltage drop,and its limit is the maximum current allowed by the converter,while the reac-tive current output limit of the DFIG stator is a linear function of the depth of voltage drop.An optimized scheme for allocating reactive current among the STATCOM,DFIG stator,and grid-side converter is proposed.The scheme maximizes the output of active current while satisfying the standard requirements for reactive current output.Com-pared to traditional schemes,the proposed LVRT optimization strategy can output more active power during the LVRT period,effectively suppressing the rate of rotor speed increase,and improving the LVRT performance and fault recov-ery capability of wind farms.Simulation results verify the effectiveness of the proposed scheme.
