电网换相换流器高压直流输电系统(Line Commutated Converter based High Voltage Direct Current,LCC-HVDC)在功率传输特性、线路故障时的自防护能力、过负荷能力等方面均优于交流输电,但却无法向弱交流系统和无源网络供电。电压源换...电网换相换流器高压直流输电系统(Line Commutated Converter based High Voltage Direct Current,LCC-HVDC)在功率传输特性、线路故障时的自防护能力、过负荷能力等方面均优于交流输电,但却无法向弱交流系统和无源网络供电。电压源换流器高压直流输电系统(Voltage Source Converter based HVDC,VSC-HVDC)可实现向无源网络供电的目的,但由于电力电子技术的局限性,VSC-HVDC系统投资成本过高。结合两者的优势,提出了一种新型混合高压直流输电系统(Hybrid High Voltage Direct Current,H-HVDC)。该系统的整流侧为两个6脉动LCC接一交流网络,逆变侧为三相二电平VSC接无源网络。在此基础上,对该H-HVDC的稳态数学模型、启动特性、稳态特性与暂态特性、单极闭锁进行了研究。仿真结果表明,该H-HVDC系统能实现向无源网络供电,且具有较高的稳定性,为混合直流的进一步发展提供了理论基础。展开更多
An HVDC link with line-commutated converter(LCC)as a rectifier at the power sending end and with a serial-connected LCC and voltage source converter(VSC)hybrid inverter(SLVHI)at the power receiving end,has been adopte...An HVDC link with line-commutated converter(LCC)as a rectifier at the power sending end and with a serial-connected LCC and voltage source converter(VSC)hybrid inverter(SLVHI)at the power receiving end,has been adopted for the forthcoming Baihetan HVDC engineering project in China.To realize the AC fault ride-through(FRT)of SLVHI,a new strategy based on DC chopper(DCC)is proposed in this paper.Firstly,the mathematical model is built to investigate the VSC DC overvoltage mechanism after SLVHI commutation failure(CF)and related factors.Secondly,a modified DCC topology of SLVHI is designed to adjust the unbalanced power dissipation based on voltage drop depth.Thirdly,an enhanced voltage-dependent current order limiter(VDCOL)is proposed to deal with the unbalanced power after DCC switch-off.With the cooperation between modified DCC and enhanced VDCOL,the proposed FRT strategy can realize CF mitigation and VSC DC overvoltage suppression simultaneously.Finally,the inverter side AC FRT performances of the HVDC link with SLVHI were studied using PSCAD software/EMTDC algorithm.The simulation results validate the effectiveness and superiority of the proposed strategy,with better CF mitigation and VSC DC overvoltage suppression abilities than offered by other existing FRT strategies under different fault scenarios.展开更多
文摘电网换相换流器高压直流输电系统(Line Commutated Converter based High Voltage Direct Current,LCC-HVDC)在功率传输特性、线路故障时的自防护能力、过负荷能力等方面均优于交流输电,但却无法向弱交流系统和无源网络供电。电压源换流器高压直流输电系统(Voltage Source Converter based HVDC,VSC-HVDC)可实现向无源网络供电的目的,但由于电力电子技术的局限性,VSC-HVDC系统投资成本过高。结合两者的优势,提出了一种新型混合高压直流输电系统(Hybrid High Voltage Direct Current,H-HVDC)。该系统的整流侧为两个6脉动LCC接一交流网络,逆变侧为三相二电平VSC接无源网络。在此基础上,对该H-HVDC的稳态数学模型、启动特性、稳态特性与暂态特性、单极闭锁进行了研究。仿真结果表明,该H-HVDC系统能实现向无源网络供电,且具有较高的稳定性,为混合直流的进一步发展提供了理论基础。
基金This work was supported by the State Grid Science&Technology Foundation“NY71-19-037:Research on power transmission of large-scale renewable power bases by VSC-LCC hybrid HVDC”.
文摘An HVDC link with line-commutated converter(LCC)as a rectifier at the power sending end and with a serial-connected LCC and voltage source converter(VSC)hybrid inverter(SLVHI)at the power receiving end,has been adopted for the forthcoming Baihetan HVDC engineering project in China.To realize the AC fault ride-through(FRT)of SLVHI,a new strategy based on DC chopper(DCC)is proposed in this paper.Firstly,the mathematical model is built to investigate the VSC DC overvoltage mechanism after SLVHI commutation failure(CF)and related factors.Secondly,a modified DCC topology of SLVHI is designed to adjust the unbalanced power dissipation based on voltage drop depth.Thirdly,an enhanced voltage-dependent current order limiter(VDCOL)is proposed to deal with the unbalanced power after DCC switch-off.With the cooperation between modified DCC and enhanced VDCOL,the proposed FRT strategy can realize CF mitigation and VSC DC overvoltage suppression simultaneously.Finally,the inverter side AC FRT performances of the HVDC link with SLVHI were studied using PSCAD software/EMTDC algorithm.The simulation results validate the effectiveness and superiority of the proposed strategy,with better CF mitigation and VSC DC overvoltage suppression abilities than offered by other existing FRT strategies under different fault scenarios.
