The fault recovery of VSC-HVDC transmission system is often influenced by many factors, such as the reactive power compensation characteristics of the inverter and the dynamic performance of DC controllers. In this pa...The fault recovery of VSC-HVDC transmission system is often influenced by many factors, such as the reactive power compensation characteristics of the inverter and the dynamic performance of DC controllers. In this paper, the PSCAD/ EMTDC simulation tool is used to study the dynamic recovery performance of VSC-HVDC system for several different var compensating devices in VSC-HVDC inverter-Fixed capacitor (FC), Static Var compensator (SVC), and Static synchronous compensator (STATCOM) when VSC-HVDC is subject to various faults, including three phase groundings, single phase grounding and three phase breakings. The result shows that the recovery process of the whole system will be slowed down due to its negative influence on the strength of AC power system with the application of SVC, while the STATCOM can improve VSC-HVDC recovery performance greatly for its advantages over other compensating devices in areas such as voltage support ability and DC power recovery.展开更多
模块化多电平换流器的高压直流输电(Modular Multilevel Converter based High Voltage Direct Current,MMC-HVDC)系统中极间短路故障是最严重的直流侧故障类型,目前多侧重于分析闭锁前电容放电过程及相应的故障保护策略,而对MMC极间短...模块化多电平换流器的高压直流输电(Modular Multilevel Converter based High Voltage Direct Current,MMC-HVDC)系统中极间短路故障是最严重的直流侧故障类型,目前多侧重于分析闭锁前电容放电过程及相应的故障保护策略,而对MMC极间短路故障发展全过程分析不够深入,由于极间短路故障暂态过程发展迅速,故障发展各阶段联系紧密、相互影响,为了更好地对直流断路器进行选型和调整继电保护设备,因此有必要对其故障全过程进行分析。文章分析了MMC拓扑结构及其子模块的三种工作状态;根据电容、电感充放电机理,给出换流器闭锁前、后各阶段故障电流路径,建立故障各阶段的等效电路及数学模型,研究了故障距离对直流侧故障电流、电压波形及换流器闭锁时间的影响;基于PSCAD/EMTDC仿真软件,搭建71电平MMC-HVDC双端直流输电模型,验证了故障特性分析的正确性和有效性,对保护设备阈值具有工程意义。展开更多
More and more high voltage direct current(HVDC) converters are being located in a load area in the Yangtze River Delta Region in China. It's large transmission capacity and intensive placement are hardly seen in o...More and more high voltage direct current(HVDC) converters are being located in a load area in the Yangtze River Delta Region in China. It's large transmission capacity and intensive placement are hardly seen in other countries. Accurate and reliable study tools and methods are extremely needed for power system engineers and researchers to deal with such problems which were never met before and otherwhere. A novel approach on electromagnetic modeling of alternating current / direct current(AC/DC) system is proposed and simulation is carried out to replay a real AC 3-phase to ground fault on a multi-infeed high voltage direct current(MIHVDC) system. AC system is specially simplified. Dynamic models and real parameters are adopted in main AC/DC equipments concerned and retained. Modeling and simulation are based on the power system computer aided design/electro-magnetic transient in direct current(PSCAD/EMTDC) system software package.Comparisons between simulation results and the records from the fault recorders are studied including both AC and DC quantities.展开更多
针对高压直流输电(high-voltage direct current,HVDC)系统发生换相失败的问题,运用统一潮流控制器(unified power flow controller,UPFC)减小HVDC系统发生换相失败的概率,并对UPFC的原有控制策略进行改善。当系统交流侧发生故障,UPFC...针对高压直流输电(high-voltage direct current,HVDC)系统发生换相失败的问题,运用统一潮流控制器(unified power flow controller,UPFC)减小HVDC系统发生换相失败的概率,并对UPFC的原有控制策略进行改善。当系统交流侧发生故障,UPFC并联侧控制策略采用交流侧母线电压参考值调节方法抑制换相失败的发生。引入故障水平FL来表征HVDC系统的故障严重程度,通过理论分析和PSCAD/EMTDC仿真验证:当故障水平FL为18.7%时,UPFC原有控制策略与改善后的控制策略均可抑制换相失败的发生;故障水平FL为23.1%时,只有改善后的控制策略可有效抑制换相失败的发生;故障更为严重,当故障水平达到FL为93.56%时,改善后的控制策略可有效降低连续换相失败的发生概率。运用UPFC动态无功补偿能力可增强HVDC系统受端交流系统强度,提高换相失败的抵御能力,从而有效改善了HVDC系统的运行特性。展开更多
为了在特高压环境下正确应用变压器差动保护,需要对特高压变压器进行合理建模,并进行相应的电磁暂态仿真。根据三绕组自耦变压器星型等值电路的原理,用电磁暂态仿真软件EMTDC中的统一电磁等效电路(unified magnetic equivalent circuit,...为了在特高压环境下正确应用变压器差动保护,需要对特高压变压器进行合理建模,并进行相应的电磁暂态仿真。根据三绕组自耦变压器星型等值电路的原理,用电磁暂态仿真软件EMTDC中的统一电磁等效电路(unified magnetic equivalent circuit,UMEC)普通三绕组变压器模型来模拟1000MVA/1050kV三绕组自耦变压器,将特高压变压器参数折算成UMEC模型参数,形成特高压变压器模型。在特高压环境下,分别进行励磁涌流和故障电流仿真,并用于考察应用得最为广泛的2次谐波闭锁的变压器差动保护的动作可靠性。分析表明:当合闸角和剩磁满足一定条件时,特高压变压器三相励磁涌流的2次谐波含量都会在10%以下,即使采用一相制动三相的2次谐波闭锁策略,如果2次谐波门槛值维持在15%～20%,也不能避免差动保护误动;另外,在某些轻微故障的情况下,故障初期故障电流的2次谐波含量成分较高,会使保护动作短暂延迟。展开更多
文摘The fault recovery of VSC-HVDC transmission system is often influenced by many factors, such as the reactive power compensation characteristics of the inverter and the dynamic performance of DC controllers. In this paper, the PSCAD/ EMTDC simulation tool is used to study the dynamic recovery performance of VSC-HVDC system for several different var compensating devices in VSC-HVDC inverter-Fixed capacitor (FC), Static Var compensator (SVC), and Static synchronous compensator (STATCOM) when VSC-HVDC is subject to various faults, including three phase groundings, single phase grounding and three phase breakings. The result shows that the recovery process of the whole system will be slowed down due to its negative influence on the strength of AC power system with the application of SVC, while the STATCOM can improve VSC-HVDC recovery performance greatly for its advantages over other compensating devices in areas such as voltage support ability and DC power recovery.
文摘模块化多电平换流器的高压直流输电(Modular Multilevel Converter based High Voltage Direct Current,MMC-HVDC)系统中极间短路故障是最严重的直流侧故障类型,目前多侧重于分析闭锁前电容放电过程及相应的故障保护策略,而对MMC极间短路故障发展全过程分析不够深入,由于极间短路故障暂态过程发展迅速,故障发展各阶段联系紧密、相互影响,为了更好地对直流断路器进行选型和调整继电保护设备,因此有必要对其故障全过程进行分析。文章分析了MMC拓扑结构及其子模块的三种工作状态;根据电容、电感充放电机理,给出换流器闭锁前、后各阶段故障电流路径,建立故障各阶段的等效电路及数学模型,研究了故障距离对直流侧故障电流、电压波形及换流器闭锁时间的影响;基于PSCAD/EMTDC仿真软件,搭建71电平MMC-HVDC双端直流输电模型,验证了故障特性分析的正确性和有效性,对保护设备阈值具有工程意义。
文摘More and more high voltage direct current(HVDC) converters are being located in a load area in the Yangtze River Delta Region in China. It's large transmission capacity and intensive placement are hardly seen in other countries. Accurate and reliable study tools and methods are extremely needed for power system engineers and researchers to deal with such problems which were never met before and otherwhere. A novel approach on electromagnetic modeling of alternating current / direct current(AC/DC) system is proposed and simulation is carried out to replay a real AC 3-phase to ground fault on a multi-infeed high voltage direct current(MIHVDC) system. AC system is specially simplified. Dynamic models and real parameters are adopted in main AC/DC equipments concerned and retained. Modeling and simulation are based on the power system computer aided design/electro-magnetic transient in direct current(PSCAD/EMTDC) system software package.Comparisons between simulation results and the records from the fault recorders are studied including both AC and DC quantities.
文摘针对高压直流输电(high-voltage direct current,HVDC)系统发生换相失败的问题,运用统一潮流控制器(unified power flow controller,UPFC)减小HVDC系统发生换相失败的概率,并对UPFC的原有控制策略进行改善。当系统交流侧发生故障,UPFC并联侧控制策略采用交流侧母线电压参考值调节方法抑制换相失败的发生。引入故障水平FL来表征HVDC系统的故障严重程度,通过理论分析和PSCAD/EMTDC仿真验证:当故障水平FL为18.7%时,UPFC原有控制策略与改善后的控制策略均可抑制换相失败的发生;故障水平FL为23.1%时,只有改善后的控制策略可有效抑制换相失败的发生;故障更为严重,当故障水平达到FL为93.56%时,改善后的控制策略可有效降低连续换相失败的发生概率。运用UPFC动态无功补偿能力可增强HVDC系统受端交流系统强度,提高换相失败的抵御能力,从而有效改善了HVDC系统的运行特性。
文摘为了在特高压环境下正确应用变压器差动保护,需要对特高压变压器进行合理建模,并进行相应的电磁暂态仿真。根据三绕组自耦变压器星型等值电路的原理,用电磁暂态仿真软件EMTDC中的统一电磁等效电路(unified magnetic equivalent circuit,UMEC)普通三绕组变压器模型来模拟1000MVA/1050kV三绕组自耦变压器,将特高压变压器参数折算成UMEC模型参数,形成特高压变压器模型。在特高压环境下,分别进行励磁涌流和故障电流仿真,并用于考察应用得最为广泛的2次谐波闭锁的变压器差动保护的动作可靠性。分析表明:当合闸角和剩磁满足一定条件时,特高压变压器三相励磁涌流的2次谐波含量都会在10%以下,即使采用一相制动三相的2次谐波闭锁策略,如果2次谐波门槛值维持在15%～20%,也不能避免差动保护误动;另外,在某些轻微故障的情况下,故障初期故障电流的2次谐波含量成分较高,会使保护动作短暂延迟。
