磁通耦合型饼式线圈短时直流冲击特性研究

Researches on DC instantaneous over current impulse characteristics of flux coupling type pancake coil

基于电压源型换流器的高压直流输电(VSC-HVDC)技术在经过多年的研究后取得了一定的进展,并且已有多项工程在运行中。然而直流短路故障的处理仍然是VSC-HVDC电网亟待解决的问题之一,目前的断路器难以在短时内开断如此大的故障电流,因此要与限流器进行配合。电阻型超导限流器(RSFCL)已经在交流情况下进行了大量的研究,它被认为是最具有潜力的直流限流技术。然而传统的双绕无感线圈并不适用于直流输电场合,由于结构特殊使其在直流高压故障中容易发生闪络,造成超导限流器发生不可控的后果,因此需要新型的线圈结构来满足柔性直流输电保护的需求。本文基于连续式单饼限流线圈结构,对不同磁通耦合连接方式的磁场分布进行了仿真分析,建立了短时直流大电流冲击平台;同时设计了磁通耦合型饼式线圈,并对其进行了高压过电流冲击实验与分析,计算了冲击电阻过程中的电阻和热量变化并进行了讨论。本文的分析结果对电阻型直流超导限流器的设计,以及阈值与裕量的确定有一定的指导意义。

Over the last few years, there are exciting advances in voltage sourced converter high voltage direct current (VSC-HVDC) technology and some VSC-HVDC projects have been put in operation. However, how to solve the DC short circuit faults is still an urgent problem of VSC-HVDC power system. The circuit breakers can not meet the requirements of the operation time and current level so they need to cooperate with the current limiter. Resistive superconducting current limiter (RSFCL) is a focus in the development of current limit technology, especially in the field of AC transmission. But the traditional double-wound non-inductive coil has an inevitable defect. Due to its special structure the flashover would occur easily during the fault in high voltage environment. That would make the SFCL working in an uncontrolled state. So a novel coil structure is demand to meet the protection of VSCHVDC. In this paper the magnetic distribution of different flux-coupling connection modes of the coils has been analyzed through the simulations based on single pancake coil. The high voltage DC short circuit impulse platform has been set up and a flux coupling type pancake coil has been devised and manufactured. The impulse process of the coil has been analyzed through simulations and experiments. The resistance and heat during the impulse have been discussed. The results of this paper have certain guiding significance in both the design of DC RSFCL and the determination of threshold value and allowance.