中高压直流开断技术

Medium and High Voltage DC Breaking Technology

直流电网在高压柔性输电、新能源接入、轨道牵引以及未来城市配网方面有着广泛的应用前景。直流断路器作为重要的控制和保护设备,是直流电网供电安全的重要保证。与交流相比,直流开断的要求更高、其实现也更加困难。根据开断原理的区别,目前的直流断路器主要分为空气断路器、电流注入式断路器和混合式断路器三类。分别对三类直流断路器进行了综述,介绍了相应的开断原理与开断方法,着重分析了中高压直流分断方面的最新技术。空气式直流断路器通过建立足够高的电弧电压实现分断,结构简单、可靠性高,在低电压等级系统中已经得到了广泛的应用。电流注入式直流断路器利用储能元件产生的反向电流注入来实现直流分断,短路分断速度较快,可用于中高压直流系统。混合式直流断路器主要利用全控型电力电子器件来实现电流分断,开断速度极快,对于不同电压等级适用性较强,然而较高的成本限制了其广泛应用。

DC power grid has wide application prospects in the high-voltage flexible transmission as well as in the access to new energy, track traction, and the future urban distribution networks. As the crucial equipment for the control and protection, DC circuit breaker is an important guarantee for the DC grids security. Compared with AC interruption, DC interruption has higher requirements and its implementation is more difficult. According to the differences of breaking principles and methods, there are mainly three types of DC circuit breaker（DCCB）, i.e., air DCCB, current injection DCCB, and hybrid DCCB. These DCCBs are reviewed in detail, including the introduction of principles and operations of breaking concepts and the analyses on the latest technological achievements in the breaking of medium-voltage（MV） and high-voltage（HV） DC current. The air DCCB realizes the current breaking by producing a sufficiently high arc voltage, which has been widely used in the low-voltage applications for its simple structure and high reliability. The current injection DCCB achieves the current breaking by injecting a counter current from the energy-storage components, and it has relatively short breaking time and is suitable for MV and HV DC system. The hybrid DCCB utilizes the full-controlled power electronic switches to forcedly cut off the current, which has the favorable properties in the rapid breaking process and is adaptable for various voltage classes. However, the relative high cost of hybrid DC breaker restricts its application.