基于线路电流二阶导数的中压直流系统故障识别方法

直流线路故障的快速有效识别是基于电压源型换流器的中压直流配电系统发展的关键技术之一。直流线路故障电流上升十分迅速,系统中电力电子器件过载能力小。因此以串入直流线路限流电感的中压直流配电系统为基础,分析直流系统的故障特性,在此基础上提出基于线路电流二阶导数的中压直流配电系统直流线路故障快速识别方案。该方案能够实现故障侧、故障类型及故障线路极性的快速识别,进而实现对线路的保护。最后基于Matlab验证了所提故障检测方案的有效性,并与基于线路电流一阶导数的故障检测方案进行了对比。仿真结果表明所提方法在故障电阻、故障距离及负载发生变化的情况下仍可实现直流线路故障的快速准确检测,且相比基于线路电流一阶导数的直流线路故障检测方案具有更好的选择性。

DC line fault identification scheme for a medium-voltage DC power system based on the second derivative of line current

The rapid and effective identification of DC line faults is one of the key requirements for the development of a Medium-Voltage DC (MVDC) distribution system based on the Voltage Source Converter (VSC). The DC line fault current is characterized by rapidly increasing speed, and the overload capacity of the power electronic device in the system is low. Therefore, based on an MVDC distribution system with DC line current-limiting reactors, the DC line fault mechanism of the system is analyzed. On this basis, a fast identification method for DC line faults in an MVDC distribution system based on the second derivative of the line current is proposed. This scheme can quickly identify the fault side, the fault type and the fault line polarity. Finally, the effectiveness of the proposed fault detection scheme is verified by Matlab, and compared with the fault detection scheme based on the first derivative of line current. The simulation results indicate that the proposed method can still realize the rapid and accurate detection of DC line faults when the fault resistance, fault distance and load change. Moreover, compared with the DC line fault detection scheme based on first-order derivative of line current, the proposed scheme has better selectivity. This work is supported by National Key Research and Development Program of China (No. 2018YFB0904700) and Science and Technology Project of State Grid Corporation of China (No. SGJS0000YJJS1801250).