CCC的补偿度对HVDC系统的影响分析

利用MATLAB中的SIMULINK仿真工具对逆变器为电容换相换流器(CCC)的高压直流(HVDC)输电系统的稳态特性和暂态特性进行了仿真计算,并对仿真结果进行了详细的分析。研究了整流侧定电流、逆变侧定电压控制方式下,CCC中串联电容器补偿度对稳态运行中的HVDC输电系统的熄弧角、换流器与系统间交换的有功功率、无功功率、换流母线电压以及换流器的基波功率因数等的影响。对整流站换流母线处分别发生单相接地和相间短路两种故障形式进行了仿真计算,并研究了换流母线电压的恢复过程及电压暂降与临界补偿度的关系。研究表明考虑到稳态和暂态特性,在整流侧定电流、逆变侧定电压这种控制方式下,CCC的串连电容器补偿度的选择要兼顾防止换相失败和防止引起交流系统不稳定来考虑,并非越大越好。

Influence Analysis of Series Capacitors on HVDC System with CCC

This paper presents a detailed analysis of static and dynamic characteristics of an HVDC transmission system with capacitor commutated converter(CCC) based on a SIMULINK simulation.The control mode under investigation sets a constant current on the rectifier side and a constant voltage on inverter side.The influences of the compensation factor of series capacitors in CCC have been investigated on the HVDC transmission system's extinction angle,the active and reactive power flows between the converter and the AC system,voltage of the bus at converter stations,and fundamental power factor of the converter.Furthermore,the single-phase earth fault and phase-to-phase short-circuit fault in the main bus at rectifier station are respectively simulated with an emphasis on the recovering process of bus voltage and the relationship between the bus voltage sag and the critical compensation factor.The simulation results indicate that under the control mode,the compensation factor of series capacitors should be selected in such a way that the commutation failures could be avoided and AC system's instability could be maintained as much as possible.It is also found that a bigger compensation factor does not necessarily bring a better result.