交流网严重故障引发LCC-UHVDC功率振荡机理及控制优化方法

Mechanism and Improved Control Scheme of LCC-UHVDC Oscillation Caused by AC Network Severe Fault

直流输电工程在长期发展中形成相对固定的控制策略,完善该策略对提高交直流混联电网的稳定性有重要意义。近年来,使用机电–电磁混合仿真技术进行稳定分析,在大电网交流侧某些严重故障下,多条基于电网换相换流器的特高压直流(ultra-highvoltageDCbasedonline commutatedconverter,LCC-UHVDC)工程均出现了持续大幅度功率振荡,表明现有控制策略需要一步完善。该文介绍了各UHVDC工程中出现的相似功率振荡现象,并以某工程为例,深入分析直流控制器中换相裕度面积计算(commutation margin area calculation module,AMINCALC)、设置最大熄弧角输出(maximumarcanglelimiteddirect outputmodule,GAMMA0)及低压限流(voltagedependent current order limiter,VDCOL)等多个控制环节共同诱发功率振荡的机理;研究抑制该类直流振荡可能的控制措施及实用的控制优化方案。实际电网的仿真证明了该方案的有效性。

In the long-term development,DC transmission projects may form a relatively fixed control strategy.Ameliorating the strategy is of great significance to improving the stability of AC/DC hybrid power grid.In recent years,the electromechanical electromagnetic hybrid simulation technology has been used for stability analysis.Under some serious faults on the AC side of large power grid,several ultra-high voltage DC(UHVDC)projects based on line commutated converter(LCC-UHVDC)are found to have the risk of continuous large-scale power oscillation by using the simulation technology,indicating that the existing control strategy may be further improved.This paper introduces the similar power oscillation phenomenon in several UHVDC projects,and takes an UHVDC project as example to deeply analyze the mechanism of power oscillation induced by some modules of LCC controllers,such as commutation margin area calculation module(AMINCALC),maximum arc angle limited direct output module(GAMMA0)and voltage dependent current order limiter(VDCOL).The possible control measures to suppress this kind of oscillation and the practical control optimization scheme are studied.The effectiveness of the scheme is proved by the simulation of the actual power grid.