含多馈入直流输电的交流系统谐振特性

Resonance Characteristics of AC Systems with MIDC Transmission Systems

针对由6回高压直流输电及特高压直流输电组成的超大规模多馈入直流输电系统共同接入的电网——华东电网,首先分析了12脉动换流器向电网注入谐波的工作机理以及电网谐振发生的原因。采用PSASP程序对上海电网所有500 k V及部分220 k V变电站进行谐振扫描,扫描类型包括正常运行及可能导致电网谐振的故障工况。结果表明:正常运行时,一些变电站存在低次频率的串联及并联谐振频率;而在故障工况下,某些变电站的谐振特性将发生很大改变,将新增针对第8次、11次及13次的并联谐振频率,因此可能与交流系统第7次背景谐波以及12脉动换流器的第11次及13次特征谐波产生谐波放大甚至谐振,从而产生谐振过电压及过电流。最后提出了抑制谐振的措施。

In allusion to the East China Power Grid connected with super-large scale multi-infeed direct current （MIDC） transmission systems, which were composed of six HVDC and UHVDC transmission systems, firstly, the working mechanism of 12-pulse converter producing harmonic in grid and the reasons of power system resonance were analyzed. In addition, resonance scan was conducted for all 500 kV and part of 220 kV substations of Shanghai Power Grid with using PSASP program, scan types consisted of normal operation condition and fault operation conditions that might cause resonance in AC system. The results show that： in normal operation condition, some substations have serial and parallel resonance under low-order harmonic; while in fault operation condition, huge change may happen in some substations, the 8th, llth and 13th harmonic parallel resonance may appear in these substations, which may cause harmonic amplification even harmonic resonance in 7th background harmonic in the AC system and the characteristic harmonics of 12-pulse converters： llth and 13th harmonic, thereby leading to harmonic overvoltage and overcurrent. At last, the harmonic suppression measures were proposed.