摘要
双主动全桥(dual active bridge,DAB)直流变压器能够通过直流线路互联多个电压等级的交流配电网形成交直流混合配电网,该系统的故障类型多样,故障特性复杂,该文对其故障特性进行详细研究。分析该系统发生交流网侧单相接地故障、交流阀侧单相接地故障以及直流母线单极接地故障后的故障特性,研究换流站直流侧电容中点采用直接接地和高阻接地两种接地方式的系统中,DAB对系统故障特性的影响。探究发生上述故障后,系统交流侧和直流侧的相互影响,并进行详细对比分析,提出含DAB系统的故障分析方法。最后,通过Matlab仿真平台对上述分析进行仿真验证,指出DAB对直流侧电容中点直接接地系统故障特性的影响更突出,且DAB能够隔离交直流侧故障的相互影响,为交直流混合配电网接地方式的选择、保护系统的设计等提供理论依据。
Dual active bridge(DAB) converter can connect several AC distribution networks with different voltage levels by a common DC bus. The fault characteristics of this system are complicated and need to be investigated in detail. In this paper, the fault characteristics of the DAB based multi-voltagelevel AC/DC hybrid distribution network were analyzed in detail. Firstly, fault characteristics of single-phase grounding fault in AC grid/VSC side and pole-to-ground fault in DC side were investigated thoroughly. Then the effects of DAB on fault characteristics of the system under different grounding schemes of DC capacitor were analyzed and compared. Based on this,the interactions between AC and DC system during the fault were investigated and compared comprehensively. Besides, a method to analyze the fault characteristic of the system with DAB was proposed. Finally, the results were verified by Matlab simulations. The conclusions were derived that the DAB has more influence on the fault characteristics of system with the direct grounding scheme and DAB can reduce the influence between the AC and DC system, which provide a theoretical basis for the design of grounding and protection schemes.
引文
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