Influence Mechanism and Suppression Control of the MMC on Short-Circuit Current Under AC Faults

IEEE Access

Zheng Xu¹  Jian Yang¹  Xiaodong Li¹  Shurui Mao¹ 

[1] College of Electrical Engineering, Zhejiang University, Hangzhou, China;

关键词: Modular multilevel converter;    symmetrical and asymmetrical AC faults;    short-circuit current;    suppression control;   

DOI  :  10.1109/ACCESS.2020.3012149

来源: DOAJ

【 摘 要 】

Modular multilevel converter based high voltage direct current (MMC-HVDC) transmission systems may increase the short-circuit current and affect the AC fault clearing of circuit breakers. To address this issue, this paper analyzes the influence of the MMC on the short-circuit current when a symmetrical or asymmetrical fault occurs in the AC system. Firstly, the influence mechanism of the MMC on the short-circuit current under symmetrical AC faults is studied. It is found that the short-circuit current magnitude at the fault point is mainly affected by the q -axis output current of the MMC. For the single-phase line-ground fault, the three-sequence equivalent circuit of the MMC is analyzed, and the calculation method of the three-sequence short-circuit current is presented. It is observed that the negative- and zero-sequence currents at the valve side of the MMC are both zero, and the positive-sequence current is determined by MMC operating conditions. Besides, the short-circuit current magnitude under the single-phase line-ground fault is also mainly related to the q -axis output current of the MMC. Based on these results, an additional controller is proposed to reduce the short-circuit current under the symmetrical and asymmetrical faults. Finally, the effectiveness of the proposed mechanism and suppression control is verified by PSCAD/EMTDC simulations.

【 授权许可】

Unknown