Fault Characteristics and Control & Protection Strategy of Three-Terminal LCC-MMC Hybrid HVDC Transmission System

doi:10.3969/j.issn.1000-7229.2017.08.010

Abstract

Abstract: ABSTRACT： This paper studies the AC/DC fault characteristics and control & protection strategies of the three-terminal hybrid DC transmission system with line commutated converter （LCC）-modular multilevel converter （MMC） converters. Based on the analysis of the existing fault crossing control strategy, the coordination strategy of the minimum triggering angle control, the maximum modulation ratio of the MMC and the DC voltage deviation control of the inverter side LCC is proposed for the AC side fault. In order to solve the DC fault, the DC line fault current transient variable can be used to identify the fault location and break the fault by the DC circuit breaker by arranging the boundary condition of the current limiting reactor at both ends of the DC link, which can quickly isolate the DC link fault and narrow the scope of the impact of failure. Finally, a hybrid DC transmission system model is established in PSCAD/EMTDC, and the feasibility of the proposed strategy is verified by simulation. The results show that the proposed control strategy can improve the transmission power of the DC system and reduce the probability of the power transmission interruption when the AC fault condition is rectified. The DC current mutation rate protection scheme based on the DC circuit breaker can quickly isolate the fault, and improve power supply reliability.

Key words: hybrid DC transmission, multi-terminal DC transmission, AC/DC fault, suddenly changed current protection, coordination control strategy

CLC Number:

TM 72

HONG Chao, SHI Bonian, SUN Gang, ZHANG Ye, YANG Jian, LIU Bin. Fault Characteristics and Control & Protection Strategy of Three-Terminal LCC-MMC Hybrid HVDC Transmission System

[J]. Electric Power Construction, 2017, 38(8): 73-.

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