基于晶闸管直流变压器的新能源基地分区直流汇集方案OA

To achieve cost-effective DC collection and transmission for large-scale renewable energy bases,this paper proposes an active-assisted commutation DC transformer(AAC-DCT)based on the thyristor.The AAC-DCT employs front-to-front connected 6-pulse thyristor bridges and diode bridges as the main conversion components,and incorporates a submodule chain(SMC)composed of a small number of fully controllable device submodules to assist in thyristor commutation.The AAC-DCT is designed to provide only DC voltage transformation and electrical isolation.Therefore,the SMC only needs a low-voltage output capability(approximately 15％of the rated DC voltage on the low-voltage side)to generate commutation voltage and drive the six thyristor bridge arms to conduct alternately.Based on the AAC-DCT,a partitioned multi-terminal DC collection scheme suitable for 10-gigawatt-level renewable energy bases is proposed.Power from multiple small-to-medium partitioned zones is transmitted to a collection station via lower-voltage DC collection lines,then boosted to ultra-high-voltage DC level by the AAC-DCT for centralized transmission.This scheme can solve the problems of reactive power compensation and voltage control encountered in AC collection schemes,and significantly reduce the investment cost of converters and lines in the DC collection system.Although the AAC-DCT lacks flexible control capability,the multi-terminal DC system formed by it can still achieve flexible power flow control through voltage regulation of the sending-end and receiving-end converters.Finally,the simulation verifies the feasibility of the AAC-DCT and the partitioned multi-terminal DC collection scheme.