基于二极管整流器-MMC枢纽的大型海上风电场交直流混合汇集与高压直流输电系统

Conventional offshore wind farm(OWF)integra-tion systems typically employ AC cables to gather power to a modular multilevel converter(MMC)platform,subsequently de-livering it to onshore grids through high-voltage direct current(HVDC)transmission.However,scaling up the capacity of OWFs introduces significant challenges due to the high costs as-sociated with AC collection cables and offshore MMC plat-forms.This paper proposes a diode rectifier(DR)-MMC hub based hybrid AC/DC collection and HVDC transmission system for large-scale offshore wind farms.The wind farms in proximi-ty to the offshore converter platform utilize AC collection,while distant wind farms connect to the platform using DC collection.The combined AC/DC power is then transmitted to the offshore DR-MMC hub platform.The topology and operation principle of the DR-MMC hub as well as the integration system are pre-sented.Based on the operational characteristics,the capacity de-sign method for DR-MMC hub is proposed.And the control and startup strategies of the integration system are designed.Furthermore,an economic comparison with the conventional MMC-HVDC based offshore wind power integration system is conducted.Finally,the technical feasibility of the proposed inte-gration scheme is verified through PSCAD/EMTDC simulation with the integration scale of 2 GW.