A Novel AC/DC Power Flow Algorithm Considering MMC-HVDC Connected Offshore Wind Farms and System Regulation Characteristics

Modular multi-level converter based high voltage direct current transmission (MMC-HVDC) technology has been widely used in offshore wind power projects. Besides, massive integration of offshore wind power causes conventional power flow, which assumes fixed bus types and a slack bus to fully accommodate system power unbalance, hard to converge. To tackle the aforementioned power flow challenges associated with AC/DC power systems connected by MMC-HVDC, a novel power flow algorithm is proposed in this study, which also considers the regulation characteristics of generators and loads to reveal real system response to offshore power fluctuations. Specifically, a DC power flow model is firstly established for the MMC-HVDC based offshore grid-connected system. Then, an AC power flow model that considers the regulation characteristics of generators and loads is formulated for onshore AC grid. On this basis, a novel AC/DC power flow model combining the offshore DC and onshore AC models above is presented and solved by an alternating iterative strategy. In the end, the accuracy and effectiveness of the proposed model and method are verified through simulation on the modified example system.