This paper analyzes multilevel lumped DBR circuits which are based on the H-bridge inverter unit and simple lumped air-cooled resistors, introducing their structural topology, parameter design and control method, and demonstrates the FRT performance of multilevel lumped DBR circuits by comparing with the modular multi-level DBR circuits. For the offshore wind farm connected by flexible HVDC transmission system, combining the AC-voltage magnitude reduction method of wind farm converter station, the FRT coordination control strategy is designed by using WTGs’ ability of regulating wind farms’ power. Under the premise of ensuring system’s FRT performance, the study reduces DBR circuits’ required capacity thus to adapt for large-capacity and high-voltage situations. Based on parameters of German Borwin1 project, a flexible three-terminal HVDC system model is established in PSCAD/EMTDC software and simulation results show that the coordination control strategy has good FRT control effect.
