Grid-Forming Control and Startup Strategy for Diode Rectifier Unit Based Offshore Wind Power System

Offshore wind farm is the main trend of wind power development in the future. Diode rectifier unit (DRU) shows great potential in offshore wind farm because of its economic and reliability advantages. In this paper, firstly, the mathematical model of system based on DRU is established and the basic principle of grid-forming control is analyzed. Then the stability under standard operating conditions is proved. Secondly, a startup strategy based on improved active power loop is proposed in order to avoid the AC voltage fluctuation in the starting process. Then, the synchronization strategy of multiple wind turbines (WTs) and current decouple strategy are proposed. Finally, the simulation results show that the strategies have good effects during the startup process.