Self-Synchronizing Control and Frequency Response of Offshore Wind Farms Connected to Diode Rectifier Based HVDC System

Abstract

Light-duty offshore wind power system has been a research hotspot in recent years. The diode rectifier based HVDC scheme is a promising solution and has attracted more and more attention. In this paper, a self-synchronizing control for offshore wind farms connected to diode rectifier based HVDC system is proposed. The active power of each wind turbine is controlled by regulating the amplitude of the AC voltage, while the reactive power is used to adjust the offshore frequency. The proposed control is a decentralized scheme. Thus, no communication network or GPS is required and only the local information is used in the control system. The synchronization of wind turbines is achieved by the proposed self-synchronizing frequency control instead of using phase-lock loop. Besides, in order to make offshore wind farms provide necessary frequency support to the onshore power system, a communication-less frequency regulation scheme with artificial coupling method is proposed. The feasibility and effectiveness of the proposed self-synchronizing control and frequency regulation scheme are verified through simulation studies in PSCAD/EMTDC platform.