Series Connection of VSC Modules for Offshore Wind Farm Application

A DC series connection structure of offshore wind farm connecting to the main grid via HVDC link with a single centralized VSI is studied. Compared with the most existing topologies, this topology contributes to simplifying the system configuration and operation, decreasing the number of converters and removing offshore centralized converter, and increasing the DC voltage level. Moreover, to keep DC voltage stable at grid side and extract the maximum wind power from the offshore wind farm, a dual-power mode control algorithm applied to wind farm side converters and DC-bus voltage regulation with power feed-forward, to improve the dynamics response of DC voltage, used to grid side converter. Finally, a case study of 100MW offshore wind farm consisting of 50 individual 2MW PMSG-based wind turbines and which connects to the grid by HVDC system is developed in MATLAB/SPS. Simulation results verified, based on a DC series connection structure of offshore wind farm connected to the main grid via HVDC link, the whole control system works well.