High voltage direct current (HVDC) system has gained number of applications in offshore wind farm, and the majority of studies that are being conducted on the HVDC system focus most on the transmission line; where HVDC contributes efficiently to power conditioning, compensation, and power filtering. This paper investigates the use of DC system for the design of power generating plant of the offshore wind farm; or DC collection grid for a wind farm. Recent studies have contributed a lot in this direction. A DC collection grid system can be provided through series or parallel interconnection of wind energy conversion units (WECUs); each conversion unit includes a wind-turbine-generator and a power converter. The studies that are being done on the design of DC collection grid for wind farm use the full-bridge voltage source converter (VSC) as the topology of power converter. This paper describes some advantages and drawbacks of using the full-bridge VSC layout. The paper proposes another topology which is the single-controlled-switch converter. Comparison of these systems is done in terms of control performance and power loss. The dynamics of the WECU circuits is modelled and analysed. Power Simulator (PSim) and Matlab software are used to test the results.
