Current source DC/DC converter based multi-terminal DC wind energy conversion system

• Main Author: Fan, Shixiong
• Published: University of Strathclyde 2012
• Subjects: 621.312136
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.570634

Wind power energy conversion is growing rapidly in the world. There are two main wind farm types, namely ac grid-based and dc grid-based wind farms. The dc grid-based approach reduces the size and weight of the magnetic components and cables. In the dc system, the step-up dc/dc converter is the key component when interfacing the wind turbine to the ac grid, via its low/medium voltage generator. This thesis focuses on the control and design of a wind energy conversion system based on dc/dc current source converters. An optimized One-Power-Point method for maximum power tracking is proposed. It incorporates One-Power-Point control and Maximum Power Differential Voltage control to allow the wind turbine to extract more energy during rapid wind speed changes. A current output hard-switched full bridge converter and serial-parallel resonant converter with an intermediate high frequency transformer are investigated for interfacing wind turbines to a local dc grid. These converters are assessed and compared in terms of semiconductor stresses and losses. A new modified One-Power-Point control method is proposed for the dc/dc converter, which tracks the maximum power during wind speed changes. A design procedure for the serial-parallel resonant converter is presented, based on its characteristics specific to a wind energy conversion system (WECS). A current source dc/dc converter based multi-terminal dc WECS is presented, investigated, and simulated. A practical multi-terminal dc WECS verifies its feasibility and stability, using two dc current output wind turbine units. Furthermore, a coordinated de-loading control scheme for the current sourcing based WECS is proposed, to cater for ac grid demand changes. It combines pitch control, dc dumping chopper control, and dc/dc converter control, to safely and quickly establish de-loading control. Both simulation and experimental results verify the de-loading scheme.