Design of a controller for a test-rig for a variable speed wind turbine

One of the most promising of the sources of renewable energy for the UK is wind power. Over the last ten years there has been considerable development in the associated technology and the cost of power generated by wind turbines has been reduced markedly. Nevertheless, further progress is required for wind power to become fully competitive on a commercial basis. The Dutch Department of Energy is funding a research programme, FLEXHAT, with the stated aim of reducing the cost of wind power by 30%. It is envisaged that the reduction in cost might be achieved by a flexible variable speed horizontal axis wind turbine. The drive-trains of light-weight flexible variable speed wind turbines are highly resonant. ECN in Holland have constructed a test-rig, IRFLET, to investigate the problems arising from the resonant drive-train. The test-rig has a resonance at 3 Hz approximately with a damping factor less than 0.005. To maintain a variable speed wind turbine at the correct operating point for most effective operation, it is necessary to actively control the wind turbine through the generator reaction torque. It might also be feasible to utilise the control system to regulate the resonance. The purpose of this paper is to report the design and test of a controller to achieve this aim