Suppression Scheme for WECS's Forced Torsional Vibration Under Continuous Wind Disturbance Considering Power Yield and Smoothness

The main control objectives of wind energy conversion system include maximizing power yield and minimizing unnecessary mechanical loads. Under continuous wind disturbances, the forced torsional vibration with broad frequency-band has been detected on the drive train, which share the similar spectrum with the wind fluctuations. It is also found that the existing active damping control cannot effectively suppress the forced torsional vibration, some of which may even have adverse effects. Besides, the suppression of such wide broadband torsional vibration may worsen power tracking and power fluctuations. In order to solve the above problems, this paper first defined a closed loop transfer function to describe the forced torsional vibration characteristic. The demand of electrical damping reshaping for suppressing torsional vibration is revealed, and then a controller structure featuring frequency-distinct electrical damping configuration is proposed. The impacts of control parameter <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">τ</i> on multiple objectives are analyzed qualitatively, then a quantitative design method of optimal control parameter <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">τ</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">opt</sub> combining three closed-loop transfer functions and the Van der Hoven spectrum is proposed to give full consideration of power tracking ability, power smoothing and torsional vibration suppression. The controller hardware-in-loop simulation based on GH Bladed and Beckhoff C6930 is established for the verification of the proposed method. The test results show that the proposed method can effectively reduce the forced torsional vibration while keeping maximizing the power tracking and minimizing power fluctuation under continuous wind disturbance.