A demonstration on the similarity of pitch response between MW wind turbine and small-scale simulator

Abstract

This study demonstrates the similarity in the pitch responses of a target multi-MW wind turbine and a small-scale simulator by reflecting the nonlinearity of the aerodynamic torque. A 3.5 kW simulator is used to emulate a target 2 MW wind turbine with similar dynamic characteristics of the pitch controller. The pitch controller, consisting of a proportional-integral (PI) controller and a gain-scheduler for the 3.5 kW simulator, is designed to provide similar pitch responses to those of the target 2 MW wind turbine for the entire wind speed region above the rated. The highly nonlinear aerodynamic properties with varying wind speed and their effects on the two poles of the closed-loop pitch control system are investigated. The pitch PI gain values and gain-scheduler are designed such that the natural frequencies and damping ratios of the closed-loop pitch control systems for the target 2 MW wind turbine and the 3.5 kW simulator will be almost the same at both the design and cut-out wind speeds. The overspeed, overpower, and settling time for pitch responses to step wind speeds are investigated, and their values for the target 2 MW wind turbine and the 3.5 kW simulator are compared quantitatively. Through both numerical simulations and experiments, it is demonstrated that the 3.5 kW simulator has similar dynamic characteristics to the target 2 MW wind turbine in terms of pitch response.