Abstract
This paper proposes a new variable structure control scheme for a variable-speed, fixed-pitch ducted wind turbine, equipped with an annular, brushless permanent-magnet synchronous generator, considering a back-to-back power converter topology. The purpose of this control scheme is to maximise the aerodynamic power over the entire wind speed range, considering the mechanical safety limits of the ducted wind turbine. The ideal power characteristics are achieved with the design of control laws aimed at performing the maximum power point tracking control in the low wind speeds region, and the constant speed, power, and torque control in the high wind speed region. The designed control laws utilize a Luenberger observer for the estimation of the aerodynamic torque and a shallow neural network for wind speed estimation. The effectiveness of the proposed method was verified through tests in a laboratory setup. Moreover, a comparison with other solutions from the literature allowed us to better evaluate the performances achieved and to highlight the originality of the proposed control scheme.
Highlights
In recent years, wind energy has been the fastest growing among renewable energy sources [1].In particular, micro and small wind turbines are an attractive solution for distributed generation in urban areas, self-energy production, and microgrids [1,2,3,4,5,6,7,8,9,10,11]
The most common approach used for variable-speed and fixed-pitch (VSFP) wind energy conversion system (WECS) operations under high wind speeds is the soft stall method [11,14,15,16,17,18,19,20], which reduces the shaft speed to force the turbine to operate below its maximum efficiency
We propose a wind speed estimator (WSE) consisting of a shallow neural network (NN) whose inputs are the estimated aerodynamic torque, the measured shaft speed, and the q-axis current of the annular brushless PMSG (ABPMSG)
Summary
Wind energy has been the fastest growing among renewable energy sources [1]. To the best of the authors’ knowledge, the VSFP WECS was operated with respect to the rated aerodynamic power of the wind turbine at high wind speeds only in [14,20] In these studies, the proposed control strategies performed constant aerodynamic power soft stall control. A tripartite control scheme based on the soft stall method is proposed for the DHAWT operation under high wind speeds This operating range is subdivided into constant shaft speed, constant aerodynamic power, and constant aerodynamic torque subregions. The contributions of this study are as follows: the achievement of the soft stall method with a back-to-back power converter topology, the operation of the wind turbine once the aerodynamic torque limit is reached, and the experimental validation of a discretised LO.
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