Design and implementation of a fractional nonlinear synergetic controller for generator and grid converters of wind energy conversion system

Abstract

In this paper, a fractional nonlinear synergetic controller is developed for efficient power extraction and operation of a variable speed wind energy conversion system. The proposed fractional nonlinear synergetic control scheme includes: (1) rotational speed regulation for maximum power extraction at the generator converter side through the DC-DC boost converter; (2) DC link voltage regulation and active-reactive power regulation, by controlling the direct-quadratic components of the current, for power transfer at unity power factor, at the grid side converter through the inverter. Analytical design of aggregated regulator has been used in the nonlinear synergetic control design with the introduction of a fractional macro-variable in order to increase the degree of freedom of the classical synergetic controller. The stability of the closed loop system using the macro-variable is guaranteed and a fast convergence can be reached through the design parameter. Experimentation, on a permanent magnet synchronous generator based wind turbine setup, is conducted to validate the proposed fractional nonlinear synergetic control system for operating the generator and the grid sides of the power system. Different cases are studied and the experimental results have shown that the system controlled by the proposed control method is stable and tracks perfectly the desired reference.