Robust control of a HESG for a wind energy application

摘要

Lately, robust control strategies have been of much interest in the domain of Wind Conversion System (WCS). The purpose of this paper is to validate a robust control scheme for a stand-alone WCS, based on a Hybrid Excitation Synchronous Generator (HESG), in its maximum power point tracking (MPPT) zone. This research is motivated by the use of a HESG in a WCS. Previous works involving HESG deal mostly with the structural features of this innovative generator. Here, the focus is mainly on the development of an efficient and reliable control strategy for the hybrid generator in the wind energy field. The control is synthesized using a PI controller for the excitation current loop and an H-infinity controller for the velocity loop.A step-by-step procedure for designing the velocity controller is presented. In the proposed approach, an accurate equivalent model of a WCS is implemented under Matlab-Simulink software. A two-mass mechanical model of a wind turbine is proposed in order to properly analyze the dynamics of the flexible shaft and thereby avoid any possible instability of the drive train. The effects of the generator's space harmonics and converters' commutations on the control are taken into account. Robustness tests are performed. Despite the generator complexity, good simulation results are obtained. An experimental implementation on a test bench is realized in order to further validate the efficiency of the proposed control strategy and thereby prove the applicability of a HESG in the wind energy field.