Robust control of hybrid excitation synchronous generator for wind applications

The purpose of this paper is to develop a robust control law for a hybrid excitation synchronous generator (HESG) for wind power applications. In a HESG, the excitation flux is created by both permanent magnets and excitation coils, so the output voltage can be controlled by the DC excitation field. For isolated loads, it is then possible to use a very simple and reliable wind generator architecture composed only by a HESG, a rectifier and a DC/DC converter to control the excitation flux. However, the control of such a structure is not easy, especially if the system parameters are not well known. In this paper, the wind generator architecture is presented, modeled and simulated. The control is performed using a cascade control scheme: PI controller for the excitation current inner loop and H∞ controller for the speed outer loop. The obtained results prove that robust control can be used for this architecture and can provide good dynamic responses despite large uncertainties on the electrical parameters.