Nonlinear co-ordinated control of excitation and governor for hydraulic power plants

A nonlinear decentralised excitation and governor co-ordinated controller design for hydraulic power plants is proposed to enhance power system transient stability. First, the excitation system and hydro-governor system, considering non-elastic water hammer effect, is modelled as a whole. Then, based on differential geometric theory, the original nonlinear system for multi-machines is exactly linearised by appropriate co-ordinate transformation. After that, linear optimisation control is applied such that the final optimised nonlinear excitation and governor co-ordinated control law can be obtained. To demonstrate the efficiency and analyse the co-ordination mechanism of the proposed controller, simulations on an OMIB system and the EPRI-36 system are performed. Comparison with classical excitation and governor control, nonlinear optimal excitation control, nonlinear robust governor control, the suggested decentralised and co-ordinated control can achieve considerably better performance in improving the transient stability of power systems.