Contribution à la compréhension de la dynamique des rotors des alternateurs hydroélectriques

Abstract

In hydropower plants, turbine-generator units are subject to multiple dynamic forces and torques that under certain conditions can generate noise, vibration and network interaction problems, even equipment failures. The objective of this thesis is to develop and study the model of the hydro-generator in the presence of eccentricities, non-uniformity of the measured air gap and the inter-turns short-circuit in rotor winding, in order to contribute to a better understanding of the dynamic behavior of turbine-generator groups. Hydro-generators always have non-uniform air gaps. Thus, the study stretches to develop the model of the alternator using finite element and the accurate measurement of the real air gap of an existing hydro-generator to study and determine the electromagnetic forces that might excite its structure. Since the air gap is affected by thermal expansion, stator and rotor shapes, and rotor motion this numerical modeling is necessary to render the generator behavior very close to reality. On the other hand, among the most common defects that can appear in the rotor of a hydro-generator is the rotor inter-turns short-circuit. The inter turn short-circuit bring a significant increase in vibrations. These two faults play an important role in the calculation of electromagnetic forces. Depending on the intensity of the fault, rotor movement and electromagnetic force can be significant. The model makes it possible to study and evaluate, more precisely, the impact of these defects on the electromagnetic forces of the hydro-generator. In addition, the present study is also interested in modes and frequencies that are likely to generate vibrations of the stator structure following electromagnetic excitations. The Fast Fourier Transform of the electromagnetic force density and the total resultant force show the existence of subharmonic components that have not exhibited in other types of electrical machines. These subharmonics cause significant vibrations on the shaft of the turbine-generator unit, as well as on the stator and rotor of the generator. Experimental results also support numerical and analytical results in the identification of force spectra. In this work, the numerical analysis has contributed to the study of the dynamic behavior of shafts of hydroelectric turbine-generator units as part of the project SAMH (Numerical Simulations Applied to Hydraulic Machines) of the research institute of Hydro-Québec.

Date	22 Jan 2019
Original language	French
Awarding Institution	École de technologie supérieure
Supervisor	Kamal Al-Haddad (Supervisor) & Arezki Merkhouf (Co-supervisor)