Electro-mechanical modelling and analysis of hydroelectric rotor systems

Sammanfattning: Hydroelectric power generation supplies about 20 percent of the world's electricity and is the most important renewable energy converting industry. The installed capacity of Hydro-electrical power generation is approximately 700GW with a production of 2600TWh/year. The technically feasible potential of hydro power is 14000TWh/year. In many countries, the hydroelectric generation where build in the 20th century on a regulated energy market, where the units served base load. Nowadays hydroelectric generation are more and more used to serve intermittent load on a deregulated market. This has lead to a new way to use old constructions, and it becomes interesting to study the characteristics of these machines, used for the demands of the 21th century. The aim of the research project of this thesis is to characterise, model and simulate old in service hydro electrical power generating units, to improve the design to the demands of today. This thesis presents three different models for hydro power rotor systems. The first model is developed to study the fundamental dynamics of the whole rotor system and includes simplified models for the unsymmetrical electro- magnetic field and the fluid interaction in the turbine. The model has been evaluated with on-site measurements. From the first model it has been shown that the fundamental excitation frequencies due to the electro-magnetic field can be described on a simple form. The results from this model also indicate that the fluid dynamical interaction in the turbine has to be model more in detail to determine both amplitudes and frequencies of excitations. The second model is concerning the generator of the rotor system. The model is divided into one electro-magnetic finite element model and one simplified mechanical model. Simulation and analysis are carried out due to the reactive power produced by the generator. It has been shown that the reactive power influence the natural frequencies, steady state response and stability of the rotor system. The third model presented in the thesis is developed for characterisation of hydro power rotor systems by use of the electro-mechanical interaction in the generator. The model consists of a finite element model with rotor dynamical applications. Simulations are carried out for one commercial hydro power unit and the results are compared with measurements. The results indicates that the suggested method excite a few eigenfrequencies. It is concluded that the method needs to be improved in order to separate response due to electro-mechanical and fluid dynamical excitations.