Study On Vibration Of Rotor Shaft Of Generator Sets And Discontinuous Bifurcations Of Network-Generator System

Operating conditions of whole generator set and network are affected by safety and reliability of rotor shaft of the generators. Vibration of the rotor shaft excited by electromagnetic force is a key factor that leads to accidents. Hence it is important to study the vibration. Discontinuous factors of a network-generator system may lead to discontinuous bifurcations. Having information of the bifurcations will be helpful in controlling the system. The work of the paper is divided into four parts based on the above considerations. 1 Calculating method of zero mode natural frequency (ZMNF) that is excited by electromagnetic force is derived from the point of view of magnetic field energy. Laws of ZMNF varying with active power and excited current are discussed and verified by experiments. A three-mass model is established based on some actual parameters of a large turbine generator. Then coupled lateral and torsional vibration of the shaft system is studied when considering rest eccentricity, rotating eccentricity and rest swing eccentricity. Characteristic curves are derived with energy method when rotating speed is near ZMNF. 2 The first approximate equations are gotten from the coupled equations with improved averaging method. Twofold resonances λ1 ??=0, λ4 ?3λ1=0, twofold resonances fυ? λ4 = 0, 3λ4 ? λ2=0and threefold resonances λ,λ4 ?3λ1=03λ4 ? λ2= are studied with Gather-and-Sift Method which is a new effective method used to solve nonlinear equation sets. A group of characteristic curves of the multiple resonances is obtained. Meanwhile, effects of eccentricity on the vibration are studied. 3 Bifurcation problems of fixed points of non-smooth continuous system are studied. At first, a set of 27 rank nonlinear equations of coupled mechanical and electrical system is established. Through introducing amplitude-limit control of excitation system to the coupled system, the equation set becomes a piecewise continuous system. Jumps of eigenvalues of fixed points affected by electromagnetic parameters are studied, and bifurcations resulted from jumps of eigenvalues are derived. At last, the results are testified by numerical analysis. The results show that jumps of eigenvalues can lead to a kind of bifurcation that is similar to bifurcations of smooth systems. 4 Bifurcations of periodic solutions in non-smooth continuous systems are studied. At first, a set of 24 rank non-smooth equations of a network-generator system is established. Concepts and calculating methods of zero time discontinuous mapping (ZDM) and Poicare discontinuous mapping (PDM) are given, and testified by the network-generator system. On the basis of the PDM, domain of existence, stabilities and bifurcations of the periodic solutions are found with XL and Xc as a pair of parameters as well as R and Xc as a pair of parameters.