| In modern power system,with the rapid development of wind energy generation,solar energy generation,high voltage direct current(HVDC)transmission,the application rate of power electronics technology in power system has been greatly increased.At the same time,the electronic power system has some new characteristics compared with the traditional power system.The three-phase voltage source converter is a typical power electronic device,therefore,this paper takes voltage source converter as the research object.The nonlinear phenomena such as saddle node bifurcation,hopf bifurcation,unstable limit cycle,parameter bifurcation tree,parameter space and stability domain under the influence of nonlinear factors are studied.Specific research contents include the following aspects:(1)Combined with the basic topology of voltage source converter,the small signal model is analyzed by means of linearization under the two conditions of ignoring and considering the phase-locked loop control.The similarities and differences between the two models are compared.The conditions of saddle node bifurcation and hopf bifurcation are obtained by theoretical analysis and numerical calculation.Numerical simulation tool MATLAB is used to verify the correctness of bifurcation condition under dc voltage time scale.(2)According to the analysis of nonlinear dynamics,it is found that the voltage source converters have unstable limit cycles when the phase-locked loop is not considered.The existence of the unstable limit cycle is verified by using poincare mapping as the theoretical basis and numerical simulation tool MATLAB.In this paper,the parameter space and parameter bifurcation tree of dc voltage time scale are analyzed.The stability domain of voltage source converter is described by numerical simulation when only dc capacitance dynamics,dc voltage control and terminal voltage control are considered.Based on this stability domain,some phenomena of power system stability are analyzed. |
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