The Analysis Of Power System Dynamic Voltage Based On Bifurcation

In recent years,many voltage collapse incidents have occurred at home and abroad successively, which cause huge economic losses and great social disorders.At the same time,due to the rapid growth of the load demand,power system is closer and closer to the limit of stable operation, the stability is facing serious challenges,so this makes the voltage stabiliy problem become research focus of electricity academic field.There are many factors that affect the voltage stability in power system,with the development of grid,the introuduction of Flexible AC Transmission System(FACTS) and High Voltage Driect Current (HVDC) increases the complexity of the problem.Making use of bifurcation theory,this paper analyzes the impact of key equipments on voltage stability,and studies the feature of voltage stability in AC/DC system,the researching results is summarized as:1) Based on two different load models,the influence of excitation system and Static Var Compensator(SVC) on voltage stability is studied.This paper analyzes the effect of magnification on improving voltage stability by simulating PV curves and bifurcation points.The influence of excitation system output limit is studied, Limit Induced Bifurcation isn’t appeared at this time,minimum value of output that excitation system shuould be setted up is discussed.2) Two-dimensional parameter bifurcation boundary is simulated.This paper researchs the impact of parameter change on system bifurcation,and analyzes the bifurcation type which restrict system stability in different situation,receives the excitation magnification which is most likely to make induction motor produce Hopf bifurcation,indicates that the higher excitation reference voltage can eliminate Hopf bifurcation.3) The impact of excitation and SVC on improving AC/DC power system voltage stability is studied.This paper analyzes the influence of excitation output limit on PV curves and bifurcation points,because of huge reactive demand, excitation output limit makes the AC/DC power system produce Limit Induced Bifurcation easily.This paper testes the correctness of conclusion by time-domain simulation,that is different to pure AC system.SVC can delay the Hopf bifurcation effectively,but it increases the singularity of Jacobian matrix and makes the system produce Singularity Induced Bifurcation firstly.4) The distribution of stble scetion on PV curve is discussed,by tracking eigenvalue orbit,this paper obtains the reason for the change of stability on PV curve,indicates that the lower half of the PV curve may be asymptotically stable,test and verify the concrectness of the conclusion through time-domain simulation,and illustrates whether the system can operate normally according to AC control angle changing curve.