Research On Power System Transient Stability Analysis Method Based On Resistance Margin

With the expansion of power grid,the transient stability problem is more and more prominent,after disturbance,it is important for us to quickly determine system stability.This paper focuses on the judgement of transient stability,and proposes a transient stability analysis method based on resistance margin.This method combines the features of the critical machine and the resistance margin,making the multi-machine system transient stability analysis into the research of angle stability resistance margin index on critical machine.Based on the Thevenin equivalent principle,this paper proposes relative comprehensive dynamic equivalence principle.By studying the dynamic equivalent circuit for PV nodes,we can obtain the resistance margin for PV nodes,and quickly analysis system angle stability.Simple system transient stability analysis shows that during first cycle the swing angle which after the power system disturbances can reaches a maximum limited value is the necessary condition to maintain the system stability.Based on this theoretical basis,and according to the cosine relationship between the resistance margin and angle,we define resistance margin dynamic saddle point.Dynamic saddle point is not only a track feature point on system instability,but also as an observation point which can quantify the system instability degree.According to the rule that system will lose stability over the of dynamic saddle points,we put forward a continuous resistance margin method,this method is used on identifying the transient stability of simple system.This article will promote the continuous resistance margin method of simple system to complex multimachine system.Supposing multi-machine system lost stability between two machine groups,ahead of the critical machine and delayed non-critical machine constitute a critical machine pair.This paper proves that transient stability of critical machine pairs equivalent reflect the stability of whole system.We discusse the Equal Area Criterion methold of two machine equivalent system which consists of a pair of critical machines,and get a simple and practical Equal Area Criterion method for transient stability criterion.We look from the critical machine,and use the relative comprehensive dynamic equivalence principle on multimachine system.This paper researches continuous resistance margin of critical machine,and demonstrates the effectiveness of the judgment to multimachine system stability.This paper also discusses the transient stability limits of critical machine,and proposes a fast estimation method based on resistance margin.The method of critical machine in combination with the resistance is simple and practical,without cluster partition and equivalence,only identifying a small amount of critical machines,rather than the entire critical cluster,reducing the reliance on global information and improving efficiency.The simulation on New England 10 machines and 39 nodes system verify the effectiveness of this method.