Research On Interactive Impact Assessment Of Voltage Stability And Power Angle Stability

The stability of power system is related to whether the power system can operate safely,stably and reliably,which has far-reaching research significance in power research.Voltage stability and power angle stability are two major parts of stability-related problems.The time intervals between them are almost the same.They are closely related and interact with each other at the same time,which may promote the development of power system to a more unsafe instability situation.Therefore,the mechanism and degree of interaction between voltage stability and power angle stability are very important for the prevention and follow-up measures of system faults.Based on the definition and essence of system voltage stability and power angle stability,the influence mechanism of power angle on voltage stability is discussed based on the transmission characteristics of tie-line,load characteristics and reactive power support at the receiving end.A set of index system for quantifying the impact of power angle on voltage stability is constructed,including total reactive power and load active power variation index,tie-line reactive power loss index,load bus voltage amplitude index and load power factor index.Combining with the theory of fuzzy mathematics,the membership function of each index is determined by assignment method,and the weight factor of each index is determined by grey relational degree method.The final fuzzy comprehensive function is obtained by summing the values of each index after fuzzy standardization according to the weight factor.A two-machine small system model is constructed and applied to the two-machine small system.A value of fuzzy function is obtained,which is between 0 and 1.The effect of power angle on voltage stability is quantitatively evaluated when the power angle of a system swings greatly.Then,the method is applied to a regional power grid,and the impact of power angle instability on voltage stability is quantitatively analyzed,which verifies the validity and rationality of the criterion proposed in this paper.Based on the power angle characteristics and the transmission power characteristics of tie-line,the influence mechanism of voltage on power angle stability is discussed.The theory of power cut-off magnitude related to the influence of voltage stability on power angle stability is put forward.The simulation of p ower cut-off magnitude of the two-machine small system and the instability mode of a regional power grid verifies the correctness of the theory.