Mechanism Research Of Transient Voltage Stabiolity In Receiving-End Grid

This dissertation conducts research work on the mechanisms, mathematics modeling and analysis methods of voltage stability in receiving-end grid. The relationship of transient voltage stability and transient angle stability is discussed thoroughly. The accident characteristics of transient voltage collapse and modes of transient voltage instability are expatiated. The criterions of transient voltage instability are presented.The reactive power isn't the ultimate reason of voltage instability. The transient voltage stability problem of receiving-end grid belongs to whole stability problem, which should be expounded from transmit electricity power ability limit of transmission lines, dynamic characteristics of load and insufficient reactive power supply in receiving-end grid. From mathematics point of view, the power system has stability and instability. But from physics point of view, voltage stability and rotor angle of powr system are different in essence. The division of transient voltage stability and transient rotor angle stability is essential. The dynamic characteristics of load have very great influence to transient voltage stability of power system, but load isn't the only factor, transient voltage stability shouldn't equal to load stability completely.In transient time frame, the mathematics modeling division between transient voltage stability and transient rotor angle stability isn't very clear. The transient rotor angle stability modeling considering dynamic and static load characteristics already can describe transient voltage stability problem. It is very important that the load model used in transient angle rotor stability and used in transient voltage stability should be identical, it isn't correct to adopt different load model because of different research problem. The relations of induction motor stability, transient voltage stability and transient rotor angle stability are studied detailedly by time domain simulation. The induction motor instability or not doesn't have direct corresponding relation to transient voltage instability and transient rotor angle instability. Especially, the induction motor instability doesn't equal to voltage collapse.The power system transient analysis is studied through adopting transient energy function method including induction motor. Structure preserving energy function including induction motor model is founded, and potential energy boundary surface (PEBS) mothed is introduced. Under the light of energy function method, transient rotor angle instability and transient voltage instability can be thought as different unstable mode, and be distinguished from each other by characteristic of unstable equilibrium point. The possible unstable mode is influenced by load model, load location, network structure and system operation mode etc.A transient voltage stability analysis method is put forward based on time domain simulation, energy function method and Singularity Induced Bifurcation (SIB) theory. The transient stable domain of power system is made up of stable manifold of unstable equilibrium point and singularity surface. In the time domain simulation process, the singularity of algebra equations and potential energy peak value should be watched. If transient track intersect with singularity surface, then transient voltage instability will be happen; if transient track intersect with PEBS surface, then transient voltage instability of transient rotor angle instability maybe happen, it should be studied from UEP mode; if transient track doesn't intersect with these surfaces, then system is transient stability.A dynamic thevenin sequivalent parameters tracking method in transient stability is put forward. Its basic thinking is:thevenin sequivalent parameters is calculated in each step of transient stability process, then the transient stability is judged based on simple thevenin sequivalent system. The dynamic thevenin sequivalent parameters tracking calculation method based simulation is solved basicly, the method based on measure should be perfected. The voltage weakness node, voltage load-center node and oscillation center node are put forward. The transient voltage instability criterion based on dynamic thevenin sequivalent is studied. The arithmetic flow applying to actual system is put forward, and the simulation checkout is done.Through the transient voltage stability simulation analysis of actual power grid, the transient voltage collapse characteristics are resolved. Combining with accident characteristics analysis, three transient voltage instability modes are put forward. Faced with actual power grid, the criterions of transient voltage instability are brought forward combining the whole research.