Grid Dynamic Equivalence And Its Trend Of Convergence Of The Study

Analysis on power system transient stability is an important subject of supplying power safely. But power system transient stability calculation is a process of solving differential equation and algebraic equation. When taking on calculation of transient stability of modern power system, the amount of memory is large and costs long time. We need all information of system. Furthermore, we can not make reasonable explanation on hundreds of swing curves.In fact, when we analyze large scale power system, we are usually interested in some part which called studied system and not interested in some part which called outside system. An idea of simplifying outside system was bring up. We call above process dynamic equivalence. The essence of dynamic equivalence is using a simplified model to replace original system's influence on studied system.This thesis adopts dynamic equivalence based-on identification of coherent generator. Solving grammian of differential equation based-on state space can nominate sufficient and necessary condition of coherence. Equivalent system's model is real power system's model. So we can use these models in transient stability directly. This equivalent method is adapted to non-linear and big disturb. It's conveniently to control the precision of dynamic equivalence.Transient stability calculation is composed of four parts: identification of coherent generator, dynamic equivalence, power flow calculation, transient stability calculation.We need calculate power flow before transient stability calculation. Then it comes power flow convergence. This thesis studies power flow convergence deeply. Make improvement on existing program. Bring up several measurements on improving power flow convergence. These measurements include optimization of assigning a number to node, using Chinese as marks of nodes, changing the initial condition of iteration.This thesis shows an example of transient stability simulation. Compare transient stability calculation results of original system and equivalent system. Quantitative and qualitative analyze system scale and calculation time and generator swing curve and voltage before and after equivalence.