The Analysis Of Power System Stability And Load Modeling Based On PSASP

Along with openness and commercial operation of modern power network, the scale of power network gets more huge, the operation of power system is at its limits. The economy and stability of power system are restricted each other. It makes safety and stability of power system more complicated. Once the power system stability being destroyed, it will result in vast economic loss and catastrophic consequence. Studies on power system stability become much more important.Based on the transient stability model in PSASP, multi-machine system was simulated in the time domain simulation under large disturbance. This paper analysed the influence of different cases on voltage and rotor angle stability under large disturbance. The different cases were load models, fault clearing time, undervoltage load shedding and different proportion of induction motor. Researches indicate that it is profitable for the voltage stability when the fault clearing time is fast. It is disbennifit for voltage stability when the proportion of induction motor in load is high. Undervoltage load shedding benefits to voltage stability, the more and the faster load shedding, the better the voltage recovers, but it makes the rotor angle curve wave largely.This paper analysed the influence of different network structure on voltage and rotor stability. The influence of AVR and PSS on rotor stability was analysed in a single-machine to infinite-bus system. Researches indicate that only using AVR can reduce the rotor swing at the initial stage, but it increases rotor swing after the following swing. Rotor easily lost stability in weak-connection system. Using fast and high amplification AVR and PSS can improve the rotor angle stability in weak-connection system effectively. In the analysis of single-machine load system, it shows that critical clearing time is different in different position. When fault occurs in the same position, the critical clearing time is longer in strong-connection system.Based on the above analysis, it can get the conclusion that load and structure of the network have an important effect on power system stability. They should be modeled more precisely. This paper added distribution network to load modeling and gave a clearly formula deduction about distribution network flow after equivalence. The initial value and power of induction motor were deducted too. As a example, a load of WSCC9 was substituted by a load which containing distribution network. The parameter of distribution network equivalented was identified by using genetic algorithm. Then the parameter of load containing ZIP and induction motor was identified. By comparing identified system with original system under the same disturbance, it shows that identified system can reflect the dynamic characteristic of load precisely. Based on simulation function of PSASP, it can provide better advice for the power system operation according to the need of system operation.