An Analysis Of Small Disturbance Voltage Of The Load Center Contained Power Plant

Preventing voltage instability is an important aspect of safety and stability in power system. Along with the development of industry, the improvement of living standard and some other reasons, load centers get together gradually, large-scale power plants in distance send electricity through high-voltage transmission line to load centre. Receiving-end grid voltage problem is much worse. It is necessary to study the voltage stability of the load bus, analyze mechanism of voltage instability in theory, research voltage stability index which is used on-line, offer theoretic warranty for detecting, preventing and correcting, avoid malignant voltage collapse, and provide technical direction for taking the suitable way to raise voltage stability.In our country, there are large amounts of small coal-power plants, gas-turbine generator units, small hydro-power plants, wind-power plants, inverters of photovoltaic plants which based on virtual synchronous generator in the load center. Because these power plants are close to the load, the electricity is sent to living quarters directly without remote transmission. These power plants joint on load bus directly or make micro-grid, then joint on load bus. In all kinds of those power plants, the different types make different effects to voltage stability.Now, most papers have not considered small power plants when analyze voltage stability of load bus. This thesis uses the synthesis load model contained small power plant to analyze voltage stability and deeply discusses the theory of voltage instability. This thesis mainly researches the load model of small disturbance voltage stability analysis which contains synchronous generator in load center. Finally, it suggests the on-line index that can quickly judge the level of small disturbance voltage stability. This thesis researches for the unit in load center as the synchronous generator as follow:â‘ Built the mathematic model to analyze small disturbance voltage stability of synchronous generator in load center. Analyzed the synchronous generator how to affect the eigenvalues of the dynamic Jacobian matrix and present a striking contrast to the condition without the generator in load center.â‘¡Got the index to show small disturbance voltage stability by modal analysis method.â‘¢Researched how the partial parameters'changes affect the index of small disturbance voltage stability and how the small power plant jointed affect the P/V curves of load bus.This thesis uses typical testing cases and a real power system to simulate the conclusions. The simulation results indicate the small power plant enhances the voltage stability. If we only change the amplification factor of the speed control system, there is no use for voltage stability. High amplification factor of the excitation system is benefit for the voltage stability, but it needs large reactive-load compensation capacity. According to the simulation P/V curves, we know that P/V curve moves towards the right when the local power plant is working. If the load consumes the same power, the load bus can maintain higher voltage level. If the load bus maintains the same voltage level, load can consume more power safely.