Research Of Transient Stability Of Grid-Connected Inverter-Interfaced Distributed Generators

With the rapid development of the global economy,the crisis of energy supply shortage has become increasingly severe,and the problem of environmental pollution has worsened.Renewable energy is an important source of energy to solve the global energy crisis and achieve environmentally friendly development.Distributed power generation technology with flat,wide-area,and high-efficiency characteristics has become an important issue for consuming renewable energy and achieving green development of the power grid.However,there is a problem of transient instability in grid-connected inverter-type distributed power sources.This thesis takes the transient stability of grid-connected inverter-type distributed power generation as the main topic and conducts researches on its mechanism,transient stability diagnosis and stable control.The results are as follows:(1)Through the analysis of the development history and research status of gridconnected distributed power generation technology,the key problems faced by gridconnected inverter-interfaced distributed power generation in transient stability are summarized.The transient stability research methods are summarized.(2)Researches are conducted to build the basic structure and operating principle of the grid-connected inverter-type distributed power supply,to establish the gridconnected model and control model of the inverter-type distributed power supply,and to propose the inverter-type distributed power supply according to its operating active power angle curve and reactive voltage curve.Transient stability mechanism and the influence of droop factor and external power grid parameters on transient stability are studied.The proposed transient stability mechanism is verified through simulation.(3)According to the second theorem of Lyapunov’s stability,the theory of the energy function of grid-connected inverter-type distributed power is proposed and the transient energy function of grid-connected inverter-type distributed power is proposed by analogy with synchronous generator.The transient stability domain and the discrete calculation method of transient stability region are proposed.Simulations verify the validity and accuracy of transient stability region.(5)The short-term reserve method of distributed energy power and the calculation method of reserve capacity are proposed.System constraints under the transient stability demand of the microgrid are analyzed.Reserve strategies of the distributed power generation under different operating scenarios is systematically proposed,which effectively improves the overall transient stability and operating economy.(6)A microgrid transient stability control method is proposed.A microgrid transient stability hardware-in-the-loop simulation platform is built.The simulation simulates the state changes of microgrid switching off,on-off and off-grid switching,state switching and black start,verifying the microgrid effectiveness of transient stability control.Finally,the paper summarizes the results of the study,and points out the direction for further research.