Research On The Propagation Mechanism Of Cascading Failures In AC/DC Power Grid And The Recognizing Of The Weak Parts

With the rapid development of the global economy, the large-scale interconnection power grid has become an inevitable trend for development of power system, and the widely used in HVDC as well as increasing of AC/DC transmission systems, the complexity of the power grid also increases. Although the characteristics of AC and DC transmission are totally different, the two have very close contact and very complicated interaction in the operation of actual power grids. The improving economy of power system operation proposes an even more stringent requirement for the reliability of power supply. The fault in some part of the grid might spread to the nearby power grid, and induce a chain reaction. The fault in some part of power grid might spread to the neighboring regional power grid, and induce a chain reaction, finally resulting in widespread power outages and even the collapse of the entire power grid. Research scholars of cascading failures made a lot of achievements and breakthroughs. But for AC/DC power grid cascading failure also rarely studied. Therefore, the study of cascading failure mechanism in AC/DC power grid and recognizing the weak parts is to avoid cascading failure in AC/DC power grid caused a major blackout key and has practical significance.Firstly, the thesis summarizes the research status of analysis methods for cascading failure, and the weaknesses identification of the power grid cascading failures. The mechanism of power grid cascading failures are derived. Research on the mathematical model of AC/DC power grid. Discusses the impact of due to DC into AC system and AC systems for DC line based on the model, and gives cascading failure mechanism in AC/DC power grid based on mutual influence between AC and DC systems.Based on the model, study and propose recognizing the weak parts method of cascading failure mechanism in AC/DC power grid including key lines and nodes. For effectively prevent and control cascading failure to lay the foundation.Finally, using China Southern Power Grid 2015 summer big load date to recognize the weak parts of the AC/DC power grid, verify the proposed theory is correct and effective. Provided an effective method for prevent the occurrence of cascading failure in AC/DC power grid.