Voltage Stability Research Of Microgrid Based On Bifurcation Theory

Microgrid fully realized the advantages of distributed generation. The characteristics ofmicrosources and loads determined the voltage stability problems of micogrid. The currentanalysis methods for microgrid voltage stability are defective, which cannot take the dynamiccharacteristics of components into considerate, or cannot give margin information and otherproblems. So, the analysis method of the voltage stability plays a great importance role inmicrogrid. Therefore, we carry out the following, and come to the conclusions.Firstly, this paper analysis the micro grid characteristics and used bifurcation theory foranalysis microgrid voltage stability. The mathematical models of microsources likeasynchronous wind generator, photovoltaic cell and fuel cell, and loads like asynchronousmotor and ZIP load were established. The simulation models of these components were alsoconstructed in PSCAD, in which a simulation operating with stabilization done by fuel cellwhile a simulation operating with disturbance done by asynchronous wind generator.Secondly, the voltage stability margin of a9nodes microgrid was calculated by usingSNB point of bifurcation theory being for locating the voltage stability boundary. ContrastiveAnalyses of accuracy were implemented between bifurcation theory and static continuouspower flow. The influences of the forms, capacities and connected positions of microsourcesto the voltage stability margin were analysis by using bifurcation theory. The result showsbifurcation theory can be applied to strike a microgrid voltage stability margin as well as theposition of the critical point, and it is accuracy and applicability to judgment the microgridvoltage stability boundary. The different kinds of microsources shows different characteristicsand voltage stability margin of micro networks based on microsource capacities and gridpositions.Lastly, because of the need to evaluate voltage stability online, this paper provided anonline voltage stability index which based on synchronized pharos measurement technology.The WSCC-9system was be used for verify the effectiveness of this index. And the index wasused to analysis the influences of the forms, capacities and connected positions ofmicrosources to the voltage stability margin. The index could correctly reflected the rules of the influences, and it could use in voltage stability online distinguish based on synchronizedpharos measurements in the load nodes with weak voltage standard.