Analysis On Stability Constraints Of Coordinated Leading Phase Operation Of Multimachine Systems

During valley load period, the excess reactive power in power grid leads to voltage of some central points increasing, which is a serious threat to safe and stable operation of the system. Using the method of leading phase operation of generators to adjust system voltage requires no additional investment and is simple.Firstly, the thesis introduces the basic principle of leading phase operation of non-salient pole synchronous generators and main factors which limit the capacity of leading phase operation, including heating problem of the terminal of stator, static stability limit, the voltage drop of auxiliary power, generator stator overcurrent,influence of transient stability, low excitation limit and field loss protection, etc. The thesis also points out that stability constraint is one of the most important factors limiting leading phase operation capacity of generators. Current research methods on single leading phase operation of single generator and coordinated leading phase operation of multimachines are introduced, as well as some disadvantages of these methods. Then eigenvalue analysis method based on state variable is introduced to calculate leading phase depth of generators, which minutely explains how to establish dynamic model of network system and calculate all dimensional eigenvalues.Because power flow distribution of network system is needed to calculate, it also introduces basic principles of state estimation and the newton-raphson power flow algorithm.Moreover, how to utilize eigenvalue analysis method based on state variable to determine maximum leading phase depths of single leading phase operation of single generator and coordinated leading phase operation of multimachines is introduced.And the thesis gives the flow charts of determining maximum leading phase depths.Finally, based on the actual operating data of a provincial power grid, eigenvalue method is used to calculate stability operation boundary and maximum leading phase depth of single generator under different conditions. It emphasizes the maximum leading phase depths of coordinated leading phase operation of two generators andthree generators as well as regulation function on system voltage. It concludes that with active power gradually increasing, the value of maximum leading phase depth of corresponding generator will gradually decrease, and static stability margin will also decrease. But with the increasing number of generators operating in leading phase condition, the voltage regulation effect of the power system is better. From the point of system stability, it should leave several generators operating in leading phase condition with appropriate leading phase depth simultaneously, enabling the system running in steady state operation as well as reducing the system voltage.