Research On Voltage Stability Of High Voltage Direct Current System Using Non-Linear Bifurcation Theory

In recent years, high voltage direct current (HVDC) transmission is increasingly common applicated in electric power industry. With huge economic benefits are gained through HVDC transmission, new challenges are also brought to power system stability. The voltage stability problems are more prominent, becoming one of the restraining factors for safe and stable operation of HVDC system. Studing the voltage stability problems deeply is the foundation to ensure the safe and stable operation of HVDC system. Bifurcation theory is proved a powerful tool to study voltage stability problems. It is a new task to research the voltage stability of HVDC system using bifurcation theory, and the subject has important theoretical significance and application value.Based on a typical HVDC transmission system, voltage stability problems of HVDC system is studied using nonlinear bifurcation theory. The main jobs are completed as following.Firstly, though comprehensive comparison of various research methods of bifurcation theory, a continuation method taking pseudo arc length as the main idea is chosen. The method can track manifold and judge bifurcation point of HVDC system. System control parameters are taken as independent state variables, and the arc length of manifold as a new parameter in the process. Non-convergence can be prevented at bifurcation point caused by singular with this method.Secondly, based on the deeply study of generator, load and HVDC system models, differential algebra equation of an AC/DC system is gained. For a typical AC/DC system, bifurcation points are tracked and single parameter analysis is carried on with the mature bifurcation analysis software AUTO.Finally, bifurcation point tracking program and the corresponding graphic user interface program are designed using MATLAB. The bifurcation point tracking program is used to search the static and dynamic bifurcation points of the typical AC/DC model. Through the graphic user interface, bifurcation points tracking programs are operated easily. Cumbersome process of parameters input and program invocation are avoided, and the computation result is shown more clearly.