A variable-order variable-structure transmission line model with provision for frequency dependent parameters

There are numerous modeling approaches and algorithms for the simulation of high-voltage transmission networks with various degrees of accuracy and computational complexity. For the simulation of switching transients, the so-called Bergeron model is perhaps the most widely used approach as implemented in the renowned Electromagnetic Transients Program (EMTP). Therein, the transmission line is represented as forward and backward current waves implemented using standard queues with purely algebraic boundary equations. This representation is very efficient for the calculation of switching transients; however, it is inherently a fixed-time-step approach that is not conducive to the study of longer-term transient and dynamical phenomena such as the inter-area inertial oscillations that occur following major disturbances and can lead to transient instabilities. This restriction has led to a completely separate class of computer programs, i.e. transient stability programs, in which electromagnetic transients are completely neglected. In this thesis, a new transmission line modeling structure is set forth that is able to accurately portray the high-frequency switching transients but has a dynamically changing order and structure so that, after the fast switching transients subside, the lower-frequency phenomena can be simulated using a much larger and variable time step. It is argued that the resulting transmission line structure accurately portrays switching transients and, concurrently, is much more efficient than the Bergeron model when simulating long-term transients. The significance of the proposed transmission line modeling structure is that it obviates the need for separate computer programs that focus on specific time frames