Expert symbolic transient simulator based on quadratic integration method

Expert-system-based approaches to complex computational procedures of transients in power systems are desirable because power systems contain complex and nonlinear elements. We propose the use of symbolically-aided modeling as the basis for the design of expert transient simulators. The symbolic approaches work well when (a) the user interface is "symbolized" and (b) the underlying computational algorithms are robust. This paper presents advances in both of these areas and for the specific application of numerical integration of large complex nonlinear systems. We present a method for symbolically defining complex nonlinear systems. The methodology includes a human interface for symbolic manipulations of the system model. The system model is symbolically quadratized. The quadratized model is integrated with a numerical method that belongs to the general class of collocation-based implicit Runge-Kutta methods. The presented methodologies are superior to previous approaches used by the authors using symbolic manipulations and trapezoidal integration. The methodology is illustrated with a simple example system including nonlinear and switching elements