4. METHOD OF SOLUTION
The theoretical model consists of a set of ana- lytical state and nonlinear ordinary differential equations of first order:
- The steady state (= starting) values are determined by putting in the set of equations the time derivatives equal to zero and sol- ving the resulting set of nonlinear algebraic equations by using the solution method of a linear algebraic equation system in a recursive way.
- Eliminating the steady state parts from the differential equation system and regarding the variables as (absolute) difference values (with respect to its steady state) the calculation of the transient behaviour of the system is performed in a normal- precision way, thus avoiding the more capacity and time-consuming double-precision procedure. The solution of the non-linear ordinary differential equation system of first order is obtained by applying the digital DIFSYS method, an explicit integration procedure based on a method established by Bulirsch and Stoer.