State variable analysis

Abstract

In the state variable solution it is the set of first order differential equations, rather than the system of individual elements, that is solved by numerical integration. The most popular numerical technique in current use is implicit trapezoidal integration, due to its simplicity, accuracy and stability. Solution accuracy is enhanced by the use of iterative methods to calculate the state variables. State variable is an ideal method for the solution of system components with time-varying non-linearities, and particularly for power electronic devices involv ing frequent switching. This has been demonstrated with reference to the static a.c.-d.c. converter by an algorithm referred to as TCS (Transient Converter Simu lation). Frequent switching, in the state variable approach, imposes no overhead on the solution. Moreover, the use of automatic step length adjustment permits optimising the integration step throughout the solution.