Topological index‐calculation of DAEs in circuit simulation

In electric circuit simulation we are confronted with highly nonlinear DAEs with low smoothness properties. They may have index 2 but they do not belong to the class of Hessenberg form systems that are well understood. The classic and the charge-oriented modified analysis are shown to lead to the same DAE-index if the circuit models satisfy some natural assumptions. We present a topological criteria for calculating the index. This makes it possible to determine the index also for high-dimensional circuit equation systems.