Reliable Time-Domain Analysis of Nonlinear Lumped Circuits with Topology Issues, Suitable for Transients of AC Drives

Time-domain analyses of analog circuits based on mathematical models with differential algebraic equation systems allow more flexibility of the numerical algorithms to optimize the stability, accuracy or required hardware resources compared to the SPICE-type resistive models. In order to exploit them while taking advantage of the modified nodal approaches, some restrictions related to the circuit topology occur. In this context, the paper treats briefly a novel and reliable approach based on modified nodal equations which allows treating nonlinear analog circuits of any topology, including floating capacitors and/or any type of excess element. It is suitable for time-domain analysis of transients of AC drives with power inverters, where the load is always nonlinear and it contains an inductor cutset, and the DC-link contains a floating capacitor. The method was implemented in a program which builds the mathematical model in symbolic form and solves it numerically. An example was included here to prove the effectiveness of this approach.