We present an event driven adaptive time stepper for the simulation of the dynamics of switching electronic circuits with an application to power inverters. We show that in this context, variable time-stepping is both more efficient and more accurate than commonly used fixed-step integration methods using interpolation and extrapolation for event location and handling.
We also show that impacts are needed to resolve certain types of transitions accurately. The stepping scheme is based on a nonsmooth variational method and can also handle complementarity conditions for nonsmooth elements such as diodes and transistors for instance. The combination of variable step size and impacts yields a method of second order according to numerical tests. We also introduce a parallel, strongly coupled co-simulation method which allows to simulate many inverters with nearly linear complexity on multicore CPUs. The parallelization avoids the linear increase of switching events with the increase in number of phases or inverters, which leads to quadratic computational complexity. To do this, we used the effective admittances of subcircuits to enforce the voltages at common nodes. Our tests indicate that this is nearly as accurate as a fully coupled simulation. We have found that the combination of variable time-stepping and our parallelization technique allow for the simulation of several inverters in real-time.
We wrote prototype software which indicates that single inverters can be simulated faster than real-time, and slightly less than real-time for several ones, despite the additional numerical linear algebra necessary.