Accurate Real-Time Simulation of Converters with Frequent Current Commutation Using Sub-Step Events

Executing real-time simulations with a fixed time step presents a challenge for the calculation of discrete switching events in power electronic converters. The instants of forced and natural commutation of the converter currents will generally not coincide with the simulation step. This problem is particularly evident with DC/DC converters such as the Dual-Active Bridge (DAB) or LLC operating at high switching frequencies where the simulation time step is in the range of the switching period. Moreover, the currents typically commutate twice in each switching period. In this paper, a "sub-step event" approach is presented that splits the fixed simulation step into intervals delimited by switching events. The events include forced switching and natural current commutation. The real-time performance of the sub-step event approach is explained and assessed using a dual-active bridge converter as an example. The performance assessment comprises both the simulation accuracy and the computational effort.