A Fast Graph-Theory-Based Algorithm for Waveform Reconstruction and Loss Calculation in Voltage Source Converters

It is time-consuming to obtain performance metrics for feasible topologies during the design of power electronic converters. This article proposes a graph-theory-based algorithm that achieves fast loss calculation and waveform reconstruction for voltage source converters (VSCs) in steady-state operations. The VSC is modeled as a directed graph comprising a set of vertices connected by semiconductor devices or passive components. The current-conducting capacity of semiconductor devices is represented by a directed edge or a pair of directed edges in both directions. This allows all potential current paths to be identified by the graph search algorithm. With the current-path-based converter calculation model, the steady-state current of VSC is calculated in the frequency domain by voltage spectrum and load impedance. The loss distribution on each device is further calculated using the device loss model. Compared to the state-of-the-art methods, the proposed method balances the requirements of high accuracy and speed. Finally, the calculation results are contrasted with experimental data from a back-to-back loss test platform, demonstrating that the calculated waveforms can well accurately describe the steady-state response of the converter and the relative loss error remains below 5%.