A Generalised Harmonic Model of an Integrated Three Dual Active Bridge Converter with Different Transformer Configuration

The rapid growth of solar photovoltaic (PV) systems is driving the demand for efficient and reliable medium voltage (MV) grid-connected inverters. Multilevel converters, especially cascaded H-Bridge (CHB) inverters, are suited to this application due to their modular design, scalability, and isolated inputs for each module, allowing for multiple MPPT operation. To facilitate isolated operation and enhance power extraction from PV, this work utilises an integrated three dual active bridge (I3DAB) converter as the input stage for CHB inverters. The modelling of this converter was previously limited to certain operating conditions and used only a wye-connected transformer. This paper presents a novel harmonic modelling approach for the I3DAB converter in both wye- and delta-connected transformer configurations to analyse and understand the performance of each configuration. Further, the model can estimate the voltages and currents for all operating conditions. Furthermore, the developed harmonic model is applicable without limitation across all duty cycles of the converter. Finally, the accuracy of the model is validated through MATLAB simulations.