Increasing the efficiency of the Modular Multilevel Converter with MOSFET switches using Lagrange multipliers

This work proposes an approach to minimize the power losses of the Modular Multilevel Converter with MOSFET switches by applying a circulating current reference calculated using Lagrange multipliers. The optimized circulating current changes the loss distribution between the converter elements and improves the total converter efficiency. For the considered 25kW converter designs, an efficiency increase of 0.3 to 0.6 per cent was achieved which corresponds to the loss reduction of 6 to 11 per cent.