Comparison of two analytical methods to estimate power losses in an HVDC terminal based on modular multilevel converter

The Modular Multilevel Converter (MMC) topology has become one of the most promising solution in HVDC applications when compared with similar approaches. The evaluation of the power losses in an MMC terminal is fundamental to estimate the overall converter efficiency and size the required thermal management system. In this paper, a complete comparison of two methods to calculate conduction and switching losses in an MMC terminal is presented. The first method considers the average model of the MMC to calculate the overall losses. In addition to the average model, the second method considers the effect of the capacitor on the average current flowing through each semiconductor device. In order to compare and evaluate the two approaches, extensive time-domain simulations are carried out in an MMC terminal under different operating conditions. Analytical results show that there is a slightly difference in the overall efficiency using both methods (≈2.9%). As initial statement, the second method is more convenient to implement, since all the parameters from the manufacturer's data sheet are considered.