Analytical Conduction Loss Calculation Method for Hybrid Three-Level Converters

A new class of hybrid three-level converters (H3LC) has been recently proposed for voltage-source-converter high-voltage direct current (VSC-HVDC) transmission technology. It features both a small footprint and high efficiency. In the literature, however, the H3LC’s semiconductor losses have only been verified quantitatively through detailed simulation, and only at two operating voltages. This paper presents an analytical method to determine the H3LC’s efficiency over its entire operating range by taking into consideration the conduction power losses of its semiconductor devices, which are assumed to be dominating. Lacking in the literature, this paper presents a method to simplify the determination of the theoretical semiconductor conduction power losses for hybrid three-level converters to improve the converters’ design-to-implementation time. To verify the accuracy and effectiveness of the proposed analytical methodology for power loss calculation, the results are compared against the values obtained from the simulations using the detailed equivalent model (DEM). The proposed analytical method is demonstrated to give accurate predictions of the dominant power losses over a wide range of operating conditions, which may be used for determining the optimal design and operation the H3LCs in practice.