Modular Multilevel Converter With Different Submodule Concepts-Part II: Experimental Validation and Comparison for HVDC Application

This paper is the continuation of part I in which a modulation strategy for the modular multilevel converter, which provides voltage balancing of the capacitors of different submodules comprising the converter, is presented. Here, the validation of the studied modulation strategy is carried out by means of successful experimental results in a downscaled real test bench. First, the converter submodules are 2L topologies, and then the connections are changed to configure 3L-FC submodules showing the effectiveness and implementability of the proposed modulation in different submodule concepts. Finally, a comparison based on thermal analysis and sizing of elements among 2L, 2L serializing several insulated gate bipolar transistors per valve, 3L-FC, and 3L-NPC submodule concepts is made.