Design, Analysis and Experimental Verification of Arm Link Enhanced Modular Multilevel Converter

The Modular Multilevel Converter has gained attention in high- and medium-voltage DC-AC conversion due to its modularity, scalability, and excellent results in power quality and efficiency. However, its complexity, multiple control loops, and extensive measurements make it unsuitable for low-voltage applications. Additionally, the power ripple in sub-modules, poses challenges in low-voltage scenarios. To overcome the disadvantages of the MMC at low voltage and operate it from zero frequency to high output frequency, the Arm Link Enhanced Modular Multilevel Converter (ALE-MMC) was proposed, which employs dual active bridges to transfer power ripple between the upper and lower submodules, substantially reducing its capacitance and eliminating all voltage measurements from the submodules. This work analyzes and test the ALE-MMC in the entire operating range, giving design insights, and highlighting the various benefits the proposed topology can obtain in low voltage drives applications in terms of circulating currents control, Dual Active Bridge requirements and efficiency. Simulation results are presented in a three-phase converter to verify its operation at high power, and experimental results of a low-scale single-phase prototype are used to assess the operation under different scenarios.