Stacking Approach for Multiple Hybrid Binary Cascaded Multilevel Converter Modules with Reduced Scalability Complexity

The hybrid binary cascaded multilevel converter (HBCMLC) is a topology that employs asymmetric dc-side voltages sources in conjunction with a flying capacitor to increase the number of output voltage levels. Thus, the flying capacitor voltage (FCV) must be properly regulated to ensure safe operation and high waveform quality. To further improve the waveform quality, several HBCMLC modules could be cascaded, making the overall converter structure suitable for inductor-less dc-to-ac or ac-to-dc applications. However, stacking HBCMLC modules could increase the complexity of the system by requiring rigorous redesign of new FCV control loops and voltage states for the modulator. This paper proposes a straightforward scalability solution for the HBCMLC by introducing a slight phase shift between stacked modules. As a result, a single FCV controller and modulator structure operates the cascaded system regardless of the number of HBCMLC modules, resulting in dramatically reduced scalability complexity. Experimental verification of the proposed technique is presented for a three-module HBCLMC achieving 43 voltage levels at 1.2 kV and 720 W.