Abstract: A modulation policy for a modular multi-level convertor, determining a switching state of each submodule by combining the current direction of each bridge arm and the capacitor voltage order of the submodules based on a carrier stacking method. The beneficial effects of the modulation policy are that: each phase only needs a modulation wave and N carriers, given N submodules of each upper bridge arm or lower bridge arm of the modular multi-level convertor; the modular multi-level convertor can output N+1 levels without carrier phase shift; N devoted submodules of each phase are guaranteed at any time; and the submodules' capacitor voltage balancing can be controlled without a closed-loop control policy. The modulation policy facilitates adjustment of the modular multi-level convertor voltage and power class, has unlimited number of levels, has a high precision control algorithm, is easy to realize in engineering and saves software and hardware resources.

Abstract: A modulation policy for a modular multi-level convertor, determining a switching state of each submodule by combining the current direction of each bridge arm and the capacitor voltage order of the submodules based on a carrier stacking method.