Multi-level power converter and a method for controlling a multi-level power converter

A multi-level power converter for one or more phases, the converter comprising:

• a plurality of switching cells, each switching cell comprising:
• a plurality of switching devices and an energy storage element, which switching devices are arranged to selectively provide a connection to the energy storage element;
• and
• a controller configured to control the switching of the switching devices in the switching cells,
• wherein the switching cells comprise at least switching cells of a first type and switching cells of a second type,
• wherein the converter comprises, for each phase, a first arm of serial connected switching cells and a second arm of serial connected switching cells, which first arm and second arm are connected in parallel,
• wherein the first arm comprises more switching cells of the first type than switching cells of the second type and the second arm comprises more switching cells of the second type than switching cells of the first type, which switching cells of the first type have lower conduction loss than the switching cells of the second type, and
• wherein the converter is arranged so that a larger current flows through the first arm and a smaller current flows through the second arm and wherein switching cells of the second type have lower switching loss than the switching cells of the first type, the second arm being configured for fine-tuning of the smaller current flow.