Introduction to the main concepts involved

Standard power conversion topologies are built around the concept of commutation cell using semiconductors operating in 'SwitchMode' to regulate the energy flowing between a voltage source connected to the High Voltage side of the commutation cell and a current source connected on the Low Voltage side of the commutation cell.

Such commutation cells operate in two configurations ( full transfer of energy from one source to the other,or zero transfer of energy) and the duty cycle of utilization of these two configurations defines the average energy flowing between the two sources.

In recent years, several multicell conversion topologies have been introduced. These topologies use macro-commutation cells composed of several commutation cells connected in series and parallel, and internal passive components to allow more configurations and more degrees of freedom in the control of the energy flow. Such macro-commutation cells can be used to replace the conventional commutation cell of any standard converter. A consequence of the increased number of configurations is the creation of multilevel current or voltage chopped waveforms on respectively the High Voltage and the Low Voltage sides of the macro-commutation cell.

These principles can be combined to take advantage of both series and parallel connection of commutation cells and to improve the waveforms on both sides of sophisticated macro-commutation cell.

These topologies may seem complicated at first sight, but they can be easily understood by means of a systematic use of the concept of commutation cell.
Also, it can be shown that these circuits can be studied, designed and simulated more easily using design masks and vectorization: