A novel charge balancing control approach for a single phase 9-level inverter based on fundamental modulation strategy

In this paper, a new scheme of charge balancing control method for a practical multilevel inverter (MLI) structure which is able to generate 9-level of output voltage with only one required dc voltage source is presented. The analyzed MLI's topology is made of using four series-connected capacitors paralleled by single dc power supply besides three bi-directional and four unidirectional power switches. Regarding the proposed method, in order to keep the across voltage of capacitors at the expected value, two operating switching modes (main and auxiliary modes) based on fundamental switching frequency are defined in which they are applied to the gate of power switches for a specific time duration and therefore they can obviate the discharging problem without aiming any extra charge balancing circuits or complicated modulation strategy. Several simulation results based on MATLAB/SIMULINK software are given to confirm the correct performance of proposed method.