A new 7, 15 and 31-level modular reduced switch multilevel inverter with gating signal generation using digital output pins

This paper proposes a reduced switch modular multilevel inverter (RSM-MLI) requiring eight, thirteen, and fifteen switches per phase for 7-level, 15-level, and 31-level output voltages, respectively. For the generation of 7-level, 15-level, and 31-level output voltages, the proposed MLI employs two, three, and four designed modules, each comprising switches, diodes, and a dc source, respectively. The interconnection of modules results in the generation of unipolar staircase voltage. Further, an H-bridge inverter (HBI) facilitates dc-ac conversion. With modular construction, the levels can be easily increased in the proposed topology by adding extra modules. The merits of the proposed topology are highlighted through a comparative analysis. The higher switch count in MLI necessitates the use of multiple digital signal processors (DSPs), thereby complicating the gating circuitry. To simplify the gating requirements, this paper utilizes the digital output pins in a DSP, which are far higher in number than the PWM pins, for gate pulse generation. This negates the needs of multiple DSPs. The operation of the developed experimental prototype of the proposed 7-level, 15-level, and 31-level RSM-MLI, controlled through the digital output pins of a DSP, is analyzed for steady-state and dynamic conditions.