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Summary In this research work, a generalized structure of multilevel topology is proposed that can be extended by cascading the modules. Proposed modular topology is modified T‐type structure that requires comparative reduced number of power components than other existing structures of multilevel inverter. Each module encompasses of three DC sources and 10 power switches. Both positive and negative voltage levels can be generated without the use of H‐bridge inverter; thus, lower voltage rating power switches are employed for proposed modular topology. To generate the output voltage levels, the nearest level control is implemented on the experimental setup using dSPACE 1103 controller. To verify the performance of the proposed inverter, experimental validation of various topologies based on different algorithms is performed to generate 15‐level, 17‐level, 27‐level, and 31‐level at different load conditions. Moreover, different state‐of‐art topologies are compared with proposed topology in terms of the required number of voltage levels, DC sources, power switches, driver circuits, and total standing voltage.

Summary The proposed work shows a novel multilevel inverter (MLI) configuration to generate a large number of voltage levels with lesser number of power switches. The proposed generalized inverter comprises basic cells cascaded to each other. Each cell of the proposed inverter can generate three‐level AC voltage using the power switches of the same rating. Both single‐phase and three‐phase MLI configurations are possible for the proposed structure. To validate the performance of the proposed MLI configuration, a nine‐level inverter using six power switches and a 27‐level inverter using nine power switches are designed and simulated in the MATLAB/Simulink environment. An experimental prototype is developed in the laboratory, and the experimental results are presented to verify the simulated results. Further, to validate the effectiveness of the proposed multilevel inverter, a comparison of the proposed MLI with recently proposed multilevel inverter has been incorporated in a detailed manner.

A novel and generalised three-phase multilevel inverter (MLI) with a minimum number of switches have been proposed. The number of voltage levels can be increased to a significant value by incorporating few switches and the DC voltage sources. In the proposed three-phase MLI, the number of phase-voltage levels can be increased twice as the number of switches increased. The detailed analysis of the proposed MLI, mathematical modelling of the inverter voltage and the switching loss calculation have been done for a seven-level inverter. Modelling and simulations of the proposed generalised three-phase inverter are carried out using MATLAB/SIMULINK. The simulation results of the proposed multilevel configuration corresponding to the different voltage levels as well as at different modulation index are presented. A laboratory prototype of the proposed five-level inverter has been developed and tested for the speed control of an induction motor. The experimental results for the different modulation indexes are presented, that verifies the simulation results. A detailed comparison of the proposed MLI with the other popular multilevel configuration is presented to reflect the merits of the proposed structure for the reduced component count.

A multilevel inverter (MLI) with staircase waveform having maximum number of voltage levels at any desired voltage (or frequency) of a variable voltage, variable frequency application can play an important role in the modern power conversion system. In most of the control and modulation techniques of MLI, the number of voltage level reduces with the reduction of modulation index that increases the harmonic and total harmonic distortions (THDs). The variable voltage application of MLI using a single DC source of variable magnitude is the elementary concept of the proposed control technique. A cascaded MLI having unequal voltage sources with controlled magnitude can be used to increase the number of voltage levels. The closed-loop voltage control technique and a multi-winding transformer-rectifier based AC-link system is used to obtain the multiple variable voltage DC sources for the cascaded MLI. A nearest level modulation based control technique has been implemented for the MLI to obtain the fixed level voltage waveforms with constant THD and reduced switching losses. The whole control algorithm for a nine-level inverter is simulated and results are experimentally verified on a laboratory prototype of the three-phase induction motor drives.