Transformer Cascaded 27-Level Multilevel Inverter for Medium-/High-Voltage PV System Integration

• Published in: Iranian journal of science and technology. Transactions of electrical engineering 2023-09, Vol.47 (3), p.993-1008
• Main Authors: Molli, Krishna, Raj, P. Ajay D. Vimal, Sudhakaran, M.
• Format: Article
• Language: English
• Subjects: Electric power loss; Electrical Engineering; Engineering; Harmonic distortion; Inverters; Passive components; Research Paper; Semiconductor devices; Switches; Switching; Topology; Transformers; Voltage; Waveforms
• ISSN: 2228-6179; 2364-1827
• DOI: 10.1007/s40998-023-00606-9

Multilevel inverters (MLI) have become widely popular in research and industry due to their lower total harmonic distortion, high-quality output waveforms, and reduced switching losses. However, these advantages in conventional MLIs are at the cost of active and passive components, system size, control complexity, and power loss. In the recent past, advantages such as the higher number of voltage levels with fewer components and suitability for medium- and higher-voltage applications of transformer-based MLIs (TBMLIs) have drawn the interest of academia and industry. This paper proposes a TBMLI which offers 27 levels with one DC source and 12 switches. The proposed TBMLI is composed of three different rated isolation transformers to maximize the output voltage levels. The topology structurally exhibits the advantage of fewer semiconductor devices compared to recently reported TBMLIs. Further, the proposed MLI employs the low-operating-frequency nearest-level control switching scheme, which reduces the power loss of the devices. To validate the performance of the proposed TBMLI, a simulation of the MATLAB/Simulink environment is performed and a laboratory prototype is developed. Further, an investigation of power losses and the comparison of the topology with similar recent topologies with respect to various attributes is presented.