Multi-Winding Transformer for 18-Pulse AC–DC Converter Fed 7-Level CHB-Inverter With Fundamental Switching Based VCIMD

In this article, a new structure is used for induction motor drive (IMD). A Δ-polygon configuration based multi-winding transformer is designed in it to get an eighteen pulse AC-DC converter, which fulfill the DC-supply requirement of a 7-level cascaded H-bridge (CHB) inverter. This 7-level CHB-inverter is utilized at the drive end, to drive an induction motor (IM) and it requires less semiconductors switches and DC-supplies than the existing 7-level CHB-inverter. Therefore, a modified multi-winding transformer is designed to fulfil the need of a 7-level CHB-inverter, which also makes the input current closer to sinusoidal and reduces its THD to an acceptable value. A vector control is used to control an IM, which has good performance than v/f control. A new fundamental frequency switching technique (area equalization modulation strategy) is used in this work, to operate a 7-level CHB-inverter at fundamental frequency switching, which reduces the switching losses and increases efficiency of the system. The comparative study is also given to show the effectiveness of the system. Performance of the system is analyzed in MATLAB/Simulink under various operating conditions of IM. The simulated performances are validated from the experimental results captured from the developed laboratory prototype.