A New 7-Level Symmetric Multilevel Inverter with Minimum Number of Switches

Though the multilevel inverters hold attractive features, usage of more switches in the conventional configuration poses a limitation to its wide range application. Therefore, a renewed 7-level multilevel inverter topology is introduced incorporating the least number of unidirectional switches and gate trigger circuitry, thereby ensuring the minimum switching losses, reducing size and installation cost. The new topology is well suited for drives and renewable energy applications. The performance quality in terms of THD and switching losses of the new MLI is compared with conventional cascaded MLI and other existing 7-level reduced switch topologies using carrier-based PWM techniques. The results are validated using MATLAB/SIMULINK. 1. Introduction The term “multilevel inverter” was rooted years ago. Multilevel inverters offer various applications in voltage ranging from medium to high such as in renewable sources, industrial drives, laminators, blowers, fans, and conveyors. Small voltage step results in making the multilevel inverters withstand better voltage, fewer harmonics, high electro-magnetic compatibility, reduced switching loss, and better power quality [1]. Cascaded multilevel inverters were developed in the initial stage. Later, diode-clamped MLI’S were developed followed by flying capacitor MLI’S. These three topologies utilise different mechanisms to produce the required output. The topology introduced first, that is, the CMLI, is simply series connection of H-bridges. The diode-clamped MLI uses series capacitor bank whereas, in flying capacitor mli, floating capacitors are used in order to clamp the output voltage [1]. H-bridge inverters have isolation transformers, and then H-bridge cascaded MLIS were introduced to separate DC input sources. But they do not need either clamping a diode or flying capacitors. Absence of voltage imbalance is the main advantage of cascaded mli. Fewer components are used in CMLI compared to diode-clamped and flying capacitor mlis [2–4]. Most of the researches are carried out in cascaded MLI configuration. But still the new trends are involved in the evolution of renewed multilevel inverters. Modifications are made in its inbuilt structure. A 7-level MLI was generated with 9 switches reducing 3 switches from the main conventional CMLI [5]. It offers good results yielding desired a 7-level output with low THD. A 7 level MLI with 7 switches reducing 2 more switches from the previous topology made a far improvement in the investigation of the switch reduction [6]. Yet another topology of 7-level MLI was configured