International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 09 Issue: 06 | June 2022 www.irjet.net p-ISSN: 2395-0072 © 2022, IRJET | Impact Factor value: 7.529 | ISO 9001:2008 Certified Journal | Page 2773 A Comparative Study between Different Types of Multilevel Inverter Titas Bhaumik 1 , Sumangal Bhaumik 2 , Surajit Paul 3 , Snehashis Mitra 4 1 Assistant Professor, Dept. of EE, Abacus Institute of Engineering & Management, India 2 Dept of Applied Physics, The University of Calcutta, India 3 B. Tech Student, Dept. of EE, Abacus Institute of Engineering & Management, India 4 B. Tech Student, Dept. of EE, MCKV Institute of Engineering, India ---------------------------------------------------------------------***--------------------------------------------------------------------- Abstract - This paper compares between four different topologies of cascaded H-bridge multilevel inverter. Inverter can be defined as a power electronic device which can convert dc to ac at specified output voltage and frequency. Multilevel inverters are the preferred choice of industry for application in high voltage and high power. The basic advantage of a multilevel inverter is that it can give high power at the output while working under medium voltage source. It does so with the help of multiple dc sources at the input. The main merits of the paper are Comparative Study of Different Types of Multilevel Inverter and also study on minimizing the total harmonic distortion which will help the designer to design an appropriate multilevel inverter. Key Words: Multilevel, Inverter, Total Harmonic Distortion, IGBT, Bridge Connection 1. INTRODUCTION An inverter is a power electronic device that converts DC power into AC power at desired output voltage and frequency [1]. Generally, the two-level inverter is the one that is used to convert dc into ac. Two-level inverter produces output voltage or current utilizing two different levels. For example, if V is given as an input then the inverter will provide +V/2 and –V/2 at the output. [1] Now a day the concept of multilevel inverter is very popular and it can be termed as a modification of two-level inverter. In multilevel inverter we deal with more than two level voltages in order to create a smoother stepped output waveform. The output waveform obtained in this case has lower dv/dt and also lower harmonic distortions. Multilevel inverters generate a smooth sinusoidal waveform from several DC voltage levels at its input. The input side of a multilevel inverter have several DC sources, which can be obtained from batteries or a renewable energy source as well. It has a lot of application in wide industries. There are several topologies of multilevel inverters which are available, but the main difference is their mechanism of switching and the input source voltage. Three most commonly used multilevel inverter topologies are: • Cascaded H-bridge multilevel inverter. • Diode clamped multilevel inverter. • Flying capacitor multilevel inverter.[1][2] 2. CONCEPT OF MULTILEVEL INVERTER The origin of multilevel inverter idea is derived from the power semiconductors array design, which uses multiple input sources. In case of inverter, the sources are DC which produces AC output waveforms of multiple step voltage with variable amplitude, frequency and phase. The multilevel converters have a minimum of three voltage level to create smoother output waveform, lower dv/dt and lower harmonic distortions. The major difference between two level sources and multilevel is two levels can produce only two levels of voltage but multilevel could produce unlimited voltage levels, although multilevel inverter needs a complicated switching circuit rather than two level converters.[3] The quality of power converters is judged by the quality of its V/I waveforms. The measurement of harmonic spectra can be expressed in terms of total harmonic distortion (THD). The lower the THD value, the better its power quality. There is a similarity between level three and level two inverters, but in three level inverters, clamping diodes are used in between the two valves and are connected to the neutral between two capacitors. Three level inverter each phase leg generates the three voltage levels (+Vdc, 0, –Vdc).[4][5] 3. CASCADED H-BRIDGE MULTILEVEL INVERTER The cascaded H-Bridge multilevel inverter is the most advanced and important method of power electronic converters that analyses output voltage with number of dc sources as inputs. As compared to neutral point clamped multilevel inverter and flying capacitor multilevel inverter, the cascaded H-Bridge multilevel inverters require less number of components. It also produces high quality output voltage which is closer to sine wave. To verify the operation and to check the harmonic of the cascaded H- bridge multilevel inverter using the Sinusoidal Pulse Width Modulation (SPWM) technique, MATLAB software is used for the simulation. By increasing the number of output levels the Total Harmonic Distortion (THD) in output voltage can be reduced.[4][6]