Page 20 - Journal Cover.pdf

Received: 15 November 2020 Revised: 11 December 2020 Accepted: 26 February 2021
DOI: 10.37917/ijeee.17.1.3 Vol. 17| Issue 1| June 2021

 Open Access
Iraqi Journal for Electrical and Electronic Engineering
Original Article

Non-conventional Cascade Multilevel Inverter with

Lower Number of Switches by Using Multilevel PWM

Adala O. Abdali*, Ali K. Abdulabbas, Habeeb J. Nekad
Electrical Engineering Department, University of Basrah, Basrah, Iraq

Correspondence
*Adala Ouda Abdali
Electrical Engineering Department,
University of Basrah, Basrah, Iraq.
Email: eng.adala@gmail.com,

Abstract
The multilevel inverter is attracting the specialist in medium and high voltage applications, among its types, the cascade H
bridge Multi-Level Inverter (MLI), commonly used for high power and high voltage applications. The main advantage of the
conventional cascade (MLI) is generated a large number of output voltage levels but it demands a large number of components
that produce complexity in the control circuit, and high cost. Along these lines, this paper presents a brief about the
non-conventional cascade multilevel topologies that can produce a high number of output voltage levels with the least
components. The non-conventional cascade (MLI) in this paper was built to reduce the number of switches, simplify the circuit
configuration, uncomplicated control, and minimize the system cost. Besides, it reduces THD and increases efficiency. Two
topologies of non-conventional cascade MLI three phase, the Nine level and Seventeen level are presented. The PWM
technique is used to control the switches. The simulation results show a better performance for both topologies. THD, the power
loss and the efficiency of the two topologies are calculated and drawn to the different values of the Modulation index (ma).

KEYWORDS: multilevel inverter, non-conventional Cascade inverters, HPWM.

I. INTRODUCTION multilevel inverter which has an equal value of all DC
voltage sources while asymmetric cascade multilevel
Recently, the development of the multilevel inverter has inverter is not equal to the value DC voltage source [13,14].
caused a great evolution in industrial applications and has The higher the output voltage level in the multi-level inverter
increased the attention in medium and high power improves the power quality; therefore, the increase in the
applications in past years [1-3]. number of levels leads to an increase in the cost, the
The multilevel inverter is the power electronic system that complexity of the system, and difficulty in controlling due to
produces desired output voltage from a few input DC the increase in the number of separate DC voltage source to
sources; it can generate many voltage levels that cause control each cell and the increase in the number of switches.
harmonic content improvement, decrease the switching To overcome these problems, many proposed topologies are
losses and improve the efficiency [4-5]. presented for symmetrical and asymmetrical MLI. The main
In general, a multilevel inverter can be divided into three advantage of all these structures is reduced the number of
groups: DC sources and the number of switches.
(a) Diode clamped multilevel inverter type; the number of The proposed topology in [15] is greatly shorthand in the
diodes is high for the high number of voltage level [6-7].
(b) Flying capacitor multilevel inverter type, the balance of number of DC voltage sources and the number of switches.
To produce seven-level, one H-bridge, two switches, and
the capacitor's voltage is difficult, and in the high one DC source can be used, but in conventional cascade to
voltage levels need a high number of capacitors [8-9]. produce the same number of level you need three H-bridge.
(c) Cascade H bridge multilevel inverter type is better It is clear that every one of H- bridge needs DC source to
typology compared to the other two classic typologies. supply the switches can be extended the topology to generate
This type consists of several cells are connected in series 31 level and 127 level, also in [16] the topology is presented
and each cell needs DC voltage [10-12]. the similar concept by decreasing number of components
Cascade H bridge’ type is the focus of the debate here and it compared with present topologies in [17].
which is divided into two groups: symmetric and
asymmetric. The first type of symmetric cascade is the

This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and
reproduction in any medium, provided the original work is properly cited.
© 2021 The Authors. Iraqi Journal for Electrical and Electronic Engineering by College of Engineering, University of Basrah.
https://doi.org/10.37917/ijeee.17.1.3 https://www.ijeee.edu.iq 16