An Extensive Review of Multilevel Inverters Based on Their Multifaceted Structural Configuration, Triggering Methods and Applications

Abstract

Power electronic converters are used to transform one form of energy to another. They are classified into four types depending upon the nature of the input and output voltages. The inverter is one among those types; it converts direct electrical current into alternating electrical current at desired frequency. Conventional types of inverters are capable of producing voltage at the output terminal that can only switch between two levels. The range of output voltage generated at the output is low when they are used for high power applications. To improve the voltage profile and efficiency of the overall system, multilevel inverters (MLIs) are introduced. In multilevel inverters the voltage at the output terminal is generated from several DC voltage levels fed at its input. The generated output is more appropriate to a sine wave and the dv/dt rating is also less leading to the reduction in EMI. Though they possess many advantages compared to the conventional inverters, the structural complexity and triggering techniques involved in designing multilevel inverters are high. Many studies are being carried out in defining new topologies of MLI with reduced switch as well as with the implementation of different PWM techniques. This paper will provide an extensive review on variety of MLI configurations based on the parameters such as the number of switches, switching techniques, symmetric, asymmetric, hybrid topologies, configurations based on applications, THD and power quality.

Four-Level Quasi-Nested Inverter Topology for Single-Phase Applications

“…In this way each carrier has an amplitude of 1 3 pu. Figure 4 shows the implementation of the LS-PWM scheme for the proposed topology.…”

“…Nowadays, multilevel inverters (MLI) have become the main solution for applications where high power quality and dynamic performance are required, particularly in mediumand high-power systems [1,2]. The main reasons for their success are the reduced blocking voltage rating of the semiconductor switches, less conduction losses, and lower harmonic content, which lead to increased efficiency and reduction of manufacturing costs [3,4].…”

“…In recent years, research efforts in the field of MLI topologies have been focusing on overcoming some of the drawbacks of the conventional converters, by developing features such as single DC-source operation, avoidance of flying capacitors and reduced number and complexity of semiconductor switches [1,10,24]. In this context, the four-level double-star converter topology was developed originally by Kouro et al [25] and has been studied for applications such as grid-connected PV energy systems [26] or back-to-back connection in wind energy systems [27].…”

“…The inner switches (S 1 , S 1 , S 3 , S 3 ) blocking voltage stress is 1 4 of the nominal DCvoltage v d , representing an improvement with respect to nested topologies, like 3L-NPC, 3L-ANPC and H-Bridge, whose blocking voltage stress is 1 2 of the DC-voltage. On the other hand, the blocking voltage stress of the outer active switches (S 2 , S 2 ) is 3 4 v d , exceeding that of the 3L-NPC, 3L-ANPC and H-Bridge topologies.…”

A Framework for Optimum Determination of LCL-Filter Parameters for N-Level Voltage Source Inverters Using Heuristic Approach

“…When applied to multilevel inverter control, there should be one reference waveform signal and multi-carrier triangular waveforms. In the case of an n-level inverter, (n-1) triangular carriers are needed [38]. During the control process, each carrier waveform is compared with the reference waveform.…”