Multilevel inverters (MLIs) have gained increasing interest for advanced energy-conversion systems due to their features of high-quality produced waveforms, modularity, transformerless operation, voltage, and current scalability, and fault-tolerant operation. However, these merits usually come with the cost of a high number of components. Over the past few years, proposing new MLIs with a lower component count has been one of the most active topics in power electronics. The first aim of this article is to update and summarize the recently developed multilevel topologies with a reduced component count, based on their advantages, disadvantages, construction, and specific applications. Within the framework, both single-phase and three-phase topologies with symmetrical and asymmetrical operations are taken into consideration via a detailed comparison in terms of the used component count and type. The second objective is to propose a comparative method with novel factors to take component ratings into account. The effectiveness of the proposed method is verified by a comparative study.

Voltage Source Multilevel Inverters With Reduced Device Count: Topological Review and Novel Comparative Factors

In this paper, a novel three-phase parallel grid-connected multilevel inverter topology with a novel switching strategy is proposed. This inverter is intended to feed a microgrid from renewable energy sources (RES) to overcome the problem of the polluted sinusoidal output in classical inverters and to reduce component count, particularly for generating a multilevel waveform with a large number of levels. The proposed power converter consists of $n$ two-level $(n+1)$ phase inverters connected in parallel, where $n$ is the number of RES. The more the number of RES, the more the number of voltage levels, the more faithful is the output sinusoidal waveform. In the proposed topology, both voltage pulse width and height are modulated and precalculated by using a pulse width and height modulation so as to reduce the number of switching states (i.e., switching losses) and the total harmonic distortion. The topology is investigated through simulations and validated experimentally with a laboratory prototype. Compliance with the $\text{IEEE 519-1992}$ and $\text{IEC 61000-3-12}$ standards is presented and an exhaustive comparison of the proposed topology is made against the classical cascaded H-bridge topology.

https://hal.archives-ouvertes.fr/hal-01717607/document

Multilevel Inverter Topology for Renewable Energy Grid Integration

Recently multilevel inverters (MLIs) have received wide attention from industry and academia, as they are changing into a viable technology for diverse applications. To produce high-quality output using less switch count, development of novel reduced switch MLI (RS MLI) topologies has been a focus of current research theme. This paper presents design and control of a switched-diode dual source single switch MLI (SDDS MLI). The generalized SDDS MLI is first designed using an asymmetric basic unit. Proposed SDDS MLI requires less switch count and driver circuit count compared with the few recently developed RS MLI topologies. To improve the voltage quality by eliminating targeted low-order harmonics, a modified version of fish swarm optimization algorithm is examined for computing optimum switching angles required to control the SDDS MLI. Moreover, suitability and superiority of the derived algorithm are established by comparing with traditional selective harmonic elimination techniques. The developed topology is investigated through several MATLAB simulations as well as experimental tests in the laboratory applying the modified control approach.

Reduced Switch Cascaded Multilevel Inverter With New Selective Harmonic Elimination Control for Standalone Renewable Energy System

An inclusive review on different multi-level inverter topologies, their modulation and control strategies for a grid connected photo-voltaic system

Towards empowerment of the renewable energy sector in Pakistan for sustainable energy evolution: SWOT analysis

This paper deals with harmonics cancellation using pulse height modulation (PHM). This technique allows simultaneous optimization of the total harmonic distortion (THD) rate and the number of power switches. This leads to substantial reduction of the power switching losses as compared with PWM. A novel six-level inverter model is presented with three-phase output voltages having similar symmetry properties to a pure three-phase sinusoidal system. The proposed method allows canceling all even-order harmonics and integer multiples of the third-order harmonic. Switching angles and input dc voltage levels are determined so as to cancel most of the successive low-order harmonics (the most harmful to the network) starting from rank 2, allowing to shift the first nonzero harmonic far away from the fundamental. For 12 switching states per period, PHM allows to cancel harmonics from rank 2 to 10 with lower THD. A comparative study of the obtained output voltage and current shows their compliance with IEEE 519-1992 and IEC 61000-3-12 standards.

Kamal Meghriche

Papers

Multilevel Inverter Topology for Renewable Energy Grid Integration

On the Use of Pulse Height Modulation for Harmonic Cancellation in a Six-Level Inverter Topology