Ahmed Sheir

Bio: Ahmed Sheir is an academic researcher from University of Ontario Institute of Technology. The author has contributed to research in topics: Voltage & Electric vehicle. The author has an hindex of 5, co-authored 13 publications receiving 125 citations. Previous affiliations of Ahmed Sheir include Aswan University.

Real-Time Solution and Implementation of Selective Harmonic Elimination of Seven-Level Multilevel Inverter

Abstract: This paper proposes a new method to calculate switching angles in selective harmonic elimination technique. It is introduced as a substitute for Newton–Raphson method and similar iteration methods. By utilizing classical control such as the proportional-integral (PI) control, the proposed method can perform a real-time calculation for multilevel inverter’s (MLI) switching angles over a wide range of modulation indexes. Therefore, it is able to respond to system dynamics without the need to store precalculated large lookup tables. The proposed method is applied to seven levels cascaded full H-bridge to eliminate its third- and fifth-harmonic contents from the modulation index 0.1 to 1.04. The same procedure can be extended to the vast majority of MLI topologies. A Simulink model is built to simulate and validate the accuracy, dynamics, and continuity of the solution generated by the proposed method. An experimental prototype is also built and its results are discussed to confirm the theory and simulation of the proposed method.

A Novel Bidirectional T-Type Multilevel Inverter for Electric Vehicle Applications

Abstract: This paper introduces a new configuration of bidirectional multilevel converter in electric vehicle (EV) applications It has multilevel dc–dc converter with a dc link capacitor voltage balance feature The multilevel dc–dc converter operates in a bidirectional manner, which is a fundamental requirement in EVs Compared to the conventional configurations, the proposed one only implements two extra power switches and a capacitor to balance the voltage of the T-type multilevel inverter (MLI) capacitor over a complete drive cycle or at fault conditions Therefore, no extra isolated sensor, control loops, and/or special switching pattern are required Moreover, the proposed configuration due to the high-frequency cycle-by-cycle voltage balance between ${C_N}$ and ${C_P}$ , the bulky electrolytic capacitors used in T-type MLI, are replaced with more reliable longer life film capacitors This will result in a size and weight reduction of the converter by 20% This allows more real estate for the EV battery in the chassis’ space envelope to increase its capacity The proposed configuration is tested and validated using a matlab /Simulink simulation model A laboratory prototype of 1 kW is built to provide the proof of concept results as well

Asymmetric cascaded half-bridge multilevel inverter without polarity changer

Abstract: In this paper, New asymmetric cascaded half H bridge multilevel inverter MLI is proposed. It is driven from the conventional asymmetric cascaded half H Bridge multilevel inverter. Thus, the proposed topology inherits its simplicity, flexibility and modularity in both construction and control. By proper choice of the input DC sources values and interconnection, proposed topology can eliminate the need for polarity generation circuit which normally associated with the cascaded half H-bridge. Therefore, reduces number of switches that require high blocking voltage. The selective harmonic elimination SHE method is applied to generate switching pattern to eliminate harmonics inherently associated with MLI. The proposed topology switching pattern naturally reduces component’s voltage stress, switching losses and finally decrees MLI size and cost. Mathematical expressions and analysis have been driven as well as comparison with other topologies. The validity of the proposed topology is verified with Matlab/Simulink model and then a prototype is built and experimental results are presented.

A Novel Dual-Input High-Gain Transformerless Multilevel Single-Phase Microinverter for PV Systems

Abstract: This article proposes a novel single-phase microinverter that is fit to process the power of two photovoltaic (PV) modules in a modular way. The proposed topology combines a full-bridge inverter integrated with two dc–dc boost converters, in addition to a dc link that consists of switched capacitor (SC) networks. The operating modes of the proposed topology are illustrated. The voltage stress of all components is identified. A modulation technique along with a control system is developed for a proper operation of the proposed topology. A comparative study with other topologies is introduced, and the following merits for the proposed one are presented: 1) The power of two PV modules can be harvested individually or simultaneously without any circulating current issues; 2) very high gain can be acquired, and, thus, no series connection of PV modules is required for grid-tied applications; 3) transformerless operation; 4) multilevel shaping of the output voltage, and, thus, reduced filter size is required; and 5) self-balancing for the dc-link capacitors, and, thus, simple control systems can be used. The performance of the seven-level version of the proposed topology is validated using real-time simulation and experimental prototype under grid-tied and stand-alone conditions, respectively.

A high efficiency single-phase multilevel packed U cell inverter for photovoltaic applications

Abstract: PV systems have the drawbacks of high initial cost. The power electronics portions represents about 50% of this cost for no-battery systems. Therefore, it is important to act to decrease this cost through designing a power conditioning circuit with lower cost. This paper proposes implementation of economic and efficient multilevel inverter for PV applications. Packed U Cell (PUC) multilevel inverter is employed as a competitive converter with minimum components compared to the existing ones. Boost DC-DC converter is designed to extract the maximum power point using P&O algorithm. Only six switches and single DC source (PV) are used to deliver a better power quality output in terms of number of voltage levels, low THD, small output filter. Simulink and experimental prototype are built to investigate the effectiveness of this topology. Results show a good matching.

Multi-level conversion : high voltage choppers and voltage-source inverters

Abstract: The authors discuss high-voltage power conversion. Conventional series connection and three-level voltage source inverter techniques are reviewed and compared. A novel versatile multilevel commutation cell is introduced: it is shown that this topology is safer and more simple to control, and delivers purer output waveforms. The authors show how this technique can be applied to either choppers or voltage-source inverters and generalized to any number of switches.<>

Modular Cascaded H-Bridge Multilevel PV Inverter with Distributed MPPT for Grid-Connected Applications

Abstract: Due to the possibility of providing energy with much less dependence on the fossil fuels, renew-competent energy sources, in specified sun photovoltaic (PV) conversion have received elevated acceptance and progress in latest times. Big benefits of PV panels comprise easy and trustworthy power production and suitability for disbursed iteration. In addition the costs for photovoltaic modules is drastically lowering. To comprehend this issue, a control plan with modulation compensation scheme is likewise proposed. An exploratory three-stage seven-level cascaded H-bridge inverter has been manufactured using nine H-bridge modules (three modules for each stage). Each H-bridge module is associated with a 185-W solar panel. Simulation results are introduced to confirm the practicality of the proposed approach.

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

Abstract: 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.

Finite-Control-Set Model Predictive Control for Grid-Connected Packed-U-Cells Multilevel Inverter

Abstract: This paper presents a finite-control-set model predictive control (FCS-MPC) for grid-tied packed U cells (PUC) multilevel inverter (MLI). The system under study consists of a single-phase 3-cells PUC inverter connected to the grid through filtering inductor. The proposed competitive topology allows the generation of 7-level output voltage with reduction of passive and active components compared to the conventional MLIs. The aim of the proposed FCS-MPC technique is to achieve, under various operating conditions, grid-tied current injection with unity power factor and low total harmonic distortion while balancing the capacitor voltage. Parameters’ sensitivity analysis was also conducted. The study is conducted on a low-power case study single-phase 3-cells PUC inverter and with possible extension to higher number of cells. Theoretical analysis, simulation, and experimental results are presented and compared.

Optimal DC Source Influence on Selective Harmonic Elimination in Multilevel Inverters Using Teaching–Learning-Based Optimization

Abstract: This paper presents an optimization method for selective harmonic elimination in a cascaded multilevel inverter using teaching–learning-based optimization (TLBO). The main objective in selective harmonic elimination (SHE) strategy is to eliminate low-order harmonics by solving nonlinear equations and reaching optimal solution, while the fundamental component is satisfied. In this paper, in one side, the influence of optimal dc sources is investigated to reach the SHE goal, and in another side, comparing optimization methods is considered. In this paper, the TLBO as a recently emerged nature-inspired algorithm is presented to provide better results for the SHE in comparison with genetic algorithm, artificial bee colony, imperialistic competitive algorithm, harmony search, ant colony optimization, particle swarm optimization, and differential evolution. For better comparison of those methods and influence of optimal dc sources, 5-, 9-, and 15-level inverters are chosen and MATLAB software is used for optimization. Simulation results show the superiority of TLBO, higher precision and probability of convergence than other mentioned algorithms. Finally, to validate the influence of optimal dc sources and the accuracy of TLBO results, the experimental setup is conducted for a 5-level cascaded H-bridge inverter with optimal dc sources.