Ahmed Mohamed Salem Ali

• Jiya, Immanuel Ninma; Ali, Ahmed Mohamed Salem; Huynh, Khang & Pomarnacki, Raimondas (2023). Integrated Multiport DC-DC and Multilevel Converters for Multiple Renewable Energy Source Integration. IEEE Access. ISSN 2169-3536. 11, s. 132483–132495. doi: 10.1109/ACCESS.2023.3336567. Fulltekst i vitenarkiv Vis sammendrag

  This research introduces an innovative converter system which has been developed to seamlessly incorporate multiple sources of renewable energy into both DC and AC grids. The integration of multiple energy sources is made possible through the utilization of a unique converter system that combines a multiport DC converter topology with a multilevel inverter topology, while maintaining a low component count and hence increased overall power density and efficiency for the proposed converter system. Unlike previous literature, where each energy source needs a separate DC converter and a two-level converter is used for DC to AC conversion, this converter system features buck-boost operation, superior power quality characteristics, and fewer components. The system suggests the implementation of a DC link voltage balancing technique that relies on an auxiliary circuit to achieve equilibrium in the voltage on the DC link, as a possible substitute to the more complicated control-based balancing scheme. The operational integrity of the converter system is assessed through rigorous numerical simulations and experimentally validated using OPAL-RT’s OP5700 hardware-in-the-loop (HIL) implementation platform as well as an in-house experimental test setup.

• Jiya, Immanuel Ninma; Ali, Ahmed Mohamed Salem & Huynh, Khang (2022). Integrated Multiport DC-DC and Multilevel Converters for Energy Sources, 2022 IEEE Industry Applications Society Annual Meeting (IAS). IEEE conference proceedings. ISSN 978-1-6654-7815-1. doi: 10.1109/IAS54023.2022.9939764. Vis sammendrag

  This paper presents a novel converter system for integrating multiple renewable energy sources for both dc and ac grids. The proposed converter system is formed by integrating a novel multiport dc converter topology with a multilevel inverter topology, aiming to achieve multiple source integration with low component count and higher efficiency on the multiport converter section and efficient dc to ac conversion on the multilevel inverter section. As compared to counterparts in literature, where each energy source requires its own dc converter and the dc to ac conversion is achieved using a two-level converter, the converter system proposed in this paper has more attractive features of buck-boost operation, better power quality characteristics and low part counts. Within the framework, an auxiliary circuit-based dc link voltage balancing technique is proposed to balance the voltage on the dc link as compared to the more complex control-based balancing scheme. Open and closed loop operations of the converter system are numerically verified using simulations and validated by a high-fidelity hardware-in-the-loop implementation platform.

• Ali, Ahmed Mohamed Salem; Huynh, Van Khang; Jiya, Immanuel Ninma & Robbersmyr, Kjell Gunnar (2022). Hybrid Three-Phase Transformer-Based Multilevel Inverter with Reduced Component Count. IEEE Access. ISSN 2169-3536. 10, s. 47754–47763. doi: 10.1109/ACCESS.2022.3171849. Fulltekst i vitenarkiv
• Jiya, Immanuel Ninma; Ali, Ahmed Mohamed Salem; Huynh, Van Khang; Kishor, Nand & Ciric, Rade (2021). Novel Multisource DC-DC Converter for All-Electric Hybrid Energy Systems. IEEE transactions on industrial electronics (1982. Print). ISSN 0278-0046. 69(12), s. 12934–12945. doi: 10.1109/TIE.2021.3131871.
• Ali, Ahmed Mohamed Salem; Huynh, Van Khang & Robbersmyr, Kjell Gunnar (2021). Novel Transformer-Based Six-Level Inverter with Low Component Count. I Bossche, Alex (Red.), 2021 23rd European Conference on Power Electronics and Applications (EPE'21 ECCE Europe). IEEE conference proceedings. ISSN 978-9-0758-1537-5.
• Jiya, Immanuel Ninma; Huynh, Van Khang; Ali, Ahmed Mohamed Salem; Kishor, Nand & Ciric, Rade (2021). Novel Isolated Multiple-Input Buck-Boost DC-DC Converter for Renewable Energy Sources, IECON 2021 – 47th Annual Conference of the IEEE Industrial Electronics Society. IEEE (Institute of Electrical and Electronics Engineers). ISSN 978-1-6654-3554-3. doi: 10.1109/IECON48115.2021.9589538.
• Salem, Ahmed; Huynh, Khang & Robbersmyr, Kjell Gunnar (2021). Four-level three-phase inverter with reduced component count for low and medium voltage applications. IEEE Access. ISSN 2169-3536. 9, s. 35151–35163. doi: 10.1109/ACCESS.2021.3062110. Fulltekst i vitenarkiv
• Salem, Ahmed; Huynh, Khang; Robbersmyr, Kjell Gunnar; Norambuena, Margarita & Rodríguez, José (2020). Voltage Source Multilevel Inverters with Reduced Device Count: Topological Review and Novel Comparative Factors. IEEE transactions on power electronics. ISSN 0885-8993. 36(3), s. 2720–2747. doi: 10.1109/TPEL.2020.3011908. Vis sammendrag

  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.

• Salem, Ahmed; Huynh, Khang; Robbersmyr, Kjell Gunnar; Norambuena, Margarita & Rodriguez, Jose (2020). Novel Three-Phase Multilevel Inverter with Reduced Components for Low- and High-Voltage Applications. IEEE transactions on industrial electronics (1982. Print). ISSN 0278-0046. doi: 10.1109/TIE.2020.2998752.
• Ali, Ahmed Mohamed Salem; Huynh, Khang; Robbersmyr, Kjell Gunnar; Norambuena, Margarita & Rodriguez, Jose (2019). Novel Three-Phase Multi-Level Inverter with Reduced Components, Proceeding 45th Annual Conference of the IEEE Industrial Electronics Society - IECON 2019. IEEE conference proceedings. ISSN 978-1-7281-4878-6. s. 6501–6506. doi: 10.1109/IECON.2019.8927732.
• Ali, Ahmed Mohamed Salem; Huynh, Khang & Robbersmyr, Kjell Gunnar (2019). New Multilevel Inverter Topology with Reduced Component Count, EPE'19 ECCE Europe. IEEE conference proceedings. ISSN 978-9-0758-1531-3. doi: 10.23919/EPE.2019.8915400.

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• Ali, Ahmed Mohamed Salem; Huynh, Khang & Robbersmyr, Kjell Gunnar (2021). Multilevel Inverters with Reduced Component Count for Energy Systems. Universitetet i Agder. ISSN 978-82-8427-045-6. Fulltekst i vitenarkiv Vis sammendrag

  Multilevel inverters (MLIs) have gained increasing interest for advanced energy-conversion systems with a wide range of voltage levels, due to their attractive features of low harmonic contents, low dv/dt stress, low filtering requirements, low switching frequency, low electromagnetic interference (EMI), and employing low-rated semiconductor devices for producing high voltages. Further, some MLIs have a modularity feature, facilitating voltage and current scalability with high redundancy in switching states, allowing for fault-tolerant operations. The mentioned features are directly related to the number of generated voltage levels. However, enlarging level count renders challenges of requiring massive component counts, including DC sources, capacitors, power diodes, switches, inductors, and transformers. The high count of components negatively affects the size, cost, efficiency, lifespan, reliability, complexity of MLI-based energy conversion systems. Thus, proposing novel MLIs, which can enlarge the voltage level number with a low component count, is currently one of the most attractive topics in this research theme. In this dissertation, four three-phase topologies are proposed to mitigate the aforementioned shortcomings. Two transformerless topologies are proposed for low- and medium voltage applications, while two transformer-based topologies are intended for medium- and high-voltage applications. The proposed topologies have the key features of being capacitor-, diode-free, and low counts of DC sources, switches, and transformers. Further, three of them have a high modularity degree, allowing for higher voltage operations without increasing the voltage stress across the switches. The working principle of the proposed topologies are theoretically demonstrated, numerically verified, and experimentally validated through an in-house experimental setup. The effectiveness of the proposed topologies is proven through detailed comparative studies regarding component counts and voltage ratings. The proposed topologies are briefly described in this dissertation, while detailed explanations and results can be found in the appended papers.

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