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1. Generalized Architecture of a GaN-Based Modular Multiport Multilevel Flying Capacitor Converter

   https://doi.org/10.1109/TPEL.2023.3269800  

   Tamasas Elrais, Mohamed ; Safayatullah, Md ; Batarseh, Issa ( January 2023 , IEEE Transactions on Power Electronics)

   This paper proposes a generalized Gallium Nitride (GaN) based modular multiport multilevel flying capacitor architecture. In other words, the attractive flying capacitor multilevel (FCML) design and the full-bridge unfolding circuit are employed to develop a multiport multilevel converter architecture that fits various applications. Each module can be designed to contain any combination of AC and DC ports connected through DC-to-DC and DC-to-AC power conversion paths. These conversion paths are FCML topologies that can be designed with any number of levels; the DC-to-AC paths incorporate the full-bridge unfolding circuit. Two example prototypes with open-loop control, three-port and four-port, have verified this generalized architecture. A single module 3 kW three-port four-level prototype with two DC ports and an AC port has achieved a compact size of 11.6 in 3 (4.8 in ×4.3 in × 0.56 in) and a high power density of 258.6 W/in 3 . The three ports are connected through DC-to-AC and DC-to-DC paths that have achieved peak efficiencies of 98.2% and 99.43%, respectively. The total harmonic distortion (THD) of the AC port's voltage and current are 1.26% and 1.23%, respectively. It operates at a high switching frequency of 120 kHz because of the GaN switches and has an actual frequency (inductor's ripple frequency) of 360 kHz thanks to the frequency multiplication effect of the FCML. The four-port prototype contains three DC ports and an AC port and achieved similar high figures of merit. These experimental results of the two prototypes of high efficiency, power density, and compact size are presented in this article and highlight this architecture's promising potential. The choice of the number of modules, ports, and levels depends on the application and its specification; therefore, this proposed generalized structure may serve as a reference design approach for various applications of interest. 

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2. A Four Port Isolated PV-Based EV Charger that Supports level-2 and DC Charging

   https://doi.org/10.1109/ECCE50734.2022.9947535  

   Tamasas Elrais, Mohamed ; Rezaii, Reza ; Ghosh, Sumana ; Batarseh, Issa ( October 2022 , 2022 IEEE Energy Conversion Congress and Exposition (ECCE))

   Electric Vehicles (EV s) that are wholly charged from renewable energy resources to avoid indirect emissions are the most effective solution for climate change and energy insecurity. This paper proposes a four-port isolated PV -based EV charging architecture that contains an LLC input stage to harvest solar energy with high efficiency because of its dual PV input ports with independent MPPT capabilities that share a common resonant tank. This architecture also includes a GaN -based flying capacitor multilevel (FCML) output stage with two GaN-based FCML converter paths, DC and AC paths. These two paths transfer power with high efficiency to two output ports, a DC port for direct DC charging and an AC port for level-2 AC charging. The system has been verified by building a 2 kW prototype module, and experimental results are presented. 

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3. Resonant Multilevel Modular Boost Inverters for Single-Phase Transformerless Photovoltaic Systems

   https://doi.org/10.1109/ECCE.2018.8558049  

   Ni, Ze ; Li, Yanchao ; Johnson, Jalen ; Cao, Dong ( September 2018 , 2018 IEEE Energy Conversion Congress and Exposition (ECCE))

   This paper presents two novel single-phase resonant multilevel modular boost inverters based on resonant switched capacitor cells and a partial power processed voltage regulator. Compared with other multilevel boost inverters applied in PV systems, one remarkable advantage of the proposed topologies is that the bulky AC filtering inductor is replaced by a smaller-size one in the partial power processed buck converter. Constant duty cycle PWM method is attractive for the multilevel inverter controller design. GaN Enhancement Mode Power Transistors help both the modular resonant switched capacitor cells and the full-bridge unfolder be realized in a small size with high power density. The clamp capacitors in the resonant switched capacitor cells effectively alleviate the switch voltage spikes. These two inverter topologies are analyzed and simulated in PLECS. Simulation results verify the validity of boost inverter function. Stress analysis shows that the inverter has relatively small total normalized switch conduction power stress and total normalized switch stress ratio. Relative total semiconductor chip area comparison results reflect that the proposed topology achieves more efficient semiconductor utilization compared with typical non-resonant multilevel modular switched capacitor boost inverters. Test results indicate that the proposed topology can be used for single-phase non-isolated PV boost inverter applications with small ground leakage current, high voltage conversion ratio, small volume and potential high efficiency. 

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4. Theoretical. Simulation, and Experimental Comparison of GaN-based Two-level and Multilevel Converters

   https://doi.org/10.1109/SPEC55080.2022.10058432  

   Tamasas Elrais, Mohamed ; Batarseh, Issa ( December 2022 , 2022 IEEE 7th Southern Power Electronics Conference (SPEC))

   The size, weight, power density, cost, and efficiency are crucial factors that should be considered when designing or employing power electronics converters for a specific application. Therefore, comparing different converters to investigate which converter provides better figures of merit at the same application and operating condition is essential. This paper uses theoretical, simulation and experimental comparisons between the two-level and multilevel converters. The DC-DC two-level buck and the flying capacitor multilevel (FCML) buck converters are chosen to carry out the theoretical, simulation and experimental prototypes when both employ Gallium Nitride (GaN) power semiconductor switches. It was found that the FCML converter inherently provides superior performance and figures of merit over both the two-level and multilevel converters. Simulation and experimental results that validate each other are provided in this paper. 

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5. A 100kW SiC Switched Tank Converter for Transportation Electrification

   Ni, Ze ; Li, Yanchao ; Liu, Chengkun ; Wei, Mengxuan ; Cao, Dong ( June 2019 , IEEE Transportation Electrification Conference and Expo 2019)

   This paper compares three different dc-dc topologies, i.e. boost converter, three-level flying capacitor multilevel converter (FCMC) and one-cell switching tank converter (STC) for a 100 kW electric vehicle power electronic system. This bidirectional dc-dc converter targets 300 V - 600 V voltage conversion. Total semiconductor loss index (TSLI) has been proposed to evaluate topologies and device technologies. The boost converter and one-cell STC have been fairly compared by utilizing this index. The simulation results of a 100 kW one-cell STC working at zero current switching (ZCS) mode have been provided. A 100 kW hardware prototype using 1200 V 600 A SiC power module has been built. The estimated efficiency is about 99.2% at 30 kW, 99.13% at half load, and 98.64% at full load. The power density of the main circuits is about 42 kW/L 

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