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1. Improved Lifetime of GaN-Based Single Phase PV Inverter Using Dynamic Hardware Allocation

   https://doi.org/10.1109/ECCE47101.2021.9595850  

   Sabi, Kamal; Costinett, Daniel (October 2021, 2021 IEEE Energy Conversion Congress and Exposition (ECCE))

   Power electronic inverters for photovoltaic (PV) systems over the years have trended towards high efficiency and power density. However, reliability improvements of inverters have received less attention. Inverters are one of the lifetime-limiting elements in most PV systems. Their failures increase system operation and maintenance costs, contributing to an increased lifetime energy cost of the PV system. Opportunities exist to increase inverter reliability through design for reliability techniques and the use of new modular topologies, semiconductor devices, and energy buffering schemes. This paper presents the implementation and design for reliability for a GaN-based single-phase residential string inverter using a new topological and control scheme that allows dynamic hardware allocation (DHA). In the proposed inverter architecture, a range of identical modules and control schemes are used to dispatch hardware resources within the inverter to variably deliver power to the load or filter the second harmonic current on the DC side. This new approach more than triples the lifetime of GaN-based inverters, reducing system repair/replacement costs, and increasing the PV system lifetime energy production. 

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2. A 2.4 GHz low-power and compact 3-bit active phase shifter utilizing miller capacitance

   https://doi.org/10.1016/j.mejo.2023.105914  

   Qi, Yu; Kines, Michael; Ellicott, Samuel; Khalil, Waleed; Lavasani, Hossein Miri (October 2023, Microelectronics Journal)

   A low-power and compact 3-bit active phase shifter is designed and implemented in a 22 nm FDSOI CMOS process. A modified inverter-based topology, which takes advantage of miller capacitance, is used to create a compact and low-power solution, resulting in 10 and 90 x reduction in the power and chip area, respectively, for a given phase shift, compared to the standard inverter-based topology. At the same time, the proposed phase shifter exhibits less sensitivity to device mismatch. The proposed design measures 0.004 mm2, consumes 1.8 mW, and delivers up to 65°of phase shift with RMS phase and amplitude error of 3.85°and ±0.34 dB, respectively. The measured die-to-die variation is also confined to ±6.2°, which is 10% of the full range 

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3. Inverter-based Emulation of Single-phase Air Conditioner Loads

   https://doi.org/10.1109/ECCE53617.2023.10362629  

   Cai, Weiqian; Lu, Minghui; Johnson, Brian (October 2023, Energy Conversion Congress and Exposition)

   Laboratory experimentation of electromechanical systems can be challenging from a practical perspective and offers limited flexibility once built. Aiming at maximizing versatility and accelerating laboratory research, we propose a method of electric motor emulation via power electronics. This paper is focused on constant-frequency air conditioners based on single-phase induction machines and we show how to control a single-phase inverter to emulate the ac-terminal dynamics of such a system serving thermal loads. This approach offers a convenient method of high-bandwidth air conditioner load emulation without moving parts. Such a setup could be used to realize electrical experiments that mimic residential load dynamics with high fidelity. After outlining the system model, we propose a practical voltage-source inverter implementation and conclude with experiments on a 600 W converter. 

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4. 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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5. FIDVR Capability of Hybrid Grid-Forming PV Power Plants During Feeder Restoration

   https://doi.org/10.1109/TEC.2024.3377608  

   Mannan, Abdelrahman M; Dang, Hoang P; Villegas_Pico, Hugo N (March 2024, IEEE Transactions on Energy Conversion)

   Grid-forming inverters must optimally transfer power from dc-coupled photovoltaic arrays and batteries into an ac grid. Further, they must be able to restore single-phase induction motors (SPIMs) and withstand fault-induced delayed-voltage-recovery (FIDVR) events. These resilience and reliability challenges are addressed here by: (i) engineering a controller to optimally operate dc-coupled hybrid resources; (ii) modeling residential air-conditioning compressors for restoration/FIDVR studies; and (iii) analyzing SPIM thermal-relay performance under limited inverter currents and designing an electronic protection for stalled SPIMs. These contributions are demonstrated via electromagnetic-transient simulations and can be helpful to understand recommendations by the North American Electric Reliability Corporation. 

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