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1. A Control Scheme for a DC Extreme Fast Charger with RMS Current Minimization

   https://doi.org/10.1109/PEDG51384.2021.9494232  

   Jean-Pierre, Garry; Beheshtaein, Siavash; Altin, Necmi; Nasiri, Adel (June 2021, 2021 IEEE 12th Annual International Symposium on Power Electronics for Distributed Generation Systems)

   In this study, a power converter topology and control schemes for the power converter stages are proposed for a DC extreme fast charger. The proposed system is composed of a cascaded H-bridge (CHB) converter as the active front end (AFE), and an input series output parallel (ISOP), which includes three parallel connected dual active bridge (DAB) cells. A modified Lyapunov Function (LF) based control strategy is applied to obtain high current control response for the AFE. An additional controller to remove the voltage unbalances among the H-bridges is also presented. Additionally, the triple phase-shift (TPS) control method is applied for the ISOP DAB converter. A Lagrange Multiplier (LM) based optimization study is performed to minimize the RMS current of the transformer. The performance of the proposed converter topology and control strategies is validated with MATLAB/Simulink simulations. 

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2. A ±0.5-mV-Minimum-Input DC-DC Converter With Stepwise Adiabatic Gate-Drive and Efficient Timing Control for Thermoelectric Energy Harvesting

   https://doi.org/10.1109/TCSI.2022.3219402  

   Carlson, Eric J.; Smith, Joshua R. (February 2023, IEEE Transactions on Circuits and Systems I: Regular Papers)

   This paper presents a step-up DC-DC converter that uses a stepwise gate-drive technique to reduce the power FET gate-drive energy by 82%, allowing positive efficiency down to an input voltage of ±0.5 mV—the lowest input voltage ever achieved for a DC-DC converter as far as we know. Below ±0.5 mV the converter automatically hibernates, reducing quiescent power consumption to just 255 pW. The converter has an efficiency of 63% at ±1 mV and 84% at ±6 mV. The input impedance is programmable from 1 Ω to 600 Ω to achieve maximum power extraction. A novel delay line circuit controls the stepwise gatedrive timing, programmable input impedance, and hibernation behavior. Bipolar input voltage is supported by using a flyback converter topology with two secondary windings. A generated power good signal enables the load when the output voltage has charged above 2.7 V and disables when the output voltage has discharged below 2.5 V. The DC-DC converter was used in a thermoelectric energy harvesting system that effectively harvests energy from small indoor temperature fluctuations of less than 1°C. Also, an analytical model with unprecedented accuracy of the stepwise gate-drive energy is presented. 

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3. A Novel Solar PV Inverter Topology Based on an LLC Resonant Converter

   https://doi.org/10.1109/ECCE.2019.8912924  

   Altin, Necmi; Ozdemir, Saban; Nasiri, Adel (September 2019, IEEE Energy Conversion Conference and Expo)

   In this paper, a new topology for grid-connected solar PV inverter is proposed. The proposed topology employs an LLC resonant converter with high frequency isolation transformer in the DC-DC stage. The DC-DC converter stage is controlled to generate a rectified sine wave voltage and current at the line frequency. An unfolder inverter interfaces between this DC stage and the grid. Both phase-shift and frequency control methods are used to control the LLC resonant converter. The switching frequency is determined depending on the phase-shift angle to extend the zero-voltage switching (ZVS) region. The transformer leakage and magnetization inductances are also properly designed to provide ZVS for wide operation area. The LLC converter operates in the ZVS region except the narrow band around the zero-crossings of the inverter output current. Since the LLC resonant converter has a high frequency transformer, the line frequency transformer requirement is eliminated, and thus more compact and efficient design is obtained. The proposed topology is validated by the simulation and experimental results. 

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4. An Efficient Complementary Topology Switched-Capacitor Based DC-DC Converter

   https://doi.org/10.1109/MWSCAS.2018.8624073  

   Lu, Ruikuan; Haider, Mohammad R; Massoud, Yehia; Uddin, Nasim (August 2018, 2018 IEEE 61st International Midwest Symposium on Circuits and Systems (MWSCAS))

   This paper proposes a complementary topology for Switched-Capacitor (SC) DC-DC converter to enhance the dynamic response. For battery charging unit with faster charging time requirement, one of the major restrictions comes from the equivalent output resistance of the SC DC-DC converter. By connecting one completely symmetric SC converter as complementary topology with the original single converter, the proposed SC DC-DC converter topology decreases the equivalent output resistance down to half. Simulated in 0.13-μm standard CMOS process, the simulation results show that this complementary SC converter gains faster dynamic response, shorter charging time, and higher energy-conversion efficiency. 

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5. Design and implementation of a series resonant solid state transformer

   https://doi.org/10.1109/ECCE.2017.8095937  

   Rashidi, Mohammad; Sabbah, Mohamad; Bani-Ahmed, Abedalsalam; Nasiri, Adel; Balali, Mohammad Hasan (October 2017, 2017 IEEE Energy Conversion Congress and Exposition (ECCE))

   The focus of this study is on the design of a full-bridge unidirectional resonant LLC Solid State Transformer. The proposed topology uses a high-frequency transformer to optimize the size and weight of the converter. This converter has the capability of operating at fluctuating load conditions while it keeps the voltage regulated in different operation point. The converter is designed to maintain soft switching by using a resonant circuit in this design to minimize the switching loss of the high frequency converter. ZVS in the leading leg for turn on mode and ZCS commutation in the lagging leg for all of the modes are achieved in the H-bridge through the suggested circuitry which is analyzed mathematically in detail in this study. A combination of Pulse frequency modulation (PFM) and Phase Shifting Modulation (PSM) are utilized to control this resonant converter. The experimental setup for the suggested configuration was implemented and the results of the simulation and calculations have been verified with test results. The hardware set up was tested with two different power levels and the output results confirm that the control method works properly to feed the load and keeps the converter working in the expected frequency range and maintaining the soft switching to decrease switching loss. The results shows conversion efficiency of 97.18% is achieved. 

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