Dual-active bridge series resonant electric vehicle charger: A self-tuning method

© 2020 by the authors. Licensee MDPI, Basel, Switzerland. This paper presents a new self-tuning loop for a bidirectional dual-active bridge (DAB) series resonant converter (SRC). For different loading conditions, the two active bridges can be controlled with a minimum time displacement between them to assure zero voltage switching (ZVS) and minimum circulation current conditions. The tuning loop can instantly reverse the power direction with a fast dynamics. Moreover, the tuning loop is not sensitive to series resonant tank tolerances and deviations, which makes it a robust solution for power tuning of the SRCs. For simplicity, the power is controlled based on the power-frequency control method with a fixed time displacement between the active bridges. The main design criteria of the bidirectional SRC are the time displacement, operating frequency bandwidth, and the minimum and maximum power, which are simply derived and formulated based on the self-tuning loop’s parameters. Based on the parameters of the tuning loop, a simplified power equation and power control method is proposed for DAB-SRCs. The proposed control method is simulated in static and dynamic conditions for different loadings. The analysis and simulation results show the effectiveness of the new tuning method

Design and Sensitivity Analysis of Dynamic Wireless Chargers for Efficient Energy Transfer

Tunable Self-Oscillating Switching (TSOS) methods are a robust solution for tuning of Inductive Power Transfer (IPT) systems. However, they require deep analysis to be an appropriate choice for Dynamic Wireless Charging (DWC) systems. In this paper, the optimal operation point of TSOS in the maximum power transfer, efficiency, and Zero Voltage Switching (ZVS) realization perspectives are determined based on sensitivity analysis for DWC of Electric Vehicles (EVs). In the sensitivity analysis, all the possible states of the coupling factor and state of charge (SOC) are considered as system variables. Moreover, a new phasor modeling for constant voltage (battery) loads is proposed. The performance of this model is quite different from the conventional static model for the loads. Moreover, to limit the current of the charger under light couplings, a simple hysteresis controller is employed. A setpoint is proposed based on the sensitivity analysis method to transfer maximum energy in misaligned conditions. The proposed setpoint increases transferred energy and energy efficiency while limits the current of the charger. To analyze this method, simulation is done in the Simulink/MATLAB, and to verify the results, a laboratory prototype is implemented.This publication was made possible by Qatar University Collaborative Research grant # [QUCG-CENG-19/20-5] from the Qatar University. The statements made herein are solely the responsibility of the authors. The APC is funded by the Qatar National Library, Doha, Qatar.Scopu

Third Harmonic Operation of Current Fed Resonant Inverters for Inductive Power Transfer Systems

This paper presents Third Harmonic Operation (THO) of Current Fed Parallel Resonant Push-pull Inverter (CFPRPI) for Inductive Power Transfer (IPT) systems. THO is proposed for CFPRPI to achieve higher voltage ratio with lower switching frequency, which is essential for low input voltage IPT systems. The IPT system is considered based on PS compensation method, i.e. parallel compensation for the primary side and series compensation for the secondary side. Moreover, a phase-shift control method is presented based self-oscillating tuning loop for output voltage or power regulations. The tuning loop and IPT system are modeled and formulated in THO mode. To verify the validity of the proposed method, a laboratory prototype with resonant frequency of about 120 kHz and maximum output power of about 50 W has been implemented.ACKNOWLEDGEMENT This publication was made possible by Qatar University Collaborative Research grant # [QUCG-CENG-19/20-5] from the Qatar University. The statements made herein are solely the responsibility of the authors.Scopu

Design Optimization of Inductive Power Transfer Systems Considering Bifurcation and Equivalent AC Resistance for Spiral Coils

This paper presents a design optimization algorithm for series-series compensated Inductive Power Transfer (IPT) system based on flat spiral coils, considering bifurcation phenomenon and AC equivalent resistance of the coils. Moreover, it finds the best values in the areas where the IPT system operates in Zero Voltage Switching (ZVS) condition. Equivalent AC resistance of spiral coils is modeled based on eddy currents simulations using Finite Element Method (FEM) and Maxwell simulator. Based on the FEM simulations, a new approximation method using separation of variables is proposed as a function of spiral coil's main parameters. This paper shows that this model accurately derive equivalent resistance of the coils for a specific strand diameter, with almost 95% accuracy. Based on the proposed algorithm, several IPT systems are optimized in MATLAB software using Genetic Algorithm (GA). Finally, the proposed method has been verified using a laboratory prototype with output power of about 200 watts and operating frequency of about 85 kHz.This work was supported in part by the Qatar University High Impact Research from Qatar University under Grant QUCG-CENG-19/20-5, and the publication charges is paid by the Qatar National Library.Scopu