@article{wang_trlica_khan_dickey_adams_2015, title={A reconfigurable liquid metal antenna driven by electrochemically controlled capillarity}, volume={117}, ISSN={["1089-7550"]}, DOI={10.1063/1.4919605}, abstractNote={We describe a new electrochemical method for reversible, pump-free control of liquid eutectic gallium and indium (EGaIn) in a capillary. Electrochemical deposition (or removal) of a surface oxide on the EGaIn significantly lowers (or increases) its interfacial tension as a means to induce the liquid metal in (or out) of the capillary. A fabricated prototype demonstrates this method in a reconfigurable antenna application in which EGaIn forms the radiating element. By inducing a change in the physical length of the EGaIn, the operating frequency of the antenna tunes over a large bandwidth. This purely electrochemical mechanism uses low, DC voltages to tune the antenna continuously and reversibly between 0.66 GHz and 3.4 GHz resulting in a 5:1 tuning range. Gain and radiation pattern measurements agree with electromagnetic simulations of the device, and its measured radiation efficiency varies from 41% to 70% over its tuning range.}, number={19}, journal={JOURNAL OF APPLIED PHYSICS}, publisher={AIP Publishing}, author={Wang, M. and Trlica, C. and Khan, M. R. and Dickey, M. D. and Adams, J. J.}, year={2015}, month={May} }
 @inproceedings{wang_huang_yu_huang_2015, title={An isolated bi-directional soft-switched DC-AC converter using wide-band-gap devices with novel carrier-based unipolar modulation technique under synchronous rectification}, DOI={10.1109/apec.2015.7104672}, abstractNote={A novel carrier-based unipolar-SPWM-oriented modulation technique with synchronous rectification for isolated bi-directional soft-switched high-frequency-AC (HFAC) link DC-AC converter using SiC MOSFET is presented in this paper. The DC-AC converter is composed of a full-bridge (FB) inverter cascaded with a cycloconverter through a high-frequency transformer. In order to increase the efficiency and power density, we proposed to utilize SiC MOSFETs for the converter. A carrier-based unipolar-SPWM-oriented modulation technique is proposed to realize zero-voltage-switching (ZVS) for FB and zero-current or zero-voltage-switching (ZVS/ZCS) for cycloconverter in all load range, and to suppress the voltage spikes introduced by the transformer leakage inductance as well. Synchronous rectification is implemented to further increase the converter efficiency. With the novel modulation technique, 1/4 of the AC switches in the cycloconverter are always on which eliminates 1/4 of the switching loss. Simulation model and a 400 VDC to 240 VAC, 1.2 kW prototype have been developed to validate the effectiveness and performance of the proposed unipolar soft-switching modulation technique and SiC converter.}, booktitle={2015 thirtieth annual ieee applied power electronics conference and exposition (apec 2015)}, author={Wang, M. Q. and Huang, Q. Y. and Yu, Wensong and Huang, A. Q.}, year={2015}, pages={2317–2324} }
 @inproceedings{huang_wang_yu_huang_2015, title={Power-weighting-based multiple input and multiple output control strategy for single-phase PV cascaded H-bridge multilevel grid-connected inverter}, DOI={10.1109/apec.2015.7104646}, abstractNote={This paper presents a power-weighting-based multiple input and multiple output control strategy and performance improvements schemes for single-phase PV cascaded H-bridge multilevel grid-connected inverter. The truly individual MPPT block for each H-bridge converter realizes independent MPPT, and the sum of each voltage reference provides the system voltage reference for the voltage loop. And the sum of each PV voltage is the system voltage feedback. The output of the voltage controller delivers the peak value of the sinusoidal current reference. The output of this central current controller is assigned directly according to the PV power weighting factors to create the coordinated control signals for PWM generation of each H-bridge respectively. This approach makes the control structure for this cascaded multilevel inverter have only one central dual loop controller, and the PWM generation will be decoupled from the voltage controllers. This feature is similar with the single H-bridge inverter's dual loop control. Furthermore, to improve the dynamic response of the voltage loops, a sample and hold block at double line frequency is included in each voltage loop. Therefore, the voltage loop bandwidth will increase to 25~30Hz and the MPPT speed will be much faster as well. Besides, the power-based duty-ratio feed-forward technique is proposed to improve the current loop performance. Finally, simulated and experimental results are provided to verify the performance of the proposed control approaches.}, booktitle={2015 thirtieth annual ieee applied power electronics conference and exposition (apec 2015)}, author={Huang, Q. Y. and Wang, M. Q. and Yu, Wensong and Huang, A. Q.}, year={2015}, pages={2148–2153} }
 @inproceedings{wang_khan_trlica_dickey_adams_2015, title={Pump-free feedback control of a frequency reconfigurable liquid metal monopole}, DOI={10.1109/aps.2015.7305500}, abstractNote={We demonstrate a pump-free method to control the length of liquid metal in a capillary as a means to change the operating frequency of a monopole antenna. An applied DC voltage controls the surface tension of the liquid metal filament, causing it to lengthen or contract, varying the antenna's resonant length. A closed-loop feedback system tracks the antenna's operating frequency and adjusts the applied voltage to shape the liquid metal towards the desired response. Measurements show that the process is controlled and fully reversible, dynamically adjusting to a programmed frequency.}, booktitle={2015 ieee international symposium on antennas and propagation & usnc/ursi national radio science meeting}, author={Wang, M. and Khan, M. R. and Trlica, C. and Dickey, Michael and Adams, Jacob}, year={2015}, pages={2223–2224} }
 @inproceedings{du_huang_wang_lukic_2012, title={A novel high step-up ratio bi-directional DC-DC converter}, DOI={10.1109/apec.2012.6165870}, abstractNote={High step-up ratio bi-directional DC-DC converter is attractive in energy storage systems for renewable energy generation and in electric vehicle applications. A novel high step-up ratio bi-directional DC-DC converter and its alternative topology which can achieve soft switching in full load range and wide voltage range are proposed. The operation principle of the converter is analyzed in this paper. The modulation strategy and the optimum operation region are presented. A 400kHz 14.4V to 360V prototype was built to verify the analysis and the operation of the proposed converter. Zero voltage switching of all the switches was verified by experimental waveforms. The tested converter efficiency at 450W is 94.1%.}, booktitle={2012 twenty-seventh annual ieee applied power electronics conference and exposition (apec)}, author={Du, Y. and Huang, A. Q. and Wang, M. Q. and Lukic, S. M.}, year={2012}, pages={524–531} }