In this paper we review some of the fundamental limits of dc-dc power converters described in 1966 and 1969 and generate an averaged power model that is useful to perform high-level comparison of power converters and architectures. The model is extended to 3 port power converters, which is used to calculate the minimum possible internal power to be processed by the components of the power stage of energy buffered converters. Finally, a single stage inverter/rectifier with energy storage capability that meets the fundamental limit is synthesized.

In this article, a series–series wireless power transfer (WPT) system combined with an inverse coupled current doubler rectifier (ICCDR) is proposed, as a very appropriate WPT topology for high current applications. The ICCDR uses an autotransformer to reduce the losses on the rectifier stage, which is suitable for high-current low-voltage output applications. Furthermore, a comprehensive comparison between the proposed WPT system with ICCDR and the traditional WPT system with full-bridge rectifier is presented. In the proposed WPT system, the primary parameter configuration and circuit behavior keep the same, while the secondary side altered, contributing to a volume reduction on the resonant capacitor. The system overall efficiency and power density are improved significantly. Accordingly, a 10 kW 400 V/48 V WPT prototype for battery charging is constructed and tested to validate this proposal. The output voltage is in the range between 38 and 55 Vdc, and the rated output current is 200 A. The overall efficiency of the proposed system reaches 94%, improving 2% efficiency with 220 W energy saving with respect to the traditional diode-rectifier system, when 9.5-kW output power is delivered. Theoretical analysis and experimental results have verified that the proposed system shows great advantages in high-power WPT applications.

This work analyses the fundamental aspects of the principal resonant network topologies for Inductive Power Transfer Systems. From the analytical derivation, different features such as the variation of the coupling factor or load changes are studied. Based on this study, a resonant series-series topology is selected, which cancels the leakage inductance. Due to the specifications, the air gap distance and its tolerance ( $\pm 12\%$ ) produce a wide variation of the coupling factor of the inductive link. Therefore, through fast 3D simulations by finite elements, the inductive link is designed so that this variation is minimized. This maintains the resonance and the designed system, in turn, behaves like a voltage source regardless of power, and thus evades the implementation of a control stage. A dc-dc converter is constructed where the distance between the primary and secondary side vary from 35 mm to 45 mm, and the power ranges from 0 kW to 5 kW. The output voltage range goes from $38 V_{DC}$ to $55 V_{DC}$ . Experimental results for the dc-dc converter report an efficiency of over 94%.

We investigate with computer simulations the effect of applying an electric field on the water-to-ice transition. We use a combination of state-of-the-art simulation techniques to obtain phase boundaries and crystal growth rates (direct coexistence), nucleation rates (seeding) and interfacial free energies (seeding and mold integration). First, we consider ice Ih, the most stable polymorph in the absence of a field. Its normal melting temperature, speed of crystal growth and nucleation rate (for a given supercooling) diminish as the intensity of the field goes up. Then, we study polarised cubic ice, or ice Icf, the most stable solid phase under a strong electric field. Its normal melting point goes up with the field and, for a given supercooling, under the studied field (0.3 V nm ⁻¹ ) ice Icf nucleates and grows at a similar rate as Ih with no field. The net effect of the field would then be that ice nucleates at warmer temperatures, but in the form of ice Icf. The main conclusion of this work is that reasonable electric fields (not strong enough to break water molecules apart) are not relevant in the context of homogeneous ice nucleation at 1 bar.

This paper presents a control linearization technique for a Single-Phase Single Stage (SPSS) inverter with multiple modulation strategies. The power topology is based on a FCML inverter, and the control is based on the plant inversion. The proposed technique allows decoupling the control of the input current and the output voltage, which simplifies the control in two ways: first, the control of both variables is independent and second, the controllers are independent of the modulation applied, thanks to the plant inversion. This control is implemented in an FPGA. Since the converter operates at variable frequency, two different data acquisition alternatives are explored: sampling at variable frequency (once per switching cycle) or sampling at constant frequency (higher than the switching frequency). The proposed control is validated by simulation and experimental results with a 1 kVA prototype.

This paper presents a modulation with Zero-Voltage Switching for a single-phase, single-stage inverter intended for photovoltaic applications. In single-stage inverters, the DC-AC conversion stage is merged with the active power pulsation buffer stage. The proposed architecture uses a flying capacitor to handle the difference between the instantaneous input and output power, instead of the traditional bulky input capacitor. In this single-stage inverter, both the input current and the output voltage are controlled by the current of a single inductor. The inductor is operated in variable frequency Boundary Conduction Mode. Multiple operation modes are used along the line cycle, all of them with Zero-Voltage Switching in all transitions. The operation mode and control times are related with the target input current, target inductor current, input voltage, output voltage and flying capacitor voltage through equations that model the inductor waveform. These equations are solved with a fixed-point iteration method in a FPGA. The modulation and control are validated in a 1 kVA prototype with 400 V input and 240 Vrms, 60 Hz output.