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In this article, a coupled-inductor (CI)-based bidirectional dc–dc converter with a high voltage conversion ratio (VCR) and low voltage stress is proposed. The topology can achieve high VCR by employing two CIs; moreover, the interleaved technique overcomes the defect of large current ripple in CI. A sensorless current balance between the two CIs is also realized without an auxiliary circuit and complex control method. The pulsewidth modulation plus phase-shift control is employed, where the duty cycle D is used to adjust the VCR, and the phase-shift angle ϕ is used to control the direction and amount of the transferred power. In addition, all switches can achieve soft-switching under a wide operation range. The steady-state analysis of the proposed converter is analyzed in detail, followed by comprehensive experimental verification under a 1-kW prototype. [ABSTRACT FROM AUTHOR]

In high-power medium-voltage applications, inductors usually have multiple windings on a single core, due to the high inductance value and high current stress. The multiple coils are electronically connected in either series or parallel, with considerations of windings loss and cost. However, the differences in parasitic capacitance of inductors using parallel and series connections are not discussed. Therefore, this article reveals that in comparison to parallel connections for windings, utilizing series connection for winding can significantly reduce the parasitic capacitance in multiwindings inductors without sacrificing the power density and adding manufacturing complexities. Physics-based models of parasitic capacitance in inductors with round-cable and copper-foil windings are developed for theoretical analysis. According to the theoretical analysis, the equivalent capacitance contributed by the stored electric field energy between two layers can be halved at least. The theoretical analysis is also verified by FEM simulations. Six prototyped inductors are experimentally compared to validate the theory. [ABSTRACT FROM AUTHOR]

A circulating power suppression structure for a three-winding-transformer-based converter is proposed in this letter. The equivalent circuit models of the dual-transformer-based and three-winding-transformer-based converter are derived, which illustrates their merits and demerits. With the proposed structure, the drawbacks of these two transformer-type converters can be overcome, and their advantages can be combined. Useless circulating loss in three-winding-transformer can be reduced to mW level and can be omitted. The complex and coupled dual-transformer parameter design problem can be solved. The analysis and performance of the proposed structure are fully validated by experimental results. [ABSTRACT FROM AUTHOR]

In this article, an interleaved coupled-inductor (CI) based bidirectional dc–dc converter (BDC) is proposed with a higher voltage conversion ratio (VCR). In this proposed interleave CI-based BDC (ICI-BDC), the CIs can operate as both a filter inductor and a transformer simultaneously, so that the power density is improved. Moreover, as a transformer, the turns ratio of CIs is used to improve the VCR with a voltage stress reduction purpose. Furthermore, the interleaved technique can well achieve the low current ripple and reduced current stress in this topology. To control ICI-BDC, the pulsewidth modulation plus phase-shift (PPS) control is employed, where the duty cycle is used to match the two side voltages, and the phase-shift angle is used to control the amount and direction of power flow. Uniquely, a difference value is set between the two side duty cycles, and the duty cycle of the high voltage side is smaller than that of the low voltage side by a fixed value. In this proposed control method, all the switches can achieve soft-switching even at light load condition, which can improve transmission efficiency. Experimental results obtained from a 1-kW prototype show a nearly high efficiency under all loading conditions, validating the viability of the proposed ICI-BDC topology and control method. [ABSTRACT FROM AUTHOR]

In this article, an interleaved soft-switching bidirectional dc–dc converter (BDC) with high voltage conversion ratio (VCR) and low voltage stress is proposed for battery charging/discharging applications. A built-in transformer (BT) is integrated into conventional half-bridge BDC and three-level structure to achieve high VCR and reduced voltage stresses simultaneously. The feature of BT is that the balanced magnetic flux exists in the magnetic core, which allows for small size of the magnetic core. The current ripple in the battery side is reduced by adopting the interleaved structure. Moreover, the voltage-matching on both sides of the BT is realized by the adjustment of the duty cycle. As a result, even if the battery voltage changes, the BT always operates under the highest efficiency condition. Besides, by employing phase-shift control, power flow can be regulated monotonously. Soft-switching of all the switches within a wide range of battery voltage is obtained by employing the optimal design. The operational principles, characteristics, and design considerations are analyzed in detail. Experimental results from the BT-BDC prototype of 1-kW, 40–60 to 400 V verify the effectiveness. [ABSTRACT FROM AUTHOR]

A simplified hysteresis sliding-mode control (SMC) is proposed to improve the dynamic response of the superbuck converter operating in continuous condition mode with high duty cycle values. The controller based on the sliding surface composed of output voltage error and input current error is derived and further simplified in structure. The simplified process decreases the number of control parameters and reduces system cost. The relationship between control parameters and the performance of the proposed controller is studied and verified by simulation. An experimental prototype using the proposed controller is designed with analog devices. Moreover, a dynamical performance comparison involving the proposed sliding-mode controller and existing controller is provided. [ABSTRACT FROM AUTHOR]

In this article, the generalized symmetrical step-up multilevel inverter (MLI) using a single dc source and crisscross capacitor units (CCUs) is proposed. Compared with the conventional MLIs, the capacitor in each CCU can get self-voltage balance without auxiliary methods. The output level and boost factor of the proposed topology can be increased with fewer devices. And, importantly, its maximum voltage stress for the switching devices is limited below a low degree even though the peak output voltage increases. However, the maximum voltage stress of most other boost MLIs will rise badly with output voltage increasing. The abovementioned merits of the proposed topology in all show its suitability in renewable energy generation systems, distributed generation, and other applications of high power quality. The operation principles of the proposed MLI are fully described in the this article. The self-balance of capacitors is deduced based on the adopted modulation method. The capacitance calculation is also presented in detail. Afterward, the power loss of the proposed topology has been analyzed. And the comparative study illustrates its advantages on reduced active devices, lower voltage stress, boost ability, and self-balance against other MLIs. Finally, the simulation and the 1.2-kVA experimental prototype with two CCUs and 13-level output are implemented. The results verify the feasibility and performance of the proposed topology. [ABSTRACT FROM AUTHOR]

A nonisolated soft-switching bidirectional dc–dc converter (BDC) with interleaved technique and built-in transformer (BT) is proposed for the interface between the energy storage system and dc microgrid bus in this article. A T-type neutral-point-clamped circuit is integrated into an interleaved conventional buck–boost BDC to obtain a high voltage-gain ratio and decrease voltage stresses of power switches effectively. Compared with the couple-inductor, BT allows for a small magnetic core size, owing to its inherent saturation avoidance. The interleaved structure is employed to reduce the current ripple in the low-voltage side and helps to achieve voltage matching on both sides of the BT under pulsewidth modulation control. Thus, the circulating current can be lowered to improve efficiency. Phase-shift control is adopted to regulate the power flows of the proposed BT-BDC. Moreover, the optimal design is given for the component parameters to accomplish zero-voltage switching in a wide voltage range, which can reduce the switching losses. The operational principles and characteristics of the proposed BT-BDC are presented in detail. The analysis and performance have been fully validated experimentally on a 40–60 V/400 V 1-kW prototype. The accordance between the analysis and the experimental results further testifies the advantages. [ABSTRACT FROM AUTHOR]

The degradation kinetics of carbetamide D-(−)-N-ethyl-2(phenylcarbamoyloxy) propionamide and its potential metabolites have been measured at different temperatures in both unsterilized and sterilized alkaline soil. A very large difference in both rates and processes of degradation between compounds was found. The kinetic studies were conducted by quantitative and qualitative analysis of the transformed product using [14C]-labelled compounds. Good radioactivity recovery was obtained and the existence of an important non-extractable fraction was detected in all cases. This soil-bound fraction is attributed to either conjugation of aniline with soil organic matter or aromatic ring cleavage to give amino acid precursors. [ABSTRACT FROM AUTHOR]