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This paper introduces a direct PWM split-phase boost ac-ac converter with a high voltage gain, natural output voltage balancing, no duty-ratio limitation, and no commutation problem. Although under unbalanced load conditions, the two output voltages still are equal without auxiliary circuits and/or any dedicated controller. Moreover, the input current ripple is significantly decreased due to the interleaving effect. With a proper asymmetrical PWM scheme, the converter can work in the entire range of the duty cycle. In addition, the commutation (dead-time) problem is eliminated. The operation of the proposed structure is validated with a 500 W prototype converter. Experiment results obtained under various load conditions such as inductive, nonlinear, extreme load, and load scenarios are also provided. [ABSTRACT FROM AUTHOR]

This study proposes a novel balanced two-phase interleaved LLC resonant converter. The LLC resonant converter offers a promising solution for dc power conversion. This converter can achieve high efficiency and high-power density by implementing zero-voltage-switching (ZVS) for primary switches and zero-current-switching for secondary rectifier diodes. The input-parallel output-parallel systems that increase their power ratings by connecting two converters in parallel allow the use of low-current rated switches in high-current applications. Moreover, the input and output passive filter size requirements in the two-phase interleaved converters are reduced, and they provide higher power density and improved dynamic performance. However, the estimated tank gain characteristics become imbalanced due to the tolerances and the inevitable mismatch of the resonant parameters. Accordingly, this system operates outside the ZVS region, and a severe current imbalance with thermal runaway will occur. The proposed method achieves the perfect balance of input, output, and tank currents utilizing the existing resonant inductor magnetics without additional active or passive components, expensive sensors, and dedicated control schemes. The proposed method retains the advantages of the conventional LLC resonant converter over the operating frequency range. Mathematical analysis and experimental results are presented to validate the performance of the proposed method. [ABSTRACT FROM AUTHOR]

This paper presents a dynamic voltage restorer to solve the voltage sag problem that causes the most serious economic loss among various grid accidents. The proposed method, which uses a direct AC–AC converter, consists of a simple controller unlike methods using a voltage source inverter that is controlled using complex operations. Unlike the energy storage type, there is no additional energy storage device, which reduces system cost. In addition, unlike the back-to-back type, energy conversion loss is reduced by one stage conversion. A switching cell-structured direct AC–AC converter that solves the rectification problem without a separate sensor is a reliable structure that reduces the volumes of the passive filters by increasing the switching frequency. In addition, using interphase voltages, it can take a wide range of voltage compensations to compensate for most of the voltage sag in various situations. In this paper, the background of the study is revealed and the operating principles and control schemes of the proposed system are analyzed. Then, the validity of this study is confirmed through simulation and experiment results. [ABSTRACT FROM AUTHOR]