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In this article, a new high voltage gain quasi-Z-source (QZS) dc–dc converter suitable for renewable energy applications is presented. The proposed converter utilizes a zero voltage transition auxiliary circuit with coupled inductors to provide soft-switching conditions for all switches for a wide range of output power. In addition, a switched capacitor circuit is employed to obtain a higher voltage gain and lower voltage stress. The main advantages of the proposed converter include high voltage gain, high efficiency, reduced switch and diode voltage stress, continuous input current, and common ground between the output and input, which are important features for photovoltaic applications. In this circuit, the reverse recovery problem of diodes is alleviated. Operating principles and design considerations of the proposed converter are analyzed. Moreover, to prove the validity of the theoretical analysis, a 200-W prototype of the proposed converter is implemented and the experimental results are shown. [ABSTRACT FROM AUTHOR]

This article introduces a nonisolated bidirectional converter with high-voltage conversion ratio. In the proposed converter, by integrating the two-phase low-voltage-side (LVS)-parallel high-voltage-side (HVS)-series bidirectional converter with the coupled inductors, features, such as high voltage gain, low voltage stresses, current sharing, and current ripple cancelation, are achieved. Due to the proposed converter's operation in triangular conduction mode, the desirable benefits of zero voltage switching, diode reverse recovery elimination, and reduction of converter filter inductors and, consequently, leakage inductors are obtained. To recycle the leakage inductors’ energy and to solve the related difficulties for both operation modes, a simple passive clamp with the minimum number of elements is utilized. Also, to improve the light-loads’ efficiency, the variable frequency control is developed. The proposed converter is comprehensively analyzed, and to verify the analysis, the experimental results are provided. [ABSTRACT FROM AUTHOR]

A soft-switched nonisolated multiport bidirectional converter is proposed for hybrid energy system applications. The proposed topology improves the efficiency and expands the applications of the conventional three-port converter (TPC) by adding a soft-switching cell and a bidirectional power flow path from output to charge the energy storage device. Moreover, soft-switching conditions for all TPC switches in all operating modes are achieved. The topology uses one inductor that is shared by all power flow paths. Thus, power conversion in all operating modes is done in a single-stage and the conduction loss is reduced. To implement the soft-switching cell, coupled inductors are used to optimize the magnetic core and volume of the converter. Various converter operating modes are presented, and design considerations are discussed. Moreover, different control system operating modes are explained and designed in detail. Finally, a converter prototype to supply a 250 W–200 V load is implemented, and the theoretical analysis is validated by the experimental results. [ABSTRACT FROM AUTHOR]

This paper presents a control design approach for optimum dynamic response in single-phase grid-connected renewable converters with minimum energy storage components. This is a crucial matter in realizing compact and robust converters without use of bulky and sensitive electrolytic capacitors. Nonoptimum dynamic response results in undesired interruptions of the maximum power point tracking and reduction of the overall efficiency of the system. Common practice is to select a large dc-bus size in order to reduce the double-frequency ripples that cause harmonics and to slow down the dynamic response to avoid large fluctuations on the bus caused by random input power jumps. This paper shows that both problems can be addressed to a great extent by improving the control system and without need to excessively increase the size of the bus component. This paper proposes a control system to achieve these goals and provides an analytical design method to optimize both dynamic response and output current harmonics. The proposed method succeeds to reduce the size of bus component several times without compromising the system performance. Details of the proposed method, mathematical modeling of the bus control and current control systems, simulations, and experimental results are presented and discussed. [ABSTRACT FROM PUBLISHER]