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A series of three-port forward converters with a compact structure and extended duty cycle range is presented for the standalone renewable energy system. Bidirectional power-flow port embedding and switch device sharing can be used to derive these converters from conventional two-switches forward converters. In comparison to the conventional two-switch forward converter, only one switch and one diode are added to build an energy storage port with bidirectional power flow characteristics, which has the benefits of compact structure and low cost. Meanwhile, the embedding of the energy storage port provides an additional demagnetization loop for the magnetic inductor, which extends the duty cycle range of the forward converter so that the proposed converter no longer requires a duty cycle of less than 0.5 as in the case of conventional forward converters. The proposed converters also offer the advantages of fewer components, easy control, and independent control of power flow between multiple ports when compared to similar solutions. Finally, an experimental setup with a photovoltaic battery as an application is developed, and the experimental results verify the effectiveness and flexibility of the proposed topology and control method. [ABSTRACT FROM AUTHOR]

A multiport converter with bipolar outputs to integrate renewable energy and energy storage into the bipolar dc bus is the desirable solution due to its high reliability and efficiency. A novel symmetric bipolar outputs full-bridge four-port converter based on phase-shift modulated buck–boost voltage balancer is proposed in this article. The interleaved bidirectional buck/boost circuit with pulsewidth modulation is used as the primary side to achieve the integration of renewable energy and energy storage, whereas the phase-shift modulated buck–boost voltage balancer is derived as a secondary side circuit to generate a symmetrical and common ground bipolar output voltage. Single-stage power conversion, symmetrical bipolar output voltage, approximately decoupled control loop, and soft switching can be realized in the proposed four-port converter. Detailed analysis of the proposed converter is presented, including operation principle, steady-state performance, soft switching performance, and control method. Finally, experimental verifications are carried out to illustrate the feasibility and effectiveness of the proposed topology. [ABSTRACT FROM AUTHOR]

Three-port converters with high voltage gain are desirable solutions for integrating renewable energy and energy storage devices into high voltage dc bus. A high gain three-port converter with soft switching is proposed in this paper, which can realize zero voltage switching for all switches and zero current switching for all diodes in various operating modes. Single coupled inductor is used to achieve high voltage gain and to reduce the voltage stress of switches so that switches with low on-resistance can be selected to reduce the conduction loss. In addition, the advantages of fewer components, higher voltage gain, and very low switch voltage stresses make the proposed converter more suitable for application in renewable energy systems than similar solutions. Various operating modes, performance analysis, design considerations, efficiency analysis, and control method of the proposed converter are discussed. A laboratory prototype with 30 V renewable energy source, 48 V energy storage device and 400 V output is designed to verify the performance of the proposed three-port converter. [ABSTRACT FROM AUTHOR]

Using a multiport converter to integrate renewable energy and energy storage into the bipolar dc bus is a desirable solution due to its high efficiency and reliability. In this article, a series of bipolar output active rectifiers with center-tapped winding is proposed to serve as secondary rectification circuits. Then, a family of isolated four-port converters with symmetrical bipolar outputs is further developed to integrate renewable energy and energy storage. The proposed symmetrical bipolar output isolated four-port converters can achieve single-stage power conversion, symmetrical bipolar output voltage, soft switching, and decoupled control. A typical four-port converter, named full-bridge interleaving bidirectional buck/boost + semiactive rectifier with bipolar output converter, is specifically analyzed in detail in terms of operation principles, voltage and power relationship, port current ripples, soft switching performance, and control. Finally, experimental tests have been performed to verify the feasibility and effectiveness of the proposed topology. [ABSTRACT FROM AUTHOR]