Increasing Light Load Efficiency in Phase-Shifted, Variable Frequency Multiport Series Resonant Converters

Multiport power conversion topologies provide the capability of multiple independent converters with a single transformer having multiple windings (i.e., ports) potentially increasing power densities and enabling flexible (and bidirectional) power routing. In automotive onboard charger (OBC), the multiport approach combined with symmetrical series resonant circuits, the so-called multiport series resonant converter (MSRC), allows for a galvanic isolated connection between all ports: the grid-side converter (i.e., usually an AC/DC power factor correction (PFC) stage), vehicle’s main and the auxiliary low-voltage (LV) battery. The variation of the battery voltage significantly affects the MSRC operation, particularly for light loads at a low state-of-charge, and high losses can be experienced since zero-voltage-switching (ZVS) conditions are lost. In addition to the conventional control approach of the MSRC, where the power flow is set with a phase-shift between the individual full bridges or by changing the switching frequency, this paper proposes a novel and coordinated approach, including the manipulation of both and the additional modulation of the duty cycle as a function of the DC-link voltages, aiming to introduce a zero-voltage interval on the full bridge output voltages. A full mathematical description of the adopted converter topology is provided, including accurate simulation models that allow a comparison between the proposed duty cycle mode and the conventional control strategy. A detailed description of achieving ZVS within the connected full bridges is also included. Experimental results validate the proposal and demonstrate significant efficiency improvements compared to standard control approaches.

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Novel Universal Power Electronic Interface for Integration of PV Modules and Battery Energy Storages in Residential DC Microgrids

This paper introduces the novel concept of a highly versatile smart power electronic interface for fast deployment of residential dc microgrids. The proposed approach has bidirectional power flow control capabilities, wide operating voltage range, and high efficiency resulting from the topology morphing control utilization. This enables universal compatibility with the majority of the commercial 60- and 72-cell photovoltaic modules, as well as the efficient charge/discharge control of the 24 V and 48 V battery energy storages using the same hardware platform. The proposed concept features fully autonomous operation where switching between the photovoltaic and battery interfacing modes is automatically done using the input source identification algorithm. Moreover, the proposed universal interface converter employs droop control and solid-state protection, making it fully compatible with the emerging standards and requirements for power electronic systems used in dc microgrid environments. A 350 W prototype was developed and tested in the residential 350 V dc microgrid with droop control to validate the proposed concept experimentally.

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Meandering Pattern 433 MHz Antennas for Ingestible Capsules

A number of design challenges are associated with in-body devices, especially ingestible capsules, including selection of operation frequency and antenna design. Operation frequency, miniaturization, gain, and interference with the environment and the internal components of ingestible capsules are all challenging factors. In this work, we design and measure the performance of miniature antennas that can be included in ingestible capsules. The meandering pattern designs are implemented with a 433 MHz center frequency which is within one of the industrial, scientific and medical (ISM) bands. The antenna patterns are rolled into cylinders to reflect their configuration inside a capsule. The effects of different antenna design features, environmental dielectric changes, and the battery locations relative to the antenna traces are explored. We show that the optimized antenna can offer acceptable performance even when the center frequency shifts due to the modulation of the dielectric constant of the media and by the insertion of batteries. Both simulations and measurements provide insight into how the meandering antenna should be designed for the desired frequency that can be expanded to other ingestible and implantable systems.

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Most Popular Article of 2017: 5G Cellular User Equipment: From Theory to Practical Hardware Design

Research and development on the next generation wireless systems, namely 5G, has experienced explosive growth in recent years. In the physical layer, the massive multiple-input-multiple output (MIMO) technique and the use of high GHz frequency bands are two promising trends for adoption. Millimeter-wave (mmWave) bands, such as 28, 38, 64, and 71 GHz, which were previously considered not suitable for commercial cellular networks, will play an important role in 5G. Currently, most 5G research deals with the algorithms and implementations of modulation and coding schemes, new spatial signal processing technologies, new spectrum opportunities, channel modeling, 5G proof of concept systems, and other system-level enabling technologies. In this paper, we first investigate the contemporary wireless user equipment (UE) hardware design, and unveil the critical 5G UE hardware design constraints on circuits and systems. On top of the said investigation and design tradeoff analysis, a new, highly reconfigurable system architecture for 5G cellular user equipment, namely distributed phased arrays based MIMO (DPA-MIMO) is proposed. Finally, the link budget calculation and data throughput numerical results are presented for the evaluation of the proposed architecture.

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