DC fault protection is one challenge impeding the development of multi-terminal DC grids. The absence of manufacturing and operational standards has led to many pointto-point HVDC links built at different voltage levels, which creates another challenge. Therefore, the issues of voltage matching and DC fault isolation are undergoing extensive research and are addressed in this paper. A quasi two-level operating mode of the modular multilevel converter is proposed, where the converter generates a square wave with controllable dv/dt by employing the cell voltages to create transient intermediate voltage levels. Cell capacitance requirements diminish and the footprint of the converter is reduced. The common-mode DC component in the arm currents is not present in the proposed operating mode. The converter is proposed as the core of a DC to DC transformer where two converters operating in the proposed mode are coupled by an AC transformer for voltage matching and galvanic isolation. The proposed DC transformer is shown to be suitable for high-voltage high-power applications due to the low switching frequency, high efficiency, modularity, and reliability. The DC transformer facilitates DC voltage regulation and near instant isolation of DC faults within its protection zone. Analysis and simulations confirm these capabilities in a system-oriented approach.

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Differential-mode buck-boost inverters have merits such as reduced switch number, ability to provide voltages higher or lower than the input voltage magnitude, improved efficiency, reduced cost and size, and increased power density, especially in low-power applications. There are five buck-boost inverters that can provide flexible output voltage without the need of a large electrolytic input side capacitor, which degrades the reliability of inverters. The continuous input current of these inverters is appropriate for maximum power point tracking operation in photovoltaic and fuel cells applications. Three of the five inverters can be isolated with high-frequency-link (HFL) transformers where the common-mode leakage current can be mitigated. However, the performance and control of such converters have not been discussed in detail. In this paper, the five possible single-stage three-phase differential-mode buck-boost inverters with continuous input current are investigated and compared in terms of total losses, maximum ripple current, total harmonic distortion (THD), and device and passive element ratings. In addition, the possible methods are presented for eliminating the input third order harmonic current, resulting from the stored energy in the passive elements, as well as the output second order harmonic currents. The ability for isolating the input and output sides of the inverters with a smallhigh frequency transformers is discussed. A changeable-terminal 2.5kW bidirectional inverter is used to validate the design flexibility of the inverter topologies, when DSP-controlled.

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Abstract. Myrrh (from the stem of the Commiphora molmol tree) is an oleo gum resin that may prove efficacious for the treatment of fascioliasis. We studied 7 patients who were passing Fasciola eggs in their stools and treated them with myrrh. The drug (a formulation consisting of 8 parts of resin and 3.5 parts of volatile oils, all extracted from myrrh) was given in a dose of 12 mg/kg per day for 6 consecutive days in the morning on an empty stomach. Patients were followed for 3 months. The therapy proved to be effective, with pronounced improvement of the general condition and amelioration of all symptoms and signs. A dramatic drop in the egg count was detected at the end of treatment. Eggs were no longer detectable in the feces 3 weeks after treatment and after a follow-up period of 3 months. High eosinophilic counts, elevated liver enzymes, and Fasciola antibody titers returned to nearly normal. No signs of toxicity or adverse effects were observed. We conclude that the formulation of myrrh is safe, well tolerated, and effective for treating fascioliasis.

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