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This article presents a highly compact direct-injection power flow and quality (f/q) control topology that employs a novel hybrid switching scheme to eliminate the line transformers and discrete high-current inductors in the high-current series injection, which otherwise dominate size and cost. Moreover, the proposed design is especially suitable for the lower voltage levels from the distribution grid onward using the latest low-voltage high-current semiconductors, specifically fast-switching gallium–nitride transistors operating even with only clip-on magnetics, supported by silicon devices for sufficient over-load and fault tolerance. These floating modules are directly inserted in series with each phase and omit any ground connection, thereby only dealing with a small portion of the voltage difference, unlike series back-to-back converters that have to handle the full power. In consequence, by employing low-power components and omitting large line transformers and inductors, the circuit demonstrates remarkable compactness. This makes it highly suitable for installation in on-street utility boxes. Specifically, it occupies a mere 20% of the volume associated with transformer-injection circuits, 30% of that of series back-to-back converters, and 60% the volume of our previous purely silicon direct-injection configurations.

With the rapid development of semiconductor manufacturing technology and the booming demand in the electronics market, researchers, guided by Moore’s Law, are working toward the miniaturization and integration of devices: loading more circuits onto smaller semiconductor die and expecting smaller units to achieve superior performance. Therefore, the complexity of the transmission line routing between components or between units is rising, with iterative advanced packaging technology improving the interconnection density in integrated circuits (ICs). As a result, multiple signals in a microwave circuits inevitably intersect at one point, and the crossover comes into being.

Nowadays, demand for the development of anti-deicing technology is becoming more and more urgent. Multifunctional is the inevitable choice of application of superhydrophobic materials in the area of anti-icing. In this work, polyvinylidene fluoride (PVDF)-based superhydrophobic films were successfully prepared by an electrospinning technique. Effects of electrospinning parameters and material compositions on the films’ hydrophobic property and morphology were studied. When the drum collector rotation speed was 300 rpm, pure PVDF samples showed the best hydrophobic property, and the maximum WCA value was 145.8°. Compared with pure PVDF films and SiO2/PVDF films, PZT/SiO2/PVDF films (PZT = lead zirconate titanate) showed better hydrophobic property, whose WCA values were greater than 152° (the maximum WCA value was 158.5°), and the roll-off angle (RA) values were less than 9.5°. The microstructure of all samples was mainly composed of blocks with irregular shapes, with some microspheres, nanofibers, and holes. Nanoscale papillae and nanoparticles formed on the surface of each block and microsphere. The comprehensive effect of these factors contributed to the enhancement of hydrophobicity. At last, PZT/SiO2/PVDF films exhibited longer delay freezing time and curing time. When the added F–SiO2(SiO2modified by perfluorodecyl triethoxysilane) content was 25%, PZT-5# exhibited a delay freezing time of 50 s and a curing time of 204 s.

This article proposes a maximum power factor tracking (MPFT) technique for the LCC resonant converter which functions as a capacitor charging power supply. The proposed MPFT technique is achieved through variable dc-link voltage whose reference value can be adjusted in real time for the maximum power factor. By means of the proposed method, the dc-link voltage follows the output capacitor voltage to minimize the turn-off current of mosfets, thereby reducing the turn-off switching loss. Additionally, this technique reduces the circulating current, which in turn decreases the instantaneous reactive power in the resonant tank. In comparison with the conventional constant-current (CC) charging and constant-power (CP) charging strategies without MPFT, the proposed CC charging with MPFT (CC-MPFT) and CP charging with MPFT (CP-MPFT) both exhibit great efficiency improvement. In CC-MPFT, the efficiency can be improved by up to 26.84% under light load condition. In CP-MPFT, the efficiency can be increased by up to 11.63% under light load condition and 2.66% under heavy load condition.

In repetitive pulse power applications, the charging capacitor time occupies most of the time in a pulse period, and important parameters such as pulse repetition rate are restricted by the charging speed of the capacitor. To accelerate the charging speed and make full use of the components’ capacity, a novel adaptive optimization charging (AOC) strategy is proposed for capacitor charging power supply (CCPS). Moreover, to improve the accuracy of the inductor-capacitor-capacitor (LCC) model, a fundamental harmonic approximation model based on continuous resonant current (CRC-FHA) is put forward. Compared with conventional FHA which uses a discontinuous transformer current $i_{T}$ , the CRC-FHA model is established by adopting the continuous and more sinusoidal resonant current $i_{\mathrm{ r}}$ . The analytical expressions are derived for the maximum resonant current $I_{\max }$ , zero-voltage-switching (ZVS) boundary, and the multidimensional relationship between the output voltage, the peak value of resonant current, average output current, and switching frequency. Accordingly, the proposed AOC strategy sets the maximum resonant current boundary, the ZVS charging boundary, and the upper and lower switching frequency limits as constraints to get adaptive reference output current values in real-time to make full use of the capacity of the converter to improve the charging speed. Compared with a hybrid constant current-constant power (HCC-CP) charging profile, the proposed AOC strategy has an advantage in charging speed and soft switching range with the same maximum resonant current. Finally, the accuracy of the FHA model adopting resonant current for LCC resonant converter and the effectiveness of the AOC strategy is verified by the simulation and a 2174 W LCC resonant converter.

This article presents a novel direct-injection modular universal power flow and quality control topology exclusively using lower power components. In addition to conventional high-voltage applications, it is particularly attractive for the distribution and secondary grids, e.g., in soft open points (SOPs), down to low voltage as it can exploit the latest developments in low-voltage high-current semiconductors. In contrast to other concepts that do not interface the grid through transformers, it does not need to convert the entire line power but only the injected or extracted power difference. The proposed power flow and quality (f/q) controller comprises a shunt active front end (AFE), together with high-frequency links serving as a power supply for a series floating module per phase. Each of the floating modules is in series with one phase of the line, floating with the electric potential of that particular phase, avoiding any ground connection. Omitting bulky and dynamically limited line transformers of conventional universal power-flow controllers, the presented direct-injection f/q controller enables exceptionally small size and volume, high power density, high frequency content, and fast response. In contrast to direct-injection concepts with full back-to-back converters, it only needs to handle a fraction of the power. The circuit combines grid-voltage low-current electronics in the shunt unit and low-voltage high-current modules in the floating series injection units. Simulations and experiments demonstrate and validate the concept.