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Purpose This study aims to provide a solution of the power flow calculation for the low-voltage ditrect current power grid. The direct current (DC) power grid is becoming a reliable and economic alternative to millions of residential loads. The power flow (PF) in the DC network has some similarities with the alternative current case, but there are important differences that deserve to be further concerned. Moreover, the dispatchable distributed generators (DGs) in DC network can realize the flexible voltage control based on droop-control or virtual impedance-based methods. Thus, DC PF problems are still required to further study, such as hosting all load types and different DGs. Design/methodology/approach The DC power analysis was explored in this paper, and an improved Newton–Raphson based linear PF method has been proposed. Considering that constant impedance (CR), constant current (CI) and constant power (CP) (ZIP) loads can get close to the practical load level, ZIP load has been merged into the linear PF method. Moreover, DGs are much common and can be easily connected to the DC grid, so V nodes and the dispatchable DG units with droop control have been further taken into account in the proposed method. Findings The performance and advantages of the proposed method are investigated based on the results of the various test systems. The two existing linear models were used to compare with the proposed linear method. The numerical results demonstrate enough accuracy, strong robustness and high computational efficiency of the proposed linear method even in the heavily-loaded conditions and with 10 times the line resistances. Originality/value The conductance corresponding to each constant resistance load and the equivalent conductance for the dispatchable unit can be directly merged into the self-conductance (diagonal component) of the conductance matrix. The constant current loads and the injection powers from dispatchable DG units can be treated as the current sources in the proposed method. All of those make the PF model much clear and simple. It is capable of offering enough accuracy level, and it is suitable for applications in DC networks that require a large number of repeated PF calculations to optimize the energy flows under different scenarios.

It has always been a huge challenge to prepare the Mo back contact of inorganic compound thin film solar cells (e.g., CIGS, CZTS, Sb2Se3) with good conductivity and adhesion at the same time. High-power impulse magnetron sputtering (HiPIMS) has been proposed as one solution to improve the properties of the thin film. In this study, the HiPIMS technology replaced the traditional DC power sputtering technology to deposit Mo back contact on polyimide (PI) substrates by adjusting the experimental parameters of HiPIMS, including working pressure and pulse DC bias. When the Mo back contact is prepared under a working pressure of 5 mTorr and bias voltage of −20 V, the conductivity of the Mo back contact is 9.9 × 10−6 Ωcm, the residual stress of 720 MPa, and the film still has good adhesion. Under the minimum radius of curvature of 10 mm, the resistivity change rate of Mo back contact does not increase by more than 15% regardless of the 1680 h or 1500 bending cycle tests, and the Mo film still has good adhesion in appearance. Experimental results show that, compared with traditional DC sputtering, HiPIMS coating technology has better conductivity and adhesion at the same time, and is especially suitable for PI substrates.

A circularly polarized implantable antenna integrated with a voltage-doubled rectifier (abbr., rectenna) is investigated for microwave wireless power transfer in the industrial, scientific, and medical (ISM) band of 2.4–2.48 GHz. The proposed antenna is miniaturized with the dimensions of 7.5 mm × 7.5 mm × 1.27 mm by etching four C-shaped open slots on the patch. A rectangular slot truncated diagonally is cut to improve the circular polarization performance of the antenna. The simulated impedance bandwidth in a three-layer phantom is 30.4% (1.9–2.58 GHz) with |S11| below −10 dB, and the 3-dB axial-ratio bandwidth is 16.9% (2.17–2.57 GHz). Furthermore, a voltage-doubled rectifier circuit that converts RF power to DC power is designed on the back of the antenna. The simulated RF-to-DC conversion efficiency can be up to 45% at the input power of 0 dBm. The proposed rectenna was fabricated and measured in fresh pork to verify the simulated results and evaluate the performance of wireless power transfer.

An electrical installation that simulates an automobile DC power supply system with a voltage of 12 V has been created. An experimental simulation of a short circuit at currents up to 400 A on copper multi-wire and single-wire conductors under normal environmental conditions is carried out. The copper wires beads were annealed in a furnace at temperatures from 700 to 1000 °C for 20, 40 and 60 minutes. Metallographic analysis of copper wires beads was carried out. The temperatures and times that of at which the signs of short circuit and overcurrent are destroyed has been revealed. Obtained results contribute to improvement evidence’s researching in the fire investigation of motor vehicles electrical wiring after a fire. Keywords: Arc beads, Copper, Metallographic analysis, Electrical Short Circuit, Wires.

This paper proposes a solar-powered resonant inverter fed a high-voltage DC power supply. In this converter, switching loss is controlled through zero-voltage switching and zero-current switching. This converter comprises a solar panel, boost converter, full-bridge LLC resonant tank, power transformer, and rectifier circuit. All power switches are operated with an interleaved switching cycle to ensure equal power flow from the tank. This proposed converter is designed to produce a regulated 19.5 KV at output, with an input voltage range of 300–350 V. The proposed converter was simulated in PSpice to verify the results.

The growing demand for electrical energy calls for the assimilation of renewable energy sources to the main utility grid. Multiple renewable energy sources (RESs) like solar PV array, wind turbine, micro-hydro plant, etc. can be combined and controlled to form a microgrid. In spite of the availability of different microgrid topologies, DC microgrid largely facilitates the injection of DC power from various renewable energy sources into the stabilised DC power pool. The requirement for a minimal number of conversion stages, simple structure, economic operation, and numerous localised applications are driving factors for the DC microgrid technology. The mettle of the DC microgrid technology lies in choosing the appropriate microgrid participants for energy interchange and the suitable supervisory control to tap power from the microgrid partakers even after respecting their operating constraints. The use of high gain DC-DC converters is inevitable in DC microgrid due to the low terminal voltage levels of different RESs.