Single pixel imaging (SPI) combined with compressed sensing techniques can provide solutions for special optical imaging to avoid array detectors and raster scanning. However, the imaging speed should be further improved for real-time SPI and the challenge is to reduce the sampling time and post-processing time. This paper proposes a deep compressive and super-fast single pixel imaging protocol based on reordering Hadamard basis patterns and Fourier domain regularization inversion (FDRI) algorithm. Two reordered Hadamard basis patterns in terms of the improvement in the compressing ratio and reconstruction quality are proposed and compared to other methods. The deterministic Hadamard basis are reordered through their total variation (TV) in ascending order and total wavelet transformed coefficients (TW) in ascending order to have the best performance. Numerical simulation shows that this protocol can reconstruct a 128×128 pixels natural image at the sampling ratio of 5% with the peak-signal-to-noise ratio (PSNR) of 25.56 dB in 0.00039s. Terahertz near-field imaging experiment also verifies the proposed protocol. The inherent advantage and mechanism of reordering approaches are discussed and then revealed by comparing the coherent area generated by these reordered patterns. The TV order and TW order Hadamard basis patterns can be deterministically described mathematically and easily constructed. Meanwhile, it results in a significant improvement both in the compression ratio and image reconstruction quality. Finally, the realization this protocol in real SPI system in the future will bring the real-time SPI closer to practical applications.

Multi-break vacuum circuit breakers (VCBs) are the most potential approach for applying VCBs to high voltage power system. However, it has higher thermal stability requirements than normal single break VCBs due to its complex structure and high rated current. In this paper, a novel 363 kV/5000 A/63 kA SF6 gas insulate (GI) VCB with series and parallel structure is proposed. To analyze its temperature rise, a 3D coupled electromagnetic-thermal-fluid model is established based on actual size and calculated by finite element method under rated condition, which enables prediction of the temperature distribution of the contacts of VCB and bus bar. In the numerical model, the vacuum chamber is modelled as solid material with temperature dependent effective thermal conductivity while skin effect, nonlinear property of conductor resistivity and turbulence model are taken into consideration. The simulation results show that the hot spot is the contacts of VCB with a temperature of 102.2 K, while the temperature of busbars reach at 92.3 K. In addition, the influences of contact resistance, short circuit current on the temperature rise are discussed. Finally, the simulation results are validated by temperature rise experiment on prototype. Using the proposed model, the temperature rise and hot spot area can be predicted in advance, which could finally facilitate the design and performance evaluation of the 363 kV GI-VCB.

A balanced voltage distribution for each break is required for normal operation of a multi-break vacuum circuit breaker (VCB) This paper presented a novel 363 kV/5000 A/63 kA sextuple-break VCB with a series-parallel structure. To determine the static voltage distribution of each break, a 3D finite element method (FEM) model was established to calculate the voltage distribution and the electric field of each break at the fully open state. Our results showed that the applied voltage was unevenly distributed at each break, and that the first break shared the most voltage, about 86.3%. The maximum electric field of the first break was 18.9 kV/mm, which contributed to the reduction of the breaking capacity. The distributed and stray capacitance parameters of the proposed structure were calculated based on the FEM model. According to the distributed capacitance parameters, the equivalent circuit simulation model of the static voltage distribution of this 363 kV VCB was established in PSCAD. Subsequently, the influence of the grading capacitor on the voltage distribution of each break was investigated, and the best value of the grading capacitors for the 363 kV sextuple-break VCB was confirmed to be 10 nF. Finally, the breaking tests of a single-phase unit was conducted both in a minor loop and a major loop. The 363 kV VCB prototype broke both the 63 kA and the 80 kA short circuit currents successfully, which confirmed the validity of the voltage sharing design.

The medium-voltage medium-frequency transformer is a critical component of high-power dc converters. However, the ultrafast switching speed of wide bandgap semiconductors can induce voltage oscillations in the medium-frequency transformer, increasing the risk of primary-insulation partial discharge and leading to permanent breakdown. Existing research has focused on voltage oscillations occurring at ports, but there is insufficient knowledge about those happening within the winding. This article presents a model for calculating internal voltage oscillations. Compared to conventional models, it is simple and considers the core electrical energy for the first time. Accordingly, the physically-based analytical formulas are derived to calculate voltage oscillations. Based on the model, the relationship between voltage oscillations, port voltage, and transformer structure is analyzed. The oscillation mitigation method is presented and validated by experiment.

Vacuum circuit breaker (VCB) has a longer life and shorter opening time than SF ₆ circuit breaker, but current single‐break VCB cannot be applied in high‐voltage power system directly. Here, a fast 363 kV multi‐break VCB design is presented and its voltage distribution characteristic and stray capacitors are analysed. A three‐dimensional finite‐element model of modularised hexa‐break VCB composed of 12 vacuum interrupter modules installed on three series connected platforms is developed to calculate the voltage distribution and distributed capacitances. The result shows that the voltage distribution is uneven, and the first break shares the 67.974% of the whole applied voltage. On account of distributed capacitances parameters, an equivalent capacitance model with PSCAD is built to discuss the voltage distribution characteristic at different grading capacitance values, and the optimal grading capacitance value is determined to 10 nF.

Soft magnetic materials are widely used for magnetic components in power electronic converters. Their hysteresis effect leads to the nonlinear impedance characteristics of the magnetic cores, which can cause loss increase, waveform distortion, and electromagnetic interference issues in the converter. Due to the nonlinear behavior and the diversity of material characteristics, current Preisach hysteresis modeling remains challenging in parameter identification and probability distribution function (PDF) modeling procedure. In parameter identification, the classical methods rely on complex and restrictive double integration or repeated measurements. In PDF modeling, conventional PDF forms are constrained by a few degrees of freedom. To achieve high modeling precision, PDF forms with higher degrees of freedom are required. It also restricts the universality of the PDF, so different PDFs are needed for different magnetic materials. To address these two issues, a parameter identification approach based on the geometric interpretation of integration is proposed, which requires only a single B–H curve for ferrite. It avoids repeated testing and improves the identification efficiency significantly. Moreover, a generalized PDF form with more independent adjustable parameters is proposed. It can encompass different PDFs and model different hysteresis loop shapes of various magnetic materials. Experiments on different ferrites and silicon steels are conducted for verification. Compared with the conventional method, the proposed approach demonstrates significant improvements in accuracy, universality, simplification, and rapidity across different materials and shapes of magnetic cores.