The development of the flexible DC fault line selection technology plays an important role for DC distri-bution network. In this paper, a novel algorithm is proposed to solve the problem that there is less available fault infor-mation about the existing flexible DC fault, which makes full use of the advantages of ensemble empirical mode decom-position (EEMD), principal component analysis (PCA) and the correlation coefficient algorithm. First, the transient cur-rent sample signal is extracted, and the data matrix represented by the orthogonal basis function is obtained by EEMD. Then, the feature vector of the matrix element is transformed into the principal component based on PCA, and the sam-ple signal is projected into the principal component space to realize coordinate transformation, so as to obtain the clus-tering and identification results of the sample data. Finally, fault line identification is performed based on the correlation coefficient. The EEMD of the proposed algorithm reveals the internal variation law of the original historical data, while PCA can effectively select the effective fault features. A large num-ber of experiments show that the novel algorithm is accurate and effective. Compared with other existing methods, it has ad-vantages in the cases of unclear fault information and different transition resistances.

Building a complete spacecraft electrical power and distribution standard system is an important tool for improving the design of spacecraft electrical power and distribution system and ensuring the safety and reliability of satellite energy. In this paper, the electrical power and distribution standard systems published by European Cooperation for Space Standardization (ECSS), National Aeronautics and Space Administration (NASA), Japan Aerospace Exploration Agency (JAXA), International Standard Organization (ISO) and American Institute of Aeronautics and Astronautics (A-IAA) were investigated. The focuses of their respective standard specialties were analyzed, the corresponding content was discussed, and the standard systems of various organizations were summarized. Combined with the actual situation in China, the suggestion and reference for the spacecraft electrical power and distribution standard system are put forward.

Aimed at problems such as the setup of an additional excitation source required by active magnetic shielding and the expensive magnetic shielding materials used in passive magnetic shielding, a wireless power transmis-sion (WPT) coupling mechanism with magnetic shielding based on Halbach effect is proposed on the basis of the tradi-tional DD coil structure. First, the topology of WPT coupling mechanism with magnetic shielding effect is proposed, and the principle for the magnetic shielding effect is analyzed theoretically based on the corresponding equivalent magnetic circuit model. Second, the expression for the magnetic field intensity of the coupling mechanism on any plane in the space is derived using the micro-element method. Finally, an experimental platform was built to verify the WPT perfor-mance and magnetic shielding effect of the proposed coupling mechanism. Results show that the Halbach effect coil can effectively weaken the magnetic field intensity outside the coupling mechanism and improve the magnetic shielding ef-fect while ensuring that the power transmission efficiency is basically the same as that of the DD coil.

The advantages of a Boost-APFC circuit operating in critical conduction mode are introduced. Aimed at the disadvantages of the traditional single-phase CRM-Boost APFC voltage mode control method, such as a long PI parameter debugging time, a poor adjustment effect and increasing unstable factors, a single-phase CRM-Boost APFC voltage mode control method with a static operating point is proposed, and the advantages of this method are verified by PSIM simulations. Considering the shortcomings of the novel interleaved control method, such as a long PI parameter debugging time, increasing unstable factors and the need to use an additional voltage-controlled current source, an improved two-phase interleaved parallel CRM-Boost APFC voltage mode control method is put forward, and the PSIM simulations are completed, with a power factor as high as 99.96%. A 4 kW two-phase interleaved parallel CRM-Boost APFC experimental prototype was made, and it was experimentally debugged, with a power factor of 99.66% and an efficiency of 98.02%.

The optimal configuration of source-storage in micro energy grid(MEG) is a primary challenge at the early stage of its construction since there exist complicated energy flows. In addition, the uncertainties (especially the stochastic fluctuations of wind, solar, and multi-energy load power) in MEG are difficult to describe and overcome. To address these problems, the uncertainties of renewable energy and load demand are described as intervals, the minimization of annual converted investment cost is taken as the objective, and a linear AC power flow model is coupled. The constraints of cool/heat/electric power balance, node voltage static security, line capacity and heat pipe transmission power are taken into account, and the indeterministic constraints are transformed into deterministic ones based on the interval linear pro-gramming theory, thereby constructing an interval-based optimal planning model of MEG with the consideration of source-load uncertainties. The feasibility and superiority of this model are verified by case studies and analyses, indicat-ing that the planning scheme can adapt to different uncertain scenarios and ensure the system's stable operation.

Aimed at the problem that the power quality control equipment in distribution network is lack of collaborative allocation, an optimal allocation strategy for the control equipment of harmonics, reactive power and three-phase imbalance is proposed, which is based on the multi-objective particle swarm optimization (MOPSO) algorithm. The active power filter (APF) is used to suppress harmonics, the intelligent capacitor is used to compensate reactive power, and the phase-change switch is used to reduce three-phase imbalance. The control effect and operating cost about each power quality issue are taken as optimization objects, and the relevant power quality standards are considered as constraints. Through the MOPSO algorithm, an optimal allocation scheme for the allocation nodes and relevant access capacity of control equipment can be obtained. Furthermore, a power quality assessment model is built, and a simulation model based on an improved IEEE 18-node distribution system is also constructed. The harmonics, reactive power and three-phase imbalance loads are separately connected to simulate power quality issues, and simulation results verify the feasibility of the proposed strategy and its advantages compared with the traditional scheme for power quality control equipment.

The fast on-off switching signal is the main cause of electromagnetic interference (EMI). At present, the research on EMI suppression by chaos mainly focuses on the suppression of conducted EMI by integer-order chaos. On this basis, the suppression by fractional-order chaos on radiated EMI and the selection of optimal order are studied in this paper. First, through the analysis of spectrum characteristics of fractional-order Lorenz and Lyapunov exponent spectrum, 1.8-order Lorenz signal is selected as the best spread spectrum series. Second, based on the principle of EMI suppression technology with variable switching frequency, Lorenz chaotic spread spectrum PWM signals with fixed frequency, integer-order, 2.7-order and 1.8-order are implemented in an STM32 single chip microcomputer. A near-field radiation experiment was carried out on a 5 W flyback converter, which proved that the 1.8-order Lorenz signal had the strongest suppression effect on the near-field magnetic field radiation. Finally, experimental results showed that the prototype's overall efficiency was about 2% different when it was under the fractional-order Lorenz Chaos PWM control and constant-frequency PWM control, respectively, which verified the superiority of the fractional-order chaotic PWM in radiated EMI suppression performance.

The existing power amplifier cannot strike a balance among aspects such as its output efficiency, output power and linearity. To solve this problem, on the basis of a three-level cascade amplification method, a kind of AB class RF power amplifier based on a power synthesizer and a power splitter is proposed. Aimed at the problems of linearity and gain, the band-pass matching and T-network matching techniques are used to optimize the design of the pre-driver circuit. The problem that the output power of the final amplifier is too large is solved by using the power synthesis technique, and the stability and efficiency of the power amplifier are guaranteed. To prevent the temperature of the power amplifier from being too high, the thermal characteristics of the power amplifier cavity are analyzed. The highest temperature is 81°C, which can make the power amplifier get a good cooling. At room temperature, the RF power amplifier has an output power of 47 dBm, an amplification gain of 42 dB and a maximum power added efficiency of more than 45% at a central frequency point of 2.45 GHz. The test results were close to simulation results, indicating that the research in this paper can provide some guidance for the subsequent research and design of amplifiers.

To improve the degree of intelligence of a substation and cut down the cost of inspection, substation inspection robots instead of the human labor are employed to perform daily inspections. However, the battery life greatly limits the work of inspection robots, so the full-time inspection cannot be realized. To solve this problem, a dynamic wireless charging method is used to charge the robots, so that the robots can perform inspections while charging and realize full-time inspection. In this paper, the relationship between coil mutual inductance and system efficiency is analyzed at first. Then, aimed at the segmented primary coil rails used in the dynamic wireless charging system, a soft-switching method for rails is put forward to reduce the inrush current during the switching process, thus protecting the circuit components. Finally, the influence of coil mutual inductance on the system efficiency was verified by experimental results, and the feasibility and effectiveness of the soft-switching method for rails was also proved.

In response to the high-voltage steep pulse application demands such as those in the biomedical industry, a series and parallel high-voltage steep pulse generator circuit based on solid-state switches is designed, and a novel pulse steepening method is proposed by combining the timing control technology. The key to pulse steepening, the system's working process and the main points of design are analyzed theoretically. This method can better reduce the influences of stray parameters, wiring inductance and wire inductance on the switching speed after adding the switching tubes. An experiment was carried out with a 2 kV high-voltage DC power supply and a load resistance of 110 Ω, and experimental results show that the rising edge of load pulse signal was 50 ns approximately, the falling edge was 70 ns approximately, and the output current amplitude was 18 A approximately. The half-height width of the minimum pulse width signal was 100 ns, and the system's minimum resolution was 5 ns, which can realize a flexible adjustment of 5 ns pulse width step by step. The maximum pulse width was related to the energy storage capacitor.