To solve the problem of difficult location (especially high grounding resistances) for single‐phase grounding faults in distribution networks, a fault location method based on equivalent admittance distortion rate is proposed in this paper. The equivalent admittance distortion rates are first obtained by measuring the pre‐fault and post‐fault equivalent admittances of each phase, each feeder and each section. Then the phase with the largest equivalent admittance distortion rate in each phase is determined as the fault phase, the feeder with the largest equivalent admittance distortion rate in each feeder is determined as the fault feeder, and the section with the largest equivalent admittance distortion rate in each section is determined as the fault section. Moreover, a fault identification strategy for single‐phase grounding faults is proposed to improve the robustness of this method. By measuring bus voltages and currents before and after faults, the fault type with only one‐phase in which voltage decreased and current increased is identified as single‐phase grounding faults. Compared with the existing methods, simulation results show that the proposed method is simple to implement and has strong robustness to high grounding resistances, long grounding distances and interference harmonics.

Photovoltaic power is affected by various random and coupled meteorological factors, and its changing trend implies the non‐linear effects of these factors. According to the quantitative analysis results, a statistical prediction model is proposed to accurately predict the power, which is of great significance to the safe and efficient use of solar energy. In this study, the authors first use grey relation analysis to select four main meteorological factors affecting photovoltaic power. Further, they combine grey relation analysis with information entropy and apply grey relation entropy to similar day analysis. On this basis, they take grey relation analysis to optimise extreme learning machine model to establish the grey relation analysis‐extreme learning machine model, while taking similar day analysis to optimise firefly algorithm to establish the similar day analysis‐firefly algorithm. By combining the two sub‐models with information entropy, a hybrid prediction model for photovoltaic power generation based on information entropy is proposed. The experimental results show that in various weather conditions, the values of mean absolute percentage error, root mean square error and standard deviation of error are 2.8425%, 2.5675 and 2.2642, respectively. Therefore, the proposed hybrid model has superior prediction performance.

When electric multiple units (EMU) pass the neutral zone, the traction transformer may generate sympathetic inrush, which will cause a malfunction in the transformer differential protection. In order to study the mechanism of the sympathetic inrush of the cascaded traction transformer, the flux–current model of the transformer, line impedance, power system voltage source, and other loads was established. On the basis of the flux–current circuit model, the influence of different factors on the sympathetic inrush of the traction transformer was analyzed. The analysis results were verified by simulation. Research results show that the remanence, closing angle, line impedance, and load will affect the duration and amplitude of the sympathetic inrush.

Wind shear is among the important sources of torque fluctuation on mechanical side and output power fluctuation on electromagnetic side and grid connection point, which frequency are triple turbine rotation frequency. With the increase in wind turbine single capacity and wind power integration scale, the power fluctuation caused by wind shear cannot be ignored. The paper takes a direct-drive permanent magnet synchronous wind turbine (PMSWT) as the research object. Firstly, the fluctuation transfer mechanism model is established; then, the current ripple is extracted by a notch filter to calculate the voltage control signal to suppress power fluctuation actively by the DC link capacitor which absorbs fluctuation energy. The simulation experiment shows that the suppression strategy is effective and reliable.

This paper presents the design and optimization of a wireless power transfer (WPT) charging system based on magnetically coupled resonant technology, applied to an Unmanned Aerial Vehicle (UAV). In this paper, a charging system, including dual active transmitter coils and a single receiver coil, is proposed. The dual transmitting coils adopt a coaxial structure with different radii. This structure simplifies the calculation of the complex mutual inductance between the coils to a function of mutual inductance only related to the value of the radial misalignment. Aiming toward a constant charging power, the optimal transmission efficiency of electric energy is achieved by controlling the input voltages of the active coils, which are solved via a set of equations defined as Lagrange multipliers. The simulation results of the 570 V and 85,000 Hz system verified the validity of the proposed wireless UAV charging scheme.

Setting reasonable circuit parameters is an important way to improve the quality of inverters, including waveform quality and power loss. In this paper, a circuit system of line voltage cascaded quasi-Z-source inverter (LVC-qZSI) is built. On this basis, the double frequency voltage ripple ratio and power loss ratio are selected as optimization targets to establish a multi-objective optimization model of LVC-qZSI parameters. To simplify the calculation, an integration optimization strategy of LVC-qZSI parameters based on GRA-FA is proposed. Where, the grey relation analysis (GRA) is used to simplify the multi-objective optimization model. In GRA, the main influence factors are selected as optimization variables by considering the preference coefficient. Then, firefly algorithm (FA) is used to obtain the optimal solution of the multi-objective optimization model. In FA, the weights of objective functions are assigned based on the principle of information entropy. The analysis results are verified by simulation. Research results indicate that the optimization strategy can effectively reduce the double frequency voltage ripple ratio and power loss ratio. Therefore, the strategy proposed in this paper has a superior ability to optimize the parameters of LVC-qZSI, which is of great significance to the initial values setting.