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Wireless power transmission technology based on coil coupling has been widely applied in various fields. However, the performance of the system is affected by the malposition of the transmission coil-couple, which is inevitable in the wireless power transmission system (WPTS). In this study, a multi-transmitter coil array is proposed to build a more uniform magnetic flux density for the WPTS, intending to enhance the performance of the WPTS in the case of coil-couple malposition. The model of the transmission system is built and different coil arrangement methods are analyzed. Then, the magnetic field distributions of the proposed WPTS with different coil arrays are compared using numerical simulations. Experiments are conducted to investigate the performances of the designed WPTS. The results show that WPTS with a seven-coil array can provide a more uniform magnetic field for the WPTS, whose relative deviation of output power is less than 28.55%. This study provides some clues for improving the performance of the WPTS through different arrangements of the transmitter coils.

Electrical system planning of the large-scale off-shore wind farm is usually based on $N-1$ security for equipment lectotype. However, in this method, owing to the aggregation effect in large-scale offshore wind farms, offshore electrical equipment operates under low load for long periods, thus wasting resources. In this paper, we propose a method for electrical system planning of the large-scale offshore wind farm based on the $N+$ design. A planning model based on the power-limited operation of wind turbines under the $N+$ design is constructed, and a solution is derived with the optimization of the upper power limits of wind turbines. A comprehensive evaluation and game analysis of the economy, risk of wind abandonment, and environmental sustainability of the planned offshore electrical systems have been conducted. Moreover, the planning of an infield collector system, substation, and transmission system of an offshore electrical system based on the $N+$ design is integrated. For a domestic offshore wind farm, evaluation results show that the proposed planning method can improve the efficiency of wind energy utilization while greatly reducing the investment cost of the electrical system.

Ocean temperature, salinity, and electric conductivity are essential ocean properties. Their structure and changes directly impact physical, chemical and biological processes in oceans. Since the 1970s, numerous researches have focused on the morphological analysis of vertical profiles in oceanography. However, due to the complexity of an ocean environment, most of them are conducted at local scales or only focus on single elements, e.g., ocean temperature or salinity. This work aims to achieve the joint classification of the vertical structure of ocean properties at a global scale and present two-dimension regional characteristics. Based on 150 seawater profiles from the National Oceanographic Data Center, this work explores such characteristics of ocean temperature, salinity and electric conductivity in the deep sea and achieves global-scale joint classification. We demonstrate that their vertical features have clear regional characteristics and can be classified into four types, i.e., bidirectional gradient, homo-dromous contravariant, homo-dromous gradient, and homodromous gradient (salinity) ones. In addition, our results prove that there exist the power-law distributions of these three factors in intermediate water, which may be explained through the self-organization theory. Moreover, the `up-tail' phenomenon is widely discovered in the vertical structure of electric conductivity, and it may be considered as a combined effect caused by temperature, pressure, and salinity.

Conventional finite-control-set model predictive control (FCS-MPC) and low-complexity MPC (LC-MPC) may cause variable switching frequency and high sampling frequency. To address these concerns, a new LC-MPC scheme with a constant switching frequency has been proposed in this paper, the virtual voltage vector generated by two adjacent effective vectors applied to decrease the power control error. The scheme has been tested for power control of an AC/DC converter. Simulation and experimental results obtained have shown that the scheme generates smaller (near zero) power control error per switching period, and have a faster dynamic response and a constant switching frequency. These features have been attained without demanding for an excessively high sampling frequency. Finally, the comparison with the conventional methods is carried out in this paper, the advantages of the proposed method have been clearly illustrated.

The sensitivity of a dual-axis K-Rb-21Ne co-magnetometer is subject to the accuracy of the magnetic field compensation and the calibration coefficient, which are determined by the orthogonality of the coil system. In this paper, an ingenious method of measuring the non-orthogonal angles between the x- and z-axes coils and that between the y- and z-axes coils is demonstrated. This in situ measurement method is based on the magnetic field responses of the dual-axis co-magnetometer. The non-orthogonal angle can be obtained by solving the relevant trigonometric function of the geometric relationship. Finally, the nonorthogonal angles of about 7.93° between the z- and y-axes coils and 7.39° between the z- and x-axes coils are obtained by fitting the response formulas. Besides, the influence of the applied transverse magnetic field on the accuracy of the non-orthogonal angle calibration is analyzed. This method is also verified to be valid at different working temperatures.

In order to reduce the frequency deviation resulting from renewable energy fluctuation and load variance, the coordination control strategy for isolated wind-diesel hybrid micro-grid is proposed by taking advantage of smart neural network observer and sliding mode method. For diesel generator system side, the sliding mode load frequency control including load variance is designed to regulate the output power. For the wind turbine generator system side, the sliding mode pitch angle control considering load variance is constructed to smooth the wind turbine generator output power fluctuation. Furthermore, the different coordinated strategies are proposed to realize the plug and play for the hybrid micro-grid, it is easy to see that the control accuracy can be improved by the designed neural network adaptive observer and considering the load variation. The effectiveness of the proposed control strategy is validated through real time digital simulator platform under different operation condition.

We report InP/InGaAs modified unitraveling-carrier balanced photodiodes (PDs). The back-illuminated PDs were flip-chip bonded on diamond submounts for enhanced heat sinking. The device demonstrated a 3-dB bandwidth of 8 GHz and a 30-dB common-mode rejection ratio at frequencies of 320 mA, maximum output power of 31.7 dBm (1.5 W) into a 50-Ω load, and good linearity with a third-order intercept point of up to 47 dBm were measured at the 3-dB bandwidth frequency of 8 GHz.