Wei Gao

By applying the inverse current commutation with semiconductor devices (ICCOS) technique to the meat grinder circuit, various circuit topologies have been derived. However, these circuit topologies require pre-charging of the pulse capacitor in the ICCOS circuit module, which adds a charging device or operational steps. To simplify the pre-charging process of pulse capacitors, this article improves the currently popular meatgrinder with an SECT circuit. The improved circuit uses the primary power supply to charge both the pulse capacitor and the energy storage inductor simultaneously. In this circuit, an auxiliary inductor is added to the charging branch of the pulse capacitor to alleviate the charging current surge and ensure that the charged pulse capacitor voltage is higher than the primary power supply voltage. In this article, the influence of circuit parameters on the pre-charging of pulse capacitors was analyzed, and the feasibility of the improved circuit was verified through simulation and experiments.

The analysis of the reluctance coil launcher (RCL) basically relies on the finite element method (FEM), but the method is time-consuming and does not meet the real-time requirements for control, which seriously hampers the expansion of engineering application areas. To address this problem, this study proposes a numerical calculation method dedicated to RCL based on the mathematical equations of electromagnetic coupling, in which the magnetic saturation problem is corrected by the inductance lookup table method, and the inductance in the coupling circuit is updated in real time according to the instantaneous current and the instantaneous position of the projectile. The accuracy of the calculation method is verified and the reasons for the errors are analyzed by establishing finite element simulation model, MATLAB/Simulink model and experimental platform for a single-stage and a three-stage RCL and comparing the obtained data. When the discharge voltage of the capacitor is 300 V, the accuracy of the projectile muzzle velocity in the single-stage and three-stage is 98.42% and 98.20% respectively, which indicates that the calculation method is correct under specific conditions. The time consumed by the method is only about 1/1000 of that of FEM, which even includes the compilation time of the software MATLAB/Simulink, illustrating the advantages of the algorithm and its application prospects.

Reluctance coil launchers usually use a pulse current formed by capacitive discharge to excite the excitation coil when launching. The pulse current peaks are high, and the projectile usually undergoes deep magnetic saturation, resulting in low launching efficiency. To address this problem, this article proposes using distributed feeder circuit to drive reluctance coil launchers, replacing the traditional single set of large-capacity capacitor discharge scheme with multiple small-capacity capacitors discharged in a time-sequential manner, so as to reduce the peak current and suppress magnetic saturation problems. The study includes two main aspects, one is to study the effect of the driving method on the launch performance and analyze the reasons; the other is to propose the calculation of the time-varying data in the launch process by the time-segmented calculation method. The efficiency of the model described in the paper is only 1.301% when using a single high-capacity capacitor for launching, while the launching efficiency is increased to 3.535% when driven by the distributed feeder circuit, indicating that the method can effectively improve the launching performance.

This paper proposes a position recognition method for the receiver coil by the secondary coil current. Based on the practical value of the current of the receiver coil, the position recognition of the receiver coil in the WPT system is realized. This paper proposes a 3×3 array multi-transmitter coil grouping and control logic. The mathematical model of mutual inductance between the receiver and transmitter coil at different positions on the X-Y plane is established. A method for identifying the position of the receiver coil according to the current of the receiver coil is proposed. Compared with the traditional position recognition method of the receiver coil, this method does not need to add a detection coil and position sensor and can realize the position recognition of the receiver coil on the 2D plane.

Launch efficiency has always been the focus of reluctance coil launchers research. In a traditional launch mode, the residual current in the drive coil creates a reverse force on the projectile. This is undesirable since the reverse force is in the opposite direction of movement, reducing the launch efficiency of the system. To address this problem, a multistage discharge circuit with the residual energy recovery and utilization mode is proposed in this article. As the projectile approaches the center of each stage of the drive coil, the current in the drive coil decays rapidly to zero by using the last stage capacitor to absorb the residual energy. The residual energy from the previous stages is eventually recovered by the last stage capacitor. This capacitor with residual energy is used to power the last stage drive coil of the reluctance coil launcher. This mode effectively suppresses the reverse force on the projectile and realizes the reuse of residual energy. Taking a four-stage reluctance coil launcher as an example, this article introduces the working principle of this mode in detail. The feasibility of the model is verified by finite-element simulation and experiments. Both simulation and experimental results show that this mode performs well in the recovery and reuse of residual energy and can effectively improve the launch efficiency of system.

There are possible non-convergence problems at load power critical value while using conventional continuous power flow methods. Generally, the step control method is used in the calculation to perform the calculation in small steps at the convergence to the load power critical value, and this method sacrifices the speed of the calculation although the calculation accuracy is high. In this paper, the Levenberg-Marquardt algorithm is used to search for the load power critical value firstly, and after that the step control algorithm is designed to perform fast power flow finding with known load power critical value, which takes into account the computational accuracy and computational efficiency. The case shows that the fast calculation method for continuous power flow of microgrid based on Levenberg-Marquardt algorithm proposed in this paper can guarantee the accuracy while effectively improving the calculation speed, and is suitable for online real-time evaluation of voltage stability and preventive control aided decision online calculation of isolated microgrid with high requirements for real-time.

The soft-switching characteristics of double-sided LCC wireless power transmission systems are susceptible to system parameter disturbances. In order to improve the stability of zero voltage switches in constant-current and constant-voltage charging modes, this paper synthesizes eight resonant conditions which make the system realize constant-current/constant-voltage and Zero Phase Angle. The influence of compensating capacitance parameter disturbance on system impedance angle is studied under constant current/constant voltage operation mode. The parameter configuration methods of compensated capacitance realized by zero voltage switches under the influence of third-order harmonic in constant current/constant voltage operation mode are also given. The system’s experimental prototype verifies the theoretical analysis’s accuracy with capacitive and inductive input impedance.

The peripheral magnetic field of the motor may cause magnetic field interference to the surrounding sensors, which would reduce the accuracy of sensors and affect the safety and concealment of vessel. This article explored the environmental magnetic field distribution law of a permanent magnet (PM) motor with two-pole parallel magnetization. A no-cogging magnetic field model was obtained by solving Maxwell equations, and the relationship between the air gap flux density and the environment flux density was built considering the motor cogging effect. In addition, a mathematical model of connections between the back electromotive force (EMF) and the environmental flux density was built, and the correctness of the model was verified by COMSOL. It is concluded that the circumferential and radial components of the environmental magnetic field are distributed sinusoidally, and the magnetic flux density modulus remains constant on the equidistant circumferential line, but attenuates squarely with the distance from the motor. It provides ideas for magnetic field analysis in the peripheral environment of other types of motors, sensors, and other anti-motor electromagnetic interference, magnetic field compensation for geomagnetic measurement, and motor fault diagnosis.