Applied Mechanics and Materials Vols. 556-562

Abstract: The realization method of the explosion-proof three-level frequency conversion equipment for coal mine is introduced in this paper. The frequency conversion equipment uses diode clamped three-level inverter unit topology structure, it overcomes some disadvantages of two-level converter that harmonic content of voltage output is higher, electromagnetic interference is serious and on-off loss is higher. The frequency conversion equipment is suitable for coal mine high voltage and large power devices such as draught fan, pumps and belt conveyers.

Abstract: The paper addresses the central issues of electromagnetic compatibility (EMC) evaluation of shipborne electronic equipment. The mutual disturbance between equipments would show important influence on the capability of the devices, slight interferer may degrade the performance, severe interferer would make the equipment out of work even cause false action of weapon system, therefore, how to quantitatively describe the EMC state of equipment and harmonize the EMC assessments correctly is the key consideration of the warship’s commander and the combat system designer. Take the advantage of norm theory this paper proposed a method to evaluate the EMC state of the shipborne electronic equipment quantitatively, which would meet the requirements both warship’s EMC design and commander’s campaign operation.

Abstract: In this paper, a model of the winding area for a normal working oil-immersed power (180MVA, 220kV) was built to conduct the simulation analysis for heat transfer of fluid field. Based on the fundamental mechanisms of fluid mechanics, limited volume method was used to build the model of the winding area of the power transformer. The effect of the oil input velocity, the amount and the position of oil baffle plate were concluded. The reasonable method to control the temperature was purposed by analyzing the heat-transfer properties for different conditions. When the initial oil velocity was 0.3-0.4 m/s during forced oil circulation, the best heat transfer was achieved. For the natural oil circulation, inserting 3 oil baffle plates at the higher temperature winding ends, when the number of the next two oil baffle plates is 7, the heat delivery effect is best.

Abstract: When main discharge switch is put in discharging course of pulsed power supply in stored energy capacitor branch, the stored energy capacitor may have reverse charging phenomenon. Because of unilateral conductivity of the main discharge switch, the reverse voltage cannot be released and this would adversely affect service life of the stored energy capacitor and reduce working efficiency of the pulsed power supply. Through detailed deducing the discharging course of stored energy capacitor in pulsed power supply system, this paper analyzed relative factors affecting reverse charging voltage of stored energy capacitor and discussed necessary means that could reduce reverse charging voltage of stored energy capacitor. Based on this, a circuit structure with the main discharge switch in load branch is proposed and release of reverse charging voltage of stored energy capacitor is realized without affecting discharge current characteristics of the load. Simulation and test results show that the load current characteristics of the pulsed power supply after adjusting location of the discharge switch is basically the same as before the adjustment is made and completely meet requirement of electromagnetic emission. As a result, timely release of the reverse voltage extended working life of the stored energy capacitor and also improved efficiency of the electromagnetic emission system.

Abstract: This paper presents an active equalization method for lithium battery via SOC. The high accuracy of SOC is promised by extended Kalman filter algorithm (EKF) based on the adaptive parameters equivalent-circuit model at all SOC region. Then a small size, low loss resonant soft-switching active equalization circuit is presented. That circuit combined with SOC do precisely balance the battery pack during charge and discharge processes, which can effectively improve the battery pack’s using life.

Abstract: Based on the variable speed constant frequency doubly-fed wind turbine model, this paper increased the power factor control link for the wind farm to apply two kinds of constant voltage and constant power factor control mode of the simulation needs, and build a suitable for our country to contain a mathematical model of wind power system stability analysis.

Abstract: The dynamic model of DFIG for power flow calculation and transient simulation is proposed and becoming a hot spot of research. Based on the principle of DFIG model which is newly released by the International Electrotechnical Commission (IEC), analyzes model structure and the control block. The type 3 wind turbine generator (WTG) is implemented in PSCAD environment, Case studies under both normal and grid fault conditions are done with the implemented IEC generic models of type3 WTG, simulation results of IEC type3 WTG are compared with the full order model .The case study results show that the IEC generic models of Type3 WTG can correctly represent the performances of Type3 WTG under both normal and fault conditions, the validation of the model are verified, the model will promote the standardization of domestic wind turbine model, and provide correct and effective dynamic model of wind turbine for study of the wind power integration into grid.

Abstract: The article introduces a jaculatory acousto-optic game box that can display the numbers by LED. The box is a regular hexahedron, with different points on each side showed by LED. Its construction is similar with the dice played in mahjong. When the box stops, the LED on the upper side will be lighted, meanwhile, the buzzer will give out sounds in same number with the points.

Abstract: Energy coupling realized by contactless magnetic tank transformer as new approach of rotator excitation in synchronous machine could replace brushes and slip rings of traditional excitation. For new contactless energy transmission (CET) system, its research about energy-efficiency quality still remains a low level because application and research of CET isn’t comprehensive, especially how to improve transfer power and efficiency isn’t enough. According to characteristics of contactless energy transmission system, mutual inductance model was used to describe the loosely coupled connection between primary and secondary winding. Then, optimum energy-efficiency product was proposed. We can use this indicator to consider efficiency, system cost, reliability and so on based on maximum output power. Mutual inductance coupling parameter would be optimized through this indicator and optimum design of system energy-efficiency characteristic would be realized at minimum cost. Although the input voltage had little increase, simulation research proved that system efficiency had a quit handsome increase based on optimum energy-efficiency product which established mutual inductance coupling parameter. This work is supported by National Natural Science Foundation (51177031).

Abstract: A FPEG (flexible piezoelectric generator) composed of PVDF (polyvinylidene fluoride) piezoelectric film, conducting resin and titanium alloy substrate, which occupies less room and produces electrical energy while the axial wind flows through the oscillator surface. When the axial wind flows through the generator surface, generator begins to vibrate and produce electrical energy, as the wind speed reaches a critical value, generator yields resonance phenomenon. In this paper, more work was placed on how the substrate structure parameters such as length, width and thickness affected the power generation capacity in resonance mode.