Applied Mechanics and Materials Vols. 325-326

Abstract: This paper has made a statistic survey on the failure rate of the appliance of high-power IGBT on the Harmonious locomotive. According to the analysis ,environmental temperature and humidity have a crucial influence on failure rate, thus a set of temperature and humidity monitoring system has been designed to investigate the environment temperature and humidity of high failure rate Four-quadrant IGBT modules, analyzing factors such as temperature and humidity and the working conditions accordingly, exploring the relationship of rising temperature of IGBT ,locomotive speed ,pressure of the air cylinder, setting a foundation for later analysis on the mechanism of troubles.

Abstract: In order to propose reasonable method of harmonic suppression for EV charging station, three methods that are 6-pulse rectifier with APF, 12-pulse rectifier, PWM rectifiers are analyzed and compared. Firstly,the corresponding simulation model of charger and charging station are built based on the principle of EV charger and the main method of harmonic suppression. Then the harmonic content and power factor for different simulation model are researched. Meanwhile, the advantages and disadvantages of different simulation model are studied according to the results of simulation, the use of performance and economy. At last, the improvement measure and development direction for three methods are proposed.

Abstract: For wireless parallel inverters system, there is a high requirement of control precision: otherwise current-sharing effect would be very poor. Based on this characteristic of wireless paralleling technology, this paper represents the combination control method of repetitive control with PI-P voltage and current double close loop control (abbreviation as PI control) in this system. This control method, which combines with PI control, has relatively faster dynamic response speed, improves not only the capacity with nonlinear load and parallel circulation characteristics by characteristics of repetitive control, but also the steady state control accuracy of the system, meanwhile reduces the harmonic content. Its an outstanding composite control method. This paper proves the feasibility and superiority of this method by MATLAB simulation.

Abstract: This paper focuses a new high frequency transformer inverter technology for connecting photovoltaic (PV) panels to a single-phase grid. The information provided includes the inverter topology, control diagrams, and simulation models. The results show that the performance of the proposed inverter meets the grid connection requirements.

Abstract: Beginning with characterizing the nonlinearities of transformer, this paper uses the J-A model to represent the hysteresis of iron core, and fits the model in calculating exciting current. Compared with the other methods, such as polynomial and describing function method, J-A model is more capable in representing nonlinearity, so the calculated current would be more accurate. Then, after analyzing Maxwell equations that meet certain boundary conditions, the paper considers comprehensively the effects of skin and proximity, and then obtains the computing way of ac resistance under harmonics. At last, based on the mentioned results, paper proposes a set of three-phase transformer model which could calculate harmonic losses. The proposed model is a kind of combined time-and frequency-domain model that possesses good convergence. The introduced example has verified the correctness and effectiveness of the model which absolutely suits the engineering applications.

Abstract: According to the transformer testing information, the factors affecting of transformer remnant life assessment were analyzed. The formula which reflects the transformer health condition and remnant life is deduced and established according to the current information. The model thus is used in the health condition assessment and calculation of the remnant life for transformers. The results show that the process is consistent with the practical situation.

Abstract: Arc breaking at the function of large current is one of the bottlenecks for the development of vacuum breaker to higher voltage level. Simulation on arc is one of the most effective methods in this field. Before-arc process model of vacuum circuit breaker (VCB) whose breaking current is 20kA current and clearance is 10mm is developed here based on Boltzmann equation. Collisions between charged particles and metal vapor and electrodes are considered in the simulation. The physical nature of the sheathe and arc columns formation, the space charge densities and their effects on electric field strength before the steady state of arc plasma are simulated here.

Abstract: This paper presents simulation for the control strategy of three-phase boost-half-bridge (BHB) DC-DC converter with series voltage doubler rectifiers through three-phase high frequency transformer. The control strategy is consisting of three voltage loops. All the three voltage loops are independent of the input side and controls the input and output power balance from the secondary side of the high frequency transformers only. Moreover, the control strategy has been verified for its appropriate operation by simulating the above said configuration for the same turn ratios as well as for the mismatch turn ratios of high frequency transformers. Finally, the satisfactory simulation results for the proposed control strategy are presented.

Abstract: The PV grid-connected control system is mainly related to a few key issues that are characteristics of photovoltaic cells, maximum power point tracking and grid-connected control of three-phase inverter. In this paper, simulation analysis and study of the three-phase grid-connected PV system control strategy. The control strategy of the three-phase PV grid-connected system is analyzed and studied by simulative experiment in this paper. First, a mathematical model of solar cells is established, then the algorithms based on perturb & observe to track maximum power point is used; Secondly, the structure of three-phase PV grid-connected system is introduced, and the space vector SVPWM controller is used to control the grid-connected inverter; Finally, the simulative results on Matlab/Simulink software show that SVPWM inverter control strategy is superior to the traditional hysteresis current inverter control strategy, which illustrates the reliability and superiority of SVPWM control strategy.

Abstract: In this paper, a method for conducted electromagnetic interference (EMI) prediction in Electric Vehicle motor drive system based on components’ circuit models is presented. Firstly, the characteristics of the components are analyzed and the equivalent circuits are drew; then, the parasitic parameters of the electromagnetic device are extracted by the measurement, analytical solution and finite element method (FEM); and finally, the circuit model of the whole motor drive system in high frequency range is established. This model is verified by the measurement and simulation results in the frequency domain.