Applied Mechanics and Materials Vols. 448-453

Abstract: To ensure the normal operation, calculation of electric field in ultra-high voltage substation is particularly important. A line model is proposed to simplify current model and improve computational efficiency. Combining this model with boundary element method, this article described a method to calculate the electric field at the vicinity of complex equipment of ultra-high voltage substation. An actual substation environment is also simulated, with detailed analysis of simulation results, proposed model and method are verified as valid and effective.

Abstract: This paper elaborates a method to realize the single phase full bridge inverter digital controller based on DSP TMS320F28027 and gives the design scheme of both its hardware and its software. In accordance with SPWM duty ratio parameter calculated with DSP algorithm, utilizing the EPWM module on DSP, it finally attains the inverting control from direct current signal to sine wave signal. Compared with traditional method, this new method improves the output waveform effectively and shows stable performance.

Abstract: An optimal design for the stackable four-layered piezoelectric power generation device and its microelectric energy saving method is presented here. In this work, three different device arrangements for the piezoelectric four-layered power generation devices were firstly deposited and compared for obtaining a greater output power. Measurement results demonstrated that Sample 2 among the three different device arrangements could not only avoid the damage to PZT-5H piezoelectric materials but also achieve a grater instantaneous output power (5.359mW). Subsequently, a novel microelectric energy saving system by constructing a less power dissipation boost converter IC with its proper surrounding circuit was also exhibited. Evidence showed that among the three different IC modules, Case 1 performs an optimal microelectric energy saving system since it could effectively fully charge a 30 mAh Zn-MnO₂ battery within the shortest time duration (4 hours).

Abstract: The large span suspension structure is easy to generate larger vibration due to its smaller stiffness. For this problem, a finite element modal analysis method that considers the effect of initial pre-stress is proposed. The finite element model of the structure is established by using Link10 unit of the finite element analysis software ANSYS. Then the first four order natural frequency and vibration mode under different initial pre-stress is solved by the subspace iterative method. And the experimental test system based on MEMS sensor is designed to analyze the layout of test points and exciting vibration mode of the structure. The test system measures the inherent frequency and the first two order vibration mode under the action of different pre-stress. The results show that the numerical analysis results are basically consistent with the experimental results and the inherent frequency of the structure distributes in the plexus intensive form. And the inherent frequency of the structure is related to the pre-stress. The bigger the stiffness of the structure, the greater the inherent frequency is. It proves that the theoretical analysis results are correct and the experiment test system can be used in the structural dynamic test.

Abstract: Basic structure and operational principle of medium frequency furnace (MFF) are introduced in this paper. The characteristics of harmonic currents produced by MFF are analyzed theoretically. A harmonic analysis simulation model for MFF with 12-pulse reciter based on Matlab/Simulink is presented. The validity of it is proved for the simulation harmonic currents accord to the theoretical anticipation. This model could be used to predict the harmonic of MFF not in operation. Based on this model, potential harmonic pollution of a new steel plant is studied by simulation with Matlab/ Simulink.

Abstract: China's electricity imports and its influence factors of ten years were analyzed. On this basis, the electricity imports and the influence factors of grey correlation were calculated by using grey correlation analysis method. It makes a conclusion that every influence factors effect on electricity imports, and establishes a grey model GM (1, n) of electricity imports as well as its influence factors and determines the quantitative relationship between the selected influence factors and electricity imported. The model has high accuracy, and meets the practical requirements, so that it makes a better load forecasting for our country and provides a theoretical basis for taking some electricity import measures.

Abstract: The antenna design and its manufacturing technology is one of the gordian technique in mobile communication system, the performance of antenna influences the performance of the mobile communication system directly. To mobile communication system, the study of antenna has important significance. The development of mobile communication system brings a new request to the antennas design. This paper start from dipole antenna and the structural theory of photonic crystal, bat around the superiority of the two, and make a combination, design a dipole antenna with photonic crystal structure which can work in 2GHz frequency range, small size, return loss in low and bandwidth is suitable for CDMA2000 mobile communication system, and we simulate and test the performance of this antenna, discuss how the parametric variation will influence the performance of antenna.

Abstract: To realize the STATCOM based on Modular Multilevel Converter (MMC), a simplified double-closed loop structure, simplifying from the control method of High Voltage Direct Current (HVDC) based on MMC, is presented. Considering MMCs DC side using capacitors, a part-controlling method based on energy balancing is proposed, to solve the voltage balancing problem. With the part-controlling fixing the changing capacitors voltage and the simplified double-closed loop control method, voltage fluctuation could be reduced, and the loads reactive power could be compensated. The correctness and the effectiveness of the MMC-STATCOM controlling scheme is verified by Matlab/Simulink.

Abstract: Aiming to dealing with the problems of power factor compensation and the limitations of the conventional PI controller in the Static Synchronous Compensator (STATCOM), a new control strategy based on multi-model and neural network PI controller is proposed. This control scheme applied the multi-model and neural network technology to the PI controller to meet the accuracy and speed of the power factor compensation under different impact loads. Meanwhile, the neural network technology is used to tune the PI controller parameters values according to an optimal control law, which can meet the requirements of full range working conditions and optimality. Simulation experiments show that compared to the traditional PI controller, PI controller based on multi-model and neural network is proved to be better capable of adapting to the changes of impact loads with a higher compensating precision, which makes the power factor maintained at about 1 after compensation.

Abstract: In order to lower the switching losses and harmonic ratio, improve the precision of the STATCOM in the same time, the adaptive inverse control based on PAM+PWM method is proposed in this paper. The combination of PAM+PWM method is presented to enable the system to achieve the quality of low switching losses and good harmonic elimination effect. Furthermore, considering the nonlinear and time-varying characteristics which are caused by the introduction of the PAM and PWM method, an adaptive inverse control method is designed to adjust the parameters of the nonlinear mathematic model constantly to improve the precision of the control system. The results of simulation show the correctness of the proposed method.