Applied Mechanics and Materials Vols. 260-261

Abstract: An intelligent distribution digital terminal pulse acquisition control system, based on C8051F021 chips as control core, is designed in this paper. The pulse acquisition circuit, RS485 communication circuit and other important parts are the control objects in this system. The system demonstrates the designing methods of hardware and software architecture by adopting the advantages of single-chip microcomputer combining hardware with software, thereby realizing multiple functions of the pulse acquisition system. This method provides a new idea to enhance the cost performance of pulse acquisition of intelligent distribution digital terminal.

Abstract: The paper proposed control strategies for a large-scale photovoltaic power plant in different operating modes in order to improve the utilization of solar energy and power quality of the integration. Take one 3MW photovoltaic power plant as an example, the energy storage device was used as the node to provide frequency and voltage support during the switching period. Then the photovoltaic power generation simulation model was built based on the MW level photovoltaic power plant’s information and data on the PSCAD/EMTDC software platform. This model achieved a coordinated control between photovoltaic power generation and the grid under different operating modes. The simulation result also proved the effectiveness of the control strategies and the significance in ensuring the reliability of power supply and grid stability.

Abstract: This paper presents the comprehensive implementation of Distributed Static Series Compensator (DSSC) to limit the fault currents in power systems. This is the first time that the limitation of fault currents with D-FACTS devices is addressed. DSSC is one of the D-FACTS families whichoperate in a similar manner as Static Synchronous Series Compensator (SSSC) but in smaller size, lower price and more capability. The effectiveness of the DSSC in fault current limitation is investigated through the series voltage effect upon the line. The short circuit current limitation strategy presented here exhibited that besides of the power flow control which is carried out by DSSC; it can also perform this additional function. In the following the potency of the DSSC in reduction of instantaneous voltage dip range during fault current limiting mode is clarified. Furthermore, it is disclosed that with performing more DSSC in the power system, the entire system voltage dip will be improved. In order to validate the claims, computer simulations using PSCAD/EMTDC are exploited.

Abstract: In the paper, the three-phase ac motor is used as the controlled station and the FPGA device EP1C3T144C8 is adopted as the control core. Aiming at the flexibility of the variable frequency system based on SPWM, the DDS technique is introduced. The process of speed adjustment is conducted by AC motor by the three-phase supply with tunable frequency generated by inverter switch device based on SPWM signal. With rational structure and simplified design, this project can generate stable SPWM signal, high frequency resolution and fast switching speed.

Abstract: Heat is transferred between the fluid and the surroundings in the wellbore. Quantitative knowledge of wellbore heat transfer is important in drilling and production operations. A new model of wellbore heat transfer using finite element analysis is developed in this study. This solution assumes the heat transfer in the wellbore is steady state and only happens in radial direction. The model considers heat gained due to wellbore pressure loss in circulation, which is more accurate in temperature calculation. The overall heat resistance in the wellbore is analyzed, taking into account the film heat transfer coefficients difference between the tube and the annulus. Previous literature has been reviewed to determine the correlation which can be used in the model.

Abstract: This paper proposes the battery mathematical for modeling HEV(Hybrid Electrical Vehicle) high-power lithium-polymer battery. The nonlinear characteristics of Lithium Battery are expressed by the state equation. The battery parameters are obtained by the least square method to minimize errors using charge and discharge driving cycle data. The proposed method is verified by the battery cycler.

Abstract: A new approach is presented for analyzing gas mixtures by transforming the problem into a pattern classification one to reduce the effect of the poor repeatability of sensor response on the prediction of gas concentration. The aim of numerical simulation is to determine how successfully the approach using the combination of artificial neural networks with multi-sensor arrays can analyze multi-component gas mixtures. The results indicate that the new approach is realistic for gas mixture analysis, and numerical simulation is a powerful tool to determine the architecture of a network. By constructing improved BP neural network algorithm and basic BP neural network into sensor array signal processing and extracting 6 component as the input of neural network, Our investigation results indicated that recognition results obtained from improved BP neural network algorithm more accuracy than the results obtained from basic BP neural network.

Abstract: Inset Permanent Magnet synchronous machine (Inset - PMSM) is a specific kind of permanent magnet synchronous machine. The magnetic flux in air gap of electrical machine is one of the important parameters and it imply to the electric or mechanical energy of machine. Using radial pole structure, the characteristics of magnetic field in air gap of an Inset PMSM with 6 poles and 36 slots are simulated. In this paper, we simulated and observed the influence of axial channel rotor core of Inset-PMSM to the value/quantity of magnetic flux in air gap. Magnetic flux quality is also considered in this simulation. The simulations were compared with the conventional rotor structure. The flux density per pole in the air gap was measured with three different angles, 00, 250 and 400.

Abstract: An electrical machine is constructed with some holes or axial hollows in the rotor core for special purpose. The effects of axial hole in the proposed Inset Permanent Magnet Machine (Inset PMSM) with eight radial poles are analyzed by the magnetic flux density in air gap. The characteristics associated with magnetic flux density of every magnet poles in the air gap, magnetic flux losses in the rotor teeth, density magnetic flux in the rotor core surface and torque of the machine are also investigated and compared. Results show small direct reactance and less area in the proposed axial channel rotor core compared with the convention Inset PMSM. It imply to a lighter weight and high efficiency machine design. The finite element simulation shows the magnetic flux density per pole in air gap of the proposed rotor structure remain constant or may be a little bit drop compared with the conventional machine.

Abstract: The thermal effect experiments were carried out of a direct air-cooled system in the low speed wind tunnel. The influence of effect factors on recirculation is also discussion, after that the relationship between the thermal flows field structure and recirculation ratio under the cooling tower is analyzed. At last, the engineering measures to reduce or avoid recirculation are proposed. For certain conditions the experimental measurement shows close agreement with numerical values.