Applied Mechanics and Materials Vols. 303-306

Abstract: The solar power supply system was studied for remote automatic monitoring device on subgrade settlement. Gave the detailed design formula and circuit principle diagram, the independent solar power supply system was designed that is stable, reliable and can get a variety of output voltage. It was successfully applied to outdoor monitoring devices of subgrade settlement, the results show the solar power supply system has a high stability and efficiency, and absolutely meet the needs of project applications.

Abstract: In order to solve the problems in the optimization of filter parameters, such as large amounts of calculation and the complicated mathematical hypotheses, an approach to optimize filter parameters is presented based on the Hybrid Particle swarm optimization (HPSO) algorithm, which includes the establishing of filter model, setting up the fitness-function and optimizing filter parameters by HPSO algorithm. The application example shows that the optimization method improves the design accuracy and saves calculation, and HPSO algorithm is superior to PSO algorithm in optimization of filter parameters.

Abstract: Currently, the embedded database technology has become a very active research field, and attracted more and more attention. This paper research how to improve the storage performance of embedded database indexing mechanism using read and write characteristics of NAND flash memory. Based on the reviewed and compared of existing design of NAND flash memory, this article expressed the design and implementation of dynamic index mechanism base on B + Tree. The prototype system combines the advantages of operation of the adapted read operation disk model and write adapted write operation log model, optimal matching and converting for storage model of each node in B + tree model while running which make a variety of devices have better read and write performance.

Abstract: With the rapid development of the VSC-HVDC Power transmission and distribution grid demonstration projects, the technology of the DC transmission once again becomes a research focus. In order to meet the needs of accessing VSC-HVDC power grid of Photovoltaic power generation, the topologies suitable for photovoltaic high voltage DC grid-connected converter was analyzed, the program based on the dual-module combination of full-bridge topology structure was proposed, a detailed control strategy using dual-loop of voltage and current loops was given, and finally a 12kW simulation model to verifying the system topology and control strategy was constructed using PSIM. The simulation results show that the PV high voltage DC grid-connected converter has a good dynamic response and steady state performance.

Abstract: As the IGBT power modules have promising potentials in the application of the field of traction or new energy, the higher power density and higher current rating of the IGBT module become more and more attractive. Thermal resistance is one of the most important characteristics in the application of power semiconductor module. A new 1500A/3300V IGBT module in traction application is developed successfully by Zhuzhou CSR Times Electric Co., Ltd (Lincoln). Thermal resistance management of this IGBT module with high power density is performed in this paper. Based on thermal nodes network, an equivalent circuit model for thermal resistance of power module is highlighted from which the steady state thermal resistance can be optimized by theoretical analysis. Furthermore, thermal numerical simulation of 1500A/3300V IGBT module is accomplished by means of finite element model (FEM). Finally, the thermal equivalent model of the IGBT module is verified by simulation results.

Abstract: This paper presents a integral type Multi-ramp architecture apply to MRSS ADC (Multiple-ramp single-slope ADC).On the one hand to improve the capacitance mismatch by change voltage reference, On the other hand to reduced the power consumption greatly. Implemented in the GSMC 180nm 2P4M CMOS process, in the power supply voltage of 1.8 V, 11-bit resolution, 10 MHZ sampling frequency, the result of max power consumption is 1.33mW of single unit .The DNL < 0.1LSB and max INL < 0.49LSB .The Multi-ramp achieved requirements for high speed and high accuracy MRSS ADC.

Abstract: Regulated DC-DC converter and unregulated DC-DC transformer is the basic types of DC-DC converter. Now the research is focusing on the regulated form named regulated LLC resonant DC-DC converter. Unregulated form of LLC resonant DC-DC converter named LLC resonant DC-DC transformer is studied in this paper in order to increase the practical topology of soft-switching and high-efficiency DC-DC transformer. Design method is proposed by the gain curve analyze of LLC resonant DC-DC transformer, and load characteristic of gain and efficiency of the DC-DC transformer is analyzed specializing for optimal design. A LLC resonant DC-DC transformer prototype is designed and implemented. Experimental results verify the correctness and validity of the design method and the load characteristic analysis.

Abstract: In order to make it clear for explosion accidents of parallel capacitors occurred in 500kV substations in Sichuan power network one after another, the authors calculate and analyze the distribution of overvoltage caused by breakdown of elements within the capacitor bank. Dissecting the insulation of faulty capacitors, severe ageing of insulation is discovered; this phenomenon proves that the overvoltage on partial element should be the main factor influencing the insulating performance of capacitors. To ensure the reliable operation of parallel capacitors the setting value of unbalanced current protection at the neutral point of double star connection is modified by the calculated value of unbalanced current of 35kV capacitor bank in which there are six parallel groups of capacitors and in each group seven capacitors are connected in series.

Abstract: The traditional real-time correlation processing system in FPGA is implemented in parallel mode. It has disadvantages such as high FPGA resource-consuming, low efficiency and poor flexibility. A time-multiplexed processing architecture takes NIOS processor as system controller, connected with preprocessing module, sliding-correlation processor and memories by Avalon data bus. The transmission of large data block out of sliding-correlation processor employs DMA method for its controlling flexibility, the data transmission between computing units and memory units within the processor employs directly memory access to minimum time delay.

Abstract: As an extension to H.264, Scalable Video Coding (SVC) provides three types of scalability, which makes it more suitable for the video transmission over wireless networks. IEEE 802.11e introduces EDCA mechanism to support Quality of Service (QoS). In this paper, a scheme, based on cross-layer design between application layer and MAC layer, is proposed to improve SVC transmission over 802.11e networks. With optimized mapping mechanism and queue management, the approach has taken the SVC video priority and network congestion status into consideration. Simulation demonstrates the effectiveness of the algorithm. The experimental results show that our approach can get full use of the limited wireless channel resources, by which SVC packets with high priority can obtain better protection, thus the decoding video quality can be significantly improved.