Advanced Materials Research Vols. 756-759

Abstract: With the increasing of the number of processors in one chip, the energy consumption became increasingly important in the low power design of embedded system. In time-sharing OS, different application scenarios lead to different workload. A novel policy for energy saving is that some processors can be hot-plugged on while the workload of the system becomes high and some processors can be hot-plugged off while the workload becomes low. This paper proposed an energy-efficient workload prediction approach called PID prediction algorithm (PPA) which aims dynamic processors number changes for energy saving and reduces the frequency of processors switch on/off for saving extra energy costs. The experiments show that energy consumption is reduced by 19% and the frequency of processors switch on/off is reduced by 30%.

Abstract: Considering narrow temperature and viewpoint of LCD for most portable display system,OLED is used as display device.Focusing on the problem of low contrast of generic driver method for portable display system.

Abstract: This paper describes the design and implementation of MINIX file system for an embedded OS in technical details, including an overview of MINIX FS, an introduction of the data structures for it, key techniques of implementing it, such as cache, foundational routines and interface functions. The file system is implemented on the multi-process micro-kernel embedded operating system on ARM, which is also designed by the author of this paper with GNU tool chain. The essential functions for a MINIX FS are accomplished, e.g. mount (), open (), close (), read (), write (), lseek (), unlink (), stat (), chdir (), mkdir (), rmdir (), execve (), etc. To show the effects of the file system, some related shell commands are also designed, e.g. cat, cp, echo, ls, pwd, etc. The file system is designed as simple as possible so that the code amount of it is only about 1,600 lines. With such a small scale, the system is suitable not only for embedded application system developments but also for embedded related curriculum teaching in colleges and universities.

Abstract: This paper describes the design and implementation of primitive shell for an embedded OS in technical details, including creation of root file system on SD card, overview of the primitive shell, key techniques of implementing essential shell commands. The primitive shell is designed based on the multi-process micro-kernel embedded operating system on ARM developed by the author of this paper. The shell command files are designed simple and compact particularly suited for embedded related curriculum teaching as well as embedded operating system research.

Abstract: In most of the AC-DC hybrid power transmission system AC filters is widely applied to stabilize voltage level in addition to filter harmonic. However, the voltage stability of AC bus is greatly influenced by action sequence of switching AC filters in group. The paper presents the concept of reactive characteristics of the convertor and AC filters, using reactive and voltage control mode to switch them. The modeling, control, and principle of operation for the AC-side switching filters are described. The voltage level is controlled via regulating action of switching filters by step. The salient feature of the proposed control modes is that voltage control contributes to keep the voltage level, and reactive control has no fast response on guaranteeing voltage stability, but two methods can apply to different occasions based on the requirements of voltage stability. All analysis and control system designs are verified through building a RTDS model in a typical ±500kV power system.

Abstract: At present the transient mechanism in lumped parameter for analyzing single-phase grounding fault in indirectly grounded power system exist deviations. This paper analyzes the amplitude-frequency and phase frequency characteristics of the impedance in line-mode network and zero-mode network through the distribution parameter model of transmission lines. This paper also analyzes the mechanism of LC resonant process. A high precision model of single-phase grounding fault in system with neutral point ungrounded is established using simulation software like ATP and Matlab, and the resonance mechanism of the single-phase grounding fault transient process in the proposed system with neutral indirectly grounding system simulated and identified.

Abstract: Concerned that wind generators start up and establish the stable terminal voltage of the stator which is connected to the grid, this paper presents that wind generator can be operated as the independent generator at a certain voltage and frequency by means of capacitive excitation. The paper also deduces the calculation method for the proper capacitance value of self-exciting startup of wind generator. The paper builds a simulation model based on real time digital simulator (RTDS) and takes a case for simulating self-excited startup of wind generator. Simulation results demonstrate that the wind generator with self-excitation can successfully start up and be connected to the grid, it make a good agreement of actual situation. Furthermore, the results of RTDS simulation show that only proper capacitors value from optimized calculation can lead to a normal terminal voltage characteristic. The validity of proposal methods and designed simulation model is verified by experimental and computed results.

Abstract: The transmission tower with a big span in the freezing area is very sensitive to climate. When extreme weather approaches, the tower may collapse easily. The dynamic characteristics of transmission tower structure vary under different weather conditions. This paper, taking a 500kV long span tangent tower as the research subject, will demonstrate the dynamic characteristics of such structures when the weight of wires, the icing stiffness of tower structure and the thickness of ice are considered. The results show that icing has a great impact on the dynamic characteristics of the tower structure and it can not be neglected. When the ice is thick, the contribution of icing to the stiffness of the structure should be considered. This conclusion can provide a reference for the analysis and design of similar towers in high altitude area.

Abstract: A novel structure of a VDMOS in reducing on-resistance is proposed and experimentally demonstrated with a 200V N-channel VDMOS. With this structure, the on-resistance value of the VDMOS is reduced by 19.6% than that of a traditional VDMOS structure as the breakdown voltage almost maintained the same value, and there is only one additional mask in processing this new structure VDMOS, which is easily fabricated. By TCAD tool, the specific on-resistance value will reduce by 23%, and the value by 33% will be realized when the device is fabricated in three epitaxies and four buried layers. The novel structure can be widely used in high-voltage VDMOS and BCD areas.

Abstract: Aiming to the requirements for stable voltage of system. The topology of series-parallel dynamic voltage restorer (DVR) used in the system is proposed in this paper. The simulation results under multiple of voltage fault show that the DVR can provide voltage support continuously, and improve the reliability of bus voltage in system effectively.