Advanced Materials Research Vols. 433-440

Abstract: This paper proposes a 5kW zero voltage switch space vector modulation (ZVS-SVM) controlled three-phase boost converter. A power circuit of this converter is modified from the conventional three phase boost rectify by combine the active clamp branch. A branch composed of an active switch, a resonant inductor and a clamping capacitor. By used the control techniques to active clamp, the ZVS are occurring at the power switching components. The simulation results can confirm the superiority of this topology to increase the system efficiency up 98 percent. The system has fast response, low total harmonic distortion and steady state error with unity power factor. Moreover, both the main and the auxiliary switches have the same and fixed switching frequency.

Abstract: This thesis implements power flow application, Newton-Raphson method. The Newton-Raphson method is mainly employed in the solution of power flow problems. The network of Myanma electric power system is used as the reference case. The system network contains 90 buses and 106 brunches. The weak points are found in the network by using Newton-Raphson method. Bus 16, 17, 85 and 86 have the most weak bus voltages. The medium transmission line between bus 87 and bus 17 is compensated by using MATLAB program software. The transmission line is compensated with shunt reactors, series and shunt capacitors to improve transient and steady-state stability, more economical loading, and minimum voltage dip on load buses and to supply the requisite reactive power to maintain the receiving end voltage at a satisfactory level. The system performance is tested under steady-state condition. This paper investigates and improves the steady–state operation of Myanma Power System Network.

Abstract: In this paper secure channel coding schemes based on Turbo Codes are suggested and implemented. The design of encoder using Recursive Systematic Code (RSC) with puncturing techniques is presented. Component decoders are implemented by Log-Maximum-a-Posteriori (Log-MAP) algorithm and thereafter implementation of overall turbo decoder is illustrated in detail. Finally we have investigated low power design technique of the turbo decoder design with variable iteration techniques.

Abstract: While our planet is rapidly approaching an environmental crisis under the dominant use of depleting fossil fuels, the need for exploiting all forms of new, small carbon foot-print, renewable, and clean energy resources are increasing in the same proportion. Therefore, the need for exploring all types of clean energy resources that the world has- some of which might have not attracted sufficient attention before- is essential in order to implement sufficient, efficient, and widely use all them. In this respect, operational effectiveness of the wind and hydrokinetic turbines depend on the performance of the airfoils chosen. Using double-blade airfoils in the wind and hydrokinetic turbines, minimum wind and hydrokinetic flow velocities to produce meaningful and practical mechanical power reduces to 3- 4 m /s for wind turbines and 1-1.5 m/s or less for hydrokinetic turbines. Consequently, double-blade hydrofoils may re-define the potentials of wind power and hydrokinetic power of the countries in positive manner.

Abstract: In this paper, a combination of static and dynamic methods was used to identify effective fracture in Fractured-vuggy reservoir. An initial fracture model was established through the fuzzy neural network (FNN) and ant-tracking algorithm based on the static data (log and seismic data). We analysis the intel-well connectity and identify effective fracture based on dynamic data by pseudo-interfered well test， and then modify the fracture model. The application of this method solved the effective fracture identification problem of S48 unit .The fracture model got good result in numerical simulation.

Abstract: In the hot days of summer, the efficiency of gas turbine is extremely reduced because the input air to compressors becomes hot. For solving this problem, one can increase the efficiency of the power house by charging to decrease the input air temperature to the compressor of gas turbine. In this paper, all kinds of cooling the inlet air to the gas turbine are introduced and then the technical and economical evaluation of these installed cooling system in Shahid Rajaee, Qom, Fars and Yazd power plants are expressed and the results show that the fog system cannot prove its effectiveness in Shahid Rajaee and Qom power plants. Whereas the installation of media systems in Fars combined cycle power plant produces more megawatt than its guarantee conditions and no particular problem has been observed.

Abstract: The quality of the topology is the benchmark for the whole power system to measure the difficulty level, the possibility of expansion and ease of maintenance, and the topology is the basic for the various calculations in power system. In this paper, object-oriented technology will be used to establish the model of electric network equipment. The broad-first search method (BFS) and the depth-first search method (DFS) will be used to realize the topology analysis of the power system network, and the analysis process is fast and accurate.

Abstract: Misfire is a common fault which affects the engine performances. Because the signal-to-noise ratio of torsional vibration signal is high, torsional vibration test and analysis for the engine were performed in a variety of operating conditions, including healthy condition and single-cylinder misfire condition. In order to improve the accuracy of analysis, energy centrobaric correction method was used to correct the amplitude. Taking the corrected amplitude of main order as the fault feature, and then a BP neural-network diagnostic model can be established for misfire diagnosis. The result shows that the method of combining torsional vibration signal analysis and neural-network can diagnose engine misfire fault correctly.

Abstract: In this paper, the structure and principle of the cascade brushless doubly-fed machine are introduced and the mathematical model under rotor reference frame(d-q axis) is derived.The validity of the model has been verified by numerical simulation ,which provides the theoretical foundation for the study of control strategy and its implementation of this kind of machine in future.

Abstract: Dynamic voltage restorer (DVR) is used to mitigate the impact of the voltage sags. At first the structure of DVR and three basic compensation methods are introduced. Considering the compensation performance and the injection capability of the DVR, a generalized compensation strategy based on pre-fault compensation, energy-saving compensation and progressive phase rotation method is proposed. With this compensation strategy, the active power injected by DVR can be minimized on the premise of the quality of compensation. Simulation results demonstrate the efficacy of the proposed compensation strategy.