Advanced Materials Research Vols. 805-806

Abstract: The tap ratio of magnetic controllable reactor (MCR) has an important influence on the response speed and active power loss. With various applications of MCR, the focuses of MCRs response speed and active power loss are different, which makes the design of the tap ratio different. According to MCRs most widely application--- power system reactive power voltage control---the effect of the tap ratio on the response speed and active power loss was considered. The tap ratio of magnetic controllable reactor was optimized based on the dynamic optimal algorithm of MATLAB, which made the response speed and the active power loss of MCR stay in the equilibrium optimal state, and a general formula was given. Through the simulations of ANSYS and PSCAD software, the feasibility of this theory is verified, and a solid theoretical foundation for the wider practical application of magnetic controllable reactor is provided.

Abstract: Principles and characteristics of setpoint overshoot method are illustrated. The proposed method has been developed for PID controller tuning of an unidentified process using closed loop experiments. It requires one closed-loop step setpoint response experiment using a proportional only controller, and it mainly uses information about the first peak (overshoot) which is very easy to identify. It was applied in turbine of power plant to tune the PI parameters of load control. The application results demonstrate the validity of the proposed method.

Abstract: AlGaN/InGaN/GaN double heterostructure high electron mobility transistor (HEMT) with In composition from 0.08 to 0.26 were grown by MOCVD. 2DEG density and mobility of different channel In composition were investigated. When In composition below 0.19, 2DEG density increased nearly linearly with In composition, and the mobility decreased a bit. While In composition over 0.19, phase separation became more serious, 2DEG density nearly not changed, and the mobility dropped sharply. A high 2DEG mobility of 1163 cm²/V·s with low sheet resistance of 342Ω/ was obtained with In composition 0.19.

Abstract: When nonlinear load is powered by DC grid, harmonic currents and distortion power are produced. At first, the concept of the DC active power filter (DC-APF) is presented in this paper after the analysis of instantaneous power and power factor in the DC network. The DC-APF includes the parallel type, the series type and the series-parallel type, etc. The circuit topologies and the working principles of two kinds of DC-APF are proposed and analyzed: (1) the general type, which can compensate harmonic currents and reactive currents; (2) the correction type, which can track the DC voltage. The comprehensive simulation analysis of the double-bridge half-controlled DC-APF by means of MATLAB/SIMULINK and the experiment of the correction type prove the validity and the feasibility of these topologies and operating principles.

Abstract: High quality N-polar GaN films were grown by MOCVD on C-face 6H-SiC substrate etched by KOH eutectics at 300°C for 5min. A 50 nm high-temperature AlN buffer layer was used to release the lattice mismatch stress between GaN and SiC substrate. The N-polar GaN films grow on the C-face 6H-SiC substrate etched by KOH eutectics have a high crystalline quality and smooth surface. The full-width-at-half-maximum (FWHM) of (002) and (102) XRD spectra were 347.4 and 501.5 arcsec., respectively. The root-mean-square (RMS) of 3μm×3μm is 0.666 nm. The luminescence property of the N-polar GaN films was studied. The band-edge emission of photoluminescence spectra was at 364.6 nm with weak yellow luminescence near 560 nm. The stress in the films was also calculated from Raman spectra. The results indicated a tensile stress in the N-polar GaN films, which is mainly caused by mismatch of thermal expansion coefficient between GaN and SiC substrate.

Abstract: The management of electricity system in home environments plays an important role in generating energy consumption and improving efficiency of energy usage. At present, nonintrusive appliance load monitoring (NIALM) techniques are the most effective approach for estimating the electrical power consumption of individual appliances. This paper presents our contribution in intelligent electrical appliance decomposition in home environment. It is a modified power appliance disaggregation technique based on power harmonic features and support vector machine (SVM). It has higher recognition accuracy and faster computational speed. The experimental results of the power decomposition technique on real date are presented with promising results.

Abstract: The passive wireless temperature measurement system based on SAW is a better method than the fiber optic and the infrared temperature measurement in measuring the temperature of electrical equipment, but the environmental characteristics have an effect on it. In this paper, the effects of open space and closed space on the system are studied by experiments. The open space has a greater effect on temperature measuring signal because of the polarization direction of the antenna; In the closed space of the metal cabinet, whether there is sheet metallic object near the senor or not, it has no effects on the signal, which is mainly because that the reflections of electromagnetic signals by the internal walls of the metal cabinet make the signal power enhanced between the reader and the sensor through multi-angle reflections. Therefore, this type of measurement system is more suitable for the metallic objects in metal cabinet.

Abstract: The waveforms of the RTDS(Real Time Digital Simulator) commutation failure and ABB MACH2 system commutation failure protection have been combined to analyze the mechanism of HVDC commutation failure. Several reasons for inverter commutation failure have been found, and a detailed analysis is also been given for the missing pulse and commutation which are caused by the AC system fault. This is practical for HVDC transmission project.

Abstract: In order to study the conduction performance of the old transmission lines, we carried out a comparative study by testing the heat dissipation of the old and the new overhead conductors (35 kV aluminium cable steel reinforced (ACSR) lines, LGJ70/10). The temperature variation of two distinct types of lines under the identical current flow was investigated in details theoretically and experimentally. Our extensive experiments show that the temperature rise of old lines is higher about 11% than those of new lines with the same current flow of 255 A. By combining the theoretical analysis and experimental observations, it is concluded that the heat radiated power of the old lines is higher about 46% than that of new lines, such high radiated heat power is the main factor affecting the temperature rise of old lines.

Abstract: This paper introduces key features and the structure of a distribution network comprehensive planning platform as well as the functions and algorithms of core modules. The platform has a number of features, some of which are innovation points: 1) it provides a unified data interface compatible with IEC61968-based CIM model; 2) it adopts an effective algorithm that diagnoses and corrects input data of a relatively poor quality; 3) It converts CIM-based data into data based on calculation models, so that the calculation modules can analyze them. 4) Its reliability analysis module uses an algorithm based on zones. 5) The highly modulized platform has the provision for cloud computation in future. Furthermore, this paper has defined a number of reliability indices based on zones and feeders. The application of the platform in Tianjin urban network has desmonstrated its effectiveness: it successfully corrected data errors with no need for human intervention and yielded satisfactory results.