Applied Mechanics and Materials Vol. 577

Abstract: In order to analysis the variable-voltage energy saving theory and its implementation for induction motor with light-load in detail, This paper gives out a variable-voltage energy saving method, and discusses the design of variable frequency adjusting speed control and the points of attention. It is useful for the application of energy saving technology for induction motors.

Abstract: In this paper, a single-phase grid-connected photovoltaic (PV) inverter topology consisting of an H-bridge circuit, an inductive filter and a transformer interfacing the grid is considered. To improve the quality of the grid current and eliminate low order harmonics caused by the inverter’s dead time, a strategy of adaptive harmonic compensation method is proposed, and the parameters related are designed. The experiment results show that the proposed method has a good effect to mitigate low order harmonics and can improve the quality of current injected to the grid.

Abstract: Principle of space vector PWM was established, modulation function of load phase voltages were computed, correlation between space vector PWM and sinusoidal PWM methods was reexamined in this paper. Theory and simulation results shows SVPWM has an advantage of higher utilization of DC voltage, lower torque ripple and so on in PMSM speed regulation system.

Abstract: This paper proposes a pattern recognition approach based on the back propagation (BP) neural network for identifying insulation defects of high-voltage electrical apparatus arising from partial discharge (PD). Pattern recognition of PD is used for identifying defects causing the PD, such as internal discharge, external discharge, corona, etc. This information is vital for estimating the harmfulness of the discharge in the insulation. Since an insulation defect, such as one resulting from PD, would have a corresponding particular pattern, pattern recognition of PD is significant means to discriminate insulation conditions of high-voltage electrical apparatus. To verify the proposed approach, experiments were conducted to demonstrate the field-test PD pattern recognition of model insulators with artificial defects are purposely created to produce the common PD activities of insulators by using feature vectors of field-test PD patterns. The experimental data are found to be in close agreement with the recognized data. The experimental results show that the proposed approach is very effective for recognizing the defects of high-voltage electrical apparatus.

Abstract: This paper proposes a pattern recognition approach based on the fuzzy neural network for identifying insulation defects of cast resin current transformer (CRCT) arising from partial discharge (PD). Pattern recognition of PD is used for identifying defects causing the PD, such as internal discharge, external discharge, corona, etc. This information is vital for estimating the harmfulness of the discharge in the insulation. The PD patterns are collected by a PD detecting system in the laboratory. Several statistical methods are used on the phase related distributions in this paper to extract the features for recognition. A set of features, used as operators, for each PD pattern is extracted through statistical methods. To verify the proposed approach, experiments were conducted to demonstrate the field-test PD pattern recognition of CRCT models with artificial defects are purposely created to produce the common PD activities of insulators by using feature vectors of field-test PD patterns. The experimental data are found to be in close agreement with the recognized data. The test results show that the proposed approach may achieve quite satisfactory recognition of PD patterns.

Abstract: The boiler make-up water pretreatment system and desalination system of 2×1000MW units in Taishan power plant were investigated and analyzed,and their corrosion risk were assessed . The results showed that the change of seasons had no effect on the dosage of coagulate in boiler make-up water pretreatment system and the system had advantages of economic operation, simple maintenance, however, corrosion risk might exist in equipment; for desalination system, carbon remover could be omitted and it had a large cycle water production, and the water quality of the mixed bed is good, however, the effect of iron removal and high efficiency filter backwashing is poor, In addition, corrosion existed in both acid and alkali regeneration system as well as in drainage system, steam turbine and effluent treatment equipment.

Abstract: High-pressure direct-fired steam-gas generator (HDSG) is to produce multiplex thermal fluid (contains water, CO₂, N₂ etc.) through efficient direct-contact heat transfer, which would utilize the flue gas heat and reduce the gas emission caused by ordinary boiler. Furthermore, the multiplex thermal fluid can promote the heavy oil recovery by both steam flooding and miscible flooding. This paper introduced three kinds of HDSG: pressurized submerged combustion vaporization (PSCV), multiplex thermal fluid generator and supercritical hydrothermal combustor, which are different in work pressure and method of mixing water and flue gas. Then, we discussed the economic efficiency of HDSG used for heavy oil recovery and concluded that although the pressurization of fuel and oxygen would cost as much as the energy saved by utilizing the flue gas heat, using HDSG for heavy oil recovery has other incalculable benefits such as miscible flooding, waste water treatment and reduction of heat loss through injection well. Finally, we indicated that supercritical hydrothermal combustor will be the trendy of HDSG and pointed out the future research should be carried out on the heat and mass transfer characteristic of the combustion field when water presents and the combustion stability and completeness when pressure increases.

Abstract: Profile loss is a main part of cascade aerodynamic losses in all breakdown schemes. In previous literature, the well known and mostly accepted correlations for profile loss should be the Kacker and Okapuu design-point and the Benner et al. off-design correlations. However, the two correlations had been devised separately with different form. The present paper is motivated to combine the two correlations to form a universal correlation for all operating conditions. By defining an incidence correction factor, a universal profile loss correlation for all operating conditions is developed. The effects of incidence on the midspan profile loss are examined through numerical simulations and analyses. Beneficial conclusions are obtained in the end.

Abstract: Base on the conclusion of the DC system configuration of UHV (Ultra-high Voltage) converter substation. Analysis the settings of the 3rd DC power circuit, research on selection of automatic switching device. Provide valuable reference for the design of DC system of substation in DC transmission projects.

Abstract: Out-of-step splitting is an emergency strategy to trigger splitting devices to separate power systems into several sub-regions through capturing oscillation center before the collapse of the system. How to position the oscillation center rapidly and accurately is a key procedure in out-of-step splitting field. This paper proposes a new method to position the oscillation center based on electrical parameter frequency. Firstly the current and voltage frequency variation characteristic of out-of-step tie line is analyzed. Secondly, the electrical parameter frequency variation rules are summarizes, i.e. curves of buses voltage frequency of the oscillation center line change continuously without intersection and they have the opposite variation trend. At last, the oscillation center can be positioned accurately within half out-of-step cycle by constantly monitoring electrical parameter frequency of the transmission tie lines. The accuracy and rapidity of the method are certified by the simulation results of four machine two regional power system.