Applied Mechanics and Materials Vols. 448-453

Abstract: In primary frequency regulation (PFR) using battery energy storage system (BESS), the droop configuration for BESS needs to be considered thoroughly. This paper modified the traditional droop configuration method by considering more BESS`s internal nonlinear constraints and then proposed a variable droop strategy for operation. By doing this, a modified BESS model for PFR was constructed. Finally, the validity of BESS droop configuration method in this paper is testified with a three-area equivalent model based on the data of actual grid. The results show that variable droop strategy is more suitable for PFR than fixed traditional one.

Abstract: Smart Grid framework to achieve clean energy friendly access, to achieve energy conservation and reduction of environmental pollution, is to build the smart grid hallmark. Photovoltaic power plants grid, although to bring some impact on the grid, but also a certain role in promoting on the line loss rate decreased. This ignores the impact of other factors, only from the perspective satisfy voltage constraints, analyzing PV power plant different grid location and grid capacity for line loss rate.

Abstract: This paper presents the smart grid technical framework to support public service platform of smart energy, by means of the establishment of public service platform for communication and information services multi-network fusion, supporting smart residential construction by smart grid, to achieve coordinated and complementary among end-user.

Abstract: The stress distribution on transmission tower was found out by finite element analysis. Combined with analysis results, FBG(Fiber grating) strain sensors were fixed on upper part of tower, cross-arm of tower and body of tower, to monitor the stress of tower in dancing condition. FBG sensor measuring results and finite element analysis results are consistent, and the error is less than 10%.Research indicates that the 24^th point is the maximum point of stress at the wind speed of 20m, and the maximum value is beyond yield stress. So the part of tower needs to be reinforced to avoid danger occurring.

Abstract: Voltage sags was a common power system disturbance, usually associated with power system faults. Nowadays, there were more and more methods to detect voltage sag, involving with RMS, peak voltage detect, FFT. Owing to their defections, they were too slow when they came to being applied to detect voltages sags. This paper presents a method based on wavelet energy entropy detection voltage sags, this method can detect the drop time quickly and sensitively. In order to verify the feasibility of the proposed method, a numerical example simulation has been done based on matlab / simulink , results show that there is a significant effect.

Abstract: With the construction of UHV power grid, integration of large-scale renewable clean energy, and large-scale energy base putting into operation, the power grid dispatching faced with more and more complex challenges. On the basis of existing research results, architecture of intelligent dispatching based on situation awareness is proposed, so as to accurately achieve prevention and control of the power system. The shortcomings of traditional dispatching mode are analyzed firstly, and the concepts and characterization approaches of grid situational awareness and operation state trajectory of power grid are then introduced. The overall objective of intelligent dispatching is presented, including data processing and integrated knowledge mining, predictive perception of grid operation, risk analysis and comprehensive early warning, so as to achieve "automatic cruise under normal operating conditions, automatic navigation under abnormal operating conditions ". The functional framework of intelligent dispatching is also proposed in details, including four major aspects of the perception and forecasts, risk analysis, decision-making support, and automatic control, as well as three supporting functions such as post-assessment of dispatching, trajectory index calculation, and human-computer interaction (HCI).Technical innovations to support automatic intelligent dispatching are discussed and organised in three levels, i.e. perception, comprehension and projection. The breakthroughs are: construction of index system, trajectory recognition based on massive information and knowledge mining, trajectory projection taking into accounts the uncertainties, online risk assessment and early warning, power grid intelligent decision-making support, automatic coordination of grid operation control, online assessment, natural human-computer interaction mode, and etc... These are the future research areas of automatic intelligent dispatching.

Abstract: At present, smart grid is developing in China, in order to reach a safe and economical power system. In the process of establishment of smart grid, transformers which are dissatisfied with the demand of increasing load must be renovated or replaced. Economic costs and loss reduction and energy saving should be taken into account when choose a transformer. According to existing algorithms, a novel algorithm for energy savings of transformer after the original transformer is renovated or replaced. Combined with one practical project, the effectiveness and accuracy of this algorithm have been verified.

Abstract: In this paper, a novel method based on FRA is proposed to detect both the fault and the deformation type. Firstly, a model of the transformer winding is established based on the electrical properties of winding. Secondly, as the winding frequency response curve change in accordance with the change of the parameters of winding model, the rule of the variation of winding frequency response curve is drawn out based on the model above. Thirdly, the effect of various types of winding deformation on the changes of the parameters of transformer winding model is summarized. Finally, an experimental example of the diagnosis of deformation type is conducted on a testing transformer based on the analysis of frequency response curves, hence the validation of the correctness of the simulation results.

Abstract: The reliability of power transformer is very important to the safe operation of the power system. So a new method for power transformer risk assessment based on FTA, FAHP and GA is proposed. The method firstly establishes the power transformer fault tree; Secondly, it analyzes the fault tree through Fuzzy Analytic Hierarchy Process and constructs the fuzzy judgment matrix on transformer fault factors; Finally, it changes the question of solving the weight coefficients of each factor into a mathematical programming problem, and uses Genetic Algorithms to get the result so as to obtain the transformer reliability. In addition, the application result shows the effectiveness of the method above.

Abstract: In order to study propagation process of partial discharge ultrasonic signal in power transformer, the finite element method is used for simulation modeling and calculation. Ultrasonic waves can be activated by partial discharges (PD) in power transformers. The ultrasonic method is used for evaluating the insulation condition of power transformers by analyzing the partial discharge signals information which is detected by AE sensors. Compared with other diagnostic methods the AE method causes relatively low disturbance, and measuring apparatus is simple and easy to use. This technique is noninvasive and immune to electromagnetic noise. Simulate partial discharge sources of different positions respectively. Achieved results indicate that the space and time distributions of the acoustic pressure depend on the induction position. Furthermore, a greater pressure gradient is observed in domains with higher speed of sound while the signal amplitude decays when it moves away from the PD source.