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Wang F.,North China Electrical Power University | Mi Z.,North China Electrical Power University | Su S.,Yunnan Electric Power Research Institute | Zhao H.,North China Electrical Power University
Energies | Year: 2012

Short-term solar irradiance forecasting (STSIF) is of great significance for the optimal operation and power predication of grid-connected photovoltaic (PV) plants. However, STSIF is very complex to handle due to the random and nonlinear characteristics of solar irradiance under changeable weather conditions. Artificial Neural Network (ANN) is suitable for STSIF modeling and many research works on this topic are presented, but the conciseness and robustness of the existing models still need to be improved. After discussing the relation between weather variations and irradiance, the characteristics of the statistical feature parameters of irradiance under different weather conditions are figured out. A novel ANN model using statistical feature parameters (ANN-SFP) for STSIF is proposed in this paper. The input vector is reconstructed with several statistical feature parameters of irradiance and ambient temperature. Thus sufficient information can be effectively extracted from relatively few inputs and the model complexity is reduced. The model structure is determined by cross-validation (CV), and the Levenberg-Marquardt algorithm (LMA) is used for the network training. Simulations are carried out to validate and compare the proposed model with the conventional ANN model using historical data series (ANN-HDS), and the results indicated that the forecast accuracy is obviously improved under variable weather conditions. © 2012 by the authors.

Li Y.,Yunnan Electric Power Research Institute
Proceedings of 2010 World Non-Grid-Connected Wind Power and Energy Conference, WNWEC 2010 | Year: 2010

Vibration signals from the gearbox of a wind turbine are essentially non-stationary and nonlinear in both time and frequency. Empirical Mode Decomposition (EMD) is an ideal method for dealing with this type of signal. Yet the signal containing the fault information was contaminated by the noise, which contains two different types of white noise and impact noise. This makes it so the vibration signal cannot be processed with EMD directly, since it will produce the spurious IMF (Intrinsic Mode Function). The signal has to be pre-processed before implementing EMD. In fact, a wavelet filter is perfect for white noise de-noising and the morphological filter is suitable for impulse interference. In this paper, a confederative filter, which is combined with the wavelet and morphological filter, is designed for signal preprocessing, and a standard processing program is proposed too. An experimental case shows the accuracy and efficiency of the confederative filter and the process program. © 2010 IEEE.

Qian G.,Yunnan Electric Power Research Institute
2016 IEEE International Conference on Mechatronics and Automation, IEEE ICMA 2016 | Year: 2016

When online detecting transformer winding deformation with impulse frequency response analysis, the time domain characteristics of transient signal could not be depicted by conventional frequency response curves, and the limitations of Fast Fourier Transform could result in deletion of available information. In this paper, continuous wavelet transform is used to process transient signal, which is obtained by online impulse signal injection method, time-frequency spectrum of wavelet transform is studied to detect transformer winding deformation fault types. A single winding simulation model is constructed after theoretical deduction, the simulation analysis of different fault types is performed, the typical winding fault test is conducted, the time-frequency characteristic of detection signal is analyzed, the matrix similarity is used to quantize the diversity of the detection signal. Both the simulation analysis and experimental studies show the feasibility of the proposed method. © 2016 IEEE.

Qian G.,Yunnan Electric Power Research Institute
2016 IEEE International Conference on Mechatronics and Automation, IEEE ICMA 2016 | Year: 2016

The vibration of power transformer on oil tank is mainly come from the vibration of transformer core and winding and consists the variable information of mechanical condition. This paper through setting lack of clamping pressure in both winding and core as well as radial displacement of HV wingding in a 10/0.4 kV power transformer with three phases. Using the vibration eigenvalues in spectrum, such as the amplitude of 100Hz, the proportion of frequency, the maximum amplitude of vibration spectrum, the complexity of vibration spectrum, deals with the vibration characteristics under the above-mentioned faults. The conclusion shows that the complexity of vibration spectrum in three faults decreases and the 100Hz vibration in looseness faults rises, while in radial displacement of winding can decrease. The conclusion of this paper may make contributions to the condition monitoring technology of transformer. © 2016 IEEE.

Sun P.,Yunnan Electric Power Research Institute | Chen S.-H.,North China Electrical Power University | Zhang C.-Q.,North China Electrical Power University
Dianli Xitong Baohu yu Kongzhi/Power System Protection and Control | Year: 2012

According to some theoretical research methods of relevant equipment failure rate, and based on Marquardt parameter estimation method, the assessment method of failure rate of substation equipment life cycle is established. For example, in a power transformer, first of all, through establishing the model of power transformer failure rate, fuzzy analytic hierarchy process (FAHP) is utilized to determine the importance degree of each event, and the reliability degree of power transformer is calculated. Then Marquardt method is utilized to estimate the parameter of two-parameter Weibull distribution function, thereby obtaining the cut-off of failure rate and the distribution curve function of failure rate. Finally in accordance with the failure rate distribution circumstances obtained from distribution function, the life cycle failure rate can be assessed, so as to provide the management decisions for power transformer condition-based maintenance, technical upgrading, etc.

Wang K.,Yunnan Electric Power Research Institute
Gaoya Dianqi/High Voltage Apparatus | Year: 2013

According to the analysis of application features for different detection techniques, the comprehensive diagnostic strategy of three step sequences is summarized focusing on rapid detection of exception, and confirming exception and position using electrical detection technology, and confirming exception again using assisted detection technology. An insulation defect of 110 kV GIS is tested and analyzed following the comprehensive diagnostic strategy. The results verify the effectiveness of the comprehensive diagnostic strategy which provides a new comprehensive diagnostic strategy for insulation defects diagnosis to GIS in operation.

Wang Z.,North China Electrical Power University | Wang F.,North China Electrical Power University | Su S.,Yunnan Electric Power Research Institute
Energy Procedia | Year: 2011

A short-term solar irradiance prediction model is established based on BP neural network and time series. Firstly, several different network structures of the solar irradiance prediction model are established based on BP neural network. Secondly, the most suitable neural network is gained by the comparison of different network structures and cross-validation. Lastly, the chosen model is trained through setting the suitable network parameters. This model can avoid over-fitting and help to gain a more accurate solar irradiance prediction model. The result of simulation indicates that the model can be effectively used for short-term solar irradiance predicting © 2011 Published by Elsevier Ltd.

Li Y.,Yunnan Electric Power Research Institute
ICMREE2011 - Proceedings 2011 International Conference on Materials for Renewable Energy and Environment | Year: 2011

There is a constant need for the reduction of operational and maintenance costs of the onshore or offshore wind turbine (WT) as it suffers higher reliability risk being exposed to extreme running environment and subject to constantly variable loadings, an efficient condition monitoring system (CMS) is indispensable. Unfortunately, the majority CMS for WT are borrowed from other industry fields (such as the thermal power industry) where they achieve success, however, to date these CMS have not proved entirely satisfactory in wind industry. This article makes the analysis on the possible reasons on it, and discussion on the principles of CMS which apply to the wind energy industry. © 2011 IEEE.

Shen X.,Yunnan Electric Power Research Institute | Cao M.,Yunnan Electric Power Research Institute
Diangong Jishu Xuebao/Transactions of China Electrotechnical Society | Year: 2015

Distributed generation is usually refers to the power in a few kilowatts to several hundred megawatts of small modular, decentralized, arranged near the user's high efficiency, reliable power generation unit. Due to the development of society and economy and power system will face the great reform, distributed power generation will be the power system priority development of future direction. The distributed power usually access medium voltage or low voltage distribution system, and for distribution system will have a extensive and far-reaching impact, and power quality problems will be distributed power generation way inevitable problems. This paper of the distributed power generation three kinds of concrete form(wind, solar, and photovoltaic) of power quality problems are analyzed, and points out the power quality problems to solve the potential advantages, gives the feasible research program and the idea. ©, 2015, The editorial office of Transaction of China Electrotechnical Society. All right reserved.

A method for testing mainframe performance of different types of PD detectors based on analog voltage signal injection, the method comprises: using a function generator (19) with an adjustable output frequency of 0 to 3.5 GHz and an adjustable output amplitude of 0 to 10V, directly injecting or injecting via a DC blocking element (28) with a frequency band of 10 kHz to 10 MHz equivalent analog voltage signals generated by said function generator (19) based on PD waveforms actually tested by a pulse current PD detection sensor (6), an ultrasound PD detection sensor (12,13) and a UHF PD detection sensor (9) into mainframes of a pulse current PD detector, an ultrasound PD detector and a UHF PD detector respectively. The advantages are that the test method is universalized and standardized, the test result is reproducible and measurable, the application scope of the test object is wide, and the test content is comprehensive.

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