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Joint Conference on Society for Machinery Failure Prevention Technology Conference, MFPT 2015 and ISA's 61st International Instrumentation Symposium, IIS 2015 - Technology Evolution: Sensors to systems for Failure Prevention

作者： Liu, Chao Jiang, Dongxiang Yang, Wenguang State Key Laboratory of Control and Simulation of Power System and Generation Equipments Department of Thermal Engineering Tsinghua University Beijing100084 China

The measured parameters change with the machine degradation, where the trends of the parameters can be applied in condition prediction. The deterioration of the parameters usually present characteristics in a monotonic or low-frequency way. As the measure signal are merged with instant signals, noise and measurement error in different frequency bands, model decomposition approaches are widely applied to separate the different bands for feature extraction. Among the model decomposition methods, Variational model decomposition is recently proposed by K. Dragomiretskiy and D. Zosso as a non-recursive model which can extract modes concurrently. This work will analyze its effectiveness in degradation feature extraction and application in condition prediction in prognosis. Firstly, variational model decomposition is analyzed, where the characteristics of variational model decomposition are compared with another mode decomposition method ensemble empirical mode decomposition. simulation data is applied to test the effectiveness of the mode decomposition methods. Secondly, field data with component degradation is collected, and the degradation feature extraction is applied with the three methods mentioned above.

关键词： Empirical mode decomposition

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Study on the Prediction Methods of Aero Engine Fault Parameters

Study on the Prediction Methods of Aero Engine Fault Paramet...

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2015 International power,Electronics and Materials Engineering Conference(IPEMEC 2015)

作者： Li Dewang Jiang Dongxiang State Key Laboratory of Control and Simulation of Power System and Generation Equipments De partment of Thermal EngineeringTsinghua University

ISBN: (纸本)9781510806474

This paper uses the least squares method,BP neural network and gray GM(1,1) model for trend forecasts and predicting the remaining life of the aero-engine fault *** comparing the results of the three methods,the least squares method and BP neural network method predicting results are more exact than the gray GM(1,1) *** three methods are also used for predicting the actual data,and the result is close to the real.

关键词： aero-engine characteristic parameters prediction methods

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Virtual synchronous control of grid-connected DFIG-based wind turbines

Virtual synchronous control of grid-connected DFIG-based win...

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Annual IEEE Conference on Applied power Electronics Conference and Exposition (APEC)

作者： Yangyang Zhao Jianyun Chai Xudong Sun State Key Laboratory of Control and Simulation of Power Systems and Generation Equipment Tsinghua University Beijing China

This paper proposes a virtual synchronous control strategy for Doubly-Fed Induction Generator (DFIG)-based wind turbines. On the basis of the proposed excitation control model orientated by rotor flux, and the P-f, Q-V droop control models which emulate the governor and exciter of synchronous machine, this paper established the basic virtual synchronous control structure for DFIG. This control strategy can provide DFIGbased wind turbines with intrinsic regulation ability of frequency and voltage without using the phase-locked loop (PLL) of the grid. Considering the power limitation under certain wind speed, the proposed adaptive droop control method realized the maximum power point tracking (MPPT) of wind turbines in steady state. simulation results demonstrate the feasibility and effectiveness of the presented virtual synchronous control for grid-connected DFIG. This control strategy can not only provide the possibility of unifying the grid-connected wind turbines as the standard synchronous power, but also decrease the negative effect on the grid frequency and voltage with high penetration of wind energy.

关键词： Wind turbines Rotors Frequency control Frequency synchronization Mathematical model Voltage control Steady-state

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Short-term prediction model of module temperature for photovoltaic power forcasting based on support vector machine

Short-term prediction model of module temperature for photov...

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International Conference on Renewable power generation, RPG 2015

作者： Sun, Yujing Wang, Fei Mi, Zengaiang Sun, Hongbin Liu, Chun Wang, Bo Lu, Jing Zhen, Zhao Li, Kangping State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources North China Electric Power University Baoding Hebei Province071003 China State Key Laboratory of Control and Simulation of Power Systems and Generation Equipment Department of Electrical Engineering Tsinghua University Haidian District Beijing100084 China China Electric Power Research Institute Haidian District Beijing100192 China

ISBN: (纸本)9781785610400

To improve the prediction accuracy of photovoltaic (PV) power generation, the temperature of PV modules and its prediction is very important. A short-term step-wise temperature prediction model for PV module based on Support Vector Machine (SVM) is proposed in this paper. Firstly, the primary impact factors of PV module temperature are determined in terms of the PV module physical characteristics and the correlation coefficient between each factor and module temperature. Secondly, two kinds of prediction models, direct and step-wise models, are built to predict module temperature respectively. For direct model, the prediction model is based on SVM using the historical data. For step-wise one, the prediction models of the primary impact factors are built at the first step and then the mapping models between module temperature and the impact factors are established. In the end, the deviations of two different kinds of prediction models are analyzed and discussed based on actual operation data. The results indicate that the stepwise prediction model has better accuracy than the direct prediction model if other things are equal.

关键词： Forecasting

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Cloud identification model for sky images based on Otsu

Cloud identification model for sky images based on Otsu

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International Conference on Renewable power generation, RPG 2015

作者： Li, Hongping Wang, Fei Ren, Hui Sun, Hongbin Liu, Chun Wang, Bo Lu, Jing Zhen, Zhao State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources North China Electric Power University Baoding Hebei Province071003 China State Key Laboratory of Control and Simulation of Power Systems and Generation Equipment Department of Electrical Engineering Tsinghua University Haidian District Beijing100084 China China Electric Power Research Institute Haidian District Beijing100192 China

ISBN: (纸本)9781785610400

Irradiance changes caused by clouds movement are the mam factors, which lead to mutation of photovoltaic power. In order to increase the accuracy of the ultra-short-term photovoltaic power prediction, based on of clouds images, the cloud identification for sky images is one of the primary aspects for improving photovoltaic power accuracy. A cloud identification model for sky images is established based on Otsu. Firstly, a series of sky images are collected by Total Sky Imager (TSI) with the regions of clouds and sky are distinguished. Secondly, the color features (based on RGB values) of pixels in sample images and the spectral and texture features of the whole image are extracted;Finally, we established a cloud identification model for sky images based on Otsu according to the clouds' and sky areas' division and the general characteristics featured by pixels and images. The simulated results show that the model in this paper can identify the clouds in a sky images effectively.

关键词： Pixels

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Photovoltaic plant Operating Statuses Identification model based on support vector machine using loss quantity of electricity feature parameters

Photovoltaic plant Operating Statuses Identification model b...

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International Conference on Renewable power generation, RPG 2015

作者： Li, Kangping Wang, Fei Zhen, Zhao Sun, Yujing Mi, Zengqiang Sun, Hongbin Liu, Chun Wang, Bo Lu, Jing State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources North China Electric Power University Baoding Hebei Province071003 China State Key Laboratory of Control and Simulation of Power Systems and Generation Equipment Department of Electrical Engineering Tsinghua University Haidian District Beijing100084 China China Electric Power Research Institute Haidian District Beijing100192 China

ISBN: (纸本)9781785610400

Operating Statuses Identification (OSI) can help operators to find fault timely and minimize the loss. So it is of great significance for optimal operation of photovoltaic (PV) plants. The loss quantity of electricity (LQOE) is defined as that should have been generated but actually not, which is caused by inverter fault, PV modules fault, dust stratification or combinations of them. Firstly, mathematical models of PV cells are proposed to figure out the LQOE of each PV module. Secondly, after analysing the relation between LQOE and operating statuses, an index set of LQOE describing the distinction of different operating statuses are defined including four statistical feature parameters and a user-defined index. Thirdly, Support Vector Classification models for OSI (OSI-SVC) are built with input features extracted from the index set. Lastly, simulations are carried out to verify the effectiveness and evaluate the performance of the OSI-SVC models. The results indicated that the operating statuses can be effectively recognized by the proposed model.

关键词： Support vector machines

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Secondary voltage control considering rapid dynamic reactive power compensation

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Dianli Xitong Zidonghua/Automation of Electric power systems 2015年第2期39卷 53-60页

作者： Wang, Xuran Guo, Qinglai Sun, Hongbin Wang, Bin Zhang, Mingye Zhang, Boming Department of Electrical Engineering Tsinghua University Beijing100084 China State Key Laboratory of Control and Simulation of Power Systems and Generation Equipments Tsinghua University Beijing100084 China

This paper presents a secondary voltage control system considering rapid dynamic var compensators, such as static var compensator/static synchronous compensator (SVC/STATCOM). In order to take full advantage of the rapid adjustment feature of SVC/STATCOM in static voltage control and transient voltage stability, two independent control stages are dealt with. In the first stage, SVC/STATCOM and conventional var compensators are incorporated in the coordinate secondary voltage control model to bring the rapid adjustment feature of SVC/STATCOM into full play. In the second stage, a quadratic programming model is designed to do the optimal control of the dynamic reactive power reserves. The reactive power compensation of the slow dynamic var compensators is substituted for that of SVC/STATCOM, and the dynamic reactive power reserves level is improved. Through coordination between sequence and space, all kinds of reactive power compensators are made full use of in the secondary voltage control and transient voltage stability prevention control. Nordic system test results show that the system can greatly improve the response speed of traditional secondary voltage control while avoiding the conflict between SVC/STATCOM and the traditional reactive power compensators. At the same time, the system is able to carry out effective preventive control of transient voltage stability and improve the recovery effect of system voltage after the disturbance. ©, 2015 state Grid Electric power Research Institute Press.

关键词： Reactive power

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Quasi-Uniform Magnetic Field Generated by Multiple Transmitters of Magnetically-Coupled Resonant Wireless power Transfer

Quasi-Uniform Magnetic Field Generated by Multiple Transmitt...

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International Conference on Electrical Machines and systems

作者： Yiming Zhang Ting Lu Zhengming Zhao Fanbo He Kainan Chen Liqiang Yuan State Key Lab of Control and Simulation of Power Systems and Generation Equipment Department of Electrical Engineering Tsinghua University Beijing China

ISBN: (纸本)9781479988068

Magnetically-coupled resonant wireless power transfer (MCR-WPT) has been a research focus in recent years. Multiple transmitters are employed to improve efficiency in a wide area. In this paper, the MCR-WPT system with two transmitters supplied by the same source is modeled and its equivalent circuit is depicted. The mutual inductance between the two transmitters is considered. Proper connection of the transmitters results in the enhancement of the magnetic field in certain areas. Based on the circuit theory, the explicit expression of the efficiency is derived. The quasi-uniform magnetic field and roughly equal efficiency are analyzed.

关键词： magnetic resonance multiple transmitters uniform magnetic field wireless power transfer

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Mathematical expectation modeling of wide-area controlled power systems with stochastic time delay

Mathematical expectation modeling of wide-area controlled po...

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IEEE General Meeting power& Energy Society

作者： Chao Lu Xinran Zhang Xiaoyu Wang Yingduo Han State Key Laboratory of Control and Simulation of Power System and Generation Equipments Tsinghua University

ISBN: (纸本)9781467380416

Summary form only given: Communication network brings new challenges such as time delay and data loss to wide-area damping control of power systems. The uncertainty caused by stochastic time delay of network communication increases the difficulty of wide-area control performance analysis. This paper proposes a mathematical expectation modeling approach to model and analyze wide-area controlled power systems considering the effect of stochastic time delay. In the proposed method, mathematical expectation of stochastic time delay distribution is derived to accurately model the impact of communication network on wide-area control performance. The theoretical frame of the proposed modeling approach is presented and the effectiveness of the method is verified through the simulation of a power system with 8 generators and 36 nodes.

关键词： Mathematical model power systems Delay effects Stochastic processes control systems Data models Communication networks

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Ordinal optimization theory based planning for clustered wind farms considering the capacity credit

Ordinal optimization theory based planning for clustered win...

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第13届全国博士生学术年会——新能源专题

作者： Yi Wang Chongqing Kang Ning Zhang Qianyao Xu Rui Shi Hui Li Jinyu Xiao Zhidong Wang Shuai Wang State Key Lab of Control and Simulation of Power Systems and Generation Equipment (Department of Ele State Power Economic Research Institute ChangpingDistrictBeijing 102209China

Wind power planning aims at optimally locating and sizing wind ***,it tends to choose the wind farms with the richest wind resource in order to maximize the energy ***, the capacity benefit of wind power should also be considered in the large-scale clustered wind farm planning since the correlation among the wind farms performs an obvious influence on the capacity benefit brought by the whole wind *** paper proposes a planning model considering both energy and capacity benefit of the wind ***, the capacity benefit is evaluated by wind power capacity *** Ordinal Optimization (OO) theory, capable of handling problems with non-analytical forms, is applied to address the *** verify its feasibility and advantages, the proposed model is compared with widely-used genetic algorithm (GA) via a modified IEEE RTS-79 system and a real world case of Ningxia, *** results show that the diversity of wind farm enhances the capacity credit of wind power.

关键词： Capacity credit Correlation Ordinal Optimization Planning Wind power

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