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arXiv 2018年

作者： Chen, Xiaoshuang Lin, Jin Liu, Feng Song, Yonghua State Key Laboratory of Control and Simulation of Power Systems and Generation Equipment Department of Electrical Engineering Tsinghua University Beijing100084 China

The control schemes of distributed energy resources (DERs) in active distribution networks (ADNs) are largely influenced by uncertainties. The uncertainties of DERs are complicated, containing spatial and temporal correlation, which makes it challenging to design proper control schemes, especially when there exist temporal-correlated units such as energy units (EUs). This paper provides an Itô process model to describe the characteristics of stochastic resources and EUs in a unified way, which makes it easy to evaluate the impacts of stochastic resources on temporal-correlated units. Based the moment form of the Itô process model, a moment optimization (MO) approach is provided to transform the stochastic control (SC) problem into an optimization problem with respect to the first-order and second-order moments of the system variables. The scale of MO is comparable to that of the corresponding deterministic control problem, which means that the computational efficiency of MO is much smaller than that of traditional approaches. Case studies also show that the proposed approach outperforms existing approaches in both the performance and computational efficiency, which means that the proposed approach has attractive potential for use in large-scale applications. Copyright © 2018, The Authors. All rights reserved.

关键词： Energy resources

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Skin Effect and Eddy Current Loss in Electrical Steel Sheets under Applied Excitation Fields.

Skin Effect and Eddy Current Loss in Electrical Steel Sheets...

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International Conference on Magnetics (INTERMAG)

作者： J. Li Q. Yang S. Wang Y. Li State Key Laboratory of Control and Simulation of Power System and Generation Equipments Tsinghua University Beijing China State Key Laboratory of Reliability and Intelligence of Electrical Equipment Hebei University of Technology Tianjin China

Body: By applying electromagnetic diffusion equation, skin effect in electrical steel sheets in the condition of alternating excitation is analyzed based on Maxwell electromagnetic field theory. Due to skin effect is more significant mainly at high frequency, non-dimensionalized treatment for the diffusion equation is produced and eddy current loss is calculated by considering or not skin effect, respectively. Meanwhile, broadband magnetic losses and separation of typical electrical steel are obtained by using a 3-D magnetic properties testing system to bring to light the emergence of skin effect under rotational excitation. The simplification of magnetic constitutive equation is proposed and introduced into the diffusion equation, which is solved by employing finite elements coupled to Fredholm's equation. An approximate expression for the rotational eddy current loss component with skin effect is eventually written. The simulations show that due to the influence of skin effect, non-uniform distribution of induction flux density within electrical steel sheets will become more and more significant, the fl ux density and fi eld intensity nearby the surface are larger than that in the centre of the sheets [1, 2]. And with increasing of alternating excitation frequency, the inhomogeneity of induction flux density will be extended and growing more inhomogeneous, due to the smaller skin depth and a small increase of anomalous loss in the total core losses, as shown in Fig. 1.2. Therefore, alternating eddy current loss P as functions of the peak mean alternating flux density B mamean and the alternating excitation frequency f a can be deduced as follows: limv→∞P ae (B ma_mean f a )=[2ω a (B ma_mean ) 2 /3ρμν 2 =(σπ 2 d 2 /3ρ)(f a ) 2 (B ma_mean ) (no skin effect)[W/kg] (1) limν→0 P ae (B ma_mean f a )=[4ω a (B ma_mean ) 2 /ρμν=(4σ 1/2 π 3/2 d/ρμ 1/2 )(f a ) 3/2 (Bma_mean) 2 (considering significant skin effect) [W/kg] (2) where, ω a is the angular frequency; v = 2δ

关键词： Magnetics Conferences

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Effect of Vinyl Content on Mechanical Property and Electrical Tree Initiation in Silicone Rubber 2

Effect of Vinyl Content on Mechanical Property and Electrica...

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2nd IEEE International Electrical and Energy Conference, CIEEC 2018

作者： Sui, Jiangyuan Zhang, Ling Zhou, Yuanxiang Zhang, Xinyan Cheng, Zixia Guo, Shaowei School of Electrical Engineering Xinjiang University Urumqi830047 China State Key Lab of Control and Simulation of Power System and Generation Equipment Tsinghua University Beijing100084 China State Key Lab of Electrical Insulation and Power Equipment Xi'an Jiaotong University Xi'an710049 China School of Electrical Engineering Zhengzhou University Zhengzhou450001 China Electric Power Research Institute State Grid Jibei Electric Power Company Beijing100045 China

ISBN: (纸本)9781538653913

The vinyl content in methyl vinyl silicone oil has a significant impact on the mechanical and electrical properties of reinforced silicone rubber. In this study, mechanical property and electrical tree initiation of silicone rubber were studied by comparing different vinyl contents. The results show that shore hardness, tensile strength, elongation at break, and tear strength of insulating silicone rubber material increase first and then decrease with the of vinyl content increasing from 1% to 5%. The breakdown strength and the initiation voltage of electrical tree are basically consistent with the variation of tensile strength and tear strength. Detailed discussion are presented. This work could provide data support for the practical preparation of engineering silicone rubber. © 2018 IEEE.

关键词： Tensile strength

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Non-communication Protection for Single-Phase-to-Ground Fault Feeder in Neutral Non-Effectively Grounded Distribution system

Non-communication Protection for Single-Phase-to-Ground Faul...

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IEEE General Meeting power& Energy Society

作者： Qi Jia Xinzhou Dong Shenxing Shi Xin He State Key Lab. of Control and Simulation of Power System and Generation Equipment Tsinghua University Beijing China Power Dispatching Control Center Guizhou Power Grid Co. Ltd Guiyang China

ISBN: (纸本)9781538677049

The traditional non-communication protection for distribution system is only applicable to fault feeders in neutral effectively grounded distribution system or the phase-to-phase fault feeders in neutral non-effectively grounded distribution system. For single-phase-to-ground fault feeders in the latter system, the protection will fail to operate because the magnitude of the current flow in the fault-to-ground connection is too small. To solve this problem, this paper presents a new non-communication protection compatible with the fault detection principle based on comparing the polarities of the initial voltage and current traveling waves. In this technique, when a single-phase-to-ground fault occurs, the relays which detect the fault is in the forward direction will operate based on the conventional time grading coordination at first, after one relay makes tripping decision which has the fastest time setting, the relay on the opposite side will detect the sound phase current changes in a time window to accelerate the operation. Extensive Electromagnetic Transients Program (EMTP) simulation studies with respect to a typical double end feeder system whose neutral is non-effectively grounded show that the proposed technique is able to fast and accurately remove a single-phase-to-ground fault line section from both ends.

关键词： Circuit faults Relays Acceleration Circuit breakers Wavelet transforms EMTP

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Misalignment fault detection in dual-rotor system based on time frequency techniques

Misalignment fault detection in dual-rotor system based on t...

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Society for Machinery Failure Prevention Technology Annual Conference 2017: 50 Years of Failure Prevention Technology Innovation, MFPT 2017

作者： Wang, Nan-Fei Jiang, Dong-Xiang Han, Te State Key Laboratory of Control Simulation of Power System and Generation Equipment Department of Thermal Engineering Tsinghua University Beijing100084 China

In order to improve the energy efficiency and compact structure, the dual-rotor structure including lowpressure rotor and high-pressure rotor has been widely used in aero-engine. Misalignment is one of the most common faults in dual-rotor system, which will causes malfunctions. It is a significant task for rotor dynamics personnel to monitor and defect faults in dual-rotor system. In the paper, the dual-rotor vibration signals are applied to solve the fault identification problem by utilizing time frequency techniques. Numerical simulations are carried out through finite element analysis of dual-rotor system with misalignment fault. Two signal processing tools namely Short Time Fourier Transform (STFT) and Continuous Wavelet Transform are used to detect the misalignment fault and compared to evaluate their diagnosis performance. The effect of addition of Signal to Noise (SNR) on three frequency techniques is presented. Experiments are carried out to obtain the vibration data of dual-rotor test rig and the results from the work show that the technique can be used for the monitoring of misalignment, which will have applications in the condition monitoring and maintenance of various types of rotating machinery.

关键词： Condition monitoring

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Losses Modeling Based on Domain Wall Processes and Valida-tion Considering Rotational Excitation of Electrical Steel Sheets.

Losses Modeling Based on Domain Wall Processes and Valida-ti...

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International Conference on Magnetics (INTERMAG)

On the basis of damping principle of vibration, the domain wall processes is investigated and modeled at low-to-medium frequencies in electrical steel sheets. Due to the energy dissipation chiefly descends from a micro-vortex current caused by domain wall motion, the coupled Landau-Lifshitz-Gilbert (LLG) and Maxwell electromagnetic diffusion equations are thus considered to describe the high-frequency characteristics. The overall core losses are eventually deduced in terms of separate contributions by domain wall processes and classical eddy current. Moreover, the calculation model can be extended to rotational excitation pattern. Hence, taking the typical electrical steel sheets as example, the novel core losses calculation model is analysed and compared with the total alternating core losses supplied by electrical steel sheets manufacturers and the 3-D rotating experimental core losses of sheets specimens which are carried out by using a 3-D magnetic properties testing system.

关键词： Magnetics Conferences

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A Novel Structure Design of Iron Core for power Transformers Considering Joints Forms and Magnetostriction.

A Novel Structure Design of Iron Core for Power Transformers...

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International Conference on Magnetics (INTERMAG)

作者： J. Li S. Wang H. Gao M. Liu J. Hong State Key Laboratory of Control and Simulation of Power System and Generation Equipments Tsinghua University Beijing China State Key Laboratory of Reliability and Intelligence of Electrical Equipment Hebei University of Technology Tianjin China

Body: power transformers and reactors are important devices in power transmission systems. But their cores and windings could produce vibration and acoustic noise by magnetostrictive effect, Maxwell electromagnetic stress and Lorentz force. Noise has become a bad environmental pollution source in some situations, and its vibration and noise reduction has become an urgent problem need to be solved. The shapes, materials, magnetostriction and joints forms of iron cores, the limitations of test, modeling, and experimental measurement of vibration and noise characteristic, are all the difficult reasons to analyze the vibration and acoustic noise of transformers and reactors. 1. The magnetostrictive modeling can be divided into two steps based on the magnetic field force and materials deformation, so the magnetic field force will be fed into the structural finite element with Maxwell electromagnetic force produced on the interface between the iron core and the air to calculate the deformation of the magnetic materials and to make the model more general and consistent. In order to fully verify the correctness of the model in the magnetostrictive analysis, and to ensure the simplicity of test and avoid unnecessary interference factors, the most simple magnetostriction tests will be carried out by using a single closed circle or rectangular electrical steel sheet, as shown in Fig. 1(a). The tests will measure the relationship between magnetostriction and magnetic field of different magnetic materials, different saturations, different sizes and different shapes. 2. The joint is a necessary form for the stacking of large transformer iron cores, and the main joint form is the step jiont at present. The introduction of the joints causes the magnetic force lines to flow through the different laminations and to make the local magnetic field complicated. From simple to complex process is adopted in this paper, and the verification is gradually complicated. Based on the study of a

关键词： Magnetics Conferences

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Wind farm active voltage regulation strategy of transient support improvement

Wind farm active voltage regulation strategy of transient su...

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8th Renewable power generation Conference (RPG 2019)

作者： Cui Yang Song Peng Cheng Xuekun Qiao Ying Wang Xiaosheng Liu Jingbo State Grid Jibei Electric Power Co. Ltd. Research Institute North China Electric Power Research Institute Co. Ltd. Xicheng District Beijing China Grid-connected Operation Technology For Wind-Solar-Storage Hybrid System State Grid Corporation Key Laboratory Xicheng District Beijing China State Key Lab of Control and Simulation of Power Systems and Generation Equipment Dept. of Electrical Engineering Tsinghua University Haidian District Beijing China

ISBN: (数字)9781839531248

ISBN: (纸本)9781839531255

The cumulative installed capacity of wind power worldwide has grown rapidly in recent years. Fixed reactive power control is adopted by wind turbines (WTs) to receive cycle instruction of wind farm (WF) automatic voltage control system (AVCS). It does not have active voltage regulation (AVR) capability, which reduces the reliability of power system operation. Firstly, two ways of WTs AVR which QV droop control and Vac control mode are introduced in this paper. On the basis, the problems of reactive power circulation and control points inconsistency during multi-WTs voltage regulation are discussed. The problems are solved by coordination of WTs of WF AVR strategy. WF voltage transient support capability is promoted by the strategy. Effectiveness is verified by simulation case of the proposed method.

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power and energy balance of active distribution network considering operation-control strategy

Power and energy balance of active distribution network cons...

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IEEE Conference on Energy Internet and Energy system Integration (EI2)

作者： Lin Cheng Ning Qi Lingxiao Wei Shaojun Xu Qingshi Liu State Key Laboratory of Control and Simulation of Power Systems and Generation Equipment Tsinghua University Beijing China State Grid Beijing electric power company Beijing China

With the rapid deelopment of demand-side response and active distribution network, the new method to power and energy balance is becoming more and more important. In this paper, the architecture of power and energy balance in active distribution network is proposed, which consists of three parts: load and generation forecasting, power and energy balance. Moreover, capacity-load ratio guidance is modified combined with the peak shaving potential and trusted capacity. Besides, the energy balance method considering the operation-control of distributed energy is proposed. Finally, through numerical analysis, the feasibility and practicability of the model are verified.

关键词： Planning Forecasting Load forecasting Distributed power generation Dispatching Load modeling Capacity planning

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Deep transfer network with joint distribution adaptation: A new intelligent fault diagnosis framework for industry application

arXiv

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arXiv 2018年

作者： Han, Te Liu, Chao Yang, Wenguang Jiang, Dongxiang Department of Energy and Power Engineering Tsinghua University Beijing100084 China State Key Lab of Control and Simulation of Power System and Generation Equipment Tsinghua University Beijing100084 China

In recent years, an increasing popularity of deep learning model for intelligent condition monitoring and diagnosis as well as prognostics used for mechanical systems and structures has been observed. In the previous studies, however, a major assumption accepted by default, is that the training and testing data are taking from same feature distribution. Unfortunately, this assumption is mostly invalid in real application, resulting in a certain lack of applicability for the traditional diagnosis approaches. Inspired by the idea of transfer learning that leverages the knowledge learnt from rich labeled data in source domain to facilitate diagnosing a new but similar target task, a new intelligent fault diagnosis framework, i.e., deep transfer network (DTN), which generalizes deep learning model to domain adaptation scenario, is proposed in this paper. By extending the marginal distribution adaptation (MDA) to joint distribution adaptation (JDA), the proposed framework can exploit the discrimination structures associated with the labeled data in source domain to adapt the conditional distribution of unlabeled target data, and thus guarantee a more accurate distribution matching. Extensive empirical evaluations on three fault datasets validate the applicability and practicability of DTN, while achieving many state-of-the-art transfer results in terms of diverse operating conditions, fault severities and fault types. Copyright © 2018, The Authors. All rights reserved.

关键词： Fault detection

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