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International Conference on Electrical Machines and systems (ICEMS)

作者： Liu Shu Liu Jianzheng Zhao Zhengming Yuan Liqiang Bai Hua Zhang Haitao Department of Electrical Engineering and Applied Electronic Technology State Key Laboratory of Control and Simulation of Power System and Generation Equipment Tsinghua University Beijing China

This paper presents an accurate flux observer used in distributed multi-processor (DMP) adjustable speed drive systems. The stator flux linkage is estimated with a full-order observer, while the rotor speed is identified by using Lyapunov theorem. In order to improve the system performance in a wide speed range, the stator resistance is estimated simultaneously. In this paper, the structure of the DMP system, the principle of the full-order observer and the method for identifying the rotor speed and state resistance are all described in details. Relevant simulation results based on MATlab/SIMULINK are given to prove the performance of the method. Experiments of a real system also verify the feasibility of this scheme

关键词： Variable speed drives Stators Observers control systems Mathematical model Couplings Torque control Optimal control Sampling methods Pulse width modulation

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A hybrid converter for energy management of EV drives

A hybrid converter for energy management of EV drives

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

作者： Teng Hu Lie Xu Lin Qiu Yongdong Li Xuejun Han Department of Electrical Engineering Northeast Dianli University Jilin China State Key Lab. of Control and Simulation of Power System and Generation Equipment Tsinghua University Beijing China

This paper proposed a novel hybrid power converter topology based on cascaded H-bridge (CHB) and matrix converter (MC) in order to improve the performance of the conventional energy management systems in EV/PHEV application. The power demand by the load is supplied by the generator and batteries, which are connected to the primary winding of the medium frequency transformer (MFT) by the matrix converter and the cascaded H-bridge respectively. The power transfer between the sources and load can be controlled and isolated by using the MFT. The cascaded H-bridge, as the energy control unit, can be used to balance the voltage/SOC of battery packages individually, significantly improve the modularity, stability and safety of EV system.

关键词： Batteries Matrix converters Energy management system-on-chip Topology Voltage control Windings

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An adaptive wind power smoothing method with energy storage system

An adaptive wind power smoothing method with energy storage ...

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IEEE General Meeting power& Energy Society

作者： Hanchen Xu Can Wang Chao Lu Zhigang Lu State Key Laboratory of Control and Simulation of Power System and Generation Equipment Tsinghua University Beijing China Electric Power Research Institute of China Southern Power Grid Guangzhou China

The random and intermittent nature of wind power (WP) makes the integration of large-scale wind farms into power system problematic. The energy storage system (ESS) is an effective means to smooth the WP. This paper presents a novel Kalman filter (KF) based adaptive wind power smoothing method to determine the power output of an ESS. ESS capacity can be significantly reduced by adjusting the parameters of KF adaptively according to the WP fluctuation. Meanwhile, a fuzzy logic controller is introduced to manage the remained energy level (REL) of the ESS. By considering the current WP fluctuation, the REL and the power output of the ESS together in the controller, the REL can be successfully managed to a reasonable range without deteriorating the WP fluctuation. A test case based on data from an actual wind farm validated the effectiveness of the proposed method.

关键词： Fluctuations Wind power generation Energy storage Wind farms Kalman filters Fuzzy logic Smoothing methods

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Numerical simulation of surface discharge in oil paper insulation based on finite element method and cellular automata

Numerical simulation of surface discharge in oil paper insul...

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22nd International Symposium on High Voltage Engineering (ISH 2021)

作者： J. Chen Y. Zhou Y. Zhang X. Huang L. Zhang State Key Laboratory of Control and Simulation of Power System and Generation Equipment Department of Electrical Engineering Tsinghua University Beijing People's Republic of China

Surface discharge of oil paper insulation is one of the insulation defects in converter transformers. However, the mechanism of surface discharge in oil paper insulation remains unclear. A novel method of surface discharge in oil paper insulation based on finite element method (FEM) and cellular automata (CA) was proposed to study the mechanism and fractal characteristics. Firstly, the needle-plate electrode without normal component of electric field density was adopted as the geometric model, on which the unstructured triangular mesh generation was performed. Then, the FEM is applied to compute the distribution of potential, electric field and charge in the simulated field, which performed better than finite difference method (FDM) in accuracy and complexity of computation. Finally, the CA model was adopted to simulate the development of surface discharge with the electric field threshold. The results indicated that the numerical simulation model based on FEM-CA can simulate the dynamic process and fractal characteristics of surface discharge in oil paper insulation. According to the fractal dimension curve, the surface discharge can be obviously divided into three stages: inception, propagation and flashover. With the increase of applied voltage, the fractal dimension of surface discharge increases in inception stage, then decreases in propagation stage, and finally increases in flashover stage.

关键词： cellular automata electric fields electrodes finite difference methods finite element analysis flashover fractals mesh generation power transformer insulation surface discharges transformer oil

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Analysis of foundation grounding system buried in a horizontal multilayer soil by means of the fictitious conductivity concept

Analysis of foundation grounding system buried in a horizont...

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作者： Zou, J. Lee, J.B. Chang, S.H. Zhang, B. He, J.L. Ji, Y.F. State Key Lab. of Control and Simulation of Power Systems and Generation Equipment Department of Electrical Engineering Tsinghua University Beijing 100084 China Electrical Environment and Transmission Group Korea Electrotechnology Research Institute Changwon 641600 Korea Republic of

The theoretical model for the analysis of grounding system encased in the foundation region in a horizontal multilayer soil is presented. By means of fictitious conductivity concept, the effects of foundation are replaced by a set of equivalent current sources. The analysis of grounding system can be carried out by combining the moment method with additional equivalent current sources. The main advantage of the proposed approach is that it can be linked with the existing codes easily. The results are compared with those found in the literature and obtained by other popular software. © 2007 IEEE.

关键词： Electric grounding

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Traveling waves based fault line selection using sparse representation

Traveling waves based fault line selection using sparse repr...

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International Conference on Advanced power system Automation and Protection (APAP)

作者： Wen Xu Shenxing Shi Xinzhou Dong Guangmei Zhang State Key Laboratory of Control and Simulation of Power System and Generation Equipment Tsinghua University Beijing China Southern Power Grid Guizhou Liupanshui Power Supply Bureau Guizhou China

ISBN: (数字)9781728117225

ISBN: (纸本)9781728117232

Traveling wave method has been proved to be effective in fault line selection of power distribution system with the neutral non-effectively grounded. However, it can be easily disturbed by non-faulty traveling wave when selecting the line. For this reason, this paper proposes a new traveling wave line selection method based on sparse representation, in which current traveling wave signals are measured for the selection task. The algorithm of selection is based on the idea that all non-zero terms in the sparse coefficients of the measured signal are found to be associated with training samples from a single class, and the test samples can be easily assigned to the class. This makes it possible to distinguish between the non-faulty traveling wave and the real fault traveling wave.

关键词： Circuit faults Dictionaries Grounding Mathematical model Interference power distribution Integrated circuit modeling

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Stability Analysis and Braking system Design of Icebreaker Propulsion system Based on 3L-NPC Inverter

Stability Analysis and Braking System Design of Icebreaker P...

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Smart power & Internet Energy systems (SPIES), International Conference on

作者： Nianzhou Liu Nan Fu Pengfei Xie Wenfeng Long Kui Wang Yongdong Li Science and Technology on Ship Integrated Power System Technology Laboratory Wuhan Institute of Marine Electrical Propulsion Wuhan China State Key Lab of Control and Simulation of Power System and Generation Equipment Tsinghua University Beijing China

The icebreaker is important in the polar scientific investigation and resource exploration. There will be pulse and periodic load during the continuous icebreaking process, which may affect the propulsion system of the icebreaker. This paper mainly analyzes the effect of the impact load on the three-level neutral point clamped (3L-NPC) inverter with diode front-end, and demonstrates the relationship between the impact load and the feedback energy. Moreover, the choice of the resistance of the braking resistor is briefly discussed. The simulation results are given at last, which verify the rationality and correctness of the theoretical analysis.

关键词： Resistors Resistance simulation Energy Propulsion Inverters Stability analysis

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Study on Over-Voltage of 220 kV Transformer＇s Neutrals and Protection Strategy

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Journal of Energy and power Engineering 2011年第11期5卷 1102-1108页

作者： H.P. Yu S.M. Chen P.C. Yang H. Yin G.L. Wu State Key Lab of Control and Simulation of Power Systems and Generation Equipments Department of Electrical Engineering Tsinghua University Beoing 100084 China Chongqing Electric Power Research Institute Chongqing 401123 China

In order to limit short-circuit current and satisfy the need of relay setting, only part of the 220 kV power transformer is grounded, so on the neutrals of ungrounded transformers will appear the over-voltage. Currently the value of over-voltage on transformer neutral point and the corresponding protection strategy is based on theoretical formula. This article uses the PSCAD/EMTDC software to calculate the over-voltage on the neutral point of 4 ungrounded power transformers in Chongqing 220 kV power grid. The result shows that the power frequency transient over-voltage on the neutrals may reach 178 kV. If the single-phase grounding fault occurs in ungrounded power system, the power frequency over-voltage on the neutrals will be more serious and rise to 138.6 kV. Non-full phase operation may cause serious ferro-resonance over-voltage on the neutrals of no-load transformer, which may last for seconds and may rise to 723.7 kV, causing serious threat to the transformer neutrals and line-side equipment. The article also studies the gap parameter which should be taken on the neutrals of 220 kV transformers at the end.

关键词： Neutral point power transformer arrester gap power frequency over-voltage lightning over-voltage.

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Optimization of LNG Terminal Reserve Planning for Combined Gas and Electricity system

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Energy Procedia 2017年 105卷 3332-3338页

作者： Gang Chen Qinzhe Liu En Lu Qixin Chen Guangdong Provincial Electric Power Dispatching Center Yuexiu District Guangzhou Guangdong Province 510600 China State Key Lab of Control and Simulation of Power System and Generation Equipment (Department Electrical Engineering Tsinghua University) Haidian District Beijing 100084 China

Considering the effect of LNG supplying risk on the combined gas and electricity system's operation under the multi-gas-source supply background, the optimization planning model of the combined system's LNG reserve is developed in this paper. The optimization objective of this model is minimizing the annual cost of combined system, considering operation simulation of several typical scenarios along 52 weeks in a whole year and the annualized investment of LNG tanks. The operation objective of each scenario is determined by LNG's arrival and the operation mode of LNG terminals. A test system of IEEE-39 test system and Belgian 20-node system is formulated. The optimal LNG reserve of the test system is solved, and the effect of load level and operation mode on the reserve planning is also analyzed.

关键词： Combined gas and electricity system LNG supply Reserve planning Natural gas system Operation mode

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Study on High Impedance Grounding Fault Protection for Personal Safety Guard in Distribution Grid

Study on High Impedance Grounding Fault Protection for Perso...

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International Conference on Advanced power system Automation and Protection (APAP)

作者： Kun Liu Xin Cui Bin Wang Xinzhou Dong Dispatching and Controlling Center of Guangdong Power Grid Key Lab for Power System Protective Relaying Real Time Digital Simulation of Guangdong Power Grid Guangzhou China Tsinghua University Key Lab of Control and Simulation of Power Systems and Generation Equipment Beijing China

ISBN: (数字)9781728117225

ISBN: (纸本)9781728117232

In recent years, human electric shock accident caused by line fault of distribution system has happened all over the world. This kind of problem of high resistance grounding fault safety is becoming more and more the attention of the researchers. In this paper, typical arc high resistance grounding fault model is established to simulate the human electric shock accident and the line fell to the ground condition. The transient- state and steady-state fault characteristics of high resistance grounding fault are analyzed in the neutral point grounded through a small resistance grounding system and the resonant grounding system. The above analysis has laid a good foundation for the establishment of an effective fault detection method for high resistance grounding and the realization of human electric shock protection.

关键词： Grounding Immune system Resistance Harmonic analysis Transient analysis Electric shock Steady-state

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