|
Prospects and characteristics of fossil energy development in the near future in China and the importance of security on it’s production, storage and transportation
YAN Lu-guang1 HUANG Chang-gang1 TAN Zong-ying2 FENG Xia3
(1.Institute of Electrical Engineering,Chinese Academy of Sciences ,Beijing 100190,China ;
2. National Science Library, Chinese Academy of Sciences,Beijing 100190, China；
3.Academician Bureau of the Chinese Academy of Sciences,Beijing 100864, China)
Abstract:To guarantee the reliable and secure supply of fossile energy is one of important aspect of the energy development in China. According to the real situation and forecast, characteristics of fossil energy development in the near future in China were studied. To attach importance to the safety of production, storage and transportation of fossil energy was emphasized. The keystones are coal production safety, exploitation safety of offshore oil and storage safety, transportation safety of petroleum and natural gas on land. Some related suggestions were submitted to make farther investigation for officials and experts.
Key words: fossil energy; prospects and characteristics; safety of production; storage and transport
Rotor position estimation of PMSM based on nonlinear observer
WU Bing1, ZHU De-ming1,2, LI Ye-song1, CHENG Shan-mei1
（1. Huazhong University of Science and Technology, Wuhan 430074, China:
2. Nanjing University of Aeronautics and Astronautics Jiangsu Key Laboratory of New Energy Generation and Power Conversion, Nanjing 210016, China）
Abstract：To improve the system reliability, lower the system cost, and enhance the system applicability, the scheme of rotor position estimator of Permanent Magnet Synchronous Motor(PMSM) is proposed based on nonlinear observer. The two new state variables are constructed in the nonlinear observer based on the mathematical model of PMSM. The rotor position can be estimated through these two state variables which contain the information of rotor position. The stability of the proposed nonlinear observer is proven. Control system structure of PMSM without position sensor is given. The scheme of velocity estimation in the system is proposed. To verify the stability and feasibility of the rotor position estimator, the experiments based on TMS320F2812 have been carried out. The waveforms of rotor position, current, and velocity in different speeds are given. The experimental results show that the nonlinear observer is very effective, and the whole control system performs well over a wide speed range.
Key words: nonlinear observer; permanent magnet synchronous motor; position estimation
Study on AC-DC-AC locomotive modeling based on probabilistic harmonic current source
TIAN Yu-sheng, JIANG Qi-rong, TIAN Xu
(Department of Electrical Engineering, Tsinghua University, Beijing 100084, China)
Abstract : The AC-DC-AC locomotives’ load characteristics are very different from those of AC-DC locomotives, so it is of great significance to build a proper model of AC-DC-AC locomotive for power system safety analysis and relative power quality evaluation. On the basis of a large amount of measured data, this paper analyzes the probabilistic representation of harmonic current generated by AC-DC-AC locomotives, using an improved maximum entropy method, and a current source model is set up using the PSCAD/EMTDC software. The fundamental component, which can simulate the problems brought about by traction load to power system caused by its impact and asymmetry, is achieved from a three-level four-quadrant converter. The harmonic component is generated by a probabilistic harmonic current source with the use of MATLAB interface module, taking into consideration the effects many random factors have on harmonics. Since the harmonic current model is based on measured data, the simulation result has a better agreement with practical situation.
Key words: electric railway;AC-DC-AC locomotive modeling; probabilistic harmonic current source;
improved maximum entropy method;
Distributed generation and its impact on network loss of power system
LIU Lin，TAO Shun，XIAO Xiang-ning，LI Ying-yu
（Electric and Electronic Engineering College, North China Electric Power University, Beijing 102206, China）
Abstract : The distributed generation would have a significant impact after it has been connected to the power grid, and it has a close relationship with the transformer model, number of transformer units, location of the generator, the distributed generation capacity and operating mode. This paper came up with a simplified model under certain ideal conditions,and based on the change of the network structure before and after the introduction of distributed generation, derived the corresponding expression of the network loss. Finally, the paper analyzed the influence of the five factors on the net loss of the distribution network by using MATLAB simulation. The algorithm is simple and convenient. It provides a theoretical basis of choosing the location and capacity of distributed generation in the actual distribution network.
Key words: distributed generation; distribution network; network loss; operating mode; transformer selection
Electrical performance comparison of three inductive pulse power sources
CHU Xiang-xiang, YU Xin-jie, LIU Xiu-cheng
(State Key Lab. of Power System, Dept. of Electrical Engineering, Tsinghua University, Beijing 100084, China)
Abstract：The principles of three typical inductive pulse power sources are presented in details in this paper. On the basis of the same initial energy for inductance, simulations are done for the three topologies under the environment of Simplorer®. The parameters of the simulation are provided as a reference to implement a prototype. Two vital electrical performance indices, i.e. withstanding voltage of the main switch and the current multiplication factor, are chosen to compare the advantages and disadvantages among them. Further potential improvements are also mentioned.
Key words：inductive pulse power source; Simplorer®; electrical performance
Common mode far field radiation model & its characteristics of a flyback power supply
HE Jun-ping, JI Ke-jian, FU Qi, WANG Ru-quan
(Harbin Institute of Technology Shenzhen Graduate School, Shenzhen 518055, China)
Abstract: In this paper, a far field common mode radiation model, including equivalent driving source, radiation structure and some other key influence factors, is identified and built up for a low-power flyback power supply based on the asymmetry line antenna theory. Then the radiation characteristics of this model are analyzed by using Ansoft HFSS finite element electromagnetic software. Further more, simulation results are compared with the experiment results to verify effectiveness of the model. In the end, the radiation role of some main influence factors, such as the length of input/output cable, the impedance of AC grid, the layout of cable position and the reflect ground, are studied in detail by simulation too.
Key words: SMPS; far field electromagnetic radiation; common mode radiation model; FEM simulation
Analysis of factors influencing power and efficiency in wireless power transfer system
LI Yang 1,2, YANG Qing-xin 1,2, CHEN Hai-yan 1, YAN Zhuo 3, ZHANG Xian 1,2, XUE Ming 2
(1. School of Electrical Engineering, Hebei University of Technology,Tianjin 300130, China;
2. Tianjin Key Laboratory of Advanced Electrical Engineering and Energy Technology, Tianjin Polytechnic University ,Tianjin 300387, China;
3. China Electrotechnical Society ,Beijing 100823, China）
Abstract：RF amplifier is a key part of wireless power transfer. The power of wireless power transmission depends on the output power of RF amplifier. Impedance matching is critical for improving the output power of RF amplifier in wireless power transmission system. Equivalent impedance of wireless power transfer is presented and the influence factors on power and efficiency is analyzed. Five methods to change the impedance are proposed to improve the power and efficiency based on the impedance characteristic. In the end, the effect of five parameters of impedance matching to power and efficiency of wireless power transmission is analyzed through experiment, which provides reference for the further design to improve the power and efficiency in wireless power transmission system.
Key words: wireless power transmission; resonance coupling; maximum efficiency; impedance matching
Optimization of 12-pulse autotransformer rectifier units and design of filter inductor
JIANG Lei-lei, CHEN Qian-hong, MAO Lang
(Jiangsu Key Laboratory of New Energy Generation and Power Conversion, Nanjing University of Aeronautics & Astronautics, Nanjing 210016,China)
Abstract：Because of its simple structure, high reliability and strong overload capacity, multi-pulse rectifier is widely used for the electronic facilities applied in the aircraft. Related aviation standards require that the THD of input current of AC electrical equipments must be less than 10%. However, theoretical value of 12-pulse ATRU input current THD is 15.2%, and it doesn’t meet the related aviation standards. To satisfy the standards, AC and DC inductor are added to reduce input current THD so that the original method can meet engineering requirements. In this paper the expression of input current harmonic which provides a theoretical basis for AC and DC inductor is derived. This paper also uses Fe-Co-V alloy which has high saturation flux density to reduce system’s volume and weight. At last, this paper designed a 4kW P-type 12-pulse auto-transformer rectifier whose input current THD satisfies the aviation standards.
Key words: 12-pulse;ATRU;Fe-Co-V;inductor;THD
Extraction and implementation of differential mode inductor in annular EMI filter
ZHU Ye, WANG Shi-shan
(Jiangsu Key Laboratory of New Energy Generation and Power Conversion (Nanjing University of Aeronautics and Astronautics), Nanjing 210016, China)
Abstract: Planar EMI filter provides an effective approach for miniaturization, modularization and integration of power electronics system. Differential mode inductor in planar EMI filter is realized by the leakage inductance between common mode inductors. As the important role in restraining differential mode noise of conducted EMI, differential mode inductance has to be precisely calculated and designed. Analysis equation for differential mode inductance in annular EMI filter is solved and its numerical model is established in this paper. The comparison of these two kinds of computing methods is then given by calculated results and measurement. Besides, major factors which have great influence on leakage inductance are analyzed and approaches of adjusting leakage inductance are summarized. Based on theoretical analysis and experiment, the numerical model of calculating leakage inductance is revealed to be precise, and approaches of adjusting leakage inductance is confirmed to be effective. The theoretical system in this paper provides a beneficial instruction for realization of planar EMI filter’s differential mode inductor.
Key words: EMI filter; differential mode inductance; leakage inductance; numerical model
Analysis of influence on protective relaying of enterprise’s power system at power switching
ZHOU Xue-song, CUI Li-qiang, MA You-jie, Zhou Jin-cheng, Yang Ya-guang
(Tianjin Key Laboratory for Control Theory & Applications in Complicated Systems (Tianjin University of Technology), Tianjin 300384, China)
Abstract: When there is a switching action, it will have the impact on power system including voltage sag and impulse current. And if the impact is too large, it can cause the action of the protective relaying equipments. In this paper, the process of power transfer is theoretically studied; and the mathematical expressions for both residual voltage and impulse current are given. The paper analyzes the relay protection types likely to false operate when the power switches, as well as its reasons. Then the paper put forward some measures to make fast switch device cooperates with protective relaying. In these ways the impact of power switching will be decreased, and the false tripping of protective relaying can be prevented. Finally the success rate of power switching will be increased, and the reliability of power supply can be ensured.
Key words: fast switch device; power switching; protective relaying; voltage difference; impulse current
Axial vibration analysis of transformer active part under short-circuit
LI Yan, ZHOU Wei, JING Yong-teng, HAN Fang-xu
(Research Institution of Special Electrical Machines, Shenyang University of Technology, Shenyang 110870, China)
Abstract: Based on the mass-spring system mathematical model for the axial vibration of power transformer winding and its nonlinear characteristics，a calculation model is reasonably simplified. In this paper, according to a DFP1-240MVA/500kV type power transformer, a model simulation system of the vibration of a power transformer’s active parts vibration which compose of core, windings, spacers, tensile plates and clamp frames is established. The analysis method of power transformer active part is given, and the natural frequencies and vibration modes in different levels of axial pre-compression of active part and windings are calculated. The relations between the changes of axial pre-compression and axial vibration natural frequencies on transformer are investigated. Meanwhile, the active part vibration caused by axial dynamic short-circuit forces of windings under short-circuit conditions is analyzed. The analysis results indicate that the short-circuit force in 50Hz and 100Hz is existed and if the natural frequency of transformer is close to them and their harmonics, the resonance will happen. So, the displacement of vibration will be large, and the structure stability of transformer will be reduced.
Key words: power transformer; axial vibration; active part; pre-compression; natural frequency; short-circuit force
Research on pitch control strategy based on power and loads coordination
HE Zhou-yao1, DUAN Bin1, Su Yong-xin1 Pan Jia-qi1, LONG Xin2
(1. Xiangtan University, Xiangtan 411105, China; 2. Hara XEMC Wind Power Co. Ltd, Xiangtan 411105, China)
Abstract: The ordinary pitch control strategy is that the pitch achieves the optimum torque when turbines start-up, and achieves constant power control while wind speed is above the rated. Generally, loads change caused by the variable pitch process will not exceed the threshold range under normal condition. However, load threshold may be decreased when equipments become ageing and fatigued, which do harm to wind turbine’s security. Based on the establishment of mathematical model of wind turbine, the internal relationship between pitch angle and loads is analyzed, and pitch control strategies of power and loads coordination are proposed in the paper. When wind turbines are under overload operation, we can change ordinary pitch control strategy and adjust the pitch angle to ensure the operation of wind turbine’s safety and stable. Using GH Bladed modeling and simulation, the feasibility and effectiveness of control strategy is proved by the simulation results.
Key words: variable pitch control; loads; power control; coordinated control
Typical power supply mode planning for urban power distribution grid based on cost-benefit analysis
XU Xiao-fang1，WANG Cheng-min2，BAI Yu-dong2，Wang Pu2，Xu Fang-min1，Chen Dong1，Zhang Lin1，Yuan Yi-ming1
( 1. Pudong Power Supply Company，Shanghai 200122，China；
2. Shanghai Jiaotong University Electric Engineering Department，Shanghai 200240，China)
Abstract: An optimization model based on cost-benefit analysis is built in this paper by considering influence of branch lines in mid-voltage lines and load distribution on planning, which takes voltage level planning in line with substation planning and mid-voltage line planning as a planning unit for power supply mode with the known boundary conditions of the planning unit. The planning scheme based on blocks can be obtained by the solution of planning units. By the application in one residential district in Shanghai, this method is proved to be valid and effective.
Key words: distribution grid planning; power supply mode; cost-benefit analysis; planning unit
Harmonic source modeling based on generalized regression neural network
XIE Kang, YANG Hong-geng, ZHANG Yi,HUANG Jing
(School of Electrical and Information, Sichuan University, Chengdu 610065, China)
Abstract: A generalized regression neural network (GRNN) is proposed for harmonic source modeling based on measurement. The concept of voltage operating-degree and power load-degree is introduced; and the nonlinear mapping between them and each order of harmonic current amplitude is established with GRNN. In the model, the network smooth coefficient is optimized, and the coefficient that is related to the minimum detection error is selected for network training. The load-degree-current characteristics in different operating conditions are studied,and the harmonic amplitude is estimated by the two degrees. This model can be used for harmonic emission assessment and condition monitoring of harmonic load, and the harmonic current can be calculated according to the relationship between load-degree and harmonic current. Take a middle-frequency furnace based on measurement as an example, the results show that error of the model is very small. The proposed method has the advantages of few artificial parameters, short training time and high precision, and is an effective technique for building up harmonic source model.
Key words: power quality; harmonic source modeling;GRNN; power load-degree; measurement
Designing PI controller in thyristor controlled interphase power controller for improving transient stability of power system
LI Juan1,YAN Nai-xin 1, ZHOU Jian-ying1,YAN Nai-bo2,WU Han-bo3,WANG Kun1,CHEN Xiao-jin1
(1. College of Electrical Engineering，Northeast Dianli University，Jinlin 132012，China；
2. The Hulunbeir Power Bureau, Hulunbeir 021000，China；3.The Liaoyuan Power Supply Co., Liaoyuan 136200, China)
Abstract： Based on fundamental structure and power flow control theory of Thyristor Controlled Interphase Power Controller (TCIPC), a mathematical model of relationship between the branch current of TCIPC, port voltage and controlled transmission power in the dq0 coordinates is established. According to the power-angle characteristic of TCIPC, the mechanism of regulating the inductive branch parameters of IPC to improve the transient stability is explained. Based on the relationship between inductance parameters and tie-line transmission power, the current is selected as the synchronic signal to trigger the thyristor and the expected value of inductance is selected as reference signal, then PI fixed impedance controller of triggering angle correction is designed. Simulation of a simple system model with IPC is set up. Simulation results show that controlling the inductive parameters of TCIPC can improve the transient stability of the power system with TCIPC.
Key words: thyristor controlled interphase power controller; PI controller; fixed impedance control; transient stability
Integrated models of short-term wind speed forecasting based on wavelet transform
CHEN De-sheng，LI Pei-qiang，LI Xin-ran，DE Wei，XIAO Yuan-yuan，LIU Qian-yong
（College of Electrical and Information Engineering, Hunan University, Changsha 410082, China）
Abstract: Aiming at the characteristics such as non-stationary、non-linear and heteroscedasticity of wind speed sequence, this paper firstly adopts db3 wavelet to add multi-resolution wavelet decomposition to original wind speed sequence and single branch reconstruction to its parameters, and as a result, approximate wind speed sequence and detailed wind speed sequence on different frequency bands representing internal characteristics of wind speed sequence are acquired. Secondly, this paper builds time-sequence master model for wind sequences in different frequency ranges, adopts LM test to analyze residual series of the established model, and eventually come up with the idea that ARCH and GARCH model can be used to improve the exsiting methods, so the change pattern of wind speed is well reflected. Lastly, a practical example is used to test the improved method which has proved that the method in this paper is an effective way to improve prediction accuracy.
Key words: heteroscedasticity; wind speed sequence; wavelet transform; prediction accuracy
Calculation of theoretical research on entire parameters of transmission line based on sub-segment parameters
CUI Yu-jia1, ZHOU Ze-hong2, LIU Xiao-quan1, WU Hao 3, YAO Chen-guo3
（1. Infrastructure of Chongqing Electric Power Company, Chongqing 400014, China；
2. Chongqing Shizhu Power Supply Company, Chongqing 409100, China;
3. State Key Laboratory of Power Transmission Equipment ＆ System Security and New Technology，Chongqing University, Chongqing 400030, China）
Abstract: It is essential for the power system to acquire frequency transmission line parameters accurately and timely, otherwise inaccurate parameters may cause more serious effects or even significant power accident. At home and abroad, line parameters are usually calculated using the traditional formula. Using sub-parameters to calculate the entire parameters in middle and short transmission line construction or operation, and based on an example of a 220kV double circuit transmission line, this paper proved that it is a good application on solving the positive sequence parameters through traditional method, although there is a large error in solving the zero-sequence parameters. To improve the accuracy of the calculation on zero-sequence parameters, this paper put forward a new method on line parameters calculation and its equivalent circuit model of steady-state for the first time. That is firstly,the test on segments of the transmission line parameters is carried out, and then the entire parameters through scientific calculations are obtained, thus providing a fast and effective way to calculate transmission line parameters. Through calculating the example above, this paper proved that the error is smaller on solving the zero-sequence parameters through this new model compared to the traditional model, and this new method can be used for the middle and short transmission line parameters measurement. Moreover, some improvements of the new model are given.
Key words: transmission line; parameter measurement; subsection measure
Research progress in Lithium-ion flow battery
CHEN Yong-chong 1，WU Ming-xiao1,2 ，REN Ya-kun1 ，KANG Li-bin1 ，LI Yan-ju1,2 ，HAN Li1 ，LIN Dao-yong2 ，WANG Qiu-ping2
(1. Institute of Electrical Engineering ,Chinese Academy of Sciences, Beijing 100190, China；
2. Beijing HAWAGA Power Storage Technology Company Ltd. , Beijing 100085，China)
Abstract: Lithium-ion flow battery is a new kind of battery using the rechargeable battery technology which combines the advantages of lithium-ion battery and redox flow battery. Lithium-ion flow battery has relatively high energy density and low cost, and the power output and the energy storage are independent of each other. This paper introduced the research background, the operating principle and the primary structure of the lithium-ion flow battery. In addition, the research status at home and abroad was reviewed in detail and the key technologies needed for break-through were summarized. The research development of the lithium-ion flow battery is possible to open a low-cost and safe eco-technology route for the application as the energy storage system for the new energy grid..
Key words:lithium-ion flow battery; energy storage battery; new energy grid; principle; review
Design and fabrication of solar cell LED lighting system
GUO Feng-yi1，ZHOU Kun1, JIANG Li-li1, ZHANG Feng-long1, TU Yu2
(1. Faculty of Electrical and Control Engineering，Liaoning Technical University, Huludao 125105,China;
2. Fushun Ming Group Co., Ltd. Electric Locomotive Factory, Fushun 113004, China)
Abstract: Considering the development of solar energy, the paper designs a new solar cell LED lighting system. It takes a cheap ATMGA16 as the intelligent controller. The proposed energy management controller effectively enhances the system performance. The controller uses the maximum power point tracking (MMPT) scheme to precisely control the battery charge. Automatic switching between battery and utility provides power supply of the lighting system. According to the actual intensity of the sun, the controller and TPS61042 accurately control the LED brightness. The experimental results show that the system controls accurately, conversion efficiency is high, and it works stably.
Key words: solar energy; ATMEGA16; battery charging and discharging; LED lighting
Design and simulation of enhanced two-transistor forward power converter
ZHU Li1，HUANG Hui-xian2
(1. Hunan College of Information, Changsha 410200, China; 2. Xiang Tan University，Xiangtan 411105, China )
Abstract: As one kind of the modern electric power converters, two-transistor forward converter has many attractive characteristics, such as low switching voltage stress and high reliability. The paper made analysis of the process of the improved circuit and the specific problems encountered in the applications, and gave the solutions of the problems. Compared with the traditional circuit, the control circuit of the improved converter has been modified and simplified, namely,one of the two main switches is working at ZCS state, synchronous rectifier circuit can overcome the effects of the dead zone and light load loop current, and the circuit's overall performance has been enhanced. Based on the simulation results, a 15V/300W power supply was developed during the experiment. The experiment proved that the power supply is stable and reliable.
Key words: two-transistor forward converter; Synchronous Rectification; high efficiency; simulation
Low-power contactless power transfer system based on loosely coupled transformer
YU Jian-ge, LV Gan-yun, WU Zhang-yong, QI Li-peng
(College of Mathematics, Physics and Information Engineering, Zhejiang Normal University, Jinhua 321004, China)
Abstract: A low-power contactless power transfer (CPT) system is designed and completed. A mutual inductance model is used to analyze the loosely coupled transformer and to compensate the primary and secondary winding.The primary and secondary winding are made of PCB spiral coil with high permeability magnetic core. The inductor coil with core geometry and physical parameters is given. The energy is transferred by high-frequency square-wave between the primary and secondary winding.Finally the circuit diagrams of the whole system are given. Results show that when the distance between the primary and the secondary winding coil is less than 5mm, the efficiency of power transfer is high and the system can be used for charging small power device such as mobile phones, etc.
Key words: loosely coupled transformer; low power; contactless power transfer; PCB spiral coil; high-frequency square-wave
|
