Suggestions to strengthen development and utilization of coal and coalbed methane in Xinjiang
YAN Lu-guang, ZHAO Zhong-xian, WU Cheng-kang, CHEN Jun-wu, FEI Wei-yang,
ZHOU Xiao-xin, DAI Jin-xing, CAI Rui-xian, LIU Jia-qi, XIA Xun-cheng, ZHOU Feng-qi, CHEN Yong, WU Jia-chun, WANG Jun-min, GAO Zhuang, LV Shao-qin, CHEN Xiang-sheng, HU Guo-yi, SUN Yu-han, HU Wen-kang, ZHAO Dai-qing, HUANG Chang-gang, MA Yang,
LIU Feng-song, SHEN Yi-min
(Academic Divisions of Chinese Academy of Sciences, Beijing 100864, China)
Abstract: During the first half of 21st century, to establish the sustainable development system of energy in China it is necessary to change the primary energy structure with significant reduction of the fossil energy percentage and enhance the percentage of renewable. Xinjiang is a region abundant both in non-hydro renewable and fossil energy resources. It is necessary to raise its position on Chinese energy development and to become an important integrated energy base in future. Xinjiang is abundant in coal resource too. Its development and utilization are on good groundwork, but up to now it mainly satisfies its own requirements for social and economic development in Xinjiang only. It has not been planned to be an important coal base of the country yet. 
Academic Divisions of Chinese Academy of Sciences decided to organize academicians and experts to work with consultation study on “Study on Development and Utilization of Coal and Coalbed Methane and Integrated Energy Base in Xinjiang”. Study were divided into 5 subjects:1. resources of coal and coalbed methane in Xinjiang and its development prospect; 2. status of Xinjiang coal in China energy development; 3. development and utilization of Xinjiang coal－output of electricity and export from Xinjiang Uygur Automonous Region to outside; 4. to promote development of coal-chemical industry in Xinjiang in steady steps; 5. exploration, development and utilization of coalbed methane in Xinjiang.
　  In this paper the study results were presented briefly and main suggestions were included. 5 Refs. In Chinese.
Key words: Xinjiang; coal; coalbed methane; development; utilization
 // Adv. Tech. of Elec. Eng. & Energy, 2009, 28(4). 1—5.

Control strategy of two-stage matrix converter under unbalanced input voltages
LI Gang, SUN Kai, HUANG Li-pei
(State Key Lab of Security Control and Simulation of Power Systems and Large Scale Generation Equipments, Tsinghua University, Beijing 100084, China)
Abstract: Two-stage matrix converter (TSMC, also named indirect matrix converter) is a novel topology of matrix converters, which is a direct three-phase AC to AC power conversion device. It has a real DC link, but without energy-stored capacitor or inductance. Input voltage unbalance in the source of TSMC can immediately reflect to the output side and lower its performance. In order to reduce the effect of input voltage unbalance, a compensation method based on instantaneous reactive power theory is proposed in this paper. Under unbalanced input voltages, the active power of input side is controlled as constant. The positive and negative sequence components of the unbalanced input voltages are calculated and the input current reference space vector is constructed. The rectifier and inverter can use space vector PWM algorithms respectively. The output performance of TSMC can be stabilized. The experimental results show the proposed method can reduce the harmonics of input and output currents so as to improve the performance of TSMC. 8 Refs. In Chinese.
Key words: two-stage matrix converter; unbalance; instantaneous reactive power
 // Adv. Tech. of Elec. Eng. & Energy, 2009, 28(4). 6—9.

Research on secondary arc current under different line model
YIN Zhong-dong¹, ZHOU Li-xia¹, XIAO Xiang-ning¹, ZHENG Zheng²
(1. Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control under Ministry of Education (North China Electric Power University), Beijing 102206, China;
2. Xingtai Power Supply Corporation, Xingtai 054000, China)
Abstract: In the Extra High Voltage (EHV) transmission system, the transient single-phase to ground faults are the most frequent to occur. Even after the opening of breakers in the two sides of the fault line, an induced current still exists in the arc because of the electrostatic and the electromagnetic coupling from the other two sound phases. Along with the raise of the voltage grade, the influence of the secondary arc becomes more and more, and may probably lead to the failure of the re-closing if the secondary arc is not extinguished promptly. In this paper, the dynamic secondary arc model (including recovery voltage and the secondary arc current) in single-phase asymmetric breaking is established based on the distribution parameters of EHV long-line. The method of twice-mode transformation is adopted to calculate the steady-state value of the secondary arc current and recovery voltage. Furthermore, the affects of different overhead line models on the secondary arc current are also analyzed through the real time digital simulation. 11 Refs. In Chinese.
Key words: secondary arc current; recovery voltage; EHV transmission system; overhead line model; twice-mode transformation
 // Adv. Tech. of Elec. Eng. & Energy, 2009, 28(4). 10—13.

Voltage/VAR optimal control based on switched system and implementation in Shenzhen grid
WANG Zhe, CHEN Ying, MEI Sheng-wei, LI Rui
(Department of Electrical Engineering, Tsinghua University, Beijing 100084, China)
Abstract: A practical voltage / VAR optimal control strategy based on the switched system theory has been proposed in this work. According to the different control objectives, voltage / VAR optimal control problem could be decomposed into two subsystems: to improve the voltage quality and to reduce the total line loss. The mathematical optimal control model for each subsystem as well as the inter-switch rule between them are detailed, thus the complete voltage / VAR control algorithm can be established. The proposed control algorithm has been implemented in the power grid of the Shenzhen, which is a typical urban power grid in China. The results of the field test show that the proposed control strategy can significantly improve the static voltage quality of the power system, and effectively reduce the network losses at the same time. 12 Refs. In Chinese.
Key words: switched system; voltage/VAR optimal control
 // Adv. Tech. of Elec. Eng. & Energy, 2009, 28(4). 14—18.

A sensorless vector control method for MW level permanent magnet synchronous generator
WANG Ling-xiang¹, ZHANG Xing¹, ZHANG Chong-wei¹, YANG Shu-ying¹, CAO Ren-xian²
(1. Hefei University of Technology, Hefei 230009, China;
2. Hefei Sungrow Power Supply Co., Ltd, Hefei 230088, China)
Abstract: Aimed at the application of MW level direct-drive permanent magnet synchronous generator (PMSG) wind power generating system, one sensorless vector control scheme based on phase-locked loop (PLL) and mode reference adaptive system(MARS) is proposed in this paper. The method uses the software PLL (SPLL) model to confirm the position of the stator voltage vector. On that basis, using the mathematical model of PMSG and the theory of MARS, a rotor position orientation controller is established. The proposed scheme used in the MW level wind power PMSG control system has been validated by experiments on a lab prototype platform. The experimental results show that the proposed scheme is easy to implement, and the system has good robustness and fast dynamic response in the possible running speed scope of motor, thereby verifying the accuracy and feasibility of that control scheme. 7 Refs. In Chinese.
Key words: PMSG; MARS; vector control; sensorless; PLL
 // Adv. Tech. of Elec. Eng. & Energy, 2009, 28(4). 19—22.

Study of fault line detection based on rough set neural network for distribution network
PANG Qing-le
(School of Information & Elec. Eng., Shandong Institute of Business & Technology, Yantai 264005, China)
Abstract: To overcome the shortcomings of the longtime training and the complicated structure in the neural network based single phase to ground fault line detection method for distribution network, a rough set neural network based fault line detection method is presented. A lot of zero sequence current signals of feeders are obtained in many single-phase-to-earth fault experiments by using the ATP-EMTP simulation and all kinds of steady state features and transient fault features are extracted from zero sequence current signals through wavelet transform and fast Fourier transform. These fault features are taken as condition attributes and fault states as decision attribute and the information system is established. Then by use of attribute reducing and value reducing based on rough set, the information system is reduced and the reduced fault features are taken as inputs of neural network and the reduced samples as training samples of neural network. The neural network model trained can realize fault line detection. The simulation and field verification results show that the method reaches higher training speed and lower error rate. 10 Refs. In Chinese.
Key words: distribution network; fault line detection; rough set theory; neural network
 // Adv. Tech. of Elec. Eng. & Energy, 2009, 28(4). 23—26.

Research on AGC regulation simulation for interconnected two-area hydro power system
WEN Bu-ying¹,  LIN Li-qing²
(1. College of Electrical Engineering, Fuzhou University, Fuzhou 350108, China
2. Fujian Shuikou Hydropower Generation Co, Ltd, Minqin 350800, China)
Abstract: The connected between areas is more close with the electrical power network’s developing. It is very important to study for the Automatic Generation Control (AGC) regulation of the interconnected power systems. In this paper, the traditional AGC regulation simulation model of interconnected two areas power system is improved, and a new AGC regulation simulation model of the interconnected two-area hydro power systems is proposed, and a particle swarm optimization algorithm is used to optimum its parameters of the integral gain. The new model can consider the effect of the nonlinearity characters, such as the governor dead band and the regulating rate of the units. Through the simulation studies on several AGC regulating examples of the interconnected two-area hydro power systems, the results show that the new model can provide good AGC regulating performances, and this method is effective.
Key words: automatic generation control; hydro-hydro interconnected power system; nonlinearity character;  particle swarm optimization; simulation model

Full-bridge boost mode DC-AC converter with high frequency link
CHEN Yan-hui, CHEN Dao-lian
(Power Electronics & Drives Research Institute, Fuzhou University, Fuzhou 350108, China)
Abstract: Full-bridge boost mode DC-AC converter is proposed based on Full-bridge Boost Mode AC-AC converter with high frequency link. The input cycloconverter in Full-bridge Boost Mode AC-AC converter is changed into high frequency inverter and a flyback energy feedback circuit is connected between input voltage and output voltage. This kind of inverter is constituted of input filter, storage inductor, high frequency inverter, high frequency transformer, output cycloconverter, as well as output filter. The circuit topology, control strategy and steady principle properties are deeply investigated. The design criteria for the key circuit parameters and simulation result are given. Proposed converter is suitable for fields such as low input current ripple, high reliability during short load, large output power and small volume and light weight. 4 Refs. In Chinese.
Key words: DC-AC converter; high frequency link; boost mode; flyback energy feedback circuit
 // Adv. Tech. of Elec. Eng. & Energy, 2009, 28(4). 32—36.

A novel ZCS full-bridge DC-DC converter based on auxiliary active circuit
ZHANG Yun-fang^1,2, CHEN Rong², ZHAO Yong-jian¹
(1. School of Electrical and Information Engineering, Jiangsu University, Zhenjiang 212013, China;
2. School of Information Engineering, Yancheng Institute of Technology, Yancheng 224000, China)
Abstract: This paper proposes a novel ZCS (zero-current-switching) PWM full-bridge DC-DC converter. The proposed converter can achieve ZCS for all the active switches in the entire load ranges, also it realizes soft commutation for the output rectifier diodes. The soft-switching operating principle of the converter was analyzed, and digital control system was designed using TMS320F2812 DSP chip. A 1Kw, 25kHz soft-switch power source was developed, and the experimental results have verified the principle and characteristics of the proposed soft-switching converter. 8 Refs. In Chinese.
Key words: ZCS; DC-DC converter; full-bridge; DSP control; soft-switching
 // Adv. Tech. of Elec. Eng. & Energy, 2009, 28(4). 37—41.

Influence of shielding on rail gun induction gradient
LIU Shou-bao, RUAN Jiang-jun, HUANG Dao-chun, ZHANG Ya-dong, ZHANG Gai-jie
(School of Electrical Engineering, Wuhan University, Wuhan 430072, China)
Abstract: Shielding composes the electromagnetic environment of rail gun system, and has direct influence on the rail gun’s electromagnetic property. Comparing with analytic method and experimental method, numerical method has great advantage in obtaining inductance gradient of rail gun under different shielding. In order to study the influence of shielding on the induction gradient of rail gun, this paper deduced armature’s force formulation, illustrated inductance gradient’s physical meaning, built rail gun’s 2D finite element method, calculated the induction gradient under four typical shielding materials and different shielding geometric dimensions, displayed the rail’s current distribution and spatial magnetic force line distribution under different shielding, concluded the influence laws of shielding on the induction gradient, obtained the electromagnetic properties of the materials and structure  which are suitable for rail gun shielding. The conclusions of the paper are very important for the design and manufacture of rail gun.
Key words: rail gun; shielding; inductance gradient; virtual work principle; finite element; skin effect; eddy current

Research on moisture content analysis of insulation pressboard in oil-paper transformer using polarization spectrum
 ZHANG Tao, CAI Jin-ding
(College of Electrical Engineering and Automation, Fuzhou University, Fuzhou 350002, China)
Abstract: The insulation fault diagnosis of power transformers is important to guarantee the safe and stable operation of the power system. Moisture and aging degree of oil-paper insulated power transformer has a sure influence on its insulation property. The water content in insulation pressboard is considered as an important indicator of insulation quality and the aging condition. Although chemical analyses can provide direct information on parameters, most chemical analyses must be performed under laboratory conditions and for some chemical analyses paper samples are needed. As a non-destructive diagnostic technique, return voltage measurements based on dielectric response theory have been introduced for condition assessment of transformer insulation, especially for the evaluation of water content in transformer pressboard. The study presented in this paper aims of further investigating the reliability of using the return voltage method to assess solid insulation of power transformer. The field test results show that this method is practical, which can estimate the water content in insulation paper using its polarization spectrum and dominant time constant. 11 Refs. In Chinese.
Key words: return voltage; condition assessment; insulation paper; water content; dielectric response
 // Adv. Tech. of Elec. Eng. & Energy, 2009, 28(4). 46—49.

An identification method for linear induction motor parameter based on static characteristics
HE Jin-wei^1,2 , SHI Li-ming¹
(1. Institute of Electrical Engineering Chinese Academy of Sciences, Beijing 100190, China;
2. Graduate School of Chinese Academy of Sciences, Beijing 100190, China)
Abstract: Linear induction motor (LIM) have some characteristics such as large gap length, different primary and secondary leakage inductance, and end effects. It is very difficult to measure the motor’s parameters precisely. Meanwhile, it’s not feasible to test using the rotary motor measuring method and get no-load characteristics along a line track. Because of the low position repeatability for the LIM used in linear drive subway and maglev train, it is not reasonable to carry on on-line parameter identification. This paper proposes a novel method to identify linear motor parameters including primary resistance, primary leakage inductance, secondary equivalent resistance and leakage inductance which are acquired by least-square method under different thrust and frequency. Basic parameters are obtained by using the output voltage and current of the converter with the locked-rotor standstill. Measuring equipment is only the practical drive inverter. Experimental results to a LIM based propulsion vehicle system verified the effectiveness of the proposed method.
Key words：linear induction motor; equivalent circuit; locked test; parameter identification

Construction of unified new-energy based power grid and promotion of China's smart grid
XIAO Li-ye, LIN Liang-zhen
(Key Laboratory of Applied Superconductivity, Chinese Academy of Sciences,
Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing 100190, China)
Abstract: In this paper, the background, motivation and concept of smart grid were briefly introduced. On the basis of the smart grid and the development prospects of new energy and the characteristics and the status of the renewable energies in China, a concept of new-energy based power grid (NEPG) was suggested. NEPG is a unified power grid which would be able to connect all of the large-scale new energy based power stations together, and it can be connected to the existed power grid through some joints where the charging stations for electric vehicles are built. Because the renewable energies are complementary within a wide area, and the charging stations can be used to regulate the fluctuations of the power, the NEPG would be able to transmit a comparatively stable power to the existed power grid, reducing the requests for power of energy storages and then the stability of the grid would be improved.
Key words: smart grid; new energy power generation; electric vehicles; energy storage; superconducting technology; distributed power

Discussion of 500kV digital substation network mode and VLAN partition
QIU Zhi-yong，CHEN Jian-min
(East China Grid Company Limited, Shanghai 200002, China)
Abstract: Power system is moving towards the digital power grid, smart grid development, and the digital substation as part of its foundation, in recent years, with the intelligent circuit breaker technology, electronic transformer technology, computer communications network technology development and promulgation of IEC61850 building of digital substation is at the growing rise at home and abroad. This paper discusses network mode of 500kV digital substation and gives the network scheme debated by many experts of various specialities using 500kV Haining and Lanxi digital substation as examples, and that 500kV Lanxi is the first three-tier architecture 500kV substation based on the IEC61850 digital substation. At the same time the case based on the RUGGEDCOM is presented on the paper.
Key words: 500kV digital substation; network mode; IEC61850

Research on output symmetrical control strategies for combinatorial high power three phase inverter
WU Sheng-hua, LAI Xiang-dong, ZHANG Xian-cai，QUAN Jian-zhou
(Air Force Radar Academy, Wuhan 430019, China)
Abstract: Seeing that the conventional inverter doesn't match any unbalanced loads, we proposed the circuit topology and control strategy of natural-decoupling in electrical and magnetic circuit. A sine pulse width and phase modulation was carried out by using an independent voltage-loop and phase-loop respectively in each phase, which ensures the symmetrical output voltage and the symmetrical output phase to the inverter. Simulation and experimental results of 30kW inverter show that the circuit design is feasible and of satisfactory outcome.
Key words: unbalance loads；three-phase symmetry；PLL；SPWPM

Design of new plasma ignition power supply
WAN Lei¹, HAO Rui-xiang¹, YOU Xiao-jie¹, CHEN Feng²
(1. College of Electrical Engineering, Beijing Jiaotong University, Beijing 100044, China;
2. China Academy of Aerospace Aerodynamics, Beijing 100074, China)
Abstract: As a new technology, plasma ignition becomes the first choice for thermal power plants in future due to its advantages of energy saving and environmental protection. The principle and components of plasma ignition system are introduced in this paper. According to the demand of loads, a set of power supply is designed. The principle and structure of power supply and HF arc ignition circuit is analyzed in detail. The paper described the program design method and the implementation of control functions. It is based on USS protocol of RS485 interface so that the serial communication of PLC and 6RA70 is realized. With the help of PLC, the circuit could coordinate well with power supply system to start and stabilize the arc. The field test proves the feasibility of the scheme.
Key words: plasma ignition；6RA70；HF arc ignition circuit；PLC；USS protocol

Statistics and Analysis on Papers Published on Journal ‘Advanced Technology of Electrical Engineering and Energy’
QIN Jie, LIN Liang-zhen, QI Zhi-ping, MA Yu-huan, SHEN Guo-liao, JING Bo-hong
(Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing 100190, China)
Abstract: The paper presented the statistics and analysis on papers published on the journal ‘Advanced Technology of Electrical Engineering and Energy’ from 1996 to 2008: the paper acceptance rate, the paper category, the first author’s affiliations, the top 7 first authors, the top 10 coauthors and also the journal evaluation indexes of the journal. It offers details of the journal to anyone interested, especially to our editorial board and our broad readers. 14 Refs. In English.
Key words: papers published on ‘Advanced Technology of Electrical Engineering and Energy’; statistics and analysis
 // Adv. Tech. of Elec. Eng. & Energy, 2009, 28(4). 76—80.