An improved three-ratio fault diagnosis based on rough set theory for power transformer
CAI Jin-ding, WANG Shao-fang
(Fuzhou University, Fuzhou 350002, China)
Abstract: The aim of this paper is to introduce an improved three-ratio fault diagnosis technique for power transformer, which is based on the Rough Set Theory. At first, a decision table can be constructed by applying the Rough Set Theory based on the IEC three-ratio fault diagnosis table. Then, the reduction of the decision table will be obtained, and a new three-ratio fault diagnosis decision table for transformer fault diagnosis can be acquired. The results of the experiment demonstrate that the improved three-ratio fault diagnosis technique extends the coding area of the earlier IEC three-ratio fault diagnosis technique, the actual malfunction diagnosis ability is proved and its diagnosis accuracy is higher as compared with the IEC three-ratio diagnosis technique. All these properties can be applied to practical projects.
Key words: rough set; decision table; transformer diagnosis

RBFNN based high voltage transmission line fault diagnosis
JIANG Hui-lan ，LIU Fei ， YANG Wei ，Xu Jian-qiang
(1. Tianjin University, Tianjin 300072, China;
2. Daqing Oil Field Management Board, Daqing 163000, China)
Abstract: On the basis of analyzing the methods of power system fault diagnosis, this paper presents RBFNN based high voltage transmission line fault diagnosis method by using radial basis function network’s capability which is adaptable to solving pattern recognition problems. A RBFNN model structure used for transmission line fault diagnosis is built, and the standard of evaluating RBF optimal clustering number is proposed. By simulation analysis and test for fault tolerance of network, the results show that the method presented in this paper can accomplish correct fault diagnosis for high voltage transmission line but also has high fault tolerance performance for distorted input signal, and therefore has practical application value in real time information processing system.
Key words：transmission line；RBFNN； fault diagnosis； LBG algorithm

An on-line monitoring system of ultra-high-frequency PD for transformers
WANG Guo-li1 2, HAO Yan-peng1 2, LI Yan-ming3
(1. Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055, China; 
2. Department of Electrical Engineering, Tsinghua University, Beijing 100084, China; 
3. Xi’an Jiaotong University, Xi’an 710049, China)
Abstract：An on-line monitoring system of ultra-high-frequency (UHF) PD was investigated for transformers in this paper. Based on frequency mixing technique, the hardware of this system, including UHF sensor and UHF receiver, was developed. The software of this system, consisting of data acquisition, signal processing and analysis, database and data communication, was constructed using National Instruments’ Measurement Studio software. By using this system, the PD of transformer windings was measured. Experimental results show that the system can effectively measure the time and the amplitude of the high-frequency (adjustable center frequency between 400~800 MHz with minimum steps of 5 MHz) and narrowband (10, 20, 40 or 80MHz) signals emitted from PD, and accurately calculate phase resolved PD patterns and statistical operators. This system has wider bandwidth, stronger ability of interference suppression, and higher stability, and can be useful for on-line monitoring and intelligent diagnosis of UHF PD in transformers.
Key words: transformer; partial discharge (PD); ultra-high-frequency (UHF); on-line monitoring; frequency mixing technique; virtual instruments (VI)

Rapid storage technique of coefficient matrix in finite element method
LIANG Zhen-guang1, TANG Ren-yuan2
(1. School of Electrical Engineering, Shandong University, Jinan 250061, China; 
2. Research Institute of Special Electrical Machines, Shenyang University of Technology, Shenyang 110023, China)
Abstract: In order to increase efficiency of data processing in a software package of electromagnetic field using 3D finite element method, the double scan method is studied in the paper. The application example of address matrix formation is discussed. In the first scanning, relevant nodes of all nodes are determined and stored by one iteration. In the second scan, address matrix is formed through stored relevant nodes by another iteration. The coefficient matrix is stored by row storage. Column storage address is also provided. Rapid storage of coefficient matrix in finite element method is then realized. The method is simple, effective and easy to realize.
Key words: double scan method; finite element method; coefficient matrix; rapid storage

SMES based unified power quality conditioner and its design
HOU Yong, JIANG Jian-guo
(Department of Electrical Engineering, Tsinghua University, Beijing 100084, China)
Abstract: This paper presents a SMES based power quality conditioner. This device employs only one current source commuter and SMES (superconductor magnetic energy storage) coil as storage component, which can realize multiple functions such as load voltage regulation and active filtering. In this paper, the structure and operation principle of the system are described. Two modes of power adjustment are proposed, i.e. the load voltage is maintained by only adjusting reactive power of inverter under slight voltage sag, whereas by adjusting the active power as well as reactive power under deep voltage sag condition. The effectiveness of the system structure and control is verified by experimental results. The design method of main circuit parameters is analyzed.
Key words: power quality; superconducting magnetic energy storage (SMES); parallel processing; current source inverter; parameter design

Study on SVPWM method for three-level neutral-point-clamped (NPC) inverter
SONG Wen-xiang, CHEN Guo-cheng
(School of Mechatronics Engineering and Automation, Shanghai University, Shanghai 200072, China)
Abstract: In this paper, SVPWM principle and implement method is addressed for three-level NPC inverter. In order to avoid the abrupt change of output voltage vectors during the process of desired vector changing from one section to another, a novel space vector modulation (SVM) algorithm is proposed where positive or negative small vectors are adopted as first active vector, and it is convenient to determine which section and sub-triangle the desired vector is located at by three judging rules. Also, output voltage vector to synthesize the desired vector is given and the duty time of active vectors for corresponding sub-triangle vertex is deducted. The neutral point potential stability is realized by detecting the direction of load current and neutral point voltage and designing reasonable duty time of positive and negative space vectors. Finally, the effectiveness of proposed SVM method is confirmed by simulative results.
Key words: space vector modulation (SVM); three-level inverter; control of neutral point potential 

Improving calculating of the negative sequence capability
of the evaporative cooling turbo generator
WEN Zhi-wei, GU Guo-biao
（Institute Electrical Engineering，Academia Sinica，Beijing 100080，China）
Abstract: The transient negative sequence capability of a 50MW evaporative cooling turbo-generator is studied, and a new mathematical model calculating the transient electromagnetic field and the transient temperature field in the rotor of evaporative cooling turbo-generator by means of two dimension finite element method is developed. The maximal negative sequence capability of the 50MW evaporative cooling turbo-generator has been checked. The calculated temperatures on the surface of rotor are compared with former calculating data and the experimental results in operation. The position of the maximum temperature rise in the rotor has been determined. The conclusion of the paper will provide dependable theoretical evidences for the design of cooling system and temperature inspection at field of generator operation.
Key words: evaporative cooling; turbo-generator; negative sequence; 2-D FEM

A modified unit decommitment method for unit commitment
HU Fei-xiong1, YAN Zheng2, NI Yi-xin2, CHEN Shou-sun1, WU Fe-lix2
(1. Tsinghua University, Beijing 100084, China；
(2. The University of Hong Kong, Hong Kong SAR, China)
Abstract: A modified unit decommitment method is proposed for unit commitment problems. The algorithm starts with the initial solution where all the available units are on stream. One and only one unit schedule is made in each iteration to minimize the objective function, utill the objective function cannot be further optimized. A noticeable advantage of the new method is that all the intermedia solutions during the iterations retain the feasibility. In the single-unit optimization process, minimum up and down time constraints are considered, and, instead of single time interval, the time-lag when the units must be on or off are used for scheduling. Thus, the number of the feasible solutions to be searched is reduced significantly.
Key words: unit commitment; unit decommitment; single buyer; power market

Study of regeneration technology for transient energy
LIN Zhou-bu
(Fuzhou University，Fuzhou 350002，China)
Abstract: A new energy regenerative circuits composed of passive components, are obtained with the circuit analogy means applied to passive non-dissipated circuits. So a novel of passive soft-switching technology equipped a charge pump regeneration (CPR) network is presented. The CPR network is comprised of an additional low power auxiliary winding which is magnetically coupled with the main inductor and turns ratio is 1, a small capacitor, two low power diodes. It can regenerate energy captured in the snubber capacitor fully and simply. Moreover, it not only snubs the switching devices effectively, but also has a few good features such as wider soft-switching range, lower voltage stress, simple to design, lower cost and so on. To be a demonstration, operation principle, theoretical analyses, relevant equations, simulative results, as well as experimental testing results of a typical PWM boost converter with proposed CPR are shown. All are verified that the technology is well applicable to many non-isolated DC-DC converters, especially for those want hold very wider soft-switching operation range.
Key words：power electronic circuit; passive soft-switching; regeneration

Accurate calculation for complex faults of double power lines on the same tower
LIN Jun 
(College of Electric Engineering, Fuzhou University, Fuzhou 350002, China)　　　　　　　　　　　　　　　　　　　　　　　　 
Abstract: An accurate calculation method for complex faults of double power lines on the same tower is introduced. By precise model of distributed parameter and repeated adding method, considering the effects of power line transposing and distributed capacitance, the calculation method can precisely get complex fault results of double power lines on the same tower. By example of one line to ground fault and cutting off by one side of breaker, the paper illustrates the principle of this calculation method.　　 
Key words: double power lines on the same tower; accurate calculation for complex fault;
model of distributed parameter

A novel control algorithm for cascaded shunt active power filter

WANG Geng, LI Yong-dong, YOU Xiao-jie
(Department of Electrical Engineering, Tsinghua University, Beijing 100084, China)
Abstract: In this paper a novel control scheme of cascade shunt active power filter (CSAPF) is presented. This work is motivated by the fact that the compensation ability of traditional active power filter is limited by the voltage capability of the power devices. While the converter with cascade topology has been put into practical use for years especially in high voltage and high power drives, the application of such converter to active power filter is hindered by the problem of voltage unbalance of separate DC capacitors that leads to system instability. This paper deals with the design and implementation of a new digital controller for CSAPF. Finally experimental results obtained from a laboratory system developed in this paper are presented to verify the viability and effectiveness of the proposed control algorithm.
Key words: shunt active filter, cascaded converter, control algorithm, voltage unbalance

Study on digital multiple-loop control technology of inverters
LI Jun-Lin, XIONG Jian, KANG Yong
(Huazhong University of Science and Technology, Wuhan 430074, China)
Abstract: This paper presents a digital multiple-loop control technology of inverters. The scheme incorporates a current loop with an instantaneous voltage loop, while a repetitive control outer loop is added. Since both an output voltage decoupling mechanism and a load disturbance compensation have been added, the current loop and instantaneous voltage loop controller is designed through deadbeat theory, so that the inverter’s dynamic performance is much improved, and the repetitive control outer loop improves the steady-state performance. The scheme is proved on a PWM inverter whose control system is based on DSP TMS320F240.
Key words: inverters; current-loop; voltage-loop; deadbeat; repetitive control

Sensor integrated concept based rotor position detection of a PM synchronous motor
LIU Yi, HE Yi-kang, QIN Feng, ZHANG Wei
(Department of Electrical Engineering, Zhejiang University, Hangzhou 310027, China)
Abstract: Based on the analyzing the mathematic model of a PM synchronous motor excited by a set of high-frequency signals, a novel rotor position self-estimation method was suggested in this paper on the basis of rotor saliency-tracking technology. Moreover, the principles of rotor position detection, such as high-frequency signal injection, heterodyning and the tracking observer of rotor position estimation, were all discussed and the simulation model for a sensorless vector control system of a PM synchronous motor was established using the proposed rotor position estimation method. Simulated results manifest that the proposed saliency-tracking scheme could be used in the whole speed region, including zero speed, to estimate the rotor position precisely, and the sensorless drive system, based on the integration concept of the sensor combined with the motor, possesses of proper speed-adjustable performance both in static and dynamic.
Key words: PMSM; sensor integration; saliency-tracking; rotor position estimation; vector control

Prototype magnet design for magnetic birefringence of vacuum-Q & A experiment
DONG zeng-ren1，W.-T. Ni 2，YANG Wen-hui1，WANG Zheng1
（1. Institute of Electrical Engineering of Chinese Academy of sciences, Beijing 100080, China；
2. Department of Physics, National Tsing Hua University, Hsinchu, Taiwan 30055, China）
Abstract: This paper introduces the 600mm prototype rotating permanent magnet design for magnetic birefringence of vacuum-Q & A experiment. With high performance materials used and flux concentrate technology adopted, 2.3T field is achieved in the air gap (Ø27mm). The side shield and the shaft are merged to reduce the weight. The magnet has passed the rotation test at 620rpm. The success of this magnet design lay a foundation for manufacture of 5m Rotating Permanent Magnet.
Key words: birefringence of vacuum; permanent magnet; FEM

Research on high-frequency electronic ballast for MH lamps
LIN Guo-qing1,2，CHEN Da-hua1，CHEN He-ping3，ZHANG Wen-xiong3
（1. Fudan University, Shanghai 200433, China；2. Fuzhou University, Fuzhou 350002, China；　　　　　 3. Fujian Juan Kuang Yaming Electric Limited, Fuzhou 350001, China）
Abstract: A high-frequency electronic ballast is proposed to operate MH lamps in the paper. The circuit composition and operating principle are detailed. Because of ZVS (Zero-voltage-switching) operation, it can work in high switching frequency while achieving higher efficiency. The frequency and amplitude modulation of the inverter switching pattern is used to prevent the acoustic resonance. A high-voltage ignition pulse is made by sweep frequency resonance mode and possibly increases ignition reliability. The proposed electronic ballast can eliminate a controller and three active switches, reduce size and possibly increase system efficiency and reliability over a conventional low-frequency square-wave system. The experimental measurements are used to verify the theoretical prediction and analytical discussion.
Key words: MH lamp; frequency and amplitude modulation; electronic ballast; acoustic resonance

Experimental study of PCEMFs on micronucleus rate of human lymphocytes
YAO Xue-ling1, CHEN Jing-liang1, WANG Xiang2, XU Chuan-xiang1
(Xi’an Jiaotong University, Xi’an 710049, China)
Abstract: The human peripheral lymphocytes were placed in different models of radiated PCEMFs environments, and the elementary experimental results illustrate that SCE (sister chromatid exchange) and breaking of the human lymphocytes are mainly related to the magnetic induction amplitude Bm and its rising gradient dB/dt of PCEMFs. The critical reference values of MNR are put forward, where the critical reference values of aberrance refer to 0.15T (Bm) and 1.8×104T/s (dB/dt), and the values of damage approach to 2.64T(Bm) and 3.3×104T/s(dB/dt) respectively. These data can provide a criterion to study electromagnetic protection in high pulsed current discharging environment. MNR and damage of the human lymphocytes are obviously dependent upon the space structure of pulsed electric and magnetic fields, and the PCEMFs where the electric field is orthogonal to the magnetic fields have more notable influence than others.
Key words: PCEMFs (pulsed current electromagnetic fields); MNR (micronucleus rate); critical reference values

Two-channel high-voltage trigger generator
using artificial transmission line as time-delay circuit

YANG Gao-lin, HU Yuan, WANG Xin-xin, LUO Cheng-mu
(Department of Electrical Engineering, Tsinghua University, Beijing 100084, China)
Abstract: The electric-magnetic noise immunity of a multi-channel high-voltage trigger generator was greatly enhanced by changing its operation mode from‘being triggered after being delayed’to‘being delayed after being triggered’and by replacing the time-delay system made of integrated circuit chips with an artificial transmission line. With such improvements a two-channel high-voltage trigger generator was successfully used to trigger two high current lightning generators which discharge one after another with a time interval of  .
Key words: artificial transmission line; time-delay circuit; high-voltage trigger generator; electric-
　　　　　 magnetic noise immunity