Abstracts of Vol.25, Issue 2, 2006

Sliding mode observer for sensorless vector control of PMSM.
Base on the idea of sliding mode observer, a new method of designing the sliding mode observer for PMSM control system is proposed. The algorithm for estimating position and speed of PMSM is presented, which is simple in structure and easy to be implemented by using a computer. Sensorless field orientation control system is achieved by using this observer. Experimental result showed that the observer has good robustness to load disturbance and time varying parameters. 9 Refs. In Chinese. 
Key words: sliding mode observer; PMSM; sensorless; vector control
WU Chun-hua (Shanghai University, Shanghai 200072, China), CHEN Guo-cheng, SUN Cheng-bo // Adv. Tech. of Elec. Eng. & Energy, 2006, 25(2): 1-3.

Rotor field-orientation control of induction motor based on control of rotating electromotive force.
Based on the principle of electromechanical energy conversion and reference frame transformation theory, rotor field-orientation decouples not only flux linkage and torque but also rotor transformer electromotive force (TEMF) and rotating electromotive force (REMF). The control of torque and speed in variable-frequency induction motor drive can be achieved by control of rotor REMF. The direct rotor field-orientation control based on control of REMF is proposed and it can achieve not only constant torque control with constant rotor field but also constant power control with weakening rotor field. The results of simulation show that the proposed control method has good dynamic performance and is an effective new way for the high performance speed control of induction motors is provided. 11 Refs. In Chinese.
Key words: induction motor; electromechanical energy conversion; reference frame transformation; rotating electromotive force; rotor field-oriented control
MENG Ming (North China Electric Power University, Hebei Baoding 071003, China), XU Zhen-lin // Adv. Tech. of Elec. Eng. & Energy, 2006, 25(2): 4-6.

Study on parallel operation of inverters based on droop method.
This paper analyses the basic principles of droop method for wireless parallel operation of inverters. By adopting some new technologies, the performance of parallel operation system is improved. And in this paper the single inverters based on multiple feedback loop control method and their parallel operation system are designed. To overcome the disadvantages of first order inertial element, which is adopted in traditional parallel operation system to filter the power triples, the second order oscillational element is adopted in this paper, which improves the controllability and performance of the system. And the virtual impedance, adopted in this paper, reduces the impact of the output impedance of the inverters on the performance of parallel operation system. At last, to validate this control method, a prototype is built, which is composed of two 1kVA single-phase PWM inverters based on DSP TMS320F2407A. The static and dynamic performances of the system are tested, and the results show the good performance of the system. 11 Refs. In Chinese.
Key words: wireless parallel operation; droop method; oscillational element; virtual impendence
YANG Shu-ying (School of Elec. Eng. and Automation, Hefei University of Technology, Anhui Hefei 230009, China), ZHANG Xing, ZHANG Chong-wei // Adv. Tech. of Elec. Eng. & Energy, 2006, 25(2): 7-10.

Design and analysis of power factor correction circuits to comply with new version of regulations.
The design of low-cost power supplies is influenced by the regulations on the low-frequency harmonic content in the line. As IEC 1000-3-2 regulations have just been modified, the design procedure of low-cost power supplies should also be modified. According to the new version of the above-mentioned regulations, many power supplies classified as Class D in the past are classified as Class A now. This fact allows a remarkable saving in the size of the reactive elements used to reduce the line harmonics if they have been properly designed. The minimum values of the magnetic elements used in two well-known PFC solutions (one is an S*PFC and the other is a passive filter) have been obtained in this paper for equipment classified in both the new Class A and the new Class D and for any power level between 75W and 600W. 11 Refs. In Chinese.
Key words: EMC regulations; power factor correction; cost-effective
LIN Wei-ming (College of Electrical Engineering & Automation, Fuzhou University, Fujian Fuzhou 350002, China), SONG Hui-qi, HUA Xiao-hui, et al. // Adv. Tech. of Elec. Eng. & Energy, 2006, 25(2): 11-14.

Application of non-linear partial least square regression in electricity load prediction.
The non-linear (polynomial) partial least square (NPLS) solves both the problem of multiple correlations among variables and the issue where the partial least square (PLS) could only extract linear components, thus being more advanced and its calculation results being more reliable. The paper applies the quadratic PLS (QPLS) to electricity load prediction of Quanzhou, illustrates the model-building process and proves its better prediction effects and wider application by comparing its prediction result with those of linear PLS and Logistic Model. 7 Refs. In Chinese.
Key words: QPLS; electricity load prediction; PLS
CAI Jin-ding (Fuzhou University, Fujian Fuzhou 350002, China), WANG Hui // Adv. Tech. of Elec. Eng. & Energy, 2006, 25(2): 15-17.

Study of widening switch angles in selective harmonic elimination inverter.
The selective harmonic elimination inverter can eliminate predetermined harmonics by calculating the equations set, therefore harmonics can be eliminated effectively in theory. The connection and break of switch devices all need a little time, thus the narrow pulse of the ideal output voltage waveform is difficult to realize. For obtaining practical output voltage waveform, the optimized strategy of widening a couple of switch angles is presented based on the specific requirement of on-off time of switching device. Widening a couple of switch angles may be divided into forward-widening, backward-widening and symmetry-widening, in which symmetry-widening is more favorable than forward-widening and backward-widening for reducing harmonic amplitude and total harmonic distortion. Theoretical analysis, numerical simulation and experimental results show that optimized strategy presented may achieve the aim of easy hardware implementation and little total harmonic distortion, accordingly effective means is provided for the application of selective harmonic elimination technology in engineering. 2 Refs. In Chinese.
Key words: selective harmonic elimination technology; switch angle; widening; total harmonic distortion 
ZHANG Wen-yi（Harbin Institute of Technology, Heilongjiang Harbin 150001, China）, ZHANG Rong-ling, XU Hui-ming, et al. // Adv. Tech. of Elec. Eng. & Energy, 2006, 25(2): 21-23.

Research on stator insulation structure of 135MW evaporative cooling turbo-generator.
In order to apply evaporative cooling technical to a high voltage and large capacity turbo-generator that will be used as a main power generator, the problem of designing reasonable insulation structure is to be solved. This paper offers an immerging evaporative cooling stator, with consideration of its specialties. This paper calculates and analyzes the electric field and the temperature field in immerging evaporative cooling stator insulation structure in detail, then summarizes the distribution rules or specialties of these two fields. As results this paper gives the stator insulation thickness which is reduced greatly as compared with traditional one and the corresponding current density, aiming to 135MW evaporative cooling turbo-generator. The conclusion has been tested and is worthy for reference. 6 Refs. In Chinese.
Key words: evaporative cooling; stator insulation; electric field; temperature field
LUAN Ru (Beijing Inst. of Civil Eng. & Architecture, Beijing 100044, China; Inst. of Elec. Eng., Academia Sinica, Beijing 100080, China), FU De-ping, GU Guo-biao // Adv. Tech. of Elec. Eng. & Energy, 2006, 25(2): 24-28.

Second-harmonic compensation method and capacitor-voltage time-sharing control scheme for a double conversion UPS rectifier.
In this paper, the dual closed-loop control principle of a single-phase half-bridge current -controlled PWM rectifier for the double conversion UPS is analyzed. A steady-state second-harmonic compensation method for the single-phase half-bridge PWM rectifier is proposed. It can eliminate the influence of the second harmonics in output voltage without reducing the bandwidth of the voltage feedback loop.This method needs only little program resources and computation, and is easy to be realized in a DSP controller. To ensure the capacitor voltage balancing, a time-sharing control scheme is proposed. A prototype is built based on TMS320LF2407A, and experiment results verify the effectiveness of the steady-state second-harmonic compensation method and the capacitor-voltage time-sharing control scheme. The input current waveform is shaped as a sinusoidal in phase with the input voltage by adopting the active power factor correction technique, and the output DC voltage is stable. Both the dynamic response and steady state performance are desirable. 10 Refs. In Chinese.
Key words: UPS; PWM rectifier; digital control; single-phase half-bridge
WANG Meng (State Key Lab of Power Systems, Dept. of Electrical Engineering, Tsinghua University, Beijing 100084, China), LIU Ya-dong, JIANG Zhi-hong, et al. // Adv. Tech. of Elec. Eng. & Energy, 2006, 25(2): 29-33.

Power quality disturbance signals de-noising based on improved soft-threshold method.
Recently, power quality issues have captured more attention. It is necessary to monitor power quality in order to analyze and evaluate it. But noises will influence the signals during data collection. It is hard to analyze signals correctly. Soft-threshold de-noising method based on wavelet transform is effective. Considering that the noise of power system is Gauss white noise commonly, which obeys normal distribution, this paper proposes an improved soft-threshold de-noising method based on 3 principle of normal distribution, typical power quality disturbance signals including sag, swell, interruption and transient impulse are simulated, and the reconstructed signals disturbance is detected. Comparing with universal soft-threshold de-noising method, simulation results show that the rate of accurate detection is improved by this method. 13 Refs. In Chinese.
Key words: power quality; wavelet transform; soft-threshold; de-noising
WANG Ji-dong (School of Electrical Automation Engineering, Tianjin University, Tianjin 300072, China), WANG Cheng-shan // Adv. Tech. of Elec. Eng. & Energy, 2006, 25(2): 34-38.

Cogging torque research on Flux Reversal Machine based on FEM.
A novel double salient permanent magnetic machine, flux reversal machine (FRM), was introduced. Different from other common permanent magnetic machines, in the FRM, permanent magnets and coils were placed on the stator. So its rotor structure was very sample. Because of the advantages such as high power density, small induction and low inertia, etc., the FRM was suitable for high speed applications. But this double salient structure also causes that the cogging torque in FRM is great, which can influence the smooth of the operation and the noise control. In order to reduce the cogging torque, in this paper, a 6/8 FRM was designed, and 2D finite element method was used to analyze the relationship between the cogging torque and the dimensions of the FRM such as tooth span, permanent magnet height and skewing angle. Then the prototype was manufactured. And the difference between the simulation and the experiment is about 8%, which shows that the FEM outcomes are accurate. 11 Refs. In Chinese.
Key words: FRM; FEM; cogging torque
GUO Liang (Zhejiang University, Zhejiang Hangzhou 310027, China), LU Qin-fen, YE Yun-yue, et al. // Adv. Tech. of Elec. Eng. & Energy, 2006, 25(2): 42-46.

A precise algorithm for frequency measurement of power system
ZHANG Yan-xia, WANG Liang, LIU Cui-yan
（School of Electrical Engineering and Automation, Tianjin University, Tianjin 300072, China）
Abstract: The frequency is one of the most important characters of power system. It reflects the basic state of active power requirement and supply in power system. Based on theoretical analysis and simulations, this article makes some progress to the smart discrete Fourier transform algorithm (SDFT): amending the calculate formula, smoothing the data, and setting a threshold. The results of the simulations show that the improved SDFT algorithm can track the frequency automatically to obtain its exact value when the frequency of power system deviates from the rating value. The improved SDFT algorithm has a shorter window length, and it is also easier to implement on the digital signal processor. The improved SDFT algorithm can satisfy the demand of real-time measurement and has a bright future in engineering application.
Key words: frequency algorithm; oscillation of power system

Proximity effect and optimized arrangement of cable bundles
LIANG Yong-chun1, 2, MENG Fan-feng1, WANG Zheng-gang3, LI Zhong-kui3, LI Yan-ming1
(1. Xi’an Jiaotong University, Xi’an 710049, China;
2. Hebei University of Science and Technology, Shijiazhuang 050054, China;
3. Zhengzhou Electric Power Company, Zhengzhou 450006, China)
Abstract: Ac resistance of cable conductor is an important factor to calculate the ampacity of cable bundles, and proximity effect factor is an important parameter to affect ac resistance. IEC-60287 and JB/T10181-2000 give only a formula to calculate the proximity effect of single loop cable conductor, and there are some limiting prerequisites to use the formula. On the basis of electric and magnetic field theory, the paper presents a common calculation formula which can be used to calculate the proximity effects of any cable bundles. This formula is obtained by solving the magnetic vector equation with Maxell equation and Bessel function. As examples, the paper calculates the proximities of different phase arrangement and gives a phase arrangement which proximity is the least in three layers modes.
Key words: ampacity; AC resistance; proximity effect; Bessel function

Optimum analysis on solid dielectric insulation dimension
in coaxial electrodes under nanosecond pulse voltage
HUANG Wen-li1,2, SUN Guang-sheng1, YAN Ping1, WANG Jue1
(1. Institute of Electrical Engineering, Chinese Academy of Science, Beijing 100080, China;
2. Graduate School of Chinese Academy of Science, Beijing 100039, China)
Abstract: The rapid declining of electric field in the very close vicinity of inner electrode results in non-uniform distribution of coaxial electric field in coaxial electrodes. Under the condition of keeping the inner diameter of electrode constant and increasing the outer diameter, the variation of coaxial electric field is markedly slow down following a stage of rapid decay when the gap between the inner and outer diameters is longer than a threshold. When the gap between inner and outer electrodes is keeping constant but correspondingly increasing the diameter of the outer electrode, then a slight increase of diameter of inner electrode beyond the threshold value, the variation of coaxial electric field will have the same variation as the former case. The appearance of two thresholds about two parameters of the gap between inner and outer electrodes and the diameter of inner electrode implies the optimum conception of the coaxial insulation structure of pulsed power equipments. This paper provides an empirical formula relevant to flashover gap and the inner electrode diameter on the basis of the results of ANSYS software and experiments, and the experimental results is of flashover data of polymethyl methacrylate (PMMA) and nylon 1010 in transformer oil under coaxial electric field under the applied pulsed voltage in the range of nanosecond.
Key words: nanosecond pulse; coaxial electrodes; surface flashover; transformer oil; dimension optimization

A speed identification method for induction motor based on MRAS
CHEN Wei, QU Wen-long, LU Hai-feng
(State Key Lab of Power Systems，Department of Electrical Engineering,
Tsinghua University, Beijing 100084, China)
Abstract: In this paper，a model reference adaptive system (MRAS) implemented in stationary reference frame is proposed to identify the rotor speed of an induction motor. The reference model and adjustable model used in this MRAS scheme are composed of stator equations and rotor equations respectively. Stator resistance and pure integration are removed from the reference model, resulting in robust performance in wide speed range. The adjustable model contains the information of rotor speed and a current model rotor flux observer. When the estimated speed converges to the actual rotor speed, the rotor flux observed converges to its true value, which can be used in direct field orientation control (DFOC). In addition, in order to avoid pure derivative operation on stator current, tracking-differentiator is adopted to acquire differential signals with high quality. Simulations and experimental results have verified its effectiveness.
Key words: speed identification; model reference adaptive system; tracking-differentiator; induction motor

Studies of engineering design of PMSM
WANG Bu-lai, GU Wei
(Dept. of Electrical Automation, Shanghai Maritime University, Shanghai 200135, China）
Abstract: This paper discusses the general and key points of PMSM’s design. It gives a method of engineering design of PMSM and designs a sample by using this kind of method. The method of this paper is both helpful and convenient for design engineer to design and develop PMSM. The result verifies that this kind of method of engineering design is applicable.
Key words: permanent magnetic; synchronous machines; engineering design

Analysis of capacitance of electric double layer capacitor
XU Wen-dong1,2, HUA Ben1,2, CHEN Jin-fu3
(1. Key Lab of Enhanced Heat Transfer and Energy Conservation, Ministry of Education, Guangzhou 510640, China;
2. Gas Utilizing Research Center of South China University of Technology, Guangzhou 510640, China;
3. State Key Laboratory of Heavy Oil Processing, China University of Petroleum, Beijing 102200, China)
Abstract: The applied areas and their relevant performance of EDLC were discussed, and several capacitance value measures and their difference were analyzed. So the components of capacitance, and their physical meaning and corresponding applied areas were defined. The capacitance was disparted to calculating capacitance, integral capacitance, apparent capacitance and potential capacitance. Calculating capacitance is inclined to academic study about the microstructure and the mechanism of storage energy, integral capacitance is apt to the application of spare electrical source, and apparent capacitance is used to power supply. The characteristics and the effects of apparent capacitance were studied. The results show that the micropore potential barrier is a key effect of apparent capacitance, and is essential cause of the slight increase of current when the voltage is more than 900mV in cyclic voltammogram, and thus lead to the lag of forming electric double layer, which is potential capacitance. The measures, lowing current density or raising charge voltage, were provided to increase apparent capacitance.
Key words: EDLC; capacitance; apparent capacitance; cyclic voltammogram; micropore potential barrier

High voltage nanosecond pulse generator for calibrating voltage dividers
LIU Rui, ZOU Xiao-bing, WANG Xin-xin, ZENG Nai-gong
(Department of Electrical Engineering, Tsinghua University, Beijing 100084, China)
Abstract: A high voltage nanosecond pulse generator for calibrating voltage dividers with fast time response was constructed. The generator consists of a DC high voltage source, a pulse forming line (PFL), a spark gap switch and a pulse transmission line (PTL). Polyethylene dielectric coaxial cables were used as PFL and PTL. Both cables are 10 meters long and with impedance of 50Ω. A compact coaxial switch was designed and inserted between PFL and PTL. When PFL is charged to a voltage about 10 kV a 3-mm air gap inside the spark gap switch will be broken down, which delivers a 5-kV and 100 ns voltage pulse to the load along the PTL. If higher voltage and shorter risetime are needed, pressurized gas could be filled into the switch.
Key words: high voltage nanosecond pulse generator; gas spark gap switch; pulse risetime

Study of new current-source PWM rectifier based on improved space vector
 PENG Yong-long, XIAO Miao, LI Ya-bin
(North China Electric Power University, Baoding 071003, China)
Abstract: This paper introduces a new topology of a PWM current-source rectifier (CSR) and analyzes the function of this new PWM rectifier. This new topology, modulated by improved space vector PWM algorithm, combines the advantages of the traditional six-pulse thyristor rectifier and the DC Buck chopper, which make the new PWM rectifier operate at unity power factor, and low harmonic input current. The simulating and experimental results prove that the system works well and has good performance.
Key words: PWM rectifier; current-source type; buck chopper; SVPWM

Implementation of phase-shifted full-bridge PWM inverter based on EPLD and 80C196KC
WANG Cui1, 2，SHE Zhi-ting1，PENG Yong-jin1
(1. College of Electrical and Information Engineering, Hunan University, Changsha 410082, China；
2. Hunan Institute of Technology, Hengyang 421008, China)
Abstract：Using the high-performance microcomputer and programmable logic devices to form control system of the invertors of switching power supply can meet high frequency demand. Adopting soft switching technology to reduce switch losses can improve the electric efficiency, realize the high power density and reduce the volume of the invertors. This paper designs a phase-shift PWM inverter using EPLD and 80C196KC. This control scheme takes advantages of simple hardware design and software flexibility. Its precision is very high. The method is suitable for the high-power switching power supply with high current and low voltage. Both the experiment and simulation results have verified the practicality and validity of the design.
Key words：inverter；phase-shifted；PWM；EPLD

Design of a power quality monitoring and control system based on communication net
FAN Hai-tao，WANG Shu-min
(Tsinghua University, Beijing 100084, China)
Abstract: The distributed power quality monitoring and control systems have many advantages. A distributed network power quality monitoring and control system which shows many merits in cost, reliability and performance is developed based on free software and embedded technology. The system is modularized and can be exchanged and extended easily. The paper presents the design principle and the structure of each functional layer in detail and analyzes some important conception in real-time control systems. RTAI（Real Time Application Interface）which enables uClinux to support hard real-time performance is used to improve the real-time capability for uClinux operation system and to strive for the popularization of uClinux in automation field.
Key words: power quality monitoring and control systems; free software; hard real-time; embedded system; relational database；RTAI