Abstracts of Vol.25, Issue 3, 2006

A novel 2-step commutation method in RB-IGBT based matrix converter drive system.
A 3-phase to 3-phase matrix converter is built based on 600V/100A reverse blocking IGBT (RB-IGBT) in this paper. The Indirect Space Vector Modulation (ISVM) approach is used to implement the slip frequency loop-closed constant V/F control of an induction motor. A novel two-step commutation method is proposed to ensure the reliable commutation between two bi-directional switches. This commutation method does not require any current or voltage sensors and it only depends on the RB-IGBT collector-emitter voltage sensing unit on the drive board to acquire the necessary information. Finally, the photo of the prototype and the experimental results under different load conditions are given. The experimental results have verified the effectiveness of the proposed commutation method. A good performance is also obtained using this method in the matrix converter-induction motor drive system. 3 Refs. In Chinese. 
Key words: matrix converter; RB-IGBT; two-step commutation
ZHOU Da-ning (Dept. of Electrical Engineering, Tsinghua University, Beijing 100084, China), LIU Ya-dong, HUANG Li-pei // Adv. Tech. of Elec. Eng. & Energy, 2006, 25(3): 1-4.

Voltage-differential -feedback control plus repetitive control for PWM inverters.
One digital control scheme, which is based on output voltage differential feedback control and repetitive control, is proposed in this paper. Arbitrary pole assignment can be achieved with the voltage differential feedback compensator inner loop, which can improve the dynamic characteristic of inverter; the repetitive control outer loop improves the steady state performance of inverter. The scheme, which can achieve the same control effectiveness as “state feedback pole assignment plus repetitive control” without current sensor, is proved on a PWM inverter whose control system is based on DSP TMS320F240. 10 Refs. In Chinese.
Key words: inverter; repetitive control; feedback compensation
XIONG Jian (Huazhong University of Science and Technology, Wuhan 430074, China), SHI Peng-fei, ZHANG Kai, et al. // Adv. Tech. of Elec. Eng. & Energy, 2006, 25(3): 46-49.

Study on hybrid automatic voltage control strategy of substation.
Based on hybrid control theory, this paper introduces an integrated control strategy of voltage and reactive power in substation. This strategy adopts the hierarchical balance optimization of reactive power and improves the traditional “nine-zone diagram” control method. The new hybrid control strategy not only solves the oscillating problem caused by the change of transformer tap and switching of shunt capacitor, but also responses the global optimal control command of reactive power in time. The simulations have proved the validity of the HAVC control strategy. So this paper has provided a theoretical foundation for the design of the industrial devices of HAVC system in substation. 9 Refs. In Chinese.
Key words: Hybrid Automatic Voltage Control (HAVC); substation; nine-zone diagram
WANG Zhi-tao (Dept. of Electrical Engineering, Tsinghua University, Beijing 100084, China), MEI Sheng-wei, HU Wei // Adv. Tech. of Elec. Eng. & Energy, 2006, 25(3): 5-8.

A new control strategy of power loss ride through in MV inverters.
The voltage sag or instant power loss often happens in power supply system in medium voltage (MV) inverter’s working environment. Frequent start MV inverter-motor system caused great harm to the normal production. As the most important function of MV inverters, a new control strategy of power loss ride through (PLRT) is investigated. Based on the brake of quickly reducing output frequency, the PLRT maintains the DC link voltage in a proper range. The principle, process and function design of PLRT are developed in this paper. The test results in a 55kW 3-level inverter show that this PLRT is an efficient and feasible key to the instant power loss. 13 Refs. In Chinese.
Key words: MV inverter; power loss ride through; ASD system
ZHANG Hai-tao (State Key Lab. of Control and Simulation of Power System and Generation Equipment; Depart. of Elec. Eng. and Applied Electronic Technology, Tsinghua University, Beijing 100084, China), ZHAO Zheng-ming, YUAN Li-qiang, et al. // Adv. Tech. of Elec. Eng. & Energy, 2006, 25(3): 68-72.

Design of passivity-based control system for induction motors.
Due to the great potential value in theory and application, nonlinear control strategies of induction motors, especially passivity-based control (PBC) methods, have been focused on. Passivity-based control is an undecoupling nonlinear feedback method using energy concept, and it analyzes the motor system and finds out the “workless force”. In this way, the nonlinearity of the system need not be cancelled completely in the feedback control designing, therefore the control is simplified. At the same time, the torque and flux magnitude can be asymptotically tracked. In this paper, an induction motor model described by Euler-Lagrange equations is presented and decomposed as a feedback interconnection of an electrical and a mechanical passive subsystem. On this basis, the passivity-based torque and speed controllers were designed. The resulting control algorithm is globally stable without singularities and guarantees robustness to the overall system. Both the simulation and the experimental results prove that the control system based on this control law possesses nice static and dynamic performance and tracks reference speed well. 9 Refs. In Chinese.
Key words: passivity; induction motors; speed controller; torque controller
GU Liang (Dept. of Elec. Eng., Xi’an Jiaotong University, Xi’an 710049, China), SHEN Chuan-wen, JI Xiao-long // Adv. Tech. of Elec. Eng. & Energy, 2006, 25(3): 42-45.

AC contactor performance evaluation system based on dynamic testing.
A performance evaluation system of AC contactor, which is based on dynamic characteristic testing technology, is developed. According to the data feature of dynamic characteristic, an adaptive fuzzy classification is presented. On the basis of the classification method, the fuzzy neural network for the performance evaluation system of AC contactor is modeled. The conception and method which are proposed in this paper are valuable to both the electrical apparatus R&D and product examination. 5 Refs. In Chinese.
Key words: AC contactor; dynamic testing; performance evaluation; fuzzy classification; neural network 
MIAO Xi-ren (Fuzhou University, Fuzhou 350002, China), LIN Su-bin, ZHANG Pei-ming // Adv. Tech. of Elec. Eng. & Energy, 2006, 25(3): 9-12.

Study on an actively controlled battery/ultracapacitor hybrid in stand-alone PV system.
Sound performance can be attained through battery/ultracapacitor hybrid, which makes the best of the characteristics of high energy density of battery and high power density and long circle life of ultracapacitor. An actively controlled hybrid structure was put forward and utilized in a stand-alone PV system. The model and control loop of the system were set up. Experiment results exhibited that the current of the battery is quite smooth when PV power and load power varied quickly. The small charge and recharge cycles due to irradiation variation can be reduced effectively through proper ultracapacitor bank configuration. The hybrid energy storage in PV system can become economical for the reasons that the battery capacity can be reduced for the purpose of high power requirement and that the life of the battery can be lengthened due to reduced small charging and recharging cycles. Something valuable and practical can be attained from this paper to solve the energy storage problem in stand-alone PV system and other regeneration energy systems. 12 Refs. In Chinese.
Key words: stand-alone PV system; battery; ultracapacitor; hybrid energy storage
TANG Xi-sheng1,2 (1. Institute of Electrical Engineering Chinese Academy of Science, Beijing 100080, China; 2. Graduate School of Chinese Academy of Science, Beijing 100039, China), QI Zhi-ping // Adv. Tech. of Elec. Eng. & Energy, 2006, 25(3): 37-41.

Simulation of 3D temperature distribution of immersion evaporative cooling turbo-generator combined with forced inner cooling system.
Evaporative cooling combined with inner-cooling system used in turbo-generator has ascendancy over other traditional cooling methods. It offers a more safe, reliable and effective result of insulation and cooling. So it is worthy to have a deep research in temperature distribution calculation. Based on analysis of a 50MW turbo-generator which has been run successfully for ten years, a complete simulation model in three dimensional for temperature calculating of the state with evaporative cooling core and forced inner cooling coil winding has been established for the first time. Effect on the temperature distribution of stator concerned with the change of load and inner cooling of stator coil winding has also been analyzed by numerical simulation. Result of simulation has been tested by experimented investigations and coincides well with experiment. Analysis of this paper should be provided as academic foundation for design and manufacture turbo-generator of higher capacity with evaporative cooling system. 8 Refs. In Chinese.
Key words: turbo-generator; evaporative cooling; inner cooling; heat transfer; temperature field
WEN Zhi-wei1,2 (1. Institute Electrical Engineering, Chinese Academy of Sciences, Beijing 100080, China; 2. Graduate School of the Chinese Academy of Sciences, Beijing 100039, China), FU De-ping, GU Guo-biao // Adv. Tech. of Elec. Eng. & Energy, 2006, 25(3): 13-17.

Research on method of measurement wide range AC current with high accuracy.
Usually, in relay protection system, measurement of wide range AC current is inevitable. This paper analyzes the measuring principle of AC current based on Rogowski coil and digital signal processing. Unsaturated characteristic of Rogowski coil makes it suitable for measurement wide range AC current, and with digital signal processing technology, this measurement principle can eliminate the zero drift, nonlinear error and capacity leakage. We have done some experiments with it, and it is proved that its characteristic is very good and gets good results. Adopting this principle, it is possible to measure wide range AC current precisely and simply. 13 Refs. In Chinese.
Key words: relay protection; Rogowski coil; zero drift; digital signal processing
CHEN Peng (Hebei University of Technology, Tianjin 300130, China), LU Jian-guo, LI Xin, et al. // Adv. Tech. of Elec. Eng. & Energy, 2006, 25(3): 21-24.

Research on improved harmonic detecting method based on sliding Fourier analysis.
In this paper an improved harmonic current detecting method based on the sliding Fourier analysis is presented to decrease the calculating errors when the source frequency varies. The relation between the source current frequency and calculating result is discussed in detail, and hardware of PLL was induced to detecting the variation of the source frequency. At the same time, the detecting precision of the improved method doesn’t vary with the sampling frequency. The detecting precision based on the improved method is related to the sampling frequency of the source current, and the preferable detecting precision can be attained in a less high sampling frequency. In addition, the effect of PLL’s precision to the detecting error is analyzed theoretically, and the rational scope is given. In conclusion, the proposed detecting method improves the detecting precision of hybrid active power filter. Lastly, simulation results based on the proposed approach also confirm the validity of the proposed method. 5 Refs. In Chinese.
Key words: active power filter; harmonic current detection; sliding Fourier analysis; PLL
GU Jian-jun (Energy Department of Shanghai Baosteel Co. Ltd., Shanghai 200941, China), LI Kai, XU Dian-guo, et al. // Adv. Tech. of Elec. Eng. & Energy, 2006, 25(3): 50-53.

Study of high-voltage switching power supply based on PSM technology
DU Shao-wu，YANG Yu-hui
(School of Elec. and Automatic Eng., Hefei University of Technology, Hefei 230009, China)
Abstract: The Pulse Step Modulation (PSM) technology is the combination of the Pulse Width Modulation (PWM) and the Step Modulation (SM). And it is an important technology which is used in high-voltage high-power switching power supply systems. First, the principle and characteristics of SM and PWM are introduced. Second, the basic principle of PSM and its control scheme are discussed in detail. The feasibility and advantages of power supply systems based on PSM are verified on an experimental prototype．
Key words: pulse step modulation（PSM）；pulse width modulation（PWM）；step modulation（SM）；high-voltage and high-power

Research of control method of power electronics circuit based on Finite State Machine
TANG Xiong-min, YI Na, PENG Yong-jin
(College of Electric and Information, Hunan University, Chanshang 410082, China)
Abstract：The control of power electron equipment is mainly to control the on-off condition and duration of the power switch, so the modes of power electronics equipment can be defined by corresponding states and the states can be combined as a Finite State Machine (FSM). Once the concept of FSM is introduced into the control loop of power electronics equipment, the accurate control of power electronics equipment can be achieved by controlling the switching condition of the different states. The modeling, simulation and experiment of Pulse Density Modulation (PDM) with FSM are presented in the paper. The merit of control with FSM, such as easy implementation, simple hardware and flexible control is validated, so the control method with FSM is suitable for control of power electronics equipment and is a recommendable modeling and control method.
Key words：Finite State Machine; power electron; control method; pulse density modulation

Analysis of steady-state modulation error of SPWM
 JIANG Xu, Xiao Xiang-ning, MA Yu-long, DING Hui, WANG Quan-tao
(Key Laboratory of Power System Protection and Dynamic Security Monitoring and Control
(North China Electric Power University), Ministry of Education, Beijing 102206, China)
Abstract: PWM technology is one of the key technologies on power electronics. The concept of PWM Steady-state Modulation Error (PWMSME) is proposed to analyze the affections of all kinds of factors. Taking SPWM for example, the authors produce an accurate mathematic representation of PWMSME based on Fourier transform, analyze the affections of carrier frequency, deadband and sample methods to PWMSME. And the expression of quantification is obtained. It is pointed out that, according to the theory of homalographic of impulse, there’s some calculation error in the case of low carrier frequency. At last, the simulation model of a H-bridge inverter based on unipolar SPWM is set up in EMTDC/PSCAD. By analyzing the difference between simulation and experiment results and calculation results, the conclusions are verified.
Key words: SPWM; error; Fourier transform; modulation; deadband; regular sample

Influence of frequency of voltage applied on the propagation characteristics
of electrical trees in XLPE cable insulation
XIE An-sheng 1,2， LI Sheng-tao 1， ZHENG Xiao-quan 1，G CHEN3
(1. State Key Laboratory of Electrical Insulation and Power Equipment, Xi’an Jiaotong University, Xi’an 710049, China;
2. Environment Science and Engineering College, Chang’an University, Xi’an 710064, China;
3. University of Southampton, Southampton SO17 1BJ, UK)
Abstract: In this paper the structures and propagation characteristics of electrical trees under high voltage of 50-2000Hz in the cross-inked polyethylene (XLPE) cable insulation samples are studied. It is found that there are three kinds of electrical trees, the branch-like tree, mixed tree combining branch with jungle, and pure jungle-like trees, that will appeared in the sample when frequency is less than 250 Hz due to non-uniform crystallization and micro-defects concentrated in XLPE cable insulation. Only one kind of electrical tree, the dense branch-like trees, will be developed when frequency is equal to or higher than 500Hz. The propagation mechanisms of these kinds of electrical trees are mainly decided by crystalline state of the dielectric and the frequency of voltage applied. The structures and propagation characteristics of electrical trees is closely related to aggregation state of material in low frequency, and is nothing to do with the aggregation state of material at high frequency. The propagation law of electrical trees in XLPE cable insulation at high frequency is similar as in epoxy resin and PMMA. The propagation characteristics of electrical trees not only depends upon the crystal-boundary and microspore in amorphous interface, but also depends upon the impurity concentration and the relative position between electrode tip and sphere-crystals or amorphous region in low frequency. Because the processes of injection and elicitation charge from and to dielectric by electrode are more violent at high frequency than at low frequency, it can form relatively uniform dielectric weak region at the front of needle electrode, so the initiation and propagation law of electrical trees at high frequency is similar each other.　 
Key words: XLPE; electrical trees; frequency; structure; propagation

Analysis and comparison for inductor loss of the critical conduction mode boost PFC circuit
DING Ang, WU Xin-ke, QIAN Zhao-ming
（Zhejiang University, Hangzhou 310027, China）
Abstract：The working principle and characteristic of the Boost power factor correction (PFC) circuit operating in critical conduction mode are investigated. Also core and winding loss of Boost inductor in this circuit is analyzed. In this application, it is found that fringing fields associated with high frequency current pulses cause much eddy current losses in windings of the inductor. By avoiding winding around gaps, the eddy current losses can be minimized. A finite-element analysis (FEA’s) is used to investigate the magnetic flux lines and density distribution around cores with traditional and improved winding structures. Finally, five inductors with different winding structures are built and compared. The proposed winding structure is verified with measurements on prototype operating in a 200W PFC converter.
Key words：critical conduction mode；power factor correction；inductor loss；inductor winding

Nonlinear design of linear induction motor for urban rail transit
MA Yu-jie, CHAI Jian-yun
(Department of Electrical Engineering, Tsinghua University, Beijing 100084, China)
Abstract: A nonlinear design approach of linear induction motor (LIM) for urban rail transit is presented. The method is based on coupling of two-dimensional time-step finite element method and exterior drive circuit. Magnetic saturation of yoke and back iron, and edge effect caused by velocity are considered sufficiently. Current, voltage, magnetic flux density, thrust and efficiency can be calculated directly. By comparing with linear design method, the current and thrust calculated by nonlinear method are more accurate. It provides reliable basis on selection of cooling capability of motors as well as power capacity of variable frequency drives. A calculation example is presented to demonstrate the effectiveness of the proposed method.
Key words: linear induction motor; time-step finite element method; saturation of magnetic material

A survey on location method for harmonic sources in power system
XU Zhi-xiang1,2, HOU Shi-ying1,2, LV Hou-yu1,2, ZHANG Ke1,2
(1. Institute of Electrical Engineering, ChongQing University, Chongqing 400044, China;
2. The Key Laboratory of High Voltage Engineering and Electrical New Technology, Ministry of Education, Chongqing University, Chongqing 400044, China)
Abstract：The study of the harmonic source location plays an important part in the supreme power system with complicated loads. The methods which are being used at present are analyzed and discussed. Some opinions on the developing study of the location of the harmonic source are brought forward.
Key words: power system; harmonic source location; equivalent model; harmonic state estimation

Development and result analysis of on-line device for monitoring overvoltage 
in 10kV power system
ZHOU Kai1, ZHANG Tao1, DONG Xiu-cheng1, ZHANG Bi-de1, XI Shi-you2
(1. Xihua University, Chengdu 610016, China; 2. Chongqing Qinan Power Corp., Qijiang 401420, China)
Abstract: Some overvoltage accidents usually occur in 10kV power system, and it is difficult to analyse its causes using usual fault oscilloscope. In this paper, a new device to monitor lightning impulse overvoltage and inner overvoltage in 10kV power system is presented. Design principle and key technique are discussed. Capacitance-resistance divider with excellent performance of frequency response is designed to capture overvoltage, and it is more suitable than potential transformer to transfer lightning impulse overvoltage according to result of square-wave response. Special data acquisition technique is introduced, including double buffer、suitable size of memory and pre-trigger. Data acquisition software and waveform analysis software are independent to easily analyse waveform in different computer. The precision of the device based on 50Hz Sine and standard lightning impulse is satisfied. From long-time operation, results indicate that the performance of the device for monitoring overvoltage is excellent and overvoltage captured is useful to analyse forming causes of overvoltage accident.
Key words: 10kV power system; overvotage; on-line monitoring; double buffer; capacitance-resistance divider

A trigger circuit of multi-stage reconnection electromagnetic launch system
ZHAO Chun, ZOU Ji-yan, LIAO Min-fu, LI Xiao-peng, ZHOU Zheng-yang
(Dept. of Electrical and Electronic Engineering, Dalian University of Technology, Dalian 116024, China)
Abstract: Reconnection electromagnetic launch is a kind of electromagnetic launch that utilizes electromagnetic energy to propel a projectile. The key point of a multi-stage launch is the sequential energy releasing at various stages, which demands the right and reliable action of the closing switches. Triggered vacuum switches (TVS) are used as closing switches in the study. A three-electrode-gap is used in the high voltage trigger pulse generating circuit to acquire a steepened high voltage trigger pulse, so as to ensure that the accuracy of delay time of TVS switching to outer control signal is controlled within 1μS. HFBR-0400 series of fiber optic transmitters and receivers are used in the trigger signal generating circuit to improve the ability to inhibit interference. Mis-triggering because of mutual interferences among stages is solved in the experiments of multi-stage launch. Fiber optics are used between transmitters and receivers to insolate the low voltage control unit from the high voltage triggering units. 
Key words: reconnection electromagnetic launch; trigger circuit; interference inhibition; fiber optic isolation