Abstracts of Vol.24, Issue 2, 2005

A control system with voltage feed-forward for active power filter
in independent small rating power system
LI Hong-yu, WU Lon-hui, ZHUO Fang, LEI Wan-jun, WANG Zhao-an
(Department of Electrical Engineering, Xi’an Jiaotong University, Xi’an 710049, China)
Abstract: As voltage fluctuating is serious in the independent small rating power system, the traditional active power filter (APF) which is used in the large rating power system no longer performs well. In this paper, the influence to APF caused by the voltage fluctuating is analyzed, and a voltage feed-forward control method of APF is proposed. As analyzed, it can effectively restrain the influence to APF caused by the voltage fluctuating. The experimental results also demonstrate the APF with a voltage feed-forward control has good steady-state performance, and is not sensitive to the voltage fluctuating.
Key words: independent small rating power system; voltage feed-forward control; active power filter

Secondary arc extinction at double-circuit transmission lines
using high speed grounding switches
SHANG Li-qun1,2,  SHI Wei1
(1. School of Electrical Engineering, Xi’an Jiaotong University, Xi’an 710049, China;
2. School of Elec. and Control Eng., Xi’an University of Science &Tech., Xi’an 710054, China)
Abstract: Due to the coupling between double-circuit lines, the values of the secondary arc current and the recovery voltage on the double-circuit lines are higher than that on the single-circuit line. These will affect the possibility of successful auto-reclosure. In order to ensure the successful single-pole auto-reclosure, the values of the secondary arc current and recovery voltage must be limited to be less than some values. In this paper, the method using the high speed grounding switches (HSGS) to extinction the secondary arc on the double-circuit lines is proposed. The simulation results show that the magnitude of the secondary arc current and the recovery voltage is reduced by HSGS notably. The calculation results conform to the theoretical analysis. The proposed method in this paper is a good approach to extinction the secondary arc on the double circuit transmission lines.
Key word: high speed grounding switches (HSGS); double-circuit transmission lines; secondary arc current; recovery voltage

Distributed testing technology of electrical apparatus based on network
MIAO Xi-ren，LIN Su-bin，ZHANG Li-ping，ZHANG Pei-ming
(College of Electrical Engineering and Automation，Fuzhou University，Fuzhou 350002，China)
Abstract: Based on the development of embedded electrical apparatus devices, this paper expounds the distributed testing technology of electrical apparatus and develops a three-layer network configuration testing system. This system applies LabVIEW as test and control platform, which has Web-based function. With this infrastructure, not only the electrical apparatus can be evaluated based on network, but also the products testing data can be accessed among different testing phases or application departments.
Key words: electrical apparatus testing network; embedded device; LabVIEW; characteristic evaluating

Adaptive distributed control system of the metal thread feeding machine
WU Zhong-yang1, MIAO Chang-shun2, HAI Jie1
(1. Harbin University of Science and Technology, Harbin 150080, China;
2. Shenyang Electrical Motor Factory, Shenyang 110026, China)
Abstract：Metal thread feeding machine is one of the refining equipment outside the steel-making furnace, which is quite important to improve steel-making quality. This paper presents the technical requirements and structure characteristic of the adaptive distributed control of a metal thread feeding machine with a transducer. The adaptive distributed control algorithm is introduced. The simulation experimental results show the design of the control strategy is valid. The application proves that this system has preferably economic benefit and attractive outlook for applications.
Key words: adaptive control; distributed control; metal silk feeding machine; simulation

Study on high voltage capacitor voltage divider based on Invar alloys
LI Wei-kai, ZHENG Sheng-xuan
(College of Information and Technology, Yanshan University, Qinhuangdao 066004, China)
Abstract: Basic principles of optical voltage transformer use the physical effect of functional material to measure voltages, such as pockels effect、 electro-optic(Kerr) effect or converse piezoelectric effect; However, for the withstand capacity of optic material is poor, Capacitor voltage divider is often used in the high voltage potential transformer, their applying is defined because the temperature varied affects the intrinsic standoff ratio; This paper presents a capacitor voltage divider made of Invar alloys, through the comparison with those made by copper or iron, its accuracy is well improved and smaller than 0.1% when temperature ranges from -40℃ to 80℃, and a design for capacitor voltage divider of high accuracy is given in theory.
Key words: Invar alloys; capacitor voltage divider; accuracy

Commutation torque ripple restraint in BLDC motor
ZHANG Lei, QU Wen-long, LU Hai-feng
(Department of Electrical Engineering, Tsinghua University, Beijing 100084, China)

Abstract: Brushless DC motors (BLDCM) with trapezoidal back-EMF (electromotive force) have been widely used due to their high power density and easier control method, but the non-commutation current of BLDCM is distorted because of the commutation between other two phase currents at low and high speed, and results in torque ripple. This paper proposes a method to restrain the commutation torque ripple based on indirectly controlling non-commutation current by decreasing the slope of the outgoing current at high speed and directly controlling non-commutation current at low speed, both the dip (at high speed) and the spike (at low speed) in non-commutation current are suppressed. The control system is realized by the analog circuit, moreover, the application of the proposed method only needs to add a few analog components, so the configuration of the control system is very simple and the performance of the control system is reliable. Effectiveness of the proposed control method is verified by the simulation and experimental results.
Key words: brushless DC motors; commutation torque ripple; restraint

Study on high energy density composite materials
WANG Jue1, WANG De-sheng2, YAN Ping1, YANG Shi-yong2, PAN Yang1,3, HU Ai-jun 2, ZHANG Shi-chang1
(1. Institute of Electrical Engineering, Academia Sinica, Beijing 100080, China;
2. Institute of Chemistry, Academia Sinica, Beijing 100080, China;
3. Graduate School of Chinese Academy of Sciences，Beijing 100039, China)
Abstract:  In this paper, the situation and development of high energy density composite materials and stack Blumlein were introduced. The samples were made by adding BaTiO3 of different ingredient and ratio into polyimide resin with mixing and curing. The sample’s radius was 50mm and thicknesses were from 2mm to 3mm. The electrical performance of composite material was also tested. Experiment results showed that the composite’s resistance was decreased, but dielectric constant and tgδwere increased with the increase of BaTiO3’content. Though the sample group A and B had different ingredients in that group B’s dielectric constant of BaTiO3 additive was higher than group A, the dielectric constant of them was quite close. With the increase of frequency, the composite’s dielectric constant was reduced a little, while tgδwas increased. The composite materials with dielectric constants reaching over 30 and electrical fields surpassing 300kV/cm were achieved.
Key words: high energy density; polyimide; composite material; stack Blumlein; BaTiO3

A simple and fast algorithm of space vector PWM
ZHOU Wei-ping，WU Zheng-guo
(Dept. of Electrical Eng., Naval Univ. of Engineering, Wuhan 430033, China）
Abstract: The algorithm of conventional space vector PWM needs complex co-ordinate transformations, trigonometric function and inverse trigonometric function calculations, and this leads more calculation operations and low calculation precision.  A Novel algorithm of space vector PWM for three-phase voltage fed inverter is proposed. The algorithm has not any co-ordinate transformations, trigonometric function and inverse trigonometric function calculation, and has only normal arithmetic operations. The whole algorithm becomes very simple and the calculation results become more accurate. It can be easily implemented on microprocessor or DSP, and the executing speed is much faster than the conventional space vector PWM. The experiment result of three-phase three-wire DC/AC PWM inverter under the proposed strategy is given, and the result shows its validity and feasibility.
Key words: SVPWM; novel algorithm; PWM Converter

Design of a flat quadrature RF transmit coil
for permanent magnet open MRI systems
CHU Xu, ZHU Xiao-min, JIANG Xiao-hua
(Department of Electrical Engineering, Tsinghua University, Beijing 100084, China)
Abstract: To improve the efficiency of the flat RF transmit coils, a quadrature coil is designed. The structure is optimized to achieve the best efficiency while the RF magnetic field is kept homogeneous in the imaging volume and drops off quickly outside the imaging volume. To reduce the loss of the coil, some experiments were carried out to determine the cross-section of conductors and the position of the tuning points. A π-type circuit is used to eliminate the electromagnetic coupling between unit coils. A prototype quadrature coil was constructed for a 0.3 T permanent MRI system, and the experimental results of the decouple circuit are presented.
Key words: MRI; RF coils; quadrature coils; transmit coils

A novel multi-loop control method with resonant controller for CVCF inverter
HUANG Qin1,2, LI Yao-hua1
(1. Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing 100080, China;
2. Graduate School of the Chinese Academy of Sciences, Beijing 100039, China）
Abstract: Multi-loop feedback control is the key strategy for the CVCF inverter due to its ease of implementation and excellent dynamic performance. Multi-loop systems usually include an inner current regulation feedback loop and an outer voltage regulation feedback loop. The reference for the inner current loop is generated by the outer voltage loop. Steady-state error can not be eliminated because controller used in each control loop is usually a PID controller. A novel multi-loop control method with resonant controller for the CVCF inverter is introduced here. The elimination of steady-state error is achieved by the implementation of a resonant controller in the outer voltage loop. The whole design process is described in detail. Experimental result of CVCF  inverter using a resonant controller verified the proposed control scheme.
Key words: CVCF inverter; resonant controller; multi-loop control

Study of harmonic suppression scheme based on three-winding transformer
XIE Peng1, WANG Shan-ming1, WANG Xiang-heng1, LI Long-nian1, YANG Qing2
(1. Tsinghua University, Beijing 100084, China; 2. 711 Institute, Shanghai 200011, China)
Abstract: To suppress the harmonics in isolated power system, a new scheme using a three-winding transformer, the medium voltage winding of which is connected with a set of harmonic filters, is studied in this paper. The harmonics on the load side can be effectively suppressed if the parameters of the transformer and the harmonic filters are properly set. In this paper, the principle of the scheme is presented and its operation is simulated. The validity of the scheme is verified by experiments.
Key words: harmonics; three-winding transformer; suppression; shielding

Study of frequency bifurcation phenomenon of a contact-less power transmission system
HAN Teng, ZHUO Fang, YAN Jun-kai, LIU Tao, WANG Zhao-an
(School of Electrical Engineering, Xi’an Jiaotong University, Xi’an 710049, China)
Abstract: Contact-less power transmission system is suitable for the energy transmission under flammable environments, because of its spark free and no uncovered conductors. Optimal parallel capacitor at secondly side can enhance the efficiency of contact-less power transmission system, but the parallel capacitor make the system easily to have multi-resonant frequency when load changes. This paper on the basis of high order mathematic model, described the frequency bifurcation phenomenon, and used numerical method to bound the bifurcate region of parameter. We also advanced a way to choice the secondly side parallel capacitor, and the experiment results were given at the end of this paper.
Key words: contact-less power transmission; detachable transformer; efficiency; parallel compensate; frequency bifurcation

Influence of brass mantle on transient input characteristic of XLPE cable windings
LIU Jia-qi, MOU Lei, JIA Lei, LI Yan-ming
(Department of Electrical Engineering, Xi’an Jiaotong University, Xi’an 710049, China)
Abstract: For an XLPE insulation cable transformer, due to the influence of the iron core and the outer tank, the inductance of the cable winding and the capacitance of outer semiconducting layers to ground will change, so it is important to study its influence on the transient input characteristic of this kind of transformer. In this paper, a brass mantle is added on the testing model simulate the outer tank. On the basis of research results in [1], a transient input characteristic circuit model of cable windings is presented, in which the influence of the capacitance of outer semiconducting layers to ground is taken into account. It provides a theoretical basis for the design, protection and testing of this new type of power transformer.
Key words: XLPE cable windings; input characteristic; lightning impulse