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Design and research of nonlinear inductor in PFC converter
YAN Kai-qin, LI Zhu-jun, CHEN Qian-hong
(Nanjing University of Aeronautics & Astronautics, Nanjing 210016, China)
Abstract: Powder core inductor is widely used in power factor correction occasions because of its low dissipation, high saturation magnetic induction and even gap distribution, but its nonlinearity also brings us difficulties in analysis and design. This paper discussed the design of the nonlinear inductor in a Boost PFC converter based on current ripple, and analyzed the theory in core choosing through physical concept. Then, the relationship between the current ripple of the inductor and the input voltage was discussed, so the working point of the inductor is quite convenient to be confirmed. After the design, the model of the inductor was made using the gyrator-capacitor simulation model. Both the derivation of current ripple and the inductor model proved to be valid by simulation and experiments.
Key words：nonlinear inductor; current ripple; gyrator-capacitor model; simulation
Intrinsically safe performance analysis and optimization design of staggered parallel magnetic integrated Buck DC-DC converter
YANG Yu-gang，LI Long-hua
（College of Electrical and Control Engineering of Liaoning Technical University, Huludao 125105, China）
Abstract：In this paper, the maximum peak inductor current in continuous conduction mode and discontinuous conduction mode of staggered parallel magnetic integrated Buck DC-DC converter is analyzed. The maximum peak inductor current worked in the CCM mode is the maximum inductor current within the work range. Ignoring the effects of the voltage ripple, the maximum output short-circuit release energy across the entire operating range is derived. Through comparing the maximum current of the inductor with the minimum ignition current and comparing the maximum output short-circuit more energy is released with the minimum ignition energy of the discharge to arrive the intrinsically safe parallel magnetic integrated Buck DC-DC converter. Based on the requirement of the output intrinsically safe and intrinsically safe within the scope of work, the appropriate range of inductance and capacitance can be obtained. By maximum output short-circuit released energy partial derivatives of inductance and to make it equal to zero, it can be concluded that the best design parameters of inductance and capacitance when maximum output short-circuit released energy to a minimum under the conditions can be given. Experimental results show the analysis is feasible.
Key words: intrinsic safety; Buck converter; staggered parallel magnetic integration; minimum ignition discharged energy; optimal design
Research on a new single-switch high gain boost converter
ZHANG Shi-yu, XU Jian-ping, YANG Ping
(College of Electrical Engineering, Southwest Jiaotong University, Chengdu 610031, China)
Abstract: In this paper, a hybrid topology that combining single-switch quadratic boost converter and voltage lift technique is proposed, and the proposed converter provides high voltage gain and reduced switching voltage stress, and is suitable for application of wide input voltage. The working principle of the new single-switch high gain boost converter is analyzed in this paper. The steady state characteristics of the converter and relationship among circuit parameters are studied. Compared with quadratic boost converter, the switch voltage stress of proposed converter is lower, which enables to use MOSFET switch with lower voltage and on-resistance to reduce costs as well as switching and conduction losses. Simulation and experimental results are presented to verify the theoretical analysis.
Key words：high gain boost converter; voltage-lift-technique; steady state characteristics; DC-DC converter
Power loss calculation for LLCL-filter based single-phase grid-tied inverter with different kinds of inductor selection
WU Hui-yun1, WU Wei-min1, HUANG Min2, Frede Blaabjerg2
(1. The Power Electronics and Control Research Institute, Shanghai Maritime University, Shanghai 201306, China; 2. Institute of Energy Technology of Aalborg University, Aalborg 9220, Denmark)
Abstract: Along with application of the LLCL-filter, the working state of the large current ripple ratio for a grid-tied inverter is catching more and more attention. The error may take place if the conventional efficiency analysis is adopted under this condition. In this paper, an integrated power loss calculation method is proposed, which is illustrated by analyzing the power loss of an LLCL-filter based single-phase grid-tied inverter using the discontinuous modulation. The expression of the inverter-side current of the inverter is deduced and it makes the power loss calculation more precise, where this method can be also adopted for the power loss calculation of the inverter using other modulation methods or with other type power filters. Furthermore, the efficiency curves under the different current ripple ratios are also given, which is much helpful for the selection of the LLCL-filter parameters. Finally, the calculation results are verified through the experiments on a 2 kW single–phase grid-tied inverter prototype.
Key words：LLCL-filter; single-phase grid-tied inverter; inductor; power component; power loss; efficiency
Independent photovoltaic power system based on analog circuit MPPT control
CAI Yan1, WANG Li-na1, SUN Kai2
(1. School of Automation Science and Elec. Eng., Beihang University, Beijing 100191, China;
2. State Key Lab of Power Systems, Tsinghua University, Beijing 100084, China)
Abstract: An independent photovoltaic power system based on analog circuit MPPT control is proposed in this paper. The system consists of photovoltaic array as the input, superbuck circuit as the converter and paralleled battery and load as the output. Analog circuit MPPT control, battery constant voltage control and battery constant current control work in coordination to allow the system to get the maximum power point of the photovoltaic array with the respect of battery safe charge and discharge. The system has the advantages of high solar energy usage, high reliability, small ripple wave and low cost. The simulation and experimental results show that the system can track the maximum power point accurately and maximize the use of the solar energy with the battery.
Key words: analog circuit maximum power point tracking; superbuck; photovoltaic power system
Design of passivity-based controller for synchronous motors
SONG Ke1, DAI Peng2, YUAN Qing-qing2, FU Xiao2
(1. Xinxiang Power Supply Company, Henan Electric Power Corporation, Xinxiang 453000, China; 2. School of Information and Electrical Engineering, China University of Mining and Technology, Xuzhou 221008, China)
Abstract: Passivity-based control is a kind of energy based control strategy with global definition and global stability. As a nature of nonlinear control, it enhance the robustness of the system and is insensitive to the change of parameters and disturbance. The mathematical model in Euler-Lagrange equation of synchronous motor is established in this paper. The key point of passivity-based control is to identify the workless force, which has no effect on the energy balance equation of the close loop. The passivity-based controller is designed based on the workless force. This controller is not only simple and without any singular points, but also unnecessary to have the rotor damping component observer. The simulation shows that the controller can implement the expected goals and effectively demonstrate the strategy.
Key words: synchronous motors; passivity-based control; stability
Research on rotor position measurement of direct driving permanent magnet synchronous wind generator
DENG Hui-wen, XIE Ming-li, CAO Hu, GUO Yu-hua
(School of Electrical Engineering, Southwest Jiaotong University, Chengdu 610031, China）
Abstract: This article describes characteristics and application of a variety of existing rotor position measurement methods of permanent magnet synchronous generator. All these methods can realize the rotor position detection, but all of them have limitations. The dissertation lists the shortcomings of various of methods, compares their advantages and disadvantages, then puts forward to a new method called incremental photoelectric encoder. This method makes use of the photoelectric effect to realize the rotor position detection. According to the characteristics of the permanent magnet synchronous motor, this method is more applicable for determination of the rotor position. This method is relatively simple, while its accuracy is relatively high. Then the paper analyses the initial position of motor and the experimental results of the detection. Finally, the experimental results verify that the method is feasible and correct, and can inspect the initial position of motor rotor effectively and reliably.
Key words: direct-drive; permanent magnet synchronous generator; incremental photoelectric encoder; rotor position detection
Inertia identification methods for permanent magnetic AC servo system
HAN Ya-rong1, QIU Xin2, ZHU De-ming1,2
(1. Zhongshan Technical College, Nanjing 210049, China; 2. Aero-Power Science-Technology Center,
Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China)
Abstract: The goal of this paper is to study the inertia identification methods of the rotor, which has significant effects on the dynamic property of permanent magnetic AC servo system. Based on the research of several conventional inertia identification methods, two novel methods are proposed. The improved acceleration deceleration method can identify the inertia under the rotor microseism condition and the novel bisection method can identify the load and the inertia at the same time. The two new methods expand applicability of conventional methods, which are verified by experiment results.
Key words: PM AC servo system; inertia identification; acceleration deceleration method; MRAI; bisection method
Research on doubly-fed induction generator low voltage ride-through
based on a new technology
GUO Qiang
(China Railway First Survey and Design Institute，Xi’an 710032, China)
Abstract：At present, along with increasing power output of the single generator unit and wind power grid-connected capacity, the proportion of wind power is even larger in the grid power, the grid-connected rules is more strict, and to ensure the wind power unit not to be out-of-step under grid voltage dip becomes a mandatory problem. The electromagnetic transient process is firstly analysed under grid voltage dip, the simulation spectrum analysis is also done, and then the low voltage ride-through (LVRT) control strategy by considering the stator electromagnetic transient process is proposed. The simulation and contrast analysis shows that the improved control strategy can restrain the rotor current impact effectively, and can increase the uninterrupted operation ability of doubly-fed induction generator (DFIG) under grid voltage dip. Finally, the experiment is finished in the laboratory DFIG platform, and the experimental results verify the feasibility and effectiveness of the proposed control strategy.
Key words: low voltage ride-through; doubly-fed induction generator; electromagnetic transient process; precise model
Simulation research for LVRT of DFIG with Crowbar
LIN Guan-wu，WANG Gui-feng
(College of Technology and Engineering, Lanzhou University of Technology, Lanzhou 730050, China)
Abstract: The LVRT control strategy and protection schemes of DFIG are discussed in condition of large external voltage dip．The DFIG mathematical model considering the changed grid voltage is adopted and the control model of LVRT is established．The switching strategy of Crowbar is researched in detail during simulation． The simulation results verify that Crowbar circuit and the control strategy are effective and prove that Crowbar control strategy can limit the over current in the rotor and the over voltage of the DC bus as well as the transient oscillation of the electromagnetic torque efficiently．Moreover，a reactive current is injected into the grid to assist the recovery of the grid voltage， which is in favor of achieving the LVRT of DFIG．Through the measurement results, corresponding control strategies, which are available for reference to further research on control strategy based on the standard of LVRT, are investigated.
Key words: doubly-fed induction generator; voltage sag; Crowbar circuit; low-voltage ride through (LVRT)
Control strategy on hybrid fuel cell generation system based on ADP
ZHENG Wen-di, CAI Jin-ding, LIU Li-jun
(College of Electrical Engineering and Automation, Fuzhou University, Fuzhou 350108, China)
Abstract: An approximate dynamic programming (ADP) method is used for fuel cell energy management based on studying on structure of hybrid fuel cell/supercapacitor. The principle and formation of action depended heuristic dynamic programming (ADHDP) are introduced in detail. The action network, which is used to generate control signal constituted by fuzzy-neural network instead of conventional multiple layer perceptron neural network, makes physical interpretation between input and output more clear. The layout of increment output is more satisfied by strong dynamic constraint condition caused by limits of fuel utilization. The structure and parameters adjusting method of critic network and fuzzy-neural network are described in this paper in terms of state and control variables of the system. Finally, the simulation verifies the correctness of the proposed control strategy and its good performance on load following. The fuel utilization is usual in the constraint range even in transient state that ensures the safety and efficiency of the system. Compared with conventional PI regulation, the ADP method has characteristics of fast response and small overshoot.
Key words: approximate dynamic programming; fuel cell; supercapacitor; converter; fuel utilization
Analysis of capacity requirements of battery energy storage based on forecasted wind power correction
KE Lian-jin, PAN Wen-xia, ZHU Jian-hong
(Research Center for Renewable Energy Generation Engineering, Ministry of Education, Nanjing 210098, China)
Abstract: Many problems such as deviation and instability of frequency and voltage of the power system caused by wind power paralleling in the grid can be effectively alleviated with the energy storage system. Analysis of the optimal capacity of the battery is a key issue in the research of the wind/storage system because of its high cost. This paper proposes a method to reduce the demand capacity of the battery energy storage system (BESS) based on the amending forecasted power by analyzing the reason of large demand capacity. And BESS is controlled according to the amending forecasted power, which make the curve of change of SOC (state of charge) smoother. The effectiveness and feasibility of this method is verified by the actual wind generation output data within 48 hours and the simulation results with PSCAD.
Key words: wind power; power forecasting; capacity of battery; correction
Research on key technologies in 1140V cascaded STATCOM
CAO Xue-xiang1，ZHAO Wan-yun1，XU Tian-ran1，ZHAI Fu-jun2, SHI Li-ping1
(1. School of Information and Electrical Engineering, China University of Mining and Technology,
Xuzhou 221008, China; 2. Power Supply Group of Zaozhuang Mining, Zaozhuang 277000, China)
Abstract: Based on cascaded H-bridge inverter topology, the method of CPS-SPWM (Carrier Phase Shifting SPWM) is applied to the system of STATCOM. This method can effectively improve the characteristics of AC output voltage. Meanwhile, under the lower switching frequency, it is possible to obtain a higher output voltage level and to reduce output voltage harmonic contents. In addition, combining with theory of the feedback decoupling control, we make key researches on the characteristics of STATCOM system while changing the parameters of current loop. We also build a low-voltage 1140V cascaded STATCOM test platform, and the practical range of optimal PI parameters is given in field applications. It confirms that the STATCOM has a fast response and a perfect compensation effect.
Key words: CPS-SPWM; STATCOM; feedback decoupling control; optimal PI control parameters; low-voltage 1140V
A new approach to detect fault line in resonant earthed system based on Hilbert spectrum band-pass filter and transient waveform recognition
GUO Mou-fa, LIU Shi-dan, YANG Geng-jie
(College of Electrical Engineering and Automation, Fuzhou University, Fuzhou 350108, China)
Abstract: The similarity degree of the transient zero-sequence current signals between fault line and un-fault lines was lower than that in un-fault lines after earthed fault occurring in resonant earthed system. A new approach to detect fault line which was based upon the time-frequency partial characteristics recognition of the transient fault zero-sequence current signals was presented. After extracting the first base sine cycle data on the signals of transient fault zero-sequence current, all frequency band component for each line could be obtained through Hilbert spectrum band-pass filter. Then they were divided into small time-frequency pieces which had the same frequency bandwidth and time interval. The elements of time-frequency block spectrum matrixes of all lines could be obtained by calculating the area of time-frequency pieces. Comprehensive similarity coefficient of each line could be obtained by the integration of correlation analysis and Euclidean distance calculating. Comprehensive similarity coefficient combined with criterion was used for fault line detection. Simulation results verify that the proposed approach for fault line detection could be adapted to all kinds of fault conditions and influence factors and has the characteristics of high margin and veracity.
Key words：resonant earthed system; fault line detection; transient zero-sequence current; Hilbert-Huang transform; Hilbert spectrum band-pass filter; time-frequency block spectrum matrix; waveform recognition
Analysis & applications of comb-shaped electric shielding characteristics on high frequency electromagnetic fielding shielding effect in SMPS
CHEN Qing-bin, CHEN Wei
(College of Electrical Engineering and Automation, Fuzhou University, Fuzhou 350108, China)
Abstract：Copper foil electric field shielding is commonly used in the SMPS to shield the magnetic components in order to reduce the electric coupling between the magnetic components and the ground. This paper analyzed in detail the traditional copper shielding foil, which can not only shield the electric field, but also affect the AC magnetic field distributions due to high-frequency eddy current effects and resulting in extra eddy current losses in the foil and the changes of magnetic parameters of the magnetic components. These behaviors are not suitable in many cases, where only the electric field needs to be shielded. The comb-shaped electric shielding has good electric field shielding effect, but with no effect on the magnetic field. With the new shielding sheet, the eddy current effect due to AC magnetic field can be avoided. The influence of the structure parameters of the comb-shaped electric shielding to the electric field and high frequency magnetic field is analyzed by simulation. Finally, the application example of the electric shielding in LLC integrated transformer verified the proposed comb-shaped electric shielding to be effective and feasible.
Key words：SMPS; magnetic components; EMI; electric shielding; eddy current effect
Three-phase voltage sag detection without phase lock loop
XUE Shang-qing, CAI Jin-ding，LIU Li-jun
(College of Electrical Engineering & Automation, Fuzhou University, Fuzhou 350108, China)
Abstract: Aiming at the problem that voltage sag detection methods based on dq transformation are easily affected by phase lock loop’s(PLL) signal error, a novel method for three-phase voltage detection without PLL is presented. Based on instantaneous symmetrical components and coordination transformation, the model of detecting positive and negative sequence components by 90°-leading-phase-shift operator is constructed on the orthogonal αβ reference frame. Unscented Kalman Filter is adopted to develop the phase-shift operator. Simulation studies are carried out in MATLAB/Simulink and the results verify the correctness and feasibility of the proposed method.
Key words：voltage sag detection；phase lock loop；αβ coordination transformation；90°-leading-phase-shift operator；unscented Kalman filter
Synthesis of hydrogen peroxide via hydrogen-oxygen plasma
GOU Jian-xia1, XIE Sheng-li1, XU Yue2, ZHOU Jun-cheng2, GUO Hong-chen3
(1. Department of Chemistry and Chemical Engineering, Binzhou University, Binzhou 256603, China;
2. The 718th Research Institute of CSIC, Handan 056027, China; 3. Department of Catalytic Chemistry and Engineering& National Key Laboratory of Fine Chemicals Dalian University of Technology, Dalian 116012, China)
Abstract：Hydrogen peroxide was successfully synthesized from hydrogen-oxygen plasma by atmospheric dielectric barrier discharge with tubular reactor. The effect of material of high-voltage electrode wire and corresponding optical images of H2/O2 gas discharge have been systematically studied. Results showed that when using the polyester coated copper wire as the center electrode, the polyester can be broken down. It was observed that the selectivity and the formation rate of H2O2 declined and the optical image of H2/O2 gas discharge was less uniform and mild, after the polyester being broken down. When using a thin pyrex-tube covered metal wire as high-voltage electrode, the conversion of O2, the selectivity of H2O2 and the formation rate of H2O2 were 62.1%, 58.1%% and 4.76mmol/h, respectively. And the discharge was very stable, uniform and mild. The formation rate of H2O2 strongly depends on the optical images of H2/O2 gas discharge, and the uniform and mild of the discharge is in favor of the production of H2O2.
Key words：dielectric barrier discharge; hydrogen peroxide; hydrogen and oxygen plasma; high-voltage electrode
Survey of fault diagnosis method for brush and slip ring system of doubly-fed induction generators
CHEN Tao-tao, MA Hong-zhong
(College of Energy and Electrical Engineering, Hohai University, Nanjing 210098, China)
Abstract: The brush and slip ring system plays a crucial role in the stable operation of doubly-fed induction generator (DFIG), but the system failure frequently occurs, causing much wasting of human-power and resources. Similar to the brush and slip ring system of the traditional generator, the failure mechanism of doubly-fed induction generator’s brush and slip ring system is relatively simple, but it is difficult to monitor the system in real-time and to obtain the accurate and effective results. So the paper introduces the common types of fault mechanism of brush and slip ring system firstly, and then describes and analyzes existed brush and slip ring system states monitoring methods particularly. At last, the paper gives the prospect of the trend and direction of development of the state monitoring of brush and slip ring system in doubly-fed induction generator (DFIG) in future.
Key words: DFIG; brush and slip ring; condition monitoring; spark; temperature; vibration; noise
Analysis and comparison of PWM modulation strategies for Z-source inverter
XUE Bi-cui1,2, ZHANG Cheng-hui1, DING Xin-ping1
(1. Shandong University，Jinan 250061，China；2. University of Jinan，Jinan 250022，China)
Abstract：Z-source inverter is a single-stage inverter, which has buck/boost characteristic. Compared with the widely used voltage source inverter and the voltage source inverter with cascaded boost chopper circuit, Z-source inverter has the advantages of simple structure, high efficiency and system reliability. This paper introduces the operating principle of Z-source inverter briefly, and focuses on PWM modulation strategies for Z-source inverter. Several PWM modulation strategies are presented including simple boost, maximum boost, maximum constant boost, boost modulation with third harmonic injection, short-through subsection based on SVPWM and sine carrier PWM. Through the qualitative analysis and quantity comparison, the paper contrasts the performance of different modulation strategies, sums up their advantages and disadvantages separately from boost capability, voltage stress and current ripple, and lists the parameters comparison table. All these provide a theoretical basis for system selection and application.
Key words：Z-source inverter；PWM；shoot-through states；voltage gain
High voltage frequency-variable power source for microwave oven based on LLC resonant converter
WANG Chun-fang, ZHANG Zhi-yong, ZHU Shi-pan
(School of Automation Engineering, Qingdao University, Qingdao 266071, China)
Abstract: The traditional power supply for microwave oven adopted power frequency transformer voltage doubler working mode to acquire a high output voltage, but this kind of power source has disadvantages, such as small power density, low efficiency, more switching noise and producing serious electromagnetic pollution to the electric network. In order to solve these problems, a high voltage variable frequency power source was designed. Its main circuit adopted LLC resonant soft switching converter with voltage doubler rectifier mode and in control circuit the chip L6599 used as the central controller was adopted. The DC gain of the converter was derived by the First Harmonic Approximation, and the coefficient of resonant inductance in resonant network and quality factor was analyzed, then the resonant parameter of converter was optimized. The working characteristics of the main circuit were analyzed by MATLAB and SABER simulation software. Finally, the experimental results show that the design scheme is reasonable and correct.
Key words: voltage doubler rectifier mode; LLC resonant converter; L6599; first harmonic approximation
Research and development of bipolar micro arc electrodeposition power supply system
CHEN Hai-tao1, WU Hu-lin1, MA Yue-zhou2, ZHANG Long-ping1, LI Zhong-sheng1,3
(1. No.59 Institute of China Ordnance Industry, Chongqing 400039, China; 2. State Key Lab. of Gansu Advanced Non-Ferrous Metal Materials, Gansu Lanzhou Univ. of Tech., Lanzhou 730050, China; 3. Materials Science and Engineering College, Chongqing University, Chongqing 400030，China)
Abstract: For satisfying the demand of micro-arc oxidation and cathodic micro-arc electrodeposition, a bipolar direct current impulse power-supply system was designed in this paper, which is composed of main circuit and control system. Main circuit is the one of two-stage structure, in which the fore-stage is three-phase half wave bridge rectifier circuit and its trigger circuit, and the posterior-stage is a dc-to-ac converter, including dc-to-ac converter bridge circuit, drive circuit and pulse wave pattern generator, which assured to get bipolar pulse wave pattern that frequency and duty ratio can be adjustable. Control system uses double closed loop of the power-supply system, so in which the inner loop is voltage loop, and the external loop is current loop. PI adjustment algorithm is used to implementation constant current and constant voltage control, and at the same time control system uses asynchronous serial communication to exchange data with man-machine interface.
Key words: micro-arc oxidation; cathodic micro-arc electrodeposition; bipolar pulse power supply; IGB
Application and contrast analysis of BP and RBF neural network in prediction of breakdown voltage of air gap
LUO Xin, NIU Hai-qing, LIN Hao-ran, YOU Yong
(School of Electric Power, South China University of Technology, Guangzhou 510641, China)
Abstract: Breakdown voltage of air gap is an important factor to determine the level of external insulation. Almost all the theories about the prediction of breakdown voltage now existing are based on empirical equation of one parameter. This paper discusses the application of BP neural network and RBF neural network in the prediction of breakdown voltage of air gap, illustrates the experiment process of breakdown voltage and describes both BP and RBF network constructions. Firstly both neural networks are trained by the sample data obtained in artificial climate can. Secondly networks which have been trained are used to predict the breakdown voltage. The results indicate that the application of BP neural network and RBF neural network is feasible. Through the comparison between BP and RBF neural networks we conclude that RBF neural network is superior to BP neural network in accuracy, training efficiency and ability of generalization. Thus RBF neural network is more suitable to predict the breakdown voltage of air gap.
Key words: breakdown voltage；prediction；BP neural network；RBF neural network
Development of fault diagnosis system for power transformer based on vibration
ZHU Yue-guang1, MA Hong-zhong1, CHEN Kai2, WANG Chun-ning2, LI Yong2
(1. College of Energy and Electrical Engineering, Hohai University, Nanjing 210098, China;
2. Nanjing Power Supply Company, Nanjing 210008, China)
Abstract: The on-line monitoring and fault diagnosis system for power transformer based on its vibration is built on Windows CE platform．The system uses the data acquisition card to collect its vibration data, analyzes it by Fast Fourier Transform，power spectrum，Hilbert-Huang Transform，and draws the real-time curve in time domain, spectrogram, power spectrum, core frequency Column Chart and Hilbert Huang spectrum．By analyzing its vibration the operation conditions of power transformer are obtained as safe or fault．If the power transformer is operating in fault condition，system will analyze the fault type of the transformer，then gives a fault alarm and keeps a transformer fault log．The system can effectively monitor and diagnose faults by testing in the dynamic model and simulation laboratory．
Key words: power transformer；data acquisition card；fault diagnosis；on-line monitoring system
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