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Wind speed forecasting and energy storage based power control of grid-connected wind farm
BI Da-qiang1, YANG Xin-yu2, WU Zheng-ping2
(1. State Key Lab of Power System, Dept. of Electrical Engineering, Tsinghua University, Beijing 100084, China；
2. College of Electrical Engineering & New Energy, China Three Gorges University, Yichang 443002, China）
Abstracts：Owing to the randomness of wind speed, the grid integration of large-scale wind farm brings some difficulties to power grid distribution, and even affects the stability of power system. To improve the schedulability of wind farm, the paper proposes a power conditioning and control system for grid connected wind farm based on the wind speed forecasting and Vanadium redox battery (VRB) energy storage. The BP neural network is used to forecast the wind speed in a day. According to the predicted wind speed, the power sending to the connected-grid can be calculated, and the power value is submitted to the dispatching center. The VRB is equipped at the outlet of wind farm, and it covers the deviation between the actual power and forecasted power in short time. The active power fluctuations of wind farm are effectively smoothed under the varied wind, and the operating performance of grid-connected wind farm is improved. The simulation results show that the control method can improve the coordinating ability between the wind farms and power grid, and the economic dispatch of wind farm.
Key words：wind speed forecasting; energy storage; wind farm; power generation dispatch
Research on economic dispatch of microgrid with multi-distributed generation
ZHOU Xiao-yan1, LIU Tian-qi1, SHEN Hao-dong2, SUN Guo-cheng2, DU Hong-wei2, LI Xing-yuan1
(1. School of Electrical and Information, Sichuan University, Chengdu610065, China;
2. State Grid Electric Power Research Institute, Nanjing210003, China)
Abstract: The optimal dispatch of microgrid is a new complex issue with both important social benefits and economic benefits. In this paper, based on the actual meteorological data, the actual load data, and the actual microgrid’s operation cost data, the user benefits, the environmental protection and the social benefits are quantized into the indices of operation and maintenance cost, deficient load, pollutiongas emissions and capacity shortage. Fuzzy evaluation function is adopted to convert the multi-objective into the single-objective, and the short term optimal economic dispatch model of the microgrid is proposed. The Niche-based genetic algorithm is adopted to solve the economic operation examples of typical days of a year, and then obtain the optimal output of each micro-source and the corresponding best power trading scheme in each typical case. The results demonstrate the feasibility and the effectiveness of the proposed dispatch strategies.
Key words: power system; microgrid; wind-solar-battery hybrid system; economic dispatch
Wind power prediction considering wind farm layout and wind direction
CHEN Xiang1，WANG Fu-jun2，LIU Tian-qi1, CHEN Zhen-huan2, LUO Hai-yang3, LI Xiao-hu2
(1.School of Electrical Engineering and Information, Sichuan University, Chendu 610065, China;
2. Gansu Power Company, Lanzhou730050, China; 3.Chengdu Power Company, Chengdu 610065, China)
Abstract: The paper points out the deficiencies of the extra short-term forecast of power output of the wind farm when all of the wind turbines are considered as one equivalent machine. By contrast of the forecasting actual examples, it is proved that different layout of wind turbines has influence on the power output forecast. A model for the extra short-term forecasting wind farm power output with consideration of the wind direction is established. By actual example of forecast, it is proved that the wind direction has relatively large influence on the power output. This shows the importance that not only the wind speed but also the wind direction should be considered so as to increase the precision of power output forecast.
Key words: wind farms; ultra short-term power forecasts; wind; unit layout
Transmission network planning based on multi-strategy differential evolution algorithm
NIE Hong-zhan, ZHENG Peng-fei, YU Ting, LIU Xiao-man
(School of Electrical Engineering, Northeast Dianli University, Jilin 132012, China)
Abstract: Differential evolution (DE) algorithm is a real number coding heuristic and global optimization of performance algorithm based on population. But the searching strategy of differential evolution (DE) algorithm is too unitary and the local searching capability is very poor, so more mutation strategies and local optimization strategy can raise more global and local searching ability and reduce the searching time, which adapted to solving large-scale transmission network planning. Taking line investment costs, network loss cost, the over-load cost of normal operation and transmission corridor cost as objectives, and through the results of Garver-6 system and 18 node system, it can not only prove the DE algorithm and model correctness and effectiveness in transmission network planning, but also can demonstrated that the algorithm has high computing speed and convergence, which lay the foundation to the further improving of DE algorithm.
Key words: electric power system; transmission network planning; differential evolution algorithm; MSDE algorithm
Distribution network earth fault section location based on asymmetric current
WU Xiao-qing1，YANG Hong-geng1，YE Mao-qing2
(1. School of Electrical and Information, Sichuan University, Chengdu 610065, China;
2. Sichuan Electric Power Research Institute, Chengdu 610072, China)
Abstract: This paper analyzes the character of the zero sequence and negative sequence current when single-phase fault occurs. A method for distribution network earth fault section location based on the asymmetric current is proposed. Firstly, single-phase faults occuring at each node are simulated, and the zero sequence current is obtained as the boundary value. When the real fault occurs, the zero sequence and negative sequence currents before and after fault are acquired, and compared with compare the zero sequence current with the boundary value to find all the possible fault sections and list the sections fault status matrix. Then the negative sequence currents among every lines are compared, and the lines fault status matrix is obtained. Combining the sections fault status matrix and the lines fault status matrix, the fault judgment matrix is formed to recognize the real fault section. The principle of the method is simple and easy. The monitors needed are less and the amount of data transmission is small. The simulation of PSCAD testifies the validity of the method.
Key words: distribution network；the asymmetric current；fault section location
Parameter estimation of voltage flicker based on Root-MUSIC
CHENG Zhi-you1, LIU Yang2
(1. Power Quality Engineering Research Center, Ministry of Education，
School of Electronical Engineering, Anhui University，Hefei 230039, China;
2. School of Electronical Engineering, Anhui University, Hefei 230039, China）
Abstract: In this paper, a parameter estimation method is proposed, in which the exact extraction of the flicker envelope of the voltage flicker is not a necessity. By decomposing the trigonometric function, flicker signal detection can be transformed into side frequency component detection. Root-MUSIC is directly applied in the estimation of voltage flicker. First, the covariance matrix of the sampled signal data matrix is decomposed through singular-value, and thus, the signal sub-space and noise sub-space are obtained. Then with the help of the orthogonality of these two subspaces, a polynomial is constructed. By solving this polynomial and analyzing the roots on the unit circle, the frequency and amplitude information of the side frequency component are obtained. Finally, flicker signal parameters with high precision can be attained through the solution of the formula. The high accuracy in the extraction of flicker signal parameters, as well as the great anti-noise quality of this algorithm, is proved by the simulation results.
Key words: voltage flicker; Root-MUSIC; covariance matrix; singular-value decomposition; finding roots of polynomial
Passivity-based backstepping control for multi-machine power system
WU Zhong-qiang, SONG Ming-hou, FU Li-yuan
(Key Lab of Industrial Computer Control Engineering of HebeiProvince, YanshanUniversity, Qinhuangdao 066004, China)
Abstract: With the development of interconnected power system and the reform of power industry in the worldwide, it is particularly important concerning the security, reliability stability and the economy of the power system. Investigations have shown that suitable excitation control method, as an effective and economic measure, can play an important role to ensure the transient stability of the power system. Based on multi-machine excitation control models, considering the variables and strong coupling characteristics of the system, passivity control schemes aimed at enhancing power system stability are proposed in this paper. Passivity and stability are closely related, the system can be passive so as to maintain its internal stability. The schemes which improve system robustness and simplify structure of the controller effectively have well-defined. The simulation result shows the validity of the controller.
Key words: multi-machine power system; passivity; feedback stabilization control
Integralterminal sliding modecontrol for excitation system based on ESO
LI Tian-yun，ZHANG Zhi-hua，CHEN Feng，YU Xing-lin
(Electrical Engineering Institute, Northeast Dianli University, Jilin 132012, China)
Abstract: Generator’s excitation system is an uncertain and nonlinear systems on which parameter perturbations and external disturbance have a great influence. To solve this problem, this paper estimates the uncertainty factors by constructing extended state observer (ESO) to achieve dynamic compensation linearization of nonlinear model. An error integral compensation term is introduced in the sliding surface in order to eliminate the restrictions that the derivative of the tracking signal must be known, and then using terminal sliding mode variable structurecontrol theory to design the excitation controller. The control method can effectively improve static stability and transient stability of the power system. The simulation results show the feasibility and effectiveness of this method.
Key words: extended state observer; Terminal sliding mode control; error integral; uncertain parameters
PWM algorithm for multi-level voltage source inverter with reduced common mode voltage
JIANG Wei-dong, WANG Zheng-ling, ZHAO Yong, WANG Fei
(School of Electrical Engineering & automation, Hefei University of Technology, Hefei 230009, China)
Abstract：A pulse-width modulation scheme for a multi-level voltage inverter with reduced common-mode voltage is proposed in this paper. Multi-level inverter modulation is relatively more complicated because of the increased number of DC voltage levels and redundant switching states available. By choosing proper voltage vector, the common mode voltage can be reduced to one third of the voltage of one dc cell by using partial common mode voltage reduce PWM (PCMVPWM), and can be eliminated entirely by using full common mode voltage reduce PWM (FCMVPWM). Among the all switching states in the multi-level inverter, the two PWM strategies use only part switching states. The relationship between the two PWM strategies and carrier based PWM strategy is investigated. The harmonic characteristics and common mode voltage are given and compared in detail between the three modulation mode. The strategies have been confirmed by both simulation and experimental results obtained using neutral point clamped three-level inverter.
Key words：multi-level; inverter; common mode voltage; pulse width modulation
Research on balance of voltage of neutral point clamped three-level inverter
NIE Zhen-yu1, GUO Xiao-bin2
(1. ZheJiang Ocean University, ZhouShan 316000, China; 2. Power Design Institute of Jiangxi, NanChang 330029, China)
Abstract: The paper introduced the operation principle of commonly used diode-clamped three-level inverter which is modulated by space voltage vector pulse width modulation method.The paper is aimed at analyzing the problem of unbalance capacitance voltage of the inverter in practical application, and it proclaims the method that detects the difference value of the two capacitances voltages at DC-side and instantaneous value of the current at neutral point.These values are used in hysteresis control to cut over two equivalent space vector pulse trains so as to keep the balance of capacitance voltage. The result of the experiment shows that the method can suppress the unbalanced degree of capacitance voltage effectively, and it makes the unbalanced degree of capacitance voltage less than double width of hysteresis. The switching loss of device and switching frequency is lower, and the modulation method is simpler and easier to operate in digital controller, and it has some useful value.
Key words: three-level inverter; space voltage vector; the balance of neutral point voltage; hysteresis control; DC-AC inverter
Research of three phase "UШ"shaped coupled inductor of variable coupling degree and without air gap
YANG Yu-gang，LI Tao，Feng Ben-cheng
（Faculty of Electrical and Control Engineering of Liaoning Technical University, Hu Ludao 125105，China）
Abstract：In order to meet the requirements of the multi-phase interleaved magnetic integrated converter to the coupled inductor and to reduce the electromagnetic interference of the magnetic materials on other devices, the paper proposed a structure of coupled inductor with UШ shaped magnetic core and without air gap, which has variable coupling degree and is applicable for three phase interleaved magnetic integrated converter. The paper analyses the principle of variable coupling degree, gives the expressions for the design of magnetic core, and verifies the effectiveness of the structure of the UШ-shaped coupled inductor and the feasibility of the magnetic circuit model by FEA simulation and experiments.
Key words：interleaved magnetic integrated converter; coupled inductor; couping degree; FEA simulation
Research on frequency tracking technology of electronic ballasts for electrodeless lamp
SHEN Yu, LIN Guo-qing, TANG Jian-shan
(College of Electrical Engineering and Automation, FuzhouUniversity, Fuzhou 350108, China)
Abstract: Due to the excellent features of high efficiency, high color rendering, no flash and long life, electrodeless lamp becomes a new gas-discharge light source with a good development prospect. Electrodeless lamp has a negative resistance property, so that a reliable electronic ballast assorted is needed for the lamp. Based on the analysis of the electrical model of electrodeless lamp, a novel control strategy suitable for load characteristics of electrodeless lamp is presented in the paper. The resonant frequency is searched to get the trigger high voltage by frequency sweeping. In order to achieve the maximum output power and best load matching, the phase difference between inverter output voltage and resonant capacitor voltage is adopted as the phase loop control variable to track resonant frequency automatically in normal operation. Finally, the simulation and experiment results have proved the feasibility of the proposed strategy.
Key words: electrodeless lamp; electronic ballast; load resonant; tracking resonant frequency
Differential protection and setting calculation of the new-type converter transformer
XU Jia-zhu，JIANG Fang-cai
(College of Electrical and Information Engineering, Hunan University, Changsha 410082, China)
Abstract：Aiming at the special winding connection of the new-type converting transformer, the connecting scheme of differential protection is proposed based on the establishment of the current transform matrix. Adopting the ratio braking characteristic with three-broken lines, and taking these effects into account including the unbalance current under the normal condition, current-transformer performance and existing output current when occurring internal fault, the setting values for the differential protection of the new-type converting transformer are calculated. At last, the simulation model of the differential protection is established based on the new-type converting transformer technical parameters. By means of the simulating analysis of various operating conditions of the transformer, the feasibility of the proposed scheme and the correctness of the setting calculation are verified.
Key words: new-type converter transformer；differential protection；connecting scheme；ratio braking；setting calculation
Research on traction control of 100% low floor vehicle based on multi-mode pulse width modulation
ZHAO Ming-hua1,2，DONG Kan1，ZHAO Lei-ting1，DIAO Li-jun1
（1. Beijing Jiaotong University, Beijing 100044, China；2. Changchun Railway Vehicles Co., Ltd.，Changchun 130062, China）
Abstract：Focusing on the controlling characteristics of the independently wheelset，this paper raised a strategy for traction control based on multi-mode pulse width modulation. Distinguishing the characteristics of traction motor under different frequency range, this paper designed the modulation algorithms and the traction control strategies respectively which have been analyzed and demonstrated in the content. And also, the transition between different traction control strategies is studied. To verify the strategies, this paper adopts the 100% low floor vehicle in Changchun as the experimental platform, and a lot of experiments were carried out in Changchun. The results testified that the aforesaid controlling strategy can perform well in full speed range. So far, the 100% low floor vehicle equipped with the traction inverter designed by this paper has finished almost 5000km operation mileage and has a good performance.
Key words：100% LFV; independently wheelset; multi-mode modulation; traction contro
Research on coordinated control of brake regenerative efficiency and pedal feel for electric cars
GOU Jin-fang1, 2, WANG Li-fang1, LIAO Cheng-lin1
(1. Key Laboratory of Power Electronics and Electric Drives,Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing 100190, China;
2. Graduate University of Chinese Academy of Sciences, Beijing 100190, China)
Abstract: The maximum regenerative efficiency strategy, the best brake pedal feel strategy and the strategy taking into account both regenerative efficiency and brake pedal feel are studied for energy recovery efficiency and brake pedal feel. The braking process is divided into three stages: electro-hydraulic coordination preparation stage, electro-hydraulic coordination stage and regenerative braking removal stage. The electro-hydraulic coordination preparation stage is selected as the characteristic stage for evaluating energy recovery efficiency. The electro-hydraulic coordination stage is selected for evaluating brake pedal feel. Moreover Flucped is defined to measure the fluctuation degree of the brake pedal. These three strategies are tested in an electric car. The results show that in the maximum regenerative efficiency strategy the car has the highest regenerative efficiency but the worst brake pedal feel, while in the best brake pedal feel strategy the lowest regenerative efficiency but the best brake pedal feel. The strategy taking into account both the regenerative efficiency and the brake pedal feel brings the car a good brake pedal feel. Furthermore it improves the regenerative efficiency by nearly 9.42% than the best brake pedal feel strategy.
Key words：regenerative braking; energy recovery efficiency; brake pedal feel; coordinated control; electric cars
Impact of electric vehicle charging facilities on power grid steady state
LIU Ming-zhi1,ZHANG Jun1,YU Jian-cheng1,CHI Fu-jian1, XU Ke1,LI Sheng-wei1, LIU Hong2, WANG Long2, CHEN Yu3
(1. Tianjin Electric Power Corporation, Tianjin 300010, China; 2. Key Laboratory of Smart Grid (Tianjin University), Ministry of Education, Tianjin 300072, China;
3. Tianjin TDQS Power New Technology Co. Ltd, Tianjin 300384, China)
Abstract: Reasonable planning about charging facilities of electric vehicle (EV) has become an important research topic among power system researchers around the world. The impacts of EV charging facilities on the steady state of power grid are analyzed in order to meet the requirements of EV charging facilities operation control and substation relay protection operation. Firstly, common EV charging facilities and their power characteristics are introduced. Secondly, the impacts of AC charging spots on the steady state of distribution network are analyzed. Then, the impacts of the EV station charging operation on the maximum voltage deviation and line losses ratio of distribution network are calculated and analyzed, also the impacts of discharging EV charging station on the short circuit current and supplying area of power grid are analyzed, and substation relay protection acting threshold revised strategies are proposed according to these analyzed results. At last, the impacts of battery swap and charging station on the substation supplying area, short circuit current and peak-valley ratio are analyzed. All these results provide a theoretical reference for the charging facilities operation control and suggestions for revising the substation relay protection action threshold.
Key words: smart grid; electric vehicle; charge station; AC charging spot; battery swaping and charging station
An improved ip-iq detection method based on two phase voltage sin/cos transforms
YAO Xin-li, LUO Long-fu, XU Jia-zhu, ZHANG Zhi-wen, LI Xiao-fang
（Hunan University, Changsha 410082, China）
Abstract: This paper proposed an improved detection algorithm. Which is based on two-phases voltage sin/cos transform and sliding average filtering, and through the mathematical calculation the synchronous rotation angle is produced. Then an unbalanced three phase model is established in PSIM. Results shows that this method can accurately detect the positive and negative current sequence components.
Key words: ip-iq detection algorithm; improved; sin/cos transform; sliding average
Study of intelligent control module for a novel permanent magnet contactor
NI Shou-chun1, WANG Xian-bing1, LIN He-yun2, FANG Shu-hua2
(1. Department of Electronic and Information Engineering, Chuzhou University, Chuzhou 239000, China;
2. School of Electrical Engineering, Southeast University, Nanjing 210096, China)
Abstract：Adopting the modular design method, an intelligent design integrating the detection, setting, protection and control for the permanent magnet (PM) contactor is achieved based on the microprocessor technology and intelligent control technology. The design methods and working principles of hardware circuit and the programming design of software system for each intelligent functional module are analyzed in detail. Finally, the experimental analysis is carried out based on a PM contactor of 140A by using the designed intelligent control module. The experimental results show that the high intelligent protection function and dynamic adjustment for the contacting process are realized and the first and the second contact bounces are reduced effectively.
Key words: PM contactor; intelligent control module; module; dynamic characteristic
Influence of arcing model of GIS switching to VFTO
WANG Na1,2, LIN Xin1, XU Jian-yuan1, WANG Fei-ming1
(1. School of Electrical Engineering, Shenyang University of Technology, Shenyang 110870, China;
2. School of Information Engineering, Shenyang University of Chemical Technology, Shenyang 110142, China)
Abstract: In the process of simulation calculation of very fast transient over-voltage (VFTO), establishing an accurate high-frequency arc model is a key factor to improve the accuracy of VFTO. Dynamic arcing model is presented in the paper based on segmental arcing model. In the pre-breakdown stage, hyperbolic time-varying resistance was used in this model to consider the impact of breakdown delay time on VFTO waveform; in the extinction phase, complete Mayr model was established to describe the dynamic physical processes of arc. Moreover, taking a 1100kV station as an example, this paper calculated in detail the amplitude, the frequency and the gradient of VFTO in GIS on the condition of varied arcing models, It is found that VFTO has higher magnitude, higher frequency and higher gradient under dynamic arcing model. By comparing VFTO simulation results with the measured data, it is found that the dynamic arcing model is the further improvement of segmental arcing model and has great significance for improving the accuracy of simulation calculation of VFTO.
Key words: high voltage engineering; disconnector; dynamic arcing model; gas insulated substation; very fast transient over-voltage
An improved multiple single objective Pareto sampling algorithm for many-objective optimizations
LIU Lei, YANG Shi-you
(College of Electrical Engineering, Zhejiang University, Hangzhou 310027, China)
Abstract: Multi-objective optimization problems occur frequently in electrical engineering. However, existing non-dominance based multi-objective optimization algorithms have difficulties in solving multi-objective problems with more than three objectives, termed many-objective optimization problems. To address this problem, MSOPS or MSOPS-II algorithm is proposed. This algorithm is simple in implementations and has low computational complexity. However, investigations have revealed that the algorithm frequently losses the diversity of the population. In this point of view, an improved MSOPS is proposed by incorporating a crowding operation of target vectors, a non-uniform target vector updating mechanism, and an external archive. Compared with MSOPS-II, HypE and NSGA-II in view of solving test functions, the proposed algorithm achieves a better trade-off between the convergence and the diversity towards the Pareto front. Finally, the optimization of a Yagi-Uda array validates the effectiveness of the proposed algorithm in the real-world applications.
Key words: many-objective optimization; evolutionary algorithms; MSOPS; diversity preservation
A field scheme of feeder automation system based on non-communication protection
SHI Shen-xing1, XU Gang2, DONG Xin-zhou1, YIN Di-qing2, LIU Kun1, WANG Kai2
(1. State Key Laboratory of Control and Simulation of Power System and Generation Equipment, Tsinghua University, Beijing 100084, China; 2. North City Branch of Shanghai Power Company, Shanghai 200072, China)
Abstract: Non-communication protection of feeders can quickly and selectively isolate the asymmetrical fault and recover power supply to the sound feeder sections. But how to coordinate with the protection of transformer and to cope with symmetrical fault need to be solved when applied into the field. This paper proposes a field scheme which can meet the requirements of coordinating with the protection of transformer and quickly isolating the symmetrical fault. The scheme presented in the paper configured the non-communciation protection feeders according to the time requirements of the transformer’s protection, and tripped the symmertical fault instantly and without selectivity based on three phases voltages, and then used the re-closure technology intergrated in the relay to determine the fault section and to recover the power supply to the healthy feeder sections. The field scheme can achieve isolating the fault in the feeder and recovering the power supply to the load fast without the need of communication channel.
Key words: feeder automation; symmetrical fault; non-communication protection
Theoretical analysis and application research of fault traveling waves in huge electrical generators - for relay protection and fault location
DANG Xiao-qiang, TAI Neng-ling, LIU Ji-chun
(1. Department of Electrical Engineering, Shanghai Jiaotong University, Shanghai 200240, China;
2. Department of Electrical Engineering, Sichuan University, Chengdu 610065, China)
Abstract: New detection technology based on transient fault travelling waves for electrical equipments in power system is an essential technology in the future, and at the same time it is the important research and development direction at present. Relay protection and fault location based on fault travelling waves for large generators are the important parts in this coverage. This paper presents the survey and some comments of the research work and developments in this area. Firstly, from the view of the application scope of the detection of the travelling waves of the large generator’s faults, the basis and the feasibility of its research of the fault travelling waves are briefly investigated, and then the principle and its concept and features of the propagation of the fault travelling waves are briefly introduced in combination with the single phase ground faults of the large generators. Thereafter, the principle and the analysis of the examples of the relay protection and the fault location of the single phase ground fault of the large generators are mentioned profoundly based on the information theory of the fault travelling waves. Lastly, summary and the works in future of the fault travelling waves for the relay protection and fault location in large generator’s research are given.
Key words：huge electrical generators； traveling-wave theory； relay protection；fault location；condition based maintenance
Analysis and implementation of electric power waveform data compression method with high compression ratio
DANG San-lei1, XIAO Yong1, YANG Jing-feng1, SHEN Yan-hua2
(1. Electric Power Research Institute of Guangdong Power Grid Corporation, Guangzhou 510080, China;
2. School of Materials Science and Engineering, South China University of Technology, Guangzhou 510641, China)
Abstract: Power quality monitor and waveform recorder are very important equipments for security and stability analysis of the electric power system. In those equipments, the core technology is power system waveform data compression method with high compression ratio. In this paper, commonly used data compression and coding method are studied firstly. Taking advantage of characteristics of the power system waveform data such as periodic, bounded and redundancy, compression methods based on DCT transform and lifting wavelet transform are implementated on the DSP platform. Then, implementation，performance and reduction effect of the two compression methods are comprehensively analyzed. It is found that the compression method based on lifting wavelet and EZW coding can record abrupt data changes and has the features of adjustable compression ratio and precision restoration. The method is more suitable for compression of large amounts of power system failure waveform data.
Key words: wave data; data compression; lifting wavelet transform; EZW coding
Ontology-based intelligent retrieval model for power quality monitoring information
XIE Kang, YANG Hong-geng, HUANG Jing, ZHANG Yi
(School of Electrical Engineering and Information, Sichuan University, Chengdu 610065, China)
Abstract: At present, most of PQMSs use directory-query-based retrieval methods, and it is unable to meet user’s requirements to retrieve information efficiently from the massive monitoring data which is used to evaluate power quality (PQ) by different sides. Moreover, the retrieval results also fail to reflect the mutual influence between PQ indexes. To solve these problems effectively, a model named Intelligent Retrieval Model for Power Quality Monitoring Information (IRMPQMI) is proposed; and the concept of designing of the model, ontology relation model and construction method, architecture and retrieval process of IRMPQMI are discussed. This method can help to retrieve the potential information of power quality monitoring data and give the evaluation results, which provides the basis for decision making of power supply bureau. Numerical results with fuzzy comprehensive evaluation show the implementation procedures and committed steps of IRMPQMI. The idea of IRMPQMI is a guide and has high practical value to the real Intelligent Retrieval System for Power Quality Monitoring Information.
Key words: power quality; ontology; intelligent retrieval; fuzzy comprehensive evaluation
Study of stepper motor control based on Psoc3
ZHOU Feng，LI Zhi-hua，ZHANG Shuai
(School of Electrical Engineering and Automation, Shanghai University, Shanghai 200072, China)
Abstract: Simple circuit structure, efficient control strategy, and reliable control are the common goals of control of all stepper motors. Fortunately, Cypress introduced the new PSoC3 in 2009, and simultaneously launched an integrated development environment dedicated to PSoC3-PSoC Creator, and this brings a new pattern to stepper motor control and provides the maximum possibility for its implementation. This article describes a stepper motor control technology based on PSoC3 chip. The design used two-phase bipolar control technology with simple external circuit which will save time and money. The stepper motor to be designed has many control functions: adjustable micro-step pace, adjustable motor speed, adjustable steering and so on. Finally, under the various subdivision paces of a prototype the voltage of MOS pin has been tested, and good waveform and data have been obtained.
Key words: programmable system on chip; breakdown; stepping motor; bipolar control
Information management system of protective relaying based on workflow and digital signatures technology
LI Ting-min1,ZHOU Liang2,SU Jian-hong1,SUN Wei1 , LV Fei-peng2，WANG Yong2
(1. Xichang Power Supply Company, Xichang 615000,China；2. Sichuan University, Chengdu 610065,China)
Abstract: The Relay Protection setting card management is important to ensure the security and stable operation of the power system. While the traditional setting card management is paper-based and is widely used with artificial management mode, thus brings about the results of heavy workload, poor timeliness and inconvenience of setting card query or statistics, this mode can no longer adapt for the further development. The Setting Card management system is based on B/S structure, using the sophisticated information technology and the existing conditions of computer networks and combining with the actual work of setting card operation management, and a detailed database design and LINQ to SQL-based database access technology to achieve the O/RM object-relational mapping are put forward, using Lambda expressions to achieve data on the database query, update, add, delete and other operations. The paper uses the workflow technology, digital signatures technology, digital seal technology to implement the system, and the work efficiency is greatly raised.
Key words: relay setting card management; protective relaying; workflow; digital signatures
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