ISSN 1000-1026
CN 32-1180/TP
  • ISSN 1000-1026
  • CN 32-1180/TP

Volume 31,Issue 11,2007 Table of Contents

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Invited Paper
A Review of CIGRE' 2006 on Power System Protection and Automation
ZHAO Xicai
2007, 31(11): 1-5.
[Abstract](1752)[PDF ](1024)
The members, working groups, technical reports and annual meeting arrangement of CIGRE SC B5 are introduced firstly. Impact of IEC 61850 on both protection and automation protection systems and substation automation for major disturbances are selected as the preferential subjects of the SC B5 in the 2006 session. More and more substation automation systems based on IEC 61850 have been in service nowadays, and the obtained installations and experiences are introduced therein. Rational topology of power grid and layout of substations, perfect protection system and indispensable stability control equipment are the effective means to deal with major disturbances and avoid blackout in a large area. The validity of original“three defense lines” in China power grids is further proved with the discussion during the session.
Operation Reliability and Wide Area Security Defense
A Tangent Plane Analysis of the Static Voltage Stability Region Boundary
WANG Gang, MEI Shengwei
2007, 31(11): 6-11.
[Abstract](1600)[PDF ](914)
The algorithm of the static voltage stability region's tangent plane through the characteristic vector method or the implicit function derivative method is presented in the total parameter space, which can provide quantitatively the influence degree of all kinds of parameters on the voltage stability region. The implicit function derivative method can calculate the partial derivative of state variables to independent parameter variables. Hyper-plane approximation in the cut-set space can be derived analytically based on the partial derivative through the mapping from power injection space to cut-set space, which can bypass the data fitting algorithm and improve the calculating speed. The practical voltage stability region's tangent plane, which is formed by constraints of the power system, is also presented. Three kinds of voltage stability indices based on the tangent plane analysis method are presented to assess the voltage stability level comprehensively. Simulations of the IEEE 9-bus and IEEE 39-bus system show that the research on the static voltage stability region's tangent plane can assess the voltage stability level objectively and lay the foundation for correct decision-making for secure and stable operation of power systems.
Design of Subsynchronous Damping Controller Based on Fuzzy Immune Method
WU Lingyun1 , LI Xingyuan1 , GONG Xun1 , YANG Yu2 , HONG Chao2 , XU Dapeng1 , LI Wei1
2007, 31(11): 12-16.
[Abstract](1609)[PDF ](1268)
The HVDC transmission system may lead to subsynchronous oscillation under certain circumstances. Based on the complex torque coefficient principle and fuzzy immune control method, a subsynchronous oscillation damping controller is designed. Previous subsynchronous damping control(SSDC) design methods based on linearized system equations are limited by the system's scale for the course of dimensionality problem and it is difficult or even impossible in engineering application to the complex power systems. Thus the fuzzy immune control method is proposed for these reasons. The controller proposed is easy to realize and its parameters are self-adjusted by the fuzzy immune rules to adapt to different operation conditions. Simulation results of PSCAD/EMTDC electro-magnetic programs show the validity of the proposed subsynchronous damping controller.
Coordination of Low Price Interruptible Load and High Compensation Interruptible Load
LUO Yunhu1,2 , XUE Yusheng2,1 , Gerard LEDWICH3 , Zhaoyang DONG4 , LIU Huawei5 , HU Wei5
2007, 31(11): 17-21.
[Abstract](1628)[PDF ](1030)
There are two kinds of compensation fashions for interruptible loads(IL), namely low price compensation which is independent of power cut occurrence and high compensation which is performed only after actual power cut. The interruptible loads with low price(ILL) and the interruptible loads with high compensation(ILH) have been studied separately till now. Based on the viewpoint of risk management, this paper analyzes their different economic properties, points out that their coordination is beneficial to restrain market power and reduces the cost of reserve capacity and system stability. Taking the sum of the deterministic reduction of revenue resulting from ILL and the risk of compensating ILH as the objective function, the coordination models and optimization algorithms are proposed. Simulation results are presented to validate the method.
Basic Research
AC-DC Iterative Methods for Calculating Locational Marginal Price with Losses
CHEN Zhixu, ZHANG Lizi, SHU Jun
2007, 31(11): 22-25.
[Abstract](1410)[PDF ](982)
The direct current optimal power flow(DCOPF) is a maturity method for calculating locational marginal price(LMP). It performs the simplified computation of the electric power system, so the optimum results obtained do not accord with the real status of power system. But the method of adopting alternating current optimal power flow(ACOPF) to calculate LMP is not widely used for engineering application. So the AC-DC iterative method is proposed to calculate LMP with losses. In this method, DCOPF model is adopted to complete economic dispatching, and AC power flow model is adopted to calculate the precise power flow and power losses. Both processes iterate alternatively till the method is converged, then the transpose Jacobian matrix is adopted to calculate penalty factors. LMP with losses is deduced according with LMP without losses obtained by DCOPF and the penalty factors. The feasibility of the proposed method is proved by IEEE 14 bus and IEEE 118 bus system, with the effect of the slack bus on LMP analyzed. The calculation results indicate that the proposed method has appreciable economical significance and physical meanings, and is simple for engineering application.
General Model and Algorithm for Contract Energy Decomposition
LI Canbing, HU Yajie, ZHAO Hongjun, LI Xiaohui
2007, 31(11): 26-30.
[Abstract](1479)[PDF ](999)
The contract power energy should be decomposed to each period of time in power pool. For example, the contract energy that a power plant won the bidding in year-contract market should be decomposed to each month, and month-contract energy should be decomposed to each day, etc. Decomposition of contract energy is a universal problem that should be resolved by the trading center. The decomposition of contract energy is reduced to a quadratic programming problem. The concept of rates of progress is proposed with such special problems as the maintenance, the limiting of hydraulic power and the thermal power generation taken into account and the contract energy could be decomposed step by step, making rates of progress of all power plants balance in all time slices. The model is universally adaptable. The algorithm calculates fast and the result is optimal and feasible. Finally, a case with 24 buses is studied based on IEEE RTS-96 system. It's proved that the model and algorithm are effective through case study.
Day-ahead Price Forecast with Genetic-algorithm-optimized Support Vector Machines Based on GARCH Error Calibration
LIU Da1 , NIU Dongxiao1 , XING Mian2 , NIE Qiaoping3
2007, 31(11): 31-34.
[Abstract](1526)[PDF ](893)
A new method incorporating the time sequence modeling and intelligent algorithm modeling is presented to forecast the day-ahead electricity price. With genetic algorithm(GA) adopted to optimize the model's parameters, support vector machines(SVM) model is applied to forecast the price sequence. The generalized autoregressive conditional heteroscedasticity(GARCH) models are applied to adjust the error series of price forecasted by SVM-GA models, eliminating their autocorrelations and heteroscedasticity effects. A case of forecasting the day-ahead price of PJM market in August, 2005 demonstrates the proposed method has a desirable performance with an overall mean absolute percentage error(MAPE) of 8.19 percent, which is nearly 4 percent less than data forecasted by common methods.
Transmission Network Planning Considering Electric Power System Security
FAN Hong, CHENG Haozhong, ZHANG Jietan, JIN Huazheng, JIN Yixiong, WANG Yi, ZHONG Mingming
2007, 31(11): 35-38.
[Abstract](1518)[PDF ](907)
The process of transmission network planning considering the electric power system security is designed in this paper. It has renovated the traditional planning method in which only N secure rule and N -1 secure rule are considered, and the load shedding costs of the planning network in N -2 condition are further analyzed. The fault selection step is first carried out so that the computing of the N -1 security network planning can be speeded up and the large real network planning can be realized meeting the demand of engineering applications. Tests on the 18-bus system and a real power network of 147-bus system show that the method proposed is effective.
Probabilistic Characteristic Calculation of Generator Variables Under Multi-operating Conditions
HU Jinlei, ZHANG Yao, GUO Li, XIE Huifan
2007, 31(11): 39-43.
[Abstract](1366)[PDF ](858)
In the practical power system operation, the powers of generators and loads are changing constantly, and the state variables(e.g. power angle, rotating speed) and algebraic variables(e.g. voltages and currents of dq -axis) are fluctuant within a certain range. Probabilistic characteristic of generator variables provide operators more comprehensive operating information and they are the base of the probabilistic transient stability analysis in multi-operating conditions. To some extent, expectations and covariances can describe the probabilistic distribution characteristics of these variables. Based on the operating curves of nodal injections and PV voltages and with the assumption that all generator variables obey the normal distribution, the expectation expressions and linear covariance expressions of generator variables are deduced according to the probabilistic load flow analysis and the basic property of numerical characteristics of random variables. In the end, the studies are carried out on an eight-machine system.
Aggregation of Multi Induction Motors Based on the Self-organized Neural Network and Steady State Model
ZHANG Jingchao1,2 , ZHANG Chengxue1 , YAN Anhe2 , ZHANG Pengfei2 , LI Kui2
2007, 31(11): 44-48.
[Abstract](1287)[PDF ](799)
In power system stability computation, accurate load models can ensure the reliability of computed results. Improving the aggregation precision of multi induction motors is one of the most important contents in load modeling with the component-based approach. In this paper, an aggregation method is presented, in which the multi induction motors are classified into different types using the self-organized neural network and each type of motor is aggregated with a new steady state model equivalence method. Finally, simulations are made on the typical residential and commercial induction motors data in IEEE 9 grid with the PSD-BPA program developed by CEPRI. The results have proved the validity of the method proposed.
Identification of Parameter Estimation Feasibility Based on Dominant Parameter and Non-dominant Parameter
HE Hua1 , GU Quan1 , WEI Zhinong2 , SUN Guoqiang2
2007, 31(11): 49-52.
[Abstract](1448)[PDF ](805)
By analyzing the application difficulties of parameter estimation, the parameter estimation feasibility of power system is discussed. The concept of dominant parameter and non-dominant parameter is proposed with the help of approximate analysis by using the linear model of power system. Therefore the behavior of parameter estimation practice can be explained and the inference for the software running mode of parameter estimation can be drawn from the linear model of power system. Employing the fact that the non-dominant parameter is susceptible to measurement noise, a method of identifying the non-dominant parameter based on the noise sensitivity experiments is presented. Simulation results of an IEEE sample power system are given to verify the viewpoint proposed that the non-dominant parameter should be wiped out in the parameter estimation.
Application Research
Realization of Grid-connected and Maximal Wind-power Tracking by DC Bus Voltage Control
XU Ke, HU Minqiang, DU Yansen, YANG Xiaojing
2007, 31(11): 53-58.
[Abstract](1319)[PDF ](858)
Based on the non-controllable AC/DC and controllable DC/AC configuration of permanent magnet synchronous wind generator(PMSWG), a method of realizing its grid connection and maximal wind energy tracking by DC bus voltage control is proposed. The theory of controlling DC voltage by DC/AC decoupling power is analyzed. The direct grid-connected method by DC/AC charging DC capacity voltage is proposed, and the range of charging current and limit-current resistance is discussed. The relationship between the DC bus voltage and speed is analyzed. The DC voltage variable step disturbance is proposed to replace speed fix step disturbance. The proportion value of power variation's square is proposed as disturbance value. Simulation results demonstrate that the proposed control strategy is simple and effective and can be used for grid-connected PMSWG.
Short-term Correlation and Annual Growth Based Mid-long Term Load Forecasting
QIAN Weihua1 , YAO Jiangang1 , LONG Libo2 , ZHANG Kai2
2007, 31(11): 59-64.
[Abstract](1292)[PDF ](958)
As the existing nonlinear models of mid-long term load forecasting are fairly difficult to apply and their results are not satisfactory, a novel method is presented, which transforms a nonlinear issue into a linear one based on short-term correlation and annual growth. First, linear regression models are constructed in terms of the strong short-term correlation of the preceding year's load. By using a recursive procedure, the weekly average load is then estimated for the next year. Finally, the predicted annual load growth is taken into consideration to modify the estimated values. The validity and practicability of the method proposed are tested with actual data. It is expected that this approach can provide a new feasible solution for mid-long term load forecasting.
Real-time Processing of GOOSE Message in Substation
DUAN Jiquan1 , DUAN Bin1,2
2007, 31(11): 65-69.
[Abstract](1699)[PDF ](2441)
Messages communication delay is composed of transmission delay and handling delay. According to IEC 61850 standard, the generic object-oriented substation event(GOOSE) message is mapped onto the data link layer direct, which can decrease the transmission delay. The message handling delay in an intelligent electronic device(IED) of substation is discussed, and a hard real-time operation system in IED is adopted owing to the shortcomings of the traditional foreground/background system in handling real-time messages. According to the environment of mixed message transmission of real-time message and non-real-time message, a method is designed to guarantee disposing GOOSE message in real-time on a real-time application interface(RTAI) operating system. The experiment results demonstrate that this method is valid and practicable. The research result is significant for the design of IED process layer communication with IEC 61850.
A New Method of Line Pilot Relay Communication Based on Fiber Optic Technology
QIN Hongxia, LI Ying, ZHAO Yucai, ZHANG Yueping, CHEN Qiurong
2007, 31(11): 70-73.
[Abstract](1545)[PDF ](1498)
Based on the principle of the pilot distance or zero sequence direction relay, a new design of the transmission line pilot relay using fiber communication technology is described. The signal exchange of the ultra-high voltage transmission line pilot relay is achieved through the fiber optical channel or microwave channel by using the multiplex SDH/PDH system. The new design can also resolve such problems as high-resistance fault location, complex fault phase selection, etc. using the two-terminal transmission line information.
The Research on Five-step Protection Scheme for Transmission Line
LI Xiaoming1 , LIU Yaohui2 , CAO Yan1
2007, 31(11): 74-76.
[Abstract](1285)[PDF ](761)
Traditional protection scheme for transmission line usually adopts three-step protection scheme. To promote the property of transmission line protection, this paper presents a new protection scheme for transmission line that is five-step protection scheme. The insensitive zoneⅠis used to improve the operating speed of zoneⅠof transmission line protection. The sensitive zoneⅠis used to improve the sensitivity of zoneⅠ.The insensitive zoneⅡis used to improve the operating speed of zoneⅡof transmission line protection, and it is also used to enhance property to detect arc-resistance fault. The sensitive zoneⅡis used to improve the protection sensitivity of zoneⅡand is used to improve the operating speed of backup protection of the next circuit. ZoneⅢ is used as the backup protection of the transmission line and also used as the backup protection of the next circuit. The paper analyzes the characteristics of the new protection scheme for transmission line. The analysis results show that if the protection relay is made up of microcomputers, the property of transmission line protection can be improved without increasing the hardware of microcomputer protection relay.
A New Criterion for Earth Fault Line Selection Based on Phase Comparison Statistical Method
ZHANG Dabo, LIU Zhigang, ZHANG Yajun, SU Yuxiang
2007, 31(11): 77-80.
[Abstract](1385)[PDF ](931)
The phase comparison between fault feeder and healthy feeder is one of important criteria in fault line selection for neutral non-effective grounding systems. A new criterion for earth fault line selection with phase comparison statistical method is presented based on the detailed analysis for transient process of non-solidly earthed network. The complex wavelet transform is directly adopted to extract each zero-sequence current's phase of sub-band signals that can accurately select earth fault line after the statistical comparison of every line's phase. All information of special frequency band is sufficiently utilized and the algorithm proposed is simple. The detecting process with the new criterion is not sensitive for disturbance and immune to earth mode, path resistance and inception angles. Numerical simulation results have shown the validity and reliability of the algorithm proposed.
Compensation Characteristics of Arc Suppressing Coil Controlled by TCR
2007, 31(11): 81-86.
[Abstract](1229)[PDF ](790)
The phase-controlled arc-suppressing coil is a type of adjustable arc-suppressing coil controlled by TCR(Thyristor Controlled Reactor), being capable of the large adjustable range of current and the continuously adjusted compensation current. In this paper, the working characteristics of arc-suppressing coil controlled by TCR are demonstrated and the correctness of theoretical analysis is proved by the related simulation with ATP(Alternative Transient Process) and experiments on the simulated 10 kV power distribution network. It is indicated that the distortion ratio of harmonic currents can be controlled within the finite range by the filtering circuit, which, however, slowers the response speed of the circuit and produces the cross-zero disorder. The correspondent controlling strategy has been designed through an analysis of some key problems in controlling, greatly improving the compensation effect and operating safety.
Compound Characteristic Extraction Based Fault Diagnosis of Hydroelectric Generating Unit Using RBF Neural Network
LIU Zhong, ZHOU Jianzhong, ZHANG Yongchuan, ZOU Min
2007, 31(11): 87-91.
[Abstract](1167)[PDF ](747)
In order to overcome the limitations of the traditional FFT in non-stationary signal processing and overdependence on the energy characteristics during the analysis and fault diagnosis for hydroelectric generating unit(HGU), a novel fault diagnosis method based on compound characteristic extraction and RBF neural network is proposed. This method integrates the advantages of wavelet analysis, fuzzy theory and RBF neural network. Firstly, wavelet analysis is implemented to perform multifrequency decomposition and remove noise of the stability state signal, and extract relative energy characteristics. Fuzzy technique is used to evaluate the influences of the processing parameter changes on the stability state and extract the relationship symptoms. Based on those two types of characteristics, compound characteristics containing comprehensive information are then formed. They are inputs of the trained RBF neural network based diagnosis system and the fault type and its severity degree can be determined. Engineering application results show that this proposed method is feasible and efficient in the overall characteristic extraction of HGU as well as the stability state evaluation and fault diagnosis.
A Small Vacuum On-line Extraction Technology for the Automatic Chromatographic Analysis of Gas Dissolved in Insulating Oil
ZHANG Zhousheng, XIAO Dengming
2007, 31(11): 92-96.
[Abstract](1192)[PDF ](914)
Based on the current development of the gas chromatographic analysis technology and the status quo of the automatic chromatographic analysis of gas dissolved in transformer's insulating oil, a mathematical model for the lowest concentration of gas components in the gas phase is proposed, which can be detected by gas chromatography. By using the mathematical model and conforming with the lowest detectable concentration specification of gas components in oil and the sensitivity limit to the chromatographic analysis system, the minimum volume of the oil chamber and gas chamber can be calculated and designed. Based on this, a novel small vacuum on-line extraction system(10 cm×10 cm×20 cm) and a novel automatic instrument(5 cm×5 cm×2 cm) for the sample gases transmission is designed. The volume(0.769 mL) of the quantity fixing vessel is determined by experiment on standard gases and the whole system is examined by experiment on the sample gases. The result shows that the small vacuum extraction system can be satisfactorily used for the on-line application of the chromatographic analysis of gas dissolved in transformer insulating oil.
Egineering Application
Simulation to Study the Dynamic Performance of Multi-infeed AC/DC Power Systems Including UHVDC
WANG Jingfang1 , WANG Zhidong2 , LI Xinnian1 , HU Tao1 , JIANG Weiping1 , WANG Mingxin1 , XIANG Mengqi2 , LI Huanming2
2007, 31(11): 97-102.
[Abstract](1856)[PDF ](1166)
To study the dynamic performance of the Southern China Power Grid in 2010, the system equivalence, model treatment, electromagnetic transient modeling method are presented for the multi-infeed AC/DC power system including±800 kV UHVDC. The PSCAD/EMTDC electromagnetic transient simulation software is used to establish the simulation model of 5 HVDC transmission lines, including±800 kV UHVDC from Yunnan to Guangdong. Detailed converter model is used in the study. The work has focused on the dynamic performance when various kinds of faults occur in the AC/DC system. Result presented in the paper provides the theoretical foundation for system planning and system security study in the Southern China Power Grid.
Field Application and Analysis of the Stator Earth Fault Protection with Voltage Injection for Large-sized Generator
ZHANG Qixue, XI Kangqing, CHEN Jiasheng, WANG Xiang, SHEN Quanrong
2007, 31(11): 103-107.
[Abstract](1379)[PDF ](878)
More and more large-sized generators are installed 100% stator earth fault protection with low-frequency alternating-voltage injection. The field adjustment methods of the voltage injection scheme against the stator earth fault protection are summarized and the experimental results are given. The equipment measuring accuracy(relative error is not greater than±5%) of the earth fault resistors is verified by the experimental results. Moreover, some suggestions are given by analyzing a two-point earth fault in potential transformers circuit, which can cause stator earth fault protection warning.

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CN 32-1180/TP

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