Showing papers in "Power system technology in 2009"

Survey on Smart Grid Technology

Abstract: In this paper the connotation of smart grid is expounded, the present research status of smart grid home and abroad as well as the practical significance of developing smart grid in China are summarized. As a reference for relative researchers, this paper analyzes the conditions to develop smart grid in China, and points out the key technological problems to be solved for the development of smart grid in the fields of power network topology, communication system, metering infrastructure, demand side management, intelligent dispatching, power electronic equipments, distributed generation integration etc..

Statistics and Analysis on Reliability of HVDC Power Transmission Systems of State Grid Corporation of China

Abstract: Reliability level of HVDC power transmission systems becomes an important factor impacting entire power grid.The author analyzes the reliability of HVDC power transmission systems owned by State Grid Corp.of China since 2003 in respect of forced outage times,forced energy unavailability,scheduled energy unavailability and energy utilization efficiency.Different reliability indices of HVDC power transmission system interact one another,thus to implement the maximization of property benefit of the power grid it is necessary to build a scientific and reasonable reliability evaluation system.The results of analysis on reliability indices of HVDC power transmission systems home and abroad show that the reliability level of HVDC power transmission systems owned by State Power Grid Corp.of China is in the forefront in the world.

Research Status and Development Trend of Smart Grid

Abstract: The future development trend of electric power grid is smart grid, which include such features as flexible, clean, secure, economic, friendly and so on.The concept and function characteristics of smart grid are introduced in this paper firstly;then the progress of research on smart grid home and abroad as well as the relation between key technologies and smart gird are analyzed in detail, and it is pointed out that the Agent based distributed cooperation, control, simulation and decision-making, system integeration of distributed enengy, knowledge based comprehensive decision support are the key development trend of smart grid in future.The construction of smart grids in China is a very complicated system engineering, for this reason some concrete suggestions are made, such as fully taking advantages of integrated management, carrying out architectural design of smart grids in China;drafting pilot plans and implementation schemes;coordinating secure and economic operation of power generation, transmission and distribution;paying special attention to theoretical and technological innovation and application;overall considering the planning, construction, renovation and technology upgrating of power grid, to push the research and construction of smart grid in China actively and orderly.

Discussion on Development Trend of Battery Electric Vehicles in China and Its Energy Supply Mode

Abstract: The actuality and trends of electric vehicles (EV) home and abroad are reviewed The development trend of battery electric vehicles (BEV) and its energy supply mode in China are emphatically dissertated The development stage of BEV in China is divided into two periods,namely the demonstration period and mature period,the keystone and the challenge in the current development period of BEV are analyzed Finally,for the energy supply mode of BEV,the key technology and technical direction to be researched are pointed out

Prospects of Low-Carbon Electricity

Abstract: Delivering a low-carbon economy puts ourselves on a path to cut CO2 emissions,which is the main contributor to global warming. Developing low-carbon technology in electricity industry will play an important role in helping us to be prepared for the low-carbon economy in the future since electricity always being the biggest emission source. In this paper,after describing features of CO2 emissions and corresponding reduction potential in China’s electricity sector,main difficulties and challenges in creating a low-carbon electricity industry in China are analyzed. On this base,a research framework is established,giving out a comprehensive prospect on the future development of electricity technology in a low-carbon scenario,which deeply reveals new research trends and interests of this area.

Smart Grid——A Development Trend of Future Power Grid

Abstract: Smart grid becomes the hot topic concerning future power grid development trend home and abroad in recent yearsThe R D background,concept,major characteristics,driving forces of development,core technologies,some progress in domestic power grid and some new trends abroad are described and analyzedSome points of view for developing smart grid in China are presented

A Review on Microgrid Technology Containing Distributed Generation System

Abstract: Widespread application of distributed generation systems (DGS) will bring about new opportunities and challenges to power grid operation, control and electricity market The microgrid technology that integrates DGS, energy storage element and loads will be an effective approach to solve the interconnection of large-scale DGS with power grid In this paper the concept relevant to microgrid, present research situation and advancement of microgrid technology in other countries are presented in detail; the features and superiority of microgrid technology in operation, control, protection and economy are overall expounded Combining with the feasibility and economy of microgrid technology, the development prospect and research direction of microgrid technology are analyzed in depth, and it is pointed out that the microgrid can provide more reliable power supply for sensitive consumers under islanded operation

Discussion on Smart Grid Supporting Technologies

Abstract: Power grid intellectualization is an important method to promote the development of renewable energy source and implement energy conservation and emission reduction.Along with the increasing development of power electronics,IT and communication technologies,the construction of smart grid is becoming an important development direction of electric power industry.At first the necessity of developing smart grid is demonstrated;then the required performance of smart grid are introduced,including self-government and self-healing ability,defensive quality,compatibility of power grid,high efficient operation and management,outstanding quality and friendliness,convenience of power transaction.It is pointed out that to implement smart grid it is necessary to strengthen the research and development in two respects,i.e.,the basic technologies and realization of functions.Basic technologies for smart grid mainly contain four issues,namely power equipments,measurement and communication devices,information management system,decision-making and control theory;the realization of functions mainly contain five issues,namely smart control centre,smart substations,smart transmission and distribution lines,smart relay protection system and smart demand side management.Finally,the performance appraisal system is briefly dissertated in power grid performance,economic effect and social effect.Solution of above-mentioned problems will contribute to the deep study and application of smart grid.

Key Technologies for Microgrids Being Researched

Abstract: The microgrid technologies become one of key spots in the research on distributed energy systems. In this paper,the components,systemic structure and operation modes of microgrid are presented. From the viewpoint of technical connotation,the present research situation of key technologies for the microgrid is reviewed. These technologies include new power electronic converter technologies,fault detection and protection,communication technologies,planning and design of microgrid,as well as issues related to operation control and energy management such as supervisory and control architecture,control strategies and approaches,ancillary services,operation specification,modeling and simulation research in system level and unit level and microgrid economic evaluation. The authors also point out that the optimal design of microgrid topology and optimal configuration of distributed energy units are of significance for the implementation of maximum benefit of the whole microgrid. Besides,the effective economic evaluation of microgrid is a topic to be researched in detail.

Information Communication System Supporting Smart Grid

Abstract: On the basis of presenting business demands of information and communication system (ICS) for smart grid,the architecture of ICS supporting smart grids with Chinese characteristics is proposed and a standardized architecture of ICS supporting such smart grids is given. The architecture of ICS relates to the contents in information and communication technique,the frame of ICS as well as the network management and security protection of ICS. The research focus of information and communication technique supporting smart grids in China and the construction and pilot project of ICS are prospected. It is suggested that the network management,security and protection as well as the construction of technical standard system for the ICS supporting smart grids with China characteristics should be enhanced.

Study on the Structure and the Development Planning of Smart Grid in China

Abstract: The research on the smart grid is very significant in energy conservation and economical operation of power systems.In this paper,the current situation of power system in China and the definition of smart grid are presented in brief.Then,the effects of the influences of smart grid on the constituents of power grids in China,including power generation,transmission and utilization,load composition,construction of substations and dispatching system and so on,are analyzed in detail.On this basis,the fundamental conditions,development thinking and requirements for the selection of experimental cities are pointed out.Finally,the preliminary medium-term and perspective structural diagrams for Chinese style of smart grids are given.

Particle Swarm Optimization Based Economic Operation Analysis of Microgrid Containing Multi Energy Supply System

Abstract: The economy of microgrid is analyzed in both cost and benefit.Based on its basic structure,the structure of microgrid is simplified and the microgrid structure,in which the power supply,thermal supply and fuel gas supply are integrated,is given;an economic model of microgrid,in which the emission of pollutant and greenhouse gases are taken into account and the minimum operation cost of microgrid is taken as objective function,is built.The proposed model is solved by particle swarm optimization(PSO) algorithm.Calculation example shows that the built model is effective and feasible and it is indicated that a higher economy can be achieved while microgrids are connected with large-scale power grid.

A Combination Forecasting Model for Wind Farm Output Power

Abstract: It is of significance to forecast output power of wind farm for the operation of power grid to which large amount of wind power is connected.By use of BP neural network, radial basis function neural network and support vector machine, a combination forecasting model for output power of wind farm is built.The weights are calculated by three methods, i.e., equal weight average method, covariance optimization combination forecast and time-varying weight combination forecast.Research results show that the forecast accuracy from different methods is diverse one another;even though a method can offer high forecast accuracy in total, at individual point the forecast error of this method may be larger, however combination forecasting model can avoid larger forecast error in each point, so it is favorable to improve forecast accuracy.

Assessment Index System for Smart Grids

Abstract: The intension of smart grid and its present development situation home and abroad are briefly described. Based on domestic actual condition,the significance and the key points of constructing smart grids in China are expounded. A preliminary framework of comprehensive multi-factor assessment index system for strong smart grid is proposed. This assessment system contains three first grade indices,i.e.,the scale and development level of smart grid,the technical supporting ability for smart grid and development impact of smart grid; meanwhile,ecah first grade index includes refined second grade indices and third grade indices.

Comprehensive Fuzzy Evaluation for Transmission Network Planning Scheme Based on Entropy Weight Method

Abstract: To remedy the defect that in comprehensive fuzzy evaluation the weight is impacted by subjectivity,the entropy weight method is led into comprehensive fuzzy evaluation,and the weight coefficients of factors are automatically determined according to the opinion of experts For this purpose,a comprehensive fuzzy evaluation model suitable to the assessment of distribution network planning scheme is built; by means of improving synthesis operator,whole information of all indices are fully utilized,thus the obtained evaluation results are more easy to identify Calculation results of IEEE Garver-6 show that the proposed comprehensive fuzzy evaluation system is clear in theory and convenient to calculate as well as its results are intuitive,so it is practicable

Impact of Distributed Generation on Power System Voltage Stability

Abstract: In this paper, the impact of grid-connected distributed generation on power system voltage stability is analyzed and calculated by sensitivity analysis. The impacts of the output and, interconnected location of distributed generation on system voltage are researched and both weak points and supporting points of system voltage were found. The conclusion of this research is as following: the best effect of supporting system voltage can be obtained by interconnecting distributed generation at system voltage supporting point. For some weak buses, the amount of reactive power compensation is determined, meanwhile it is necessary to adopt corresponding control measures to regulate voltage at these buses. Finally, the effectiveness of the proposed approach is verified by simulation results of IEEE 36-bus test system.

A Survey on System Problems in Smart Distribution Network With Grid-Connected Photovoltaic Generation

Abstract: The development of smart distribution network and the overview of application research on photovoltaic(PV) generation are summarized.The influence of PV generation on smart distribution network after it is connencted with the latter is analyzed in the aspects of basic research, network planning and system operation, and following contents are emphatically presented:the modeling of PV station, its basic operation performance, the planning of PV station construction and its output forecasting, the planning of smart distribution network containing PV generation, power flow in smart distribution network, balance of voltage and reactive power in smart distribution network, power quality, protective relayings, faults and reliability, dynamic charateristics of micro-grid, optimal dispatching and coordinative operation, etc., in the hope of offering references for connecting PV sources with smart distribution network and the fast development of smart grids.

Review of Power Distribution Network Planning

Abstract: The models, planning methods and solution algorithms for distribution network are summarized.The models for distribution network planning are divided into two categories, i.e., the earlier models and the later models.The earlier models describe common features of distribution network planning models, including substation planning models, network planning models, substation-network joint-planning models and multi-stage planning models;based on the earlier models, the later models research the development of planning models in different aspects, including the complication of models, the impacts of geographic information system(GIS) and the ideologies of distributed power supply and reliability management.According to the features of distribution network planning models, corresponding planning methods, including multi-objective, multi-stage and uncertainty planning methods, are analyzed, the advantages of disadvantages as well as the applicability of these solution algorithms are dissertated.Finally, the research trend of distribution network planning in future is pointed out.

Construction of Smart Grid at Information Age

Abstract: Since a couple of years ago, the topic smart grid has been discussed worldwidely by power companies, research institutes as well as communication companies.Smart grid was first proposed to accommodate renewable energy generation by utilizing the latest information and communication technologies.Then, the concept"smart"was expanded from smart measurement system, demand-side response, distribution automation to transmission grid intelligence.Smart grid becomes the trend of power grid development.By applying information technologies in the conventional power grid, smart grid improves the utilization rate of energy and power asset management.The energy saving effects of smart grid can help in emission control and global warming.A mature smart grid has two-way real-time high-speed communication channels in all sections of the power grid, and it integrates advanced technologies, such as, control, IT and management.The system is a self-healing sytem.Moreover, the power generation, distribution and utilization in smart grid can be optimized scientifically and systematically.In this paper, what is smart grid, the development and the current research of smart grid will be presented.The objectives, key technologies and potential obstacles for constructing a smart grid are discussed.Some issues relating to smart grid on power transmission and distribution as well as consumer side are also discussed.

A Smart Power Utilization System Based on Real-Time Electricity Prices

Abstract: The development course of smart power utilization technology in China is presented and the influences of electric price policy on smart power utilization are analyzedA framework for smart power utilization system based on the real-time electricity prices is proposed and the functional requirements of each several parts of this system, including master station system, remote access, smart meters, local channels, interactive terminals, smart switchers and so on, are expounded, and the information flow of smart power utilization system is givenThe differences between traditional power utilization mode and smart power utilization mode during the stage of real-time price are compared too

Architecture and Key Technologies for Generation Scheduling of Smart Grid

Abstract: The authors research connotation and extension of generation scheduling for smart grid(GSSG) and explore the development direction of GSSG.Combining with present situation of dispatching and operation as well as actual demand of power grids,the architecture frame of GSSG is constructed and corresponding key technologies are researched,meanwhile in order to enhance overall control ability of large-scale power grid,improve the secure and economic operation level of power grid and promote the construction of dispatching system for unified and strong smart grid,a brand new integrative collaboration mode for GSSG as well as its procedures and approaches are designed.

Research Survey on Multi-Infeed AC/DC Hybrid Power Systems

Abstract: In multi-infeed AC/DC power system,due to the parallel operation of AC and DC transmission lines and closer electrical distances among DC converter stations,the AC and DC power systems as well as subsystems of DC system do interact,it brings new demand to control and protection strategies for multi-infeed AC/DC power system. In this paper an overview on present situation of the research on commutation failures,post-fault recovery of DC system,angle/voltage stability of power system,interaction of harmonics and so on is given,and the features and defects of existing control and protection strategies are pointed out. The conclusion of this research is available for reference to the research on multi-infeed AC/DC power system in future.

Assessment Model on Low-Carbon Effects of Power Grid and Its Application

Abstract: During the sustainable development of human society,global climate change is one of the grand challenge problems to be faced with,and the low carbon emission based development of electric power industry is a key measure to meet the challenge Power grids are the connection facilities between power suppliers and power consumers; as the most important carrier by which the low carbon effects at power supplier side and power consumer side are implemented,power grids will play an extreme important role during the low carbon emission based development of electric power industry After the detailed analysis on the forming mechanism of low-carbon effect of power grid and its features,a concept of low-carbon effect of power grid and corresponding analyzing method are proposed,and a standardized assessment model for low-carbon effect of power grid is built to implement the quantized analysis and sensitivity judgment for different power grids under various transmission networks and energy tansmission modes On this basis,based on the typical data in China the low carbon effect of power grid during the electricity transmission is analyzed and the effectiveness of the proposed model is verified

Equivalent Along-Wind Direction Static Wind Load of Transmission Tower for 1 000 kV Double Circuit Transmission Lines on Same Tower

Abstract: Based on the test of high frequency force balance (HFFB), the equivalent static wind load of 1 000 kV double circuit transmission lines on same tower is researched. According to quasi-steady theory and the assumption that the non-dimensional self-power spectrums of the wind loads in different heights are equal, the self-power spectrums and the cross-power spectrums of the wind load at different heights of tower body are obtained. The equivalent background wind load, the equivalent resonant wind load and total equivalent static wind load of transmission tower under windage yaw angle of 0° and 90° are calculated respectively, and the gust effect factors at different heights under the two windage yaw angles are given. Results of this research are available for reference to wind load calculation of such kinds of transmission towers for UHV power transmission projects.

Short-Term Load Combination Forecasting by Grey Model and Least Square Support Vector Machine

Abstract: A short-term load forecasting method in which the least square support vector regression (LSSVR) algorithm is intelligently combined with grey model (GM) is proposed. Considering daily periodicity of power load and by means of conditional choice of historical load data, various historical load data suites are constructed, and for each historical data suite a GM(1,1) model in which the parameter β can be modified is constructed to conduct load forecasting. By use of LSSVR, the nonlinear combination of the forecasted results by different grey models is performed to obtain final forecasting result. In the proposed forecasting method the advantages of grey model such as less raw data to be required, simple to model and convenient to calculate are fully utilized and the features of LSSVR such as strong generalization ability, good nonlinear fitting ability and less samples to be required are combined, thus the forecasting accuracy can be improved. Simulation results show that the proposed combination forecasting method is effective and practicable.

Investigation on SF6 Decomposition Products in GIS and Affecting Factors

Abstract: By use of specially designed fault simulator for 110kV gas insulated switchgear(GIS),the production regularity of SF6 decomposition products,mostly SO2 and SOF2,and the effects of partial discharge strength,discharge forms,humidity of SF6 and absorbents on the content of SF6 decomposition products are researched.The availability of SF6 decomposition products in fault diagnosis of GIS equipments and the issues to be paid attention to are discussed preliminarily.

Research on Energy Shifting Benefits of Hybrid Wind Power and Pumped Hydro Storage System Considering Peak-Valley Electricity Price

Abstract: Combined operation of hybrid wind power and pumped hydro storage(WP-PHS) system can realize peak load shifting and convert cheap valley-energy to expensive peak-energy,reduce spinning reserve and obtain good economic benefits.Considering peak-valley electricity price,a quantitative model to evaluate the energy shifting benefits of hybrid WP-PHS system is built.The influence of pumped storage power station on peak load shifting by wind power generation is researched,and case simulation results validate the effectiveness of the built model.Simulation results show that under the peak-valley electricity pricing policy the hybrid WP-PHS system can realize peak load shifting and convert cheap valley-energy to expensive peak-energy,reduce spinning reserve and obtain satisfied economic benefits.Meanwhile,the output power of wind farm can be smoothed effectively and voltage fluctuation of wind power can be reduced.

Power Quality Comprehensive Evaluation Combining Subjective Weight With Objective Weight

Abstract: To improve the objectivity and rationality of power quality comprehensive evaluation,it is proposed to decide the weights of indices in power quality comprehensive evaluation by improved analytic hierarchy process(AHP),namely the subjective weight determining,and entropy weight method,namely the objective weight determining,therefore the defect of single weight determining is remedied and the decision of weights becomes more reasonable.On this basis,by use the combination of probability theory with fuzzy mathematics,the comprehensive evaluation of power quality is performed.Case analysis shows that the evaluation results by the proposed method are more rational and perfective,and conforms to reality.

Chaotic Forecasting Method of Short-Term Wind Speed in Wind Farm

Abstract: To improve security and stability of power grid containing a lot of wind power generating units and to reduce operation cost, accurate short-term wind speed forecasting is of significance On the basis of applying phase space reconstruction to wind speed time series, the wind speed is forecasted by chaotic weighted zero-order local forecasting method; and then to remedy the insufficiency of above-mentioned method, namely the forecasting is carried out by searching near phase point under high embedded dimensions, a modified weighted zero-order local forecasting method, which determines near phase point by correlation degree among phase points, is proposed and a new approach to compute weighted coefficient is put forward to improve forecasting accuracy Case study results validate the feasibility and effectiveness of the proposed short-term wind speed forecasting method

Penetration Capacity Calculation for Distributed Generation Considering Static Security Constraints

Abstract: Network-connected distributed generation(DG) brings a series of impacts on distribution network,so it is of importance to study the bearable DG capacity of a distribution system under the tendency that a lot of DGs urgently need to be connected.Based on the analysis of impacts of DG on voltage profile and power flow of distribution network as well as the impacts of the power factor and position,where the DG is grid-connected,on penetration capacity,a mathematical model of penetration capacity of DG is built when static security constraints of power grid are considered.Under the condition of multi-DGs,a bi-layer optimization model to calculate penetration capacity and corresponding optimized solution algorithm are proposed.Through the case study on actual distribution system the correctness and effectiveness of the proposed method are verified.