Abstract:During the operation of the utility boiler,the heat load distribution in the furnace of boiler is affected by a lot of factors,such as fuel types,combustion mode,furnace shape and so on.Usually,it is very difficult to accurately predict the heat load distribution in the furnace of boiler.This paper introduces a method for determining the heat load distribution in the direction of the width in the furnace of ultra-supercritical once-through boiler.Wall-tangentially combustion is the mian combustion mode of the boiler.The outlet temperature of the pipe under a certain operating condition is considered as a known condition.Combined with structural parameters of the boiler,hydrodynamic calculation of the water wall system is implemented.The pressure drop calculation model is established.The flow characteristics of the water wall system and the heat transfer characteristics of boiler furnace are studied.Then,the resistance,pressure drop and flow of the water wall can be easily determined.According to the results of the hydrodynamic calculation,the heat load distribution in the direction of the width of the water wall is obtained.Based on this calculation,the model of the heat load distribution is established.Then,another condition is calculated and analyzed under this model.The results show that the method for determining the heat load distribution proposed in this paper can accurately reflect the distribution of the total endotherm of each tube along the width of the furnace.The results of the paper can be applied to boiler safety analysis.

Abstract:In view of the existing control strategy of MMC-HVDC cannot guarantee the robustness,stability and fastness of the control system,a variable target control strategy is proposed.It divided the target value into multiple small targets,so that the system quickly reaches the target step by step without overshoot.Moreover,the setting principle of the PI parameter of the MMC-HVDC control system with variable target control and the setting method of the variable target control time are put forward.Finally,a three-terminal MMC-HVDC is built and simulated with PSCAD/EMTDC.The result of simulation demonstrates that the variable target control strategy can overcome the paradox between adjusting speed and overshoot,and the PI control unit parameter setting range is expand.The results clearly verifies enhancement in the robustness and adaptability of the system.

Abstract:Large-scale pulverized coal-fired power plants in China are frequently operated at partial loads,where NO_x emission from the furnace is generally high.The present work aimed at controlling NO_x emissions from a 1000 MW ultra supercritical boiler at partial load operation through combustion optimization.In-situ tests were conducted to optimize the combustion through evaluating the impacts of varying major operation parameters on NO_xemission and boiler efficiency and comparing testing results with historic operational data extracted from the unit digital control system.High combustion excess O₂ level and blending lean coal with bituminous coal were identified to be the major factors leading to high NO_x emissions of usual operation particularly at low loads.The optimization successfully reduced NO_x emissions from the furnace co-firing lean coal with bituminous coal at both high and low loads,significantly lower than the averages of usual operation.It demonstrated the effectiveness of combustion optimization in controlling NO_x emissions for low load operation.Additionally,it was found that,for 700 MW load operation,applying the mode of mid four mills (B,C,D and E) in service to replace the often used mode of five mills in service achieved not only low NO_x emissions but also good boiler performance.

Abstract:Limited to incompleteness of power load,electricity and other relevant data,the accuracy of network supply short-term load forecasting is hard to enhance.The data accumulation of distribution and utilization system and rapid development of big data technology provide data basis and technical support for big data based load forecasting.Firstly,the sources and types of'dirty data'are analyzed based on the characteristics of distribution and utilization big data,and the corresponding methods of data cleaning are put forward in this paper.Secondly,based on a large amount of historical power load,electricity consumption and meteorological data,industry load-temperature impact model,and industry electricity-holiday impact model are established.Finally,short-term load forecasting is carried out based on above models,and test cases show effectiveness and accuracy of proposed big data based short-term load forecasting method.

Abstract:Jiangsu's highest dispatch load is greater than 100 million kilowatts,and summer air conditioning load has a higher contribution to the highest load.Summer air-conditioning load characteristics have a great impact for the load peak,power grid planning,demand response and so on.Firstly,starting from the actual data of Jiangsu,using the benchmark load comparison method,the paper selects the typical spring and summer week as the research object,for the summer air conditioning load in-depth mining,and further quantifying the summer air conditioning load and electricity.Secondly,the sensitivity of the air conditioning load to the maximum temperature,the lowest temperature and the average temperature are respectively studied in the working day and the rest day,and the relationship between the air conditioning load and the temperature in different temperature types and different temperature ranges is obtained.Finally,the conclusion of the study on the summer air-conditioning load in Jiangsu is given,which is of great significance for the further study of the follow-up summer load forecast.

Abstract:In view of the poor applicability of the traditional load forecasting methods,this paper divides the large users by two parameters,namely monthly load rate and the ratio of load standard deviation to monthly load rate,in order to clear the classification of load characteristics of large consumers.On this basis,the typical load curve,fluctuation curve and continuous load curve of the classified users are analyzed to obtain the power mode numbers.Then,the paper formulates the targeted prediction methods according to model numbers to improve the accuracy of the prediction of schedulability capacity and to provide technical support for the rapid development of power market demand response business.

Abstract:The residual flux is an important factor which affects the transfer characteristic of current transformer.The measuring residual flux is of important significance to the application of current transformer.In order to effectively measure residual flux and its coefficient,a new method to measure residual flux with alternating current voltage source is proposed.In the process of measuring residual flux,the current transformer is deeply magnetized by applying alternating current.By recording the induction voltage of current transformer and drawing the curve of core flux,the residual flux and its coefficient are calculated.The experimental results show that the measured residual flux and its coefficient is consistent with theoretical analysis.Besides,the proposed method can accurately measure residual flux of current transformer.

Abstract:In the power user installed grid-load terminal,many important loads at low voltage are cut in large power users during emergency load shedding action.In order to reduce the adverse affect to power users,a detailed inquiry of user low voltage load is executed in fields on load character,volume and switch devices.According to the needs of precise acquisition and emergency control of user 400 V load,also for economic reasons,three schemes are proposed for user 400 V load swift shedding.A novel terminal subunit based on GOOSE communication is developed at decentralized and concentrated user loads.Through improvement,the 400 V load cutting delay is reduced and the performance can satisfy the requirements of emergency load shedding.

Abstract:In order to reduce the harmonic pollution in the grid caused by strong nonlinear loads such as rectifier and inverter,a hybrid filtering system T-SAPF composed of shunt active power filter (SAPF) and thyristor switched filter (TSF) is proposed in this paper.In view of the parallel resonance potentially arised between TSF and the grid,the resonance mechanism is analyzed in detail and a virtual damping control strategy of SAPF for suppressing parallel resonance of the system is proposed.The self-tuned filtering algorithm is used to extract the instruction of damping current and the effective range of the damping coefficient is defined by three constraint conditions.The simulation results show that the parallel resonance of the system can be effectively restrained by the proposed virtual damping control strategy,the distortion degree of the PCC voltage in the resonance is reduced,and the effect of harmonic current compensation is also guaranteed.

Abstract:As China's power grid continues to improve the level of intelligence,maintenance and application level.Power dispatching automation system plays an important role in security,economic,efficient and stable operation of the smart grid.Based on the demand analysis of the mirror system,the main design principles are summarized and a mirror system architecture based on virtualization technology is proposed.The key technologies are designed and developed such as mirroring template,data agent and mirroring management.The practical application of mirroring system is given.

Abstract:In order to achieve the integration of EMS and DMS,three feasible construction modes including Centralized Integration,Distributed Integration and Decentralized Integration are analyzed.A new construction mode and technical scheme as Integrated Power Grid Dispatching and Controlling System (IPGDCS) is proposed,which includes key technologies as integrated system support platform,distributed SCADA,integrated analysis and decision support,and integrated power grid model center.Comparing the former construction modes and technical schemes,it is concluded that different dispatching/distribution automation system integration patterns should be adopted in different scale of power grid so as to achieve the best technical and economic benefits during its whole lifecycle.

Abstract:There is a large noise signal in the partial discharge (PD) signal of the switch cabinet.The traditional FIR filter will cause the phase shift of the filtered signal.Thus,the correct rate of fault identification using power spectrum is considered.To solve the problem,a PD fault identification method using zero phase error filtering (ZPEF) method is proposed.Firstly,PD signals are collected by high speed current transformer.Then,ZPEF is used to filter the noise in the discharge signal.Secondly,the power spectrum of the discharge signal is analyzed by FFT transform.Two bands power spectra of 1.0~1.5 MHz and 2.5~3.0 MHz are used to construct the eigenvectors.Finally,least squares support vector machine (LS-SVM) is used to identify PD faults.Experimental results show that the recognition rate of PD fault can be improved by using ZPEF.A corollary is also drawn:ZPEF can improve the speed of fault identification by ensuring the same fault recognition rate.

Abstract:Because of its strong anti-multipath capability and other characteristics,UWB technology is widely used in positioning.When using UWB,unstable phenomenon of the positioning results still remained.In this paper,an improved UWB space location method which can be used in the conditions that don't need real time positioning is proposed.A distance optimization method is proposed and then the distance intersection of space method which uses three base stations to solve spatial positioning is infroduced.Experimental results show that the proposed method is simple and easy to implement.Besides,it is with small computation cost and high accuracy of positioning.At the same time,because the method only needs three base stations to measure the three-dimensional coordinates of the tested point,it can save hardware cost to a certain extent.Finally,this method is suitable for warehouse location and power plant inspection personnel positioning and other scenes in electric power department.

Abstract:It is very important for electricity sales forecasting to optimize electricity supply structure and to understand economic trends.However,traditional electricity sales forecasting models cannot extract good enough data features from electricity sales data,which will generally result in lower forecasting accuracy.In this paper,a novel electricity sales forecasting model based on long-short term memory (LSTM) network is proposed.This model can analyze the correlation between electricity sales data and the related data.The original data are firstly clustered according to the features from different industries.Then,the LTM network is trained with the clustered data results.This model can automatically learn much better data features and intrinsic relationships between electricity sales data and other related data.Experimental results show the proposed model has achieved much higher forecasting accuracy than the traditional forecasting models.

Abstract:This paper proposed a load balancing method for a multi-terminal back-to-back flexible interconnection system.Firstly,the flow control model of multi-terminal back-to-back flexible interconnection system is established,and the dynamic load rate,load following degree,feeder load evaluation coefficient and other indexes are defined.The load balancing system from single feeder to multiple feeder is established.Secondly,the improved cuckoo search with large searching range and high precision is optimized for the balanced system solution of multi-terminal back-to-back flexible interconnection system.Finally,an example is given on MATLAB to verify the necessity of dynamic load rate of multi-terminal back-to-back flexible interconnection system,the feasibility and effectiveness of load balancing.

Abstract:With the acceleration of the urbanization development process,the application scale of large capacity,long distance and large cross section power cable lines in the transmission network of major cities is on the rise.Due to the limited length of the traditional cable design,the number of cable connectors per unit length is relatively large,which leads to the increase of the investment of the project,and the probability of the operation of the power cable line also increases.This essay will start its research from the large-length power cable design,transfer test,operation and maintenance and other aspects of the study,for large long-term cable induced voltage,partial signal attenuation and other factors,high-voltage power cable to increase the key technology feasibility analysis.The demonstration project of 220 kV Qiuteng-Gaowang line provides the theoretical basis and relevant data for the practical application of cable engineering in the future.

Abstract:At present,the power wireless private network communication terminal access to the engineering exploration process usually adopts manual recording and camera recording methods to record the data of the engineering exploration,which leads to the difficulty of data sorting and high error rate in the future.In order to improve the processing efficiency of engineering exploration data,taking the construction of Jiangsu power wireless network as an example,this paper analyzes the characteristics of power service demand,expounds the present situation of power wireless network construction and terminal access engineering exploration,designs the comprehensive and practical testing system of engineering exploration,develops the corresponding "YiGongKan" APP software and the back-stage data management system.APP software can upload the engineering exploration data remotely,and the back-stage data management system can modify and delete the engineering exploration data.The APP software and the back-stage data management system truly realize the no-paper process engineering exploration process,accelerating the informatization construction of engineering exploration.

Abstract:According to the charging demand of modern tram and charging characteristics of supercapacitor,the charging method of constant current first and constant voltage second is used in this paper.It is proposed that the AC/DC side of charging device uses PWM rectification technology,and the DC/DC side adopts the control strategy of giving the initial value to integrator.The implementation scheme is analyzed in details,simulation model is built to verify the control strategy,the simulation results and experimental results show that this control-strategy greatly reduces the influence of the charging device on the power grid,the peak value of the output voltage and output current at the moment of conversion between the charging methods is very small,which have a positive impact to promote the promotion of modern tram in the major cities.

Abstract:Owing to the features of high sensitivity and good anti-jamming capability,Ultra High Frequency (UHF) is widely used in the field test of Gas Insulated Switchgear (GIS).In order to explore the relationship between UHF signals and apparent discharge magnitude,this paper established combined measurement system,partial discharges data on metal protrusions under pressures from 0.3 to 0.5 MPa were collected.The cumulative energy of UHF signals was extrated to conduct a correlation analysis with apparent discharge magnitude.It is concluded that the singnal energy has a linear relationship with the square of discharge quantity unedr different pressure.The linear slope has a strict relation with pressure.The results can lay a foundation on the calibration of UHF signals.

Abstract:The correctness of the sampled value differential protection behavior depends on the accuracy of the data window selection.Based on the hysteresis characteristics of the current transformer (CT),this paper analyzes instantaneous value and the rate of change of restraint current and differential current under the situation of busbar internal and external faults,and puts forward a data window selection method for sampled value differential protection:first select feather point of data window,then by the feather point to push down the starting point of data window,and RTDS test is carried out to verification the principle.The sampled value differential protection principle is not affected by the system frequency,the non-periodic current and CT transfer characteristics and so on,and it can still guarantee the reliability and rapidity in the complex fault condition,data window selection method is accurate and reliable,improves the sensitivity of sampled value differential protection action.

Abstract:Aiming at the shortcomings that the traditional standard particle swarm optimization (PSO) tends to fall into the local optimum and the differential evolution algorithm (DE) has a slow convergence rate in the later stage,a differential particle swarm optimization algorithm (DEPSO) is proposed to optimize both the convergence speed and the global Optimum ability,and applied to distribution network substation planning.Through the combination of Voronoi diagram in the mathematical model of substation site selection to determine the substation power supply range and planning capacity,and then verify the substation actual load rate,simplify calculations and improve search efficiency.The long-term planning example of a city city verified that the algorithm is correct and effective,which can meet the planning requirements of urban distribution network.

Abstract:Based on the research of energy storage system cooperation with intermittent energy coordination control strategy at home and abroad,from the minute and millisecond two time scales,this paper proposed a smooth output control strategy and a planned output control strategy.The simulation system includes wind power generation system and battery energy storage system and it verifies the smooth output control strategy and the planned output control strategy of the energy storage system.

Abstract:The electrical stress of high voltage and high current is the characteristics of the sub module base on MMC.And IGBT is the key component of MMC module.A calculating method for loss and junction temperature of IGBT base on MMC is very important to the heat design and type selection of IGBT in MMC engineering application.Firstly,the stress of the module under steady state operation of MMC is analyzed.Secondly,a method for calculating the IGBT loss and junction temperature of MMC module is given with current and sub module switching and junction temperature estimation model.Finally,the calculation method is verified in the back to back test system.The proposed method is proved to be effective and feasible.

Abstract:With the continuous development of the smart grid,the energy internet,the application of cloud computing,big data,data mining and virtualization technology in the power industry,the electric power telecommunication has been una-ble to satisfy the requirements of the power system.As a new network architecture,software defined network (SDN) realizes decoupling of the control function and data transmission function,which is one of the choices of future electric power telecommunication network architecture.Based on the principle of SDN network that is discussed in the paper,the key technology of electric power telecommunication network based on SDN is shown in detail.And the key technologies are as follows:performance,security,scalability,delay,link reliability,fault tolerance and compatibility.What's more,this paper discusses the application of prospect of SDN in Power System with great prospect.

Abstract:This paper studies the influence of DC bias on transformer and substation grounding grid around the grounding pole of ±1100 kV Guquan converter station.The DC bias current distribution of transformer in the surrounding AC power grid is analyzed,and the corresponding DC resistance network coupling model is established.At the same time,on the basis of the above research,combined with the withstand current limit of transformer DC bias,the corresponding DC bias control range and DC bias control scheme are proposed,and the reference for the location of grounding electrode in east China is provided.

Abstract:The energy feedback system can be used to recycle the subway braking power,can greatly save energy.But in the experiment process of the energy feedback system,the subway starting and braking environment is lacked.This paper designs a renewable energy feedback experimental system consisting of two back to back inverters,and S1 simulates subway frequent starting and braking,S2 detects unblock or blocked conditions,automatically enter the feedback or standby state.The test results show that the test system quickly unlocks during simulation of the braking process of the subway,stabilizes the DC voltage at the same time,and quickly locks into the standby state during the simulation of the subway start-up process,providing experimental support for the on-site operation of the subway energy feeding system.

Abstract:The large number of distribution automation secondary equipment is the key object to maintain the safe and stable operation of the distribution automation system.The risk assessment process is established through the identification and continuous attention to the risk points of the secondary automation of the distribution automation.The average fault is calculated according to the state score of the equipment probability,then calculate the comprehensive risk loss and quantitative risk value.Taking the minimum cost of risk and the cost of maintenance as the optimization target,to construct the maintenance optimization model of the maintenance decision-making,and the scientific and reasonable sorting of the maintenance plan is given considering both the risk and the cost.Significantly reduce the cost of maintenance of secondary equipment and unreasonable maintenance may lead to the risk of failure,to achieve better operation and maintenance management of secondary equipment.