Abstract:With the development of power electronics technology,the DC power distribution network presents its obvious advantage in technology and economic and has good prospects in the background of an energy revolution.First,the development of low-voltage DC power supply and voltage levels were discussed.Then,it summarizes and analyzes the key technologies of DC distribution network coordination control technology,protection technology and power quality control,as well as the development of key equipment.At last,the project research and application of DC power supply engineering in the world are summarized.The construction of active distribution network in Suzhou industrial park is an important exploration of urban energy transformation.

Abstract:Though the uncertainty of wind power,if demand response is considered in the power system dispatching to expand acceptance of wind power,it will be able to improve the stability of power system.The resources in the demand side are put into the optimized scheduling model.The economy of optimal is adopted as the objective function and the cost of transferring loads is included in the total cost of generating electricity,on the basis of which,the power constraint of controllable load in the demand side is added in order to improve the reliability of the scheduling operation.Mixed integer linear programming is used to optimize and then the day-ahead scheduling model considering the power constraint of demand response is set up.Finally the effectiveness of the proposed method is verified in the simulation of a 6-bus system.

Abstract:The frequency emergency coordination control system plays an important role in dealing with the frequency stability problem of power systems caused by multi-infeed HVDC systems.However,the rapidity and accuracy of the coordinated control system largely depends on the DC coordinated control function.Firstly this paper introduced the interface between DC control system and coordinated control system,and interface data processing method was appropriately designed.Then a new DC power fast decreasing control method was proposed to solve the problem that the coordinated control system cannot distinguish the decrease of DC power under the current control method.A modulation power compensation method and a commutation failure delay modulation method were also proposed to improve the accuracy and reliability during the implementation of modulation control.Finally,the correctness of the functions was verified by RTDS simulation test,which provides reference for the application of the UHVDC coordinated control function.

Abstract:In order to reduce the impact of scaled distributed power access on the original grid and improve the multiple utilization efficiency of the source grid.In this paper,by analyzing the multi-stage energy interaction scene with distributed power supply,the multi space scale of main network,distribution network,feeder and platform area,and short-term,ultra short term,quasi real time multi time scale interaction mechanism are formulated,a multi-source interactive coordinated optimal control model for distributed power supply including large wind power plants,gas turbines and centralized large capacity energy storage is established.The objective function of the model is the minimum active power fluctuation,the closest network loss and the largest economic benefit.The model sets constraints such as node power flow,wind power,and so on.Taking Chongming Island in Shanghai as an example,the multi intelligence coordinated optimization control application scene of source network is set up to simulate and verify the short-term,super-short-term and quasi-real-time optimization effects of multiple spatial scales,and to provide optimized control basis for the access of large-scale distributed power supply.

Abstract:With the increasing of distributed generation number,the development of AC/DC distribution network is unstoppable.A two-layer planning model is proposed to handle the planning problem of AC/DC distribution network.The objective functions of the first layer are system construction and operating costs.The second layer calculates the operating costs in detail by economic dispatch,which makes the result more accurate.For different bus types,branch types and network topologies,a binary coding model of AC/DC distribution network is put forward,which can be nested into intelligent algorithm conveniently.A 13-bus case study indicates that AC/DC distribution network is more economical than tradition AC distribution system in operating costs,line construction costs,VSC installation costs and generator installation costs.

Abstract:It proposes the participating network load interaction users and their interruptible load selection,participation strategy and recovery principle in different running state and demand scene of power grid.So as to achieve fast load removal and recovery in power grid frequency emergency control,on the other hand,ensure that the important load in emergency control process is not affected,and ensure the safe operation of power grid under emergency condition.

Abstract:The effective evaluation of the characteristics of power supply for low voltage distribution network is the basis and basis for the development of power supply enterprises and the decision making of low-voltage distribution network.In this paper,we put forward a kind of based on improved principal component analysis of low voltage distribution network power substation comprehensive evaluation method,combining with the advantages of traditional principal component analysis and analytic hierarchy process,established index evaluation system,and can reflect 132 power supply in economic efficiency,power supply reliability and the superiority of coordination on the adaptive nature of the three scores.Recycling system clustering method to score,to explore the different power supply in different characteristics on the development of the status quo,combined with the data from 2015,2016 two years longitudinal comparison,through the example analysis and calculation,based on improved principal component analysis of the comprehensive evaluation method of low voltage distribution network evaluation and subsequent development of power substation is practical and effective.

Abstract:Galloping is the main factor affecting the safety operation of transmission lines in winter.Aiming at the serious damage problems caused by conductor galloping,a series of researches were carried out on the full-scale galloping test line in Henan Jianshan,with consideration of damage characteristics and the cause of the damage,to find the bearing weakness parts of the spacers.On the basis of this,this research initially starting from the general technical requirements of the spacers and the special requirements of the galloping area,optimized the connection pad limit of the butterfly damping rubber,the design of double-frame plate and the selection of aluminum alloy materials.A new type of anti-galloping spacer utilized in 500kV transmission lines was developed.The ultimate bearing test of the spacers has showed that,comparing with current double-frame type spacers,the new type spacers grip strength increased by 28%,the pull pressure load increased by 114%,the centripetal load increased over 44% and the overall bearing ability increased by 22%,as such the overall mechanical performance has been greatly improved,and the special spacer is widely used in 500kV lines in Henan,and has a good application effect.

Abstract:The fracture problems of the composite insulators are the key problems to threat the security and stability of the transmission line.In order to analyze the types and causes of the fracture problem,this paper studies the fracture samples of the composite insulators and classifies the fracture types of insulator hardware and FRP rod.Studied shows that the causes included the invalidation of sealant,breakage of the sheath and splice failure between the FRP rod and the sheath.To solve the problems,three solutions including performance test,on line detection and technical transformation of the composite insulators in the important passage are proposed.And preventing suggestions to the fracture problems are provided.

Abstract:The digitalization of basic equipment is the basic requirement for the development of intelligent power plants.In order to realize remote monitoring and automatic reading of base type liquid level meters,a liquid level measuring system based on digital image processing is proposed.Image processing algorithms include color threshold segmentation,improved Canny edge detection and template matching and window search peak detection,which is new proposed.Instrument location,level interface extraction,digital recognition and camera self-calibration are respectively performed on the captured images,finally realizing the digitization of liquid level image.At the same time,the system has the function of adaptive median filtering,histogram concavity analysis and perspective distortion self-correction,improving its noise resistance and adaptive performance.As laboratory tested,the measurement system has good accuracy and can maintain the accuracy level of the original instrument.

Abstract:With the explosive growth of user load data in power consumption information collection and load control systems,traditional computing frameworks and methods are faced with tremendous computational pressure when dealing with massive user load clustering and carrying out load characteristic analysis.In this paper,with a view to increasing accuracy and computational power of graphic process unit (GPU),the fast parallel K-means clustering algorithm for load curves is proposed based on Nvidia compute uniform device architecture (CUDA).This algorithm uses parallel acceleration strategies,such as parallelization of distance computing and curves counting,and rational allocation of thread blocks,which greatly improve the clustering speed of user load curves.A number of test examples show that the proposed clustering algorithm in this paper has a high acceleration ratio and strong adaptability,which is a good way to solve the problem of massive load curve clustering.

Abstract:In order to improve the inaccurate diagnosis results caused by extracting opening and closing current feature inaccurately and make up for the deficiency of operating mechanism of circuit breakers defect diagnosis technology in the aspect of severity,a diagnostic method based on the eigenvalues of wavelet packet energy and support vector machine (SVM) as an intelligent algorithm is proposed.Meanwhile,the characteristic data is utilized to explore the trend of the defect.In conclusion,the feasibility of the method is verified through the analysis of the data of the normal operation,the control loop fault and the iron core astringent defects of the circuit breakers.

Abstract:A variety of topology structures and control strategies of active power filter (APF) are analyzed.Based on the four basic control strategies,load harmonic current control,grid harmonic current control,filter line harmonic current control and load harmonic voltage control,the steady state and dynamic state analysis of typical APF structures such as shunt hybrid APF,series hybrid APF and APF series with PF connecting to the grid are carried out.The experimental waveforms,which verifies the correctness of the theory analysis,of APF working on steady state and dynamic state are also given by an application example.The conclusions obtained in this paper is of great significance in structural selection and practical application of APF.

Abstract:There are obvious defects in the traditional HVDC technology in power regulating speed,reduce the loss,protection and control,has been unable to meet the electricity demand diversity.Emergence of VSC-HVDC not only solves the defects,but also has the power of independent controllable and has the advantage to supply power to a passive network etc,widely used in power generation,new energy and other fields of distributed micro grid.In this paper,double end DC is taken as the research object,and the mathematical model of both ends flexible and straight is set up.On this basis,the basic operation mode of the system and the control strategy of the voltage source type (VSC) converter are studied.Considering the control delay of the VSC converter and the poor responsiveness of the current closed loop control,an improved deadbeat control strategy is proposed to solve the above defects by predicting the k+2 time sampling current.Finally,the correctness and reliability of the above methods are verified by CO simulation.

Abstract:In order to better simulate the inertia of the synchronous generator and make full use of the advantages of different energy storage units,a virtual synchronous generator system with a hybrid energy storage unit composed of battery and ultracapacitor is studied and the mathematical model of the system is analyzed in detail.In the control strategy,taking into account the characteristics of the energy storage units themselves and the service life of the battery,a control strategy including battery SOC feedback is proposed.By setting up a corresponding MATLAB/SIMULINK simulation model,the system is analyzed in the normal state of charge and the SOC is reached.At the upper limit,the power distribution of the energy storage verified the correctness and effectiveness of the proposed control strategy.The results show that the proposed virtual synchronous generator system with battery SOC feedback control can achieve a reasonable power distribution when the power fluctuates,and prolongs the service life of the energy storage while maintaining the stability of the system.

Abstract:Based on the network communication platform,the islanding protection in the station domain can quickly realize the islanding state judgment which can make up for the deficiency of the principle of active and passive island protection.The current station-domain islanding judgment method which is based on the fixed grid structure analysis does not have universal applicability,so this paper proposes a method based on voltage class topology analysis to judge the isolated island in the station domain,in which the different voltage class characteristics is used to optimize the search path.Compared with the full matrix self multiplication and traditional tree search method,the proposed method is simple,small in memory and fast in computation.It is proved that the method is feasible and applicable to all kinds of grid structures in power system.In addition,this paper also puts forward the error prevention mechanism through the switch position fault tolerance verification to further strengthen the reliability of the protection algorithm.

Abstract:This paper first describes the development and characteristics of mobile application in power system,and analyzes the security risks faced by clients,servers,data transmission and management.Then,aiming at the security characteristics of mobile clients,a security mechanism detection method is put forward from the perspective of application security protection,and the detection method is described in detail from two aspects of detection means and detection points.Finally,comprehensive static analysis and penetration test method,the APP security test was carried out.The test scheme and test method proposed in this paper can find the security risk in mobile application comprehensively and efficiently.It provides technical guidance for pre-line safety evaluation.

Abstract:As the key device of sub module of converter valve,IGBT is of great practical significance to improve the reliability of the converter valve by studding the anti-short circuit ability of IGBT.Based on the operating mechanism of modular multilevel converter valve,this paper proposes an IGBT short circuit test circuit and system of sub module of converter valve.A comprehensive assessment of the transient stress by short fault and the steady stress of the converter valve is achieved.The validity of test circuit and system is verified by proposing a test platform.

Abstract:In order to solve the difficult research points of sensorless starting and low-speed operation of switched reluctance motor (SRM) used by electric vehicle.A new sensorless control method based on space vector model of phase inductance for switched reluctance motor is presented in this paper.Three-phase inductance of SRM are computed by pulse injection at startup and low-speed drive operating two different operating states,and through the cosine functional relationship between space vector model of phase inductance and angle to realize the rotor angle estimation.The realization of this sensorless method is simple and reliable.Finally,the proposed sensorless scheme is verified by simulation and experiment.The results show that the proposed method can estimate the rotor position accurately and meet the requirements of low-speed sensorless operation of SRM.

Abstract:The problem of overheating fault of high-voltage isolation switch has brought unavoidable safety hazard for power system.The temperature rise is an important index to evaluate the operation state of isolation switch.The contact resistance value is the key parameter to indicate whether the connection of the conducting circuit is good.The temperature rise of the isolator is mainly controlled by the contact resistance.When the contact resistance changes,the overall temperature distribution of the isolation switch changes.In this paper,the effects of different defects of the contact resistance and the maximum temperature rise on the contacts of GW6B-252 isolation switch are studied.The conclusion is occurred that the contact pressure of the GW6B-252 should be above 400 N,and the fouling of the contact has the greatest influence on the temperature rise of the GW6B-252 isolation switch.

Abstract:The high probability of transmission line short circuit fault is due to bad weather,external damage,insulation aging and bird damage.In order to accurately locate the fault location and speed up line repair,this paper proposed a two-terminal fault location method using voltage and current data.In this method,the uniform transmission line equation was used to derive a new fault location function based on the unsynchronized data on both sides of the line,and the specific fault point or searching range was obtained by the amplitude characteristic of the function and line equal partition method.At last,MATLAB simulation and calculation results show that the proposed fault location method is simple and easy by meeting the line-searching needs,the located result (fault point or searching range) can overcome transition resistance and the unsynchronized data on both sides of the line,and is applicable to all kinds of short circuit fault type.

Abstract:In order to shorten the testing time of DC resistance,the magnetic circuit method is usually used in the test of low-voltage winding DC resistance of large transformer.The influence on remaining magnetic in the core of different wiring mode based on magnetic circuit method is analysed,and a more ideal wiring model is selected.The wiring model optimizes the direction of charging current and voltage excitation during the test,so as to make the magnetic flux direction in the core as consistent as possible with the remaining magnetic after testing one-phase winding,and make reasonable use of the remaining magnetic in the core to assist magnetic to the trial windings.A 500 kV transformer substation's main transformer is used as an example to compare the test results of all wiring modes,the results prove that the selected wiring method can shorten the testing time to a certain extent,and improve the working efficiency.

Abstract:In order to study the effect of grounding defect on XLPE cable terminal,ANSYS finite element analysis software is used to establish the cable terminal simulation model and the physical simulation experiment is carried out in the laboratory.Study on the effect of grounding defects on XLPE cable terminal was conducted in 3 aspects:XLPE cable terminal electric parameter calculation,temperature distribution as well as product analysis.The results of simulation and physical simulation show that the grounding defect will lead to serious heating of high voltage XLPE cable terminal.Research conclusion shows that terminal grounding fault will cause voltage suspension,large current through insulation shield,abnormal temperature rise of XLPE cable terminal,with metal oxides,carboxylic acids and other compounds produced,which will cause serious impact on the safe operation of XLPE cable.

Abstract:Two different types of coal-fired units are selected to compare the NO_xconcentration,the ammonia escape rate and the NO_xconcentration of the SCR denitrification device outlet and the chimney inlet measured by CEMS before and after the ultra-low transformation.At the same time,on the ultra-low emissions after the transformation of the air preheater dust and catalyst samples are analyzed.The results show that after the ultra-low emission of the unit,there are some problems that the bad uniformity of the NO_xconcentration distribution and the increase of the escaping ammonia concentration,resulting in serious ammonium hydrogen sulfate blockage in air preheat heat.Catalyst active component of velocity is relatively serious,sulfate and alkaline earth metal elements content increased significantly.In order to solve the above problems,it is proposed to adopt multipoint monitoring,spray ammonia optimization,catalyst regularly tested,air-conditioner cold-end replacement of enamel-enriched elements and other measures.

Abstract:It is different between the action value and the setting value of UNITROL5000 excitation system low excitation limit during generator's leading phase operation,and which leads to that the unit can't play its leading phase ability,and the line voltage operates much higher,it is not conducive to the safe operation of the power grid.This paper analyzes the low excitation limit action characteristics and influence factors of two different types of excitation system.Then an optimized setting method of low excitation limit is proposed.Finally,the feasibility of the tuning method is verified by an example.The low excitation limit setting method considers the generator's leading phase ability and the excitation-loss protection,the action value is as close as possible to the generator's leading phase ability and matches the excitation-loss protection reasonably after setting the optimized value of low excitation limit.The low excitation limit setting method provides a reference in the engineering practice for UNITROL5000 excitation system.

Abstract:A 1000 MW unit USC once-through tower boiler,which had been put into operation in 2012,had a high concentration of 450 mg/m³ NO_x emission at the SCR entrance under the condition of meager coal mixed burning with bituminous coal.Thus it was difficult to realize ultra-low NO_x emission.The paper analyzed the necessity and feasibility on the combustion system retrofit to get the lower concentration of nitrogen oxides.On this basis,the technical scheme,using advanced hybrid air-staged low-NO_x combustion system,was proposed and adopted.The retrofit project was completed at 2016.After the retrofit,the NO_x emission concentration was reduced to 300 mg/m³ at the SCR entrance under the same conditions,boiler efficiency and other indicators were good,also there were no other negative effects.The benefit on economy,safety and environmental protection of the technical retrofit is satisfying.