Abstract:With the gradual development of the frequency regulation service market,the existing frequency control strategy cannot meet the needs of the market.Therefore,it is necessary to improve the existing control strategy.Based on the market,put forward the overall framework of the frequency control strategy including market mechanism,calculation method for frequency regulation capacity,research on the control strategy and the unit performance evaluation index.The experiment is carried out in a provincial power grid,and the result shows the effectiveness of the proposed scheme.

Abstract:Conventional frequency control of the power system is realized by tracking varying loads through controlling the power output of generators.In recent years,many studies have shown that the demand response can better support the frequency control of power systems.However,the response delay and communication delay in the process of demand response can adversely affect the control results.This paper models the response delay and communication delay in the controlling process respectively,analyzes its influence on control results,and studies the influence of two kinds of delay on optimal control parameters in optimal control problem.The simulation analysis shows that the optimal control strategy can improve the control effect significantly.

Abstract:From two aspects of the collection and calculation methods of reliability parameters and the selection of planning schemes,a formation and selection method of MV distribution network planning schemes considering reliability assessment is proposed in this paper,and the application of the guidance on the reliability evaluation of MV distribution network is furtherly enriched.This method includes parameter collection,reliability evaluation algorithm and formulation and comparison of schemes.Cooperating reliability and economy,the incremental net benefit model of investment is proposed based on "with&without comparison evaluation method",and the difference between the simplified model and the scheme comparison method based on life cycle cost minimization is analyzed under different power supply capacity and load demand.The investment cost&benefit is analyzed based on dynamic economic indicators,such as net present value and net present value rate,which can be used for multiple options.The case shows that the proposed method is feasible and effective.

Abstract:The cost of energy storage equipment is decreasing,which provides a new idea for load shifting and economic operation of distribution network.This paper studied the charge/discharge model and strategy of energy storage,and constructed a multi period optimal operation strategy model of distribution network with energy storage.Sparse coding automatic differentiation technology was applied to reduce coding workload,and constraint reduction of energy storage was proposed to reduce differential calculation,which enhanced the feasibility and efficiency of the model solving.Finally,the simulation results of an actual distribution network with energy storage demonstrated the accuracy of the proposed model,the efficiency of the proposed algorithm and the feasibility of the proposed solving method.

Abstract:It is conductive to improve the power supply capacity of power grid in the southern part of Suzhou based on unified power flow Controller (UPFC).However,the integration of UPFC has an impact on the reliability,selectivity and sensitivity of transmission line protection.In this paper,the fault equivalent model of 500 kV UPFC in Southern Suzhou is built combined with the control and protection logic after line fault,then the influence on distance protection action is analyzed,as well as the coping strategies are proposed.

Abstract:Field tests are conducted on the electronic transformers in Sunan 500 kV UPFC project in order to examine their performance.Test equipment and method are presented referring to DC accuracy test and transient step test.A signal source is employed to produce primary current signal as the input of transformers to be tested and the standard transformer.A transformer tester is applied to receive the output signals of the two which are compared and analyzed accordingly.Test results show that performance of the transformers utilized in the project meet the requirements of operation.In addition,the test verifies the practicability of the equipment and the method.It can provide reference for further tests on the transformers.

Abstract:As the key equipment of UPFC,the reliability of the modular multilevel voltage sourced converter operation directly affects the safe and stable operation of the whole AC system.An k-out-of-n:G system model of Sunan 500 kV UPFC-MMC and the basic analysis method for it are proposed in this paper.The relation between the reliability of valve and different redundancies is clearly described.The reliability value and MTTF of Sunan 500 kV UPFC-MMC are evaluated.And the optimal amount of redundant sub-module is analyzed basing on the indices obtained in forenamed study.The reliability design optimization of MMC valve could meet the engineering requirements Sunan 500 kV UPFC and would provide a reference for follow-up project.

Abstract:Aiming at the fault of pole-to-pole situation in the DC side of MMC,the fault current circuit of the MMC is established and the current distribution and junction temperature calculation of the diode and protective thyristor in the MMC are given for evaluating bipolar DC short circuit fault tolerance.The model and simulation of the fault current loop of the MMC is carried out under MATLAB/Simulink,and the experiment is carried out in the MMC back-to-back test system.Simulation and experimental results show that the proposed method is accurate and effective.The proposed method has important theoretical significance for checking the tolerance of pole-to-pole short-circuit fault and device selection in practical engineering in MMC.

Abstract:The establishment of offshore wind power transmission network composed by a number of offshore wind farms becomes an inevitable trend in future.Different topologies of the schemes would directly affect the investment cost of network and the reliability of the system's output power.In order to assess this new power system's reliability,the paper analyzes the reliability of offshore wind power transmission network quantitatively based on the selected reliability assessment method according to the characteristics of such new form power network.Different topologies'failure frequency and failure time are calculated based on Graph Theory,which is achieved through analysis of the network's minimal path sets.The reliability indexes of different topologies are calculated at the end and the qualified scheme are selected.

Abstract:The traditional calibration method of electronic transformer usually uses the electromagnetic transformer as the standard source.This method is easy to cause low efficiency and low accuracy of the calibration of electronic transformer,due to the problems of the electromagnetic transformer,which including ferromagnetic resonance,magnetic saturation,difficulties of increasing capacity,complicated two wire connection and the hazard of two open circuit high voltage.And this method faces the problem of direct contrast between analog signals and digital signals.Therefore,a steady-state calibration method of electronic transformer based on the improved digital filtering algorithm is proposed.First of all,the calibration process of electronic transformer is introduced,and this paper analyzes the shortcomings of traditional calibration method of the electronic transformer.Secondly,the paper describes the improved digital filtering algorithm in detail,and proposes a steady-state calibration method of electronic transformer based on the improved digital filter algorithm.Finally,a case verifies the feasibility of the proposed steady-state calibration method,and provides the reference for the large-scale popularization of electronic transformers.

Abstract:The buffer layer is an important part of HV and EHV XLPE cable,influencing the cable mechanical properties and thermal performance.In recent years,most of cross-linked polyethylene (XLPE) HV cable faults in domestic were the buffer layer discharge.The designs of domestic cable buffer layer were summarized,with different types of high voltage power cables buffer layer effect analyzed.The possible reasons including materials,running in water,buffer layer design were exposed.With the analysis of three typical cases,the design hidden trouble and the buffer layer discharge problem were exposed to provide effective reference for cable design and cable fault analysis.

Abstract:To the problem of dimensionality when the large scale unit commitment problems are solved by the traditional forward dynamic programming method,the storage of local optimizations and the small probability mutation mechanism are adopted to select the path storage in dynamic programming,which reduces the calculation of the path evaluation and also improves the exploration ability of the algorithm.In order to avoid the local extreme value of the modified algorithm,the tabu list is set up to prevent the repeated path searching.A constructing method which compresses state space based on trial stop optimization is proposed,which reduces the size of initial state space and adjusts the neighborhood path exploration method for the problem of over compression.The simulation results of 10-60 units verify the feasibility of the proposed algorithm.

Abstract:At present,the electric vehicle driver and charger are independent of each other.It would take up amount of space and increase the weight.In order to solve the problem,the integrated converter and its control strategy are studied in this paper.The main power circuit of the driver and charger share a three-phase bridge AC/DC converter.It can realize bidirectional energy transfer.The working principle of the integrated converter under driving and charging modes are proposed.The vector control strategy under two working conditions is analyzed.A unified current control structure is obtained through comparative study.The integration of driver and charger can be realized.The space and weight of the electric vehicles can be saved.The influence of control parameters on the current loop performance is also discussed.Finally the theoretical analysis are verified by the simulation results.

Abstract:The AC/DC hybrid power grid has already been built in China,which uses Ultra-High Voltage (UHV) grid as its backbone.Operation modes of power grid become more complex and diverse.The requirement for online analysis and visualization of dispatching operation will be much higher.From the view of electrical distance,this paper proposes a new method to represent the closeness degree of power equipment,which maps the high-dimensional and complicated relations of electrical distances into 2D images by using t-SNE (t-distribution stochastic neighbor embedding) algorithm,and gives dispatcher more intuitive impressions.The validation is verified by taking the actual data of power grid as an example,indicating the method can represent the variety of grid rapidly and meet online application.

Abstract:The scheme of secondary equipment outdoor layout in smart substation has become the development trend in constructing smart substation.Some schemes about out-door layout relay protection in smart substation using electronic transformer is provided and compared,which is mainly focused on technical ideas,implementation plan and their advantages and disadvantages in engineering application.In addition,aiming at the problem of changing in testing,operation and maintenance work under this new mode,a brief introduction is provided on assembly line automatically closed loop test technology of outdoor layout,miniaturization relay protection equipment.The research results have been initially applied in design,test,operation and maintenance work in smart substation.

Abstract:Considering the power system reform,the intelligent distribution network as the research object,this paper establishes the interactive system structure,puts forward the interaction mechanism,strategy and implementation method,develops the intelligent distribution network interactive scheduling decision support system,and demonstration application.The results of the research have realized the unification and interaction of the source network load,enhanced the flexibility level and the interactive response ability of the intelligent distribution network,and effectively ensured the flexible and efficient operation of the intelligent distribution network.

Abstract:Islanded microgrids lack of the support from upper power grid,so the frequency and voltage of microgrid will be influenced by the randomness of DG and the volatility of the load.Islanded microgrids probabilistic load flow calculation method considering correlated DG output based on monte-carlo method is presented,which can accurately analyze the operating state of microgrids in the islanded mode.First of all,the classification of gisle microgrid nodes is simplified,and the uniform expressions of island microgrid power flow are worked out;then the Monte Carlo method is used to calculate the result of probability flow considering correlated DG output.Finally,the Benchmark 0.4 kV low voltage microgrid system is taken as an example to verify the validity of the calculation method.

Abstract:With the rapid development of modern power electronic devices and the rapid development of the new type of power load,the problem of power quality is paid more and more attention.In order to study the voltage sags better impact on the power system,firstly,according to the source voltage sag event classification,including the main source of short-circuit fault,large motor starting and lightning,then the voltage sags caused by short circuit fault identification,can make the voltage sag monitoring system according to the waveform recognition a fault type.Finally,through the case analysis of the data waveform of the voltage sag monitoring system in Jiangsu power grid,the paper classifies the four kinds of typical short circuit faults,and verifies the feasibility of the algorithm.

Abstract:In order to solve engineering problem with the minimum phase distance of approach span,this paper establishes 3D mathematical method with every dot on the transmission line.The study can calculates the minimum phase distance based on the improved PSO algorithm quickly and accurately.It also analyzes the relationship between the minimum phase distance and the distance of the approach span,conductor tension,level difference on the MATLAB simulation.The simulation results show that with the increasing of span,the minimum phase spacing increases rapidly and then slow down;the minimum phase has a decrease with the conductor tension increased;the minimum phase decreases rapidly with the increase of level difference.At last,this paper points out that the sensitive factors have a critical value.If the sensitive factors exceed the critical value,the minimum phase can't be substandard.

Abstract:Based on the analysis of the technical characteristics of high voltage direct current (HVDC) transmission,this paper summarizes the basic requirements of DC circuit breaker in HVDC.Also,it summarizes the current types of circuit breakers used in the field of DC,analyzing their operating principles and performance characteristics.The current status of DC circuit breaker at home and abroad is briefly reviewed and the current technology problems in DC circuit breaker are analyzed.At last,it is pointed out that hybrid DC circuit breaker is the main research direction in DC transmission field.

Abstract:In the light of the demand for regenerative braking energy feedback system for subway and subway,a modular series-parallel energy-fed topology with fast fuses is adopted.This topology reduces the cost of the device,solves the problem of insufficient IGBT current,and improves the reliability of the device.In this paper,the influence of the modulated wave signal and the carrier signal on the circulation are quantitatively analyzed.The internal current control strategy and the carrier synchronization technique are used to suppress the circulation of the parallel module.The test results show that the direct parallel connection of AC and DC side can be realized through the regenerative braking energy feedback device based on multi module series parallel connection and the current deviation of the parallel inverter is less than 1%,the DC voltage deviation of the series inverter is less than 1%.

Abstract:At present,the codes of transmission towers are almost based on the construction of building codes,and the design objects are mostly aimed at the load-effect ratio not greater than 3.However,the living load effect of the transmission towers is higher than that of the existing codes,and the reliability of the components is reduced.In order to calibrate the reliability level of transmission towers,regarding the load-effect ratio as a random variable based on the point estimation method is firsly attempted,the weighted average reliability index of tower structure is obtained based on the distribution of load effect ratio as input.Firstly,the samples of wind load-effect ratio of tower structural members are obtained through a large number of structural analyses,and the distribution fitting is exploited to fit the distribution of load effect ratio.Secondly,applying the point estimation method,the abscissas of the fitted load-effect ratio distribution are selected,the reliability index of these points is calculated,and then the average reliability index according to the weight of each corresponding point.At last,the average reliability index under different wind speed and different structure importance coefficients is calculated.

Abstract:In order to coordinate the optimization of power transmission and distribution equipment in the operation of production scheduling maintenance plan,this paper designs a maintenance plan optimization decision system.Based on multi-source information which includes smart grid dispatching technical support system (D5000),generation and transmission equipment maintenance plan,base date of maintenance plan can be automatically generated.Then optimization and adjustment for maintenance plan are realized through multiple class scheduling plan security checking calculation method.Also,power supply capacity assessment of the grid is achieved.On basis of security and stability,the power network loss can be decreased by optimization of maintenance plan.So,the grid operation economy can be improved.Since the system was put into operation and dispatched production of the power grid,it has realized the optimization preparation of annual/monthly power transmission and transformation maintenance plan.Also it has improved the safety and economic operation level and production efficiency.

Abstract:Since alarm frequently reported signal analysis of power grid can effectively find strong associated influence factors of the frequently reported signal and devices that probably generate frequently reported signals,a method of alarm frequently reported signal analysis based on Weighted Frequent Pattern is proposed.Firstly,Analytic Hierarchy Process (AHP) is used to calculate the weight of each influence factor.And then Doing research on frequent pattern mining and weighted improved FP-growth algorithm is presented.Finally,weighted frequent pattern applied into alarm frequently reported signal analysis that can dig out the frequent item which can highlight significant factors.The example illustrates the feasibility of this method.

Abstract:The operation mode of sectionalized single-bus is similar to that of internal bridge scheme in 110 kV substation.Due to different primary connecting modes,protection configuration and other aspects,there are differences in operation logic of automatic switchover.The problem in automatic switchover of sectionalized single-bus scheme and different blocking and action situations of backup automatic switch with dead-zone fault of section switch are analyzed in this paper.Dead-zone fault judgment logic and action strategy in different operation modes is proposed.On the basis of ensuring safety,the action logic for automatic switchover of sectionalized single-bus scheme is optimized,which makes automatic switchover isolate the fault section reliably and restore power supply quickly when dead-zone fault occurs,and improve the recovery rate of power supply and power supply reliability.