Abstract:An algorithm of calculating the capacity of UPFC based on both system and converter strategy is proposed.The comparison of effect in normal and N-1 situation is researched.Control strategy of Nanjing UPFC project is introduced,while power flow is calculated based on UPFC parameters,voltage and reactive power control modes.Control range of UPFC is computed by PSS/E and Python with the real-time data of Jiangsu Power Grid.The result can improve the safety and reliability of Jiangsu Power Grid.

Abstract:Unified power flow controller in Suzhou 500 kV Southern Power Grid is the highest voltage class and largest capacity UPFC project in the world.It is used to solve the problems of uneven power flow distribution,over-limited sectional flow and poor dynamic reactive support ability,et al.The principle and protection configuration scheme of UPFC are summarized,and the action results of typical fault points are expounded in detail.The research of 500 kV UPFC in this paper provides a reference for the study of the protection of the flexible transmission system with higher voltage levels in future.

Abstract:500 kV series transformer is the key equipment in Suzhou 500 kV unified power flow controller (UPFC) project,which undertakes the regulation of voltage and power between the converter and the line.Because of the special connection mode and operating condition of 500 kV series transformers,there are many differences from conventional transformers.First,the main insulation of the net side winding is matched with the line voltage grade,and the longitudinal insulation of the end is determined by the overvoltage,which brings about the complex characteristics of the insulation level of the net side windings.Secondly,the lightning full wave shock test and the external AC withstand voltage test are also different from the conventional transformers in the insulation test.Finally,the special working condition of series transformer has caused the high requirement of resisting short-circuit ability and over excitation capability.In Suzhou UPFC Project,a large number of technical researches have been carried out for 500 kV oil-immersed series transformers,which overcomes the difficult problems of the complex insulation of the windings,the special test technology,the short circuit ability and the high excitation ability.In this paper,the technical analysis of 500 kV series transformers in Suzhou UPFC project is carried out from various aspects,such as operating conditions,technical characteristics and test requirements.

Abstract:With the large-scale integration of wind farms,the uncertainty of wind power poses great threat to the stability of power system.The Unified Power Flow Controller (UPFC) has been the most comprehensive Flexible AC Transmission System (FACTS) device ever since.It is advanced in power flow controlling.In this paper,UPFC is deployed to coordinate with wind power uncertainty.A multi-objective optimal power flow model incorporating UPFC is established to tackle with decision risk.Case studies on IEEE 14-bus system show that optimal decisions can be obtained by solving the proposed model and,most of all,risks can be reduced.

Abstract:In order to quantitatively evaluate the influence of UPFC device on the operation reliability of power grid,this paper takes UPFC project of 200 kV Nanjing West Ring Network as the example,and the method and process of the reliability evaluation of the system with UPFC is analyzed.First,based on UPFC subsystem division,the reliability model of each subsystem with no spare components and spare components is established.Based on this,the two-state model of UPFC system is obtained.Finally,combined with the case of Nanjing West Ring Network,it was mainly analyzed the influence of different schemes such as UPFC,new line and double capacity wires and different installation locations of UPFC on the reliability of power grid.

Abstract:Proportion of load consumption component is chosen as a characteristic of each load using for load classification and model identification in this paper.The crucial buses with high-voltage which fully participate in the system dominant oscillation mode are chosen as the observed objects in regional load model identification.The objective function of load model identification is established using the voltage of the observed objects.Gradient optimization algorithm is used for optimal value searching.Simulation results verifies the proposed method,and three load classification strategies including miscategorized method,classification according to the electrical distance between two loads and classification according to the proportion of load consumption component are compared with simulation tests.The results show that the load identification value based on classification according to the proportion of load consumption component is more accurate and applicable to other occasions.

Abstract:The traditional N-K fault analysis of power system generally adopts the method based on combination and traversal,which has the disadvantages of a large number of fault combinations and low computational efficiency.In this paper,the two-level programming model of this kind of problem is established,which can seek the fault combination causing the maximum amount of grid load through the way of optimization.Aiming at the fault combination determined by the upper-level problem,the lower-level problem simulates the operation of the grid after the accident,to meet the various types of power system operation constraints,by adjusting the generator output power to minimize the amount of grid load.Furtherly the flowchart of genetic algorithm to solve this problem is given.Finally,the validity of the model is verified through IEEE14 node and IEEE118 node example system.

Abstract:The millisecond precision load control system transforms the load-shedding control mode from the traditional centralized power cut-off of the substation load lines to the fast and accurate control of the user-interruptible branch load-carrying lines.Based on the analysis of the existing terminal access communication technology,the overall structure of the system is proposed,which consists of the control master station layer,the control sub station layer and the end user access layer,describes the function definition of each level,and also gives the overall minimum-cut control strategy in consideration of the DC fault position and the load stratification.The key technologies needed in the system implementation are introduced in detail:the STM-1 communication interface technology,the 2M channel access technology of multiuser sharing,the test technology of simulating the mass resection of large-scale interruptible load and the sequential recovery.The technical scheme proposed in this paper has been applied in the first and second phase project of the precise load shedding in Jiangsu Power Grid,and the field test shows that it satisfies the running requirements.

Abstract:Based on the multi-infeed planning power grid of Jiangsu in 2018,the chain commutation failure and HVDC pole blocking problem after three short-circuit faults occurring in AC system are studied by using electromechanical transient simulation software PSD-PBA.Besides,the multi-infeed interaction factor (MIIF) and voltage interaction factor's (VIF) laws of usage in power grid are summarized.The results show that several important AC lines'short-circuit fault will lead to more than one DC inverter's commutation failure because of the interaction between 4 HVDC transmission systems.In addition,compared to phase-to-ground faults occurring in commutation buses,faults occurring in AC line near inverter will cause more chain commutation failures because of the different coupling relationships.Since most measures of mitigating the interaction between HVDC transmission systems require a large investment,those AC faults should be given enough attention in Jiangsu power grid.

Abstract:From the perspective of power suppliers in electricity market,the multi-time scheduling model is built considering the uncertainty of photovoltaic power prediction,photovoltaic is consumed and tracked by using battery and air-conditioning demand response resource.The model ensures the economy and the sufficiency of demand response resources that can consume the error of the value of photovoltaic forecast.The uncertainty of photovoltaic power is taken as chance constraint in the day-ahead scheduling model and converted into certainty equivalent condition when solved,the minimum unbalance and minimum regulation are taken as objects in the intra-day scheduling model.Based on the simulation results,considering the error of the value of photovoltaic forecast in the day-ahead scheduling can effectively improve the consumption of new energy and the benefits of supplier is verified.The higher confidence degree causes the better photovoltaic tracking.The actual daily benefit is related to the cost of intra-day scheduling.

Abstract:Ultra-high voltage direct current (UHVDC) system hierarchical connection mode,in which the UHVDC inverter station connects to different voltage level AC system,provides an effective means to evacuate the high-capacity power of UHVDC access to the load center.DC terminal location selection is a multi-objective decision problem.Considering the characteristics and influence of UHVDC hierarchical connection to power grid,the comprehensive evaluation indexes are established,on the basis of which DC terminal location selection strategy by the use of technique for order preference by similarity to ideal solution (TOPSIS) method.Finally,an actual project of UHVDC hierarchical connection to system is taken for an example and four different UHVDC hierarchical connection schemes are discussed.The result shows that effective decision support for UHVDC hierarchical terminal location planning can be provided with the proposed method.

Abstract:Mathematics foundation is introduced,and the key points are Marchenko-Pastur Law and Single-ring Law.General method of applying large dimensional random matrices theory to condition assessment is conducted,including application condition,matrices construction method,and assessment indexes.Then the specific programing steps of single-ring law are discussed.Finally,two application scenarios are taken as examples,respectively are electrical equipment condition assessment and power gird condition assessment.The simulation results indicate that large dimensional random matrices theory is able to be applied to assess the status of a complex system,the health status of electrical equipment and the fault operation status of power grids shall be reflected through the assessment indexes.

Abstract:With the continuous development of power electronics technology,the load converters are constantly being connected to the power grid.So the power grid is progressively developing into a low inertia and less damping network,and the issues of power grid's security and stability are becoming increasingly prominent.Under the traditional control of converter,the load is difficult to participate effectively in the dynamic regulation of the power grid.Virtual synchronous motor technology can provide inertial support for the system so,it attracts people's attention.This paper introduces the principle of the load virtual synchronous motor,and establishes the small signal model of the load virtual synchronous motor,and it also gives a control parameter design method of the load virtual synchronous motor.This method can balance the stability and dynamic performance of the system.The Matlab/Simulink simulation results show that the correctness of the small signal model and the effectiveness of the design method which proves that it can provide some support for the stability of the power grid.

Abstract:A new double closed loop control strategy of three-phase voltage-sourced PWM rectifier based on IMC,which is composed of inner current loop and outer voltage loop.Based on a decoupling control with IMC,the inner current loop can obtain the decoupling of active current and reactive current.Based on the idea of power conservation and disturbance-rejection control with two-degrees-of-freedom IMC,the outer voltage loop can not only realize the linearization control of voltage loop,but also,simultaneously,achieve characteristics of fast-tracking and excellent disturbance-rejection of the DC voltage.The simulation results demonstrate the validity and the feasibility of the proposed new control strategy.

Abstract:Aiming at the problem that the workload of switch VLAN configuration and multicast is large and prone to error,a scheme of exchanging the switch configuration information based on the SCD file is proposed to realize the automatic configuration of the switch.Based on establishing switch model and physical connection model of substation,this scheme analyzes the inherent association between the virtual connection and physical topology connection and makes use of database's function to match out switch's configuration information,then output the configuration as CSD file.Downloading the CSD files into switch can complete switch's unified off-line configuration consequently reducing switch's configure and maintenance difficulty.It is proved that this method can reduce field configure work and is of great significance in engineering application.

Abstract:Yunnan Power Grid and China Southern Power Grid have became an asynchronous network.There is a new change in the out-of-step oscillation characteristics of the grid.In this paper,four kinds of multiple serious faults are studied which are under the typical mode of Yunnan Power Grid.The out-of-step oscillation sections can be divided into two types,one is the parallel section and another is the long chain section.Yunnan Power Grid is currently equipped with distributed out-of-step devices,which is not ideal for the out-of-step determination and separation for these two types of out-of-step sections.A method is presented to design an out-of-step system based on the Ucosφ criterion and the voltage phase difference criterion.Three out-of-step systems are designed respectively for northwestern Yunnan,northeastern Yunnan and southwestern Yunnan.The strategies of the out-of-step systems are also developed.

Abstract:With the development of intelligent substation technology,the transition from traditional substation to intelligent substation will continue for a long time.Aiming at the shortcomings of manual maintenance of the remote device model as heavy workload and error-prone,the characteristics of the information structure and object model of the telecontrol device are analyzed.A remote configuration upgrade conversion scheme is proposed.Combined with the specific application examples,the program design and development process of the tool software are introduced,the modules that make up the tool are put forward,and their functions are described in detail.Compared with the traditional way,the scheme can significantly reduce the difficulty of substation remote transformation and improve the efficiency of project implementation.

Abstract:1000 kV UHV Nanyang substation is a UHV AC demonstration substation engineering project in our country.The UHV transformer is an important equipment in the substation.There are two transformers,which were produced by different companies,using fully compensated and non-fully compensated regulation-compensation principle.The winding connection method and regulation-compensation principle of the two transformers are introduced.The Simulink simulation models of the two transformers are established.The simulation data of the voltage of the transformer confirms the correctness of the simulation model.Finally,some suggestions on the construction of UHV are put forward according to the comparison results,which provide reference for the construction of UHV at later stage.

Abstract:The design architecture and key technologies of the PC virtual operation platform for a protection and control device are desiged in this paper.The device is classified into management process,several real-time components and non-real-time components.The management process reads the configuration files,loads the real-time and non-real-time components libraries of each processor,and completes the initial interaction via virtual CAN bus and FIFO communication.The management process initiates the real-time thread,sets the relationship as per the task cycle,and executes the real-time tasks serially;the management process initiates several non-real-time threads,calls up non-real-time component cycle tasks,and realizes concurrent communication with several debugging clients.Data interaction between components is realized via virtual data bus and shared memory.The platform-based development method supports the simulated testing of the complete set function.Device configuration and program may be operated in the physical device and the virtual device,thus improving the developm ent efficiency.

Abstract:At present,the traffic management of the switches at the smart substation process level mainly adopts VLAN division method.Need to understand the working principle of VLAN and design artificially by information flow,so efficiency is not high.By analyzing the SPCD and SCD,the port topological relations of the switches are established,and the information flow of each intelligent electronic device (IED) device in the switch is analyzed,and the port VLAN ID is automatically assigned according to the ports (PVID) to auto-complete the generation of VLAN configuration tables in the switch.An automatically generated test case of 220 kV typical interval VLAN configuration table is designed.The test proves that this method can automatically generate the VLAN configuration table of intelligent station switch and control the flow direction according to the expected refinement,greatly improving the working efficiency of the site,has a certain practical value.

Abstract:The intelligent substation equipped with both SVG and TSC devices can use the combination advantage of them to achieve smart,flexible and dynamic compensation for the required reactive power.This paper mainly introduces the GM intelligent substation's SVG and its intelligent coordination control system with TSC from the aspects of principle,structure,performance and control strategy.At the same time,it analyzes the SVG protection tripping event,and finds out the reason,That is,the system voltage harmonic surge triggering related protection malfunction.In the end it gives the relevant rectification measures and recommendations,hopping useful for the design and inspection of the similar FACTS equipments'(such as STATCOM,UPFC,etc.).

Abstract:At present,the research on on-line diagnosis of electronic transformer soft fault is rarely seen.Aiming at line electronic transformer,the current and voltage models of the drift bias fault and transformer bias fault is established based on the physical temperature characteristics of components.The double terminal six current and single terminal four voltage of line fiber differential protection are used to set up the electronic transformer soft fault diagnosis criterions,the output current and voltage of double protection device are compared with vertical and horizontal to find the fault electronic transformer.The method could realize on-line fault diagnosis of electronic transformer on existing protection under the condition of no additional hardware and ECT without power failure and online.Matlab simulation result shows that the method is corrected and validated.

Abstract:Two new vector modes of one-cycle control three-level APF are presented in this paper.The topology of three-level four-leg inverter was studied,and the mathematical model was analyzed.Considering that the DC capacitor voltage can balance automatically,with the help of absolute switching state table two new vector modes of one-cycle control three-level APF were proposed,and the control objective equations were derived.The simulation shows that these modes are able to compensate the harmonic current effectively and reduce switching losses and neutral current,which verifies their validity and feasibility.

Abstract:The schemes of setting remote operation are investigated in this paper.Based on the analysis of typical schemes,new approach based on operating files is proposed.The setting management client obtains the protection setting model by setting file,uploads setting file to view protection setting,and downloads setting file to modify protection setting.Implementation details of this approach are described and conceived.The feasibility of this approach is proved under certain technical conditions.

Abstract:To verify the rationality of PSS placement and effect of suppressing low frequency oscillation,the IEEE-57 test system was selected to analyze the oscillation mode and damping characteristics.SAPSO algorithm was used to coordinately optimize PSS parameters in 3 steps in the test system.Firstly,PSS parameters of No.15 were optimized in single machine infinity system.Then,the No.18 generator was placed and configured with one PSS whose parameters were also optimized to improve the damping ratio of the test system.In addition,PSS parameters of No.15 and No.18 were optimized coordinately to obtain higher damping.The results of time-domain simulation under small disturbances and Prony analysis demonstrates that,the damping effect of coordinately optimized PSS parameters is better and the method of coordinated optimization and placement is feasible and available.

Abstract:In the initial stage of generator load-shedding,generator power sag protection devices can judge quickly and shut down safely.Power oscillation was caused by a power plant outlet line failure.The transmission cycle of the generator power transmitter was not matched with the set of steam turbine digital electro-hydraulic control system,and the waveform was distorted.In turn,the unit control valve was shut down by mistake,and the action of power sag protection caused the generator-tripping.This paper analyzes the causes of this action and puts forward some suggestions on how to prevent and solve similar problems in large units.