Abstract:As an effective solution to large-scale distributed energy interconnection and optimal operation of distribution network, the Active Distribution Network(ADN) becomes the trend of next generation intelligent distribution network, and has aroused extensive and deep research of scholars. This paper analyses the key technologies of ADN research status, including ADN planning technology, ADN operation control technology, ADN power supply restoration technology and ADN load management technology. This paper also introduces the ADN demonstration projects.

Abstract:V2G system can provide two-way controllable active power and reactive power into the power grid, realize the load fluctuation and stabilize the power grid peak power regulation function. This paper focuses on the power control of the V2G system in the grid-connected mode. The main circuit structure of the V2G system is introduced. To tracking current instructions precisely, the proportion feedback integral control method is proposed. The effectiveness of the proposed control strategy is verified by simulation and experiment results.

Abstract:The clean energy sources are utilized extensively due to environment protection. There will be series of challenges for distribution system operation and control with the high penetration of distributed generation (DG) in near future. This paper highlights the control framework and optimizaiton approach for the coordination of source-net-load in active distribution system, which can realize the effective accommodation distributed renewable resources and secure and economic operation. It can solve the compatibility between distribution systems with distributed generation. Simulation results validate the effectiveness of the coordinated control technology for active distrbution system.

Abstract:The voltage problems in the DC voltage bus contains the voltage fluctuation, the voltage sag and the voltage interruption problems. In this paper, the wavelet module is established based on idea of wavelet transform. The voltage pollution source in the DC bus is identified by wavelet transform. In the Matlab simulation, different wavelet function can identify the fluctuation time of the DC voltage and the corresponding wave source, which has a good identification effect.

Abstract:With constantly increasing accesses of distributed generators and diversity load development such as electric vehicles, the operational control of distribution network is facing a huge challenge. In order to make full use of active distribution network and meet the development requirement of smart grid, this paper proposes a coordinated control system in active distribution network. The paper elaborates the general architectural design, software architectural design, and functional designs including of characteristic analysis, situation awareness and coordinated control. Through the coordinated interaction and control of source-load-storage being realized, the potential of controllable resources in distribution network is fully exploited, distributed generator optimizes its power generation absorption and diversity load improves its ability of participating in electric network load adjustment basing on active distribution network in safe and reliable operation. The coordinated control system designed and developed based on this paper has been applied in Changzhou distribution network.

Abstract:With increasing penetration of distributed generation (DG), the overload of feeder lines and out of voltage limits will happen in distribution networks, which may limit the penetration of DG. Demand response can promote large-scale DG accommodation by utilizing demand side resources to participate in active distribution networks (ADN) scheduling. Therefore, a price-based demand response model is introduced to the existing multi-period optimization model for ADN, an active and reactive power coordinated economic dispatch model of three-phase ADN is developed and its solution method based on mixed integer second-order cone programming is proposed in this paper. The proposed model can reduce loss and ensure that the overload of feeder lines and out of voltage limits will not appear via optimizing the operation of DG, energy storage system and VAR compensation as well as demand response load. Simulation studies on the modified IEEE 33-bus system are presented to verify the effectiveness and advantage of the proposed model.

Abstract:As the Thevenin equivalent impedance parameter which is deviated form stability-type simulation data can hardly reflect the electromagnetic characteristics of the electromechanical-side system after fault, an improved calculating method of Thevenin equivalent impedance of electromechanical-side system for electromechanical-electromagentic hybrid transient simulation based on electromagnetic transient simulation model is proposed. The Thevenin equivalent impedance parameter is achieved through setting two three phase line to ground faults on the interface bus in the full-electromagnetic transient simulation model and solving the primary time constant equation group in which the primary time constant is based on a calculating method which is not affected by every harmonic component. Compared with the equivalent impedance calculated by the traditional method which calculates the impedance based on the stability-type simulation data and through unit current injection method, the equivalent impedance calculated with the method proposed in this paper can reflect the electromagnetic characteristics more accurately, thus improving the simulation accuracy of electromechanical-electromagnetic hybrid transient simulation during and after fault.

Abstract:The high voltage cable, especially the extra high voltage XLPE cable in the transmission operation once the breakdown, will cause great damage to the power grid, causing great losses to the country. At the same time, enterprises in the manufacturing process, once the cable partial discharge standard value (PC value) exceeded, or even withstand voltage test breakdown, the economic losses caused to the enterprise is also very great. Based on the theory of electric breakdown, this paper analyzes and studies the manufacturing process of high voltage XLPE cable in theory and practice, and finds out the key points that lead to high voltage breakdown and partial discharge standard value exceeds. Such as:Conductor burr; Electrical conductivity of conductor semi conductive shielding tape; Bump and scratch of extruder die; Bump and scratch of extruder runner; Cleaning and storage of material; Number and size of micro pore in insulation layer, and internal stress in insulation layer and so on. Through the analysis of these easily overlooked, but also extremely important part of the manufacturing process, the control method is given, in order to achieve the purpose of reducing partial discharge and breakdown frequency, improve the overall quality of high voltage XLPE cable.

Abstract:A case based defect diagnosis model is proposed in this paper. A normalized hypercube mapping method is proposed according to the distribution characteristics of oil chromatogram data. Oil chromatogram data in the hypercube space domain can be applied for diagnosing directly. Meanwhile, the case similarity degree method and the judging method of diagnosis result based on weighting election are put forward, and the selection and optimization of parameters in the model are confirmed by simulation experiments. The model shows high correct rate in the cross validation of the case database. The average accuracy rate was 88.53%, higher than the existing BP neural network and support vector machine technology. It can diagnose the defects of the oil-immersed equipment. It is verified that the model proposed in this paper has significant practical application value in engineering.

Abstract:The conventional HVDC converter valve closed cycle cooling system based on the combination of environmental conditions of high temperature and drought area, using composite cooling chillers, cold storage and air cooler combination, and according to the ambient temperature are given different cooling strategies accordingly, were used in the analysis of the different environmental conditions composite cooling method, the analysis result is validated through experiment, achieved the corresponding air cooler, refrigeration and cold storage tank cold loading and reverse unloading function according to the valve inlet temperature, make the system more reasonable and logical control is more direct, higher degree of automation, reliability, improve the cold exchange equipment valve of environmental temperature adaptability, to ensure the normal work of HVDC converter valve.

Abstract:This paper summarizes the causes of commutation failure and points out that two main causes of commutation failure are AC system ground fault and fire pulse missing. The mathematic model of the junction temperature of thyristor valve is collated and the influence of the single-phase ground fault, the two-phase ground fault, the three-phase ground fault and the fire pulse missing of the converter on the junction temperature are simulated respectively. And it is concluded that the fire pulse missing that has the greatest influence on the junction temperature. Based on the consideration of those influences, it’s suggested that the temperature characteristic of the valve needs to be taken into account when the commutation failure protection settings are fixed.

Abstract:IEC62439-3 describes parallel redundancy protocol (PRP) and high availability seamless redundancy (HSR) in detail. However, these redundancy protocols are transparent to upper layer, supervision system cannot identify the single link failure. In order to resolve this problem and achieve good maintenance experience of PRP and HSR redundant network, the implementation process of PRP and HSR redundancy is analyzed, the action principle of detecting frame is researched, and a redundancy network supervision system based on detecting frame is built. The specific redundancy detecting principle and implementation method are put forward, and the advantages of this system are summarized and analyzed, which provides an effective solution for the redundancy network supervision of smart substation.

Abstract:The field winding deformation test of the transformer with oil and gas bushing connected can be processed only by acquiring signals at the bushing tap. The influence of the bushing tap and the gas insulated line section makes the amplitude- frequency response curves different from the factory test and commissioning test. The method of constructing equivalent model of transformer is adopted, and the amplitude-frequency response curves of the field test at the bushing tap signal and the commissioning test at the winding end signal are compared. Differences and production principles are analyzed from the curve variation and amplitude variation of low frequency segments, medium frequency segments and high frequency segments. It's concluded that the curves should not be contrasted vertically, and suggestions for on-site tests are given.

Abstract:A mobile grid dispatching simulation master station environment construction and application design method is proposed, according to the shortcomings of the debugging method and the maintenance means of the existing dispatching automation system to access the substation signal. The method builds a mobile grid dispatching simulation master station test environment using a variety of means such as plant model version management, measurement table curing, application verification and so on. The proposed master station simulation test environment, do not rely on the communication status of master station and substation. It can simplify the commissioning process and steps of substation automation equipment access automatic master station, simulate and verify the correctness and validity of the access substation information, and provide technical support and means for new equipment operation.

Abstract:The research aims at exploring the possibility of GW level remote HVDC through a new type of superconducting material (MgB₂) as a cost-effective and environmental-friendly DC line and liquid hydrogen as coolant. The necessity and advantages of superconducting DC transmission are analyzed firstly. Then basic method of HVDC converter is explained. The MgB₂ superconducting cables and liquid hydrogen refrigeration system are introduced and the DC transmission control strategy based on twelve pulse converter is illustrated. Through the Pscad software, the simulation of superconducting DC transmission is completed and the line power losses between the MgB₂ HTS superconducting cable and traditional cable under the same condition are compared, which proves the advantages of low loss and unlimited capacity and provides the preliminary basis for the development of MgB₂ HTS superconductor in the field of superconducting DC transmission.

Abstract:Based on the study of the characteristics of the asynchronous operating power system, this paper provides a new method of out-of-step protection. This new method consists of three components: out-of-step element diagnostic detection, out-of-step region judgment element and out-of-step trip timing selection element. The first element(out of step diagnostic element) uses differential angle and slip angle between two ends to determine whether power system begins to oscillate. To increase the reliability, the positive sequence voltage and current are used as an auxiliary condition. The second element uses the principle of regional distance relay to judge the oscillation area. The third element uses Ucos principle to count the number of out-of-step, and use differential angle as an auxiliary criterion to select the best opportunity to trip. When these three elements operate at the same time, the out-of-step protection will operate immediately. This new method is accurate and reliable and is not affected by system operation mode, and has been verified on RTDS simulation system.

Abstract:Long-term changes in power grid operating status are tracked, making use of production and dispatching information, and computer, network and power system analysis technology. Factors that affect power grid operating characteristics are sorted out. The longitudinal analysis of the grid state is realized by classification and identification of power grid weak links. The key weaknesses are guaranteed to be resolved as soon as possible. Power grid security, stability, reliability, economic operation is also guaranteed. The frame design of the weak link tracking and analysis system is proposed. The practical case demonstrates the feasibility and effect of the power grid classification method, and the application prospect of the technology is also prospected. The objective of the technology is to achieve safe operation margin, pre-existing countermeasures, decision-making basis.

Abstract:Fiber optic displacement sensor is introduced to measure the trip of the circuit breaker’s moving contact against deficiencies of the displacement sensors used by previous online monitoring system, which leads to high-accuracy and low interference. An analysis method based on Hilbert-Huang Transform to extract moment-close point is put forward. The intrinsic mode function (IMF) component which contains speed signal partial characteristic is extracted by empirical mode decomposition(EMD). The IMF component is selected by the variance contribution rate according to the speed characteristic of the moment-close point. Thus the selected IMF component can be analyzed by instantaneous amplitude after Hilbert transform, whose feature point is the moment-close point of the circuit breaker. The experiment results shows that the analysis method could extract the moment-close point effectively and accurately, providing credible information for the fault diagnosis of circuit breaker.

Abstract:According to the application of optical fibre communication network in smart substation, this paper analyzes the status and existing problems of the monitoring of GOOSE network link. Based on the electric characteristics of the physical layer and the analysis of the optical receiving power, a fast monitoring method for optical fibre communication link is proposed, and a detailed blocking scheme is given through simplified bus protection case. This method can detect the abnormal link quickly and give the preventive measures in time, which can solve the problem of slow blocking when the communication link is abnormal and improve the reliability of protection.

Abstract:When serious HVDC transmission fault happens, emergency load shedding measures will be taken. In order to achieve the precise load shedding, it proposes a real-time load control decision technology based on user’s interruptible load. Some key technologies involved in the process of control decision are studied just like quick response, precise control, stability control security. Designed the mechanism used in the decision such as user dynamic sequence table, decision preparation, load cycle supplement, failure switch list and so on. Finally, the application scene of real-time control decision is simulated. The real-time control decision technology proposed in this paper has been applied in the large scale supply and demand friendly interactive system, and has realized real-time precision control ability to user’s interrupt after receiving the load shedding instruction.

Abstract:AAs the most severe assessment method in transformer field handover tests, partial discharge test can effectively detect insulation faults inside transformer. In UHV transformer field partial discharge test, based on calculation and analysis of capacitive and inductive power, large capacity stepless adjustable reactor sense technology and inductive reactive power real-time monitoring method are presented for the first time. Adjustable reactor can smoothly adjust the reactance value to change inductive compensation state compensation, and reactive power real-time monitoring method can reflect the real-time test and ensure the efficiency and safety of the test.

Abstract:The basic function and composition of adaptive switching input data acquisition system is introduced according to the design process of new generation high-voltage relay protection. A system design and software identification method for the data acquisition of the adaptive switching value of Power System Secondary Equipment is proposed. According to the optocoupler acquisition loop and experimental verification on the design of adaptive switch data acquisition system, the hardware and software implementation method of the data acquisition system is described. By software the system can adjust the threshold value of the adaptive switching input voltage and monitor switching power supply voltage. This system has a very important role in improving the success rate of hardware research and development, and improving the stability and reliability of the power system secondary equipment.

Abstract:Compared with the robot navigation mode, an intelligent robot inspection system for substation based on laser navigation technology is introduced to meet the new requirements of UHV substation equipment inspection. The structure function definitions, task execution of the system are discussed. The result of taking visible light picture, reading instruments data, detecting infrared thermal image by robot are compared with traditional inspection result. The practical results indicated that the inspection system can adapt the UHV substation circumstances which have numerous equipments and complex structure. Owing to long time endurance and accurate detection method, this system guarantees the reliability of equipment inspection, and provides strong support for daily operation and maintenance management of UHV substation. Finally, suggestions and improvement measures on robot system operation are provided.

Abstract:With the increasing scale of the distribution network, the increasing load of electricity, the three-phase load imbalance seriously affected the stable operation of the power grid. Not only distribution network loss increases, power quality are also reduced. The relationship between the three-phase unbalance and the increase rate of the line loss is deduced, which not only considers the asymmetry of the three-phase current, but also analyzes the influence of the phase. The relationship between unbalanced-distribution load-voltage offset is analyzed comprehensively, and the method of warning of voltage offset based on unbalance index is proposed. Results show that the three-phase imbalance has certain impact on the line loss increase rate and voltage offset, and the correlation cannot be neglected, combined with the specific engineering example of Huangdao area and above derivation formulas. It can provide reference for the operation decision of distribution system and have positive effect on the improvement of power supply quality of distribution network.

Abstract:Unified Power Flow Controller (UPFC) injects controlled voltage into the transmission line through series transformer. UPFC is equivalent to series connection of capacitance or inductance to improve transmission efficiency of power network. Series compensation (SC) adjusts line impedance through capacitance similar to UPFC. SC is widely used in EHV transmission line and the influence of SC system on the protection is analyzed in detail. As a new power electronic device, the impact of UPFC on the surrounding system and protection hasn’t been deeply studied. In this paper, the characteristics and effects of UPFC on protection and SC are analyzed. The equivalent characteristics of UPFC under various operating conditions and the solution of line protection are studied. The research improves operation reliability of UPFC system.

Abstract:UHVDC transmission capacity is large, there will be a great impact on both sides of connecting ac system while one pole is outage，leading another pole in monopolar ground circuit operation mode. At this time the high amplitude dc current flowing into ground will have negative effects on the AC system and the metal parts nearby, producing DC magnetic biasing in converter transformers in operation and transformers nearby, threatening the safety operation of converter transformers and other transformers. Optimizations of the protection strategy in UHVDC including the converter differential protection，the grounding electrode line overload protection, the grounding electrode line unbalance protection and line fault restart logic is described in this paper, extremely shortening the operation time of the monopolar ground circuit operation mode after action of above protections, reducing influence of DC current flowing into the earth on the AC system，metal parts, converter transformers and other transformers. In order to improve the electrode line protection level, the grounding electrode line differential protection and supervision are added. These strategies have been applied in Hami-Zhengzhou UHVDC project and Linzhou-Shaoxin UHVDC project, the result of field test is effective and good.

Abstract:Regenerative system is an important part of steam turbine system in power plant. The regenerative heaters models in off-design conditions are very complicated due to the heaters phase-change problem. A dimensionless model for regenerative heater is built up according to actual measurements which reflects its operation status in off-design conditions. This model is applied to the first low-pressure heater of a 660 MW ultra-supercritical steam turbine unit. Results show that the deviation of model calculation results and actual data are very small. The modeling method is simple and credible and can be used as tools for practical troubleshooting in power plant.

Abstract:Research on the ash deposition characteristics of tower boilers is carried out from the aspects of structural parameters, flue gas flow rate, and burning coal quality of the heating surface, for an ash collapsing accident in 1000 MW double-reheat tower type boiler. The causes and hazards of the heating surface ash deposition is also analyzes，and the reasons for the change of furnace pressure during the process of ash collapsing is explained. Measures to avoid serious ash deposition were put forward when the boiler heating surface operates in the low load， which can avoid frequent occurrence of ash collapsing accidents. It is of reference to the operation of the same type of boiler.