Abstract:The actual load shedding verification test of large-scale “source-grid-load” friendly interactive system is introduced. A strategy validation technique based on preset instruction release mode is proposed. A time test method of actual load shedding control command transmission according to global GPS clock synchronization technology, and a frequency measurement method according to zero-crossing detection and digital filter technology are also proposed. The system’s control time and dynamic frequency can be accurately measured. Results show that quick load shedding time and frequency changes when DC blocking fault happens meet system requirements. The feasibility of the system function design is validated.

Abstract:With the application of two-stage PV grid-tie inverter in the large-scale and medium power systems, it is widely researched that the LVRT control strategy of photovoltaic inverter based on the two power stages topology. Compared with single-stage PV inverter, it is a combination of the first power stage of DC/DC converter and the second power stage of DC/AC inverter for two-stage PV inverter. The control is more complex and it is more difficult in the low voltage ride through. Firstly, the system modeling is carried on and then the control strategy is proposed based on control mode seamless switching in LVRT. At the steady state the DC/DC conversion unit tracks the maximum power point and the DC/AC inverter unit works as a constant voltage source. In LVRT, the DC/DC conversion unit runs in the constant busbar voltage mode and DC/AC inverter unit runs in the p-q mode. The problem is resolved that the DC bus over-voltage caused by unbalanced energy between the DC/DC unit and DC/AC unit. The experiments in a 40 kW PV grid-tie inverter of two power stage verify the correctness and feasibility of the theoretical analysis finally.

Abstract:The VSC-HVDC has the characteristics of fast responding, active and reactive power decoupling and AC bus voltage stabilizing. Emergency control system with VSC-HVDC control can enhance the level of transient stability of power grid while reduce the conventional control costs of generator tripping and load shedding. The mechanism of improving transient stability by emergency HVDC power support based on Extended Equal Area Criterion (EEAC) is proposed. Based on the comparison of different kinds of HVDC power modulation, the difference control effect on power angle recovery between VSC-HVDC and LCC-HVDC is shown. The priority of different kinds of HVDC in the emergency control should be taken into consideration. A method to calculate the amount of HVDC power support and the emergency coordination control strategy considering both the priority and the amount of HVDC power support in different fault conditions are proposed.

Abstract:To deal with the problem of voltage and power factor exceeding limits caused by distributed PV integration, an improved voltage and power factor coordination control strategy of distributed PV is proposed. The strategy includes voltage control strategy and power factor control strategy, voltage control strategy regulates the voltage of integration by controlling PV reactive power firstly and reducing PV reactive power when PV reactive power reach lower limit, power factor control strategy regulates reactive power of PV and power factor of the point of common coupling, proportional integral controller is designed for two control strategies. Finally, an example is given to demonstrate the effectiveness of the proposed control strategy in a RT-LAB simulation environment.

Abstract:Large scale renewable energy such as wind power grid, photovoltaic grid and others has brought great challenges to the grid's afety and stability. Energy storage system should be configured so as to stabilize the power fluctuation and achieve energy smooth transfer. Under the application scenario of photovoltaic power plant，the echelon battery storage' optimal planning is analyzed in the mode of stabilizing the photovoltaic power fluctuation . Economic evaluation is assessed. The optimal planning and economic evaluation model of the photovoltaic power plant energy storage system is established to meet the minimum storage capacity cost under the limit of the grid fluctuation ratio. The artificial fish swarm algorithm is used for solution optimization, and the economy evaluation of echelon battery is assessed and compared with conventional energy storage system. The results show the rationality and validity of the model.

Abstract:According to the bidding mechanism in electricity market and operating principles, a profit-maximization optimized decision model is constructed under the environment of electric power market with the joint wind, solar units, loads and energy storage systems. Various technical constraints of new energy units and storages are fully considered in this model, the participation of new energy and electric vehicle in the market bidding through power generation strategy and the output arrangement of the coordinated operation of the virtual power plant are realized. Numerical examples are implemented to validate the correctness and validity of the optimal decision-making model of joint wind, solar units, loads and energy storage systems. The influences of the renewable energies output fluctuations on the joint system bidding strategies are compared under multi-operating scenarios.

Abstract:The IEC 61850 2nd Edition standard adds and improves a lot of content for substation applications. Combined with the engineering application requirements of smart substations, new improvements of the information and communication service model in 2nd edition are analyzed in depth. Some improvements can solve the current problems in substation project implementation, and some help to enhance the operation and maintenance efficiency and management level. Aiming at the important automation functions in smart substations including control, setting, GOOSE and tracking service, an engineering application method based on 2nd edition information and communication service model is proposed, and problems that should be paid attention to in engineering applications are also discussed.

Abstract:As an important tool to emulate real wind turbine, wind turbine simulator (WTS) can simplify the experimental process and shorten the development cycle for wind power research. Because the inertia of WTS is much smaller than that of the actual wind turbine, current researches are mainly concerned with the stability of the simulated wind turbine. However, the accuracy of the WTS will be significantly affected if the damping issue was not properly handled, which will result in low speed or even affect the efficiency of WTS. In this paper, the drive train model of WTS is improved and the impact of damping on the accuracy of WTS is analyzed. The improved simulation strategy based on damping compensation is designed and implemented on the WTS experimental platform. Experiments on the maximum power point tracking control of the wind turbine validate that the improved WTS can simulate the mechanical dynamics of the wind turbine with higher accuracy.

Abstract:Digital energy meters often appear error phenomenon in the actual working conditions such as frequency fluctuations, harmonics, input noise and other factors. In order to study the measurement performance of the digital energy meter under the actual working conditions, a calibration method based on the actual working condition is presented. A condition recovery device is developed. A Blackman discrete Fourier transform (DFT) + adaptive linear (Adaline) neural network algorithm is proposed. The calculation of standard electrical energy is achieved. The digital energy meter calibration method and the wattage-second method are compared and analyzed. The results of error analysis show that the digital energy meter calibration method based on the actual working conditions and the wattage-second method can be used to verify the digital energy meter. But the test results of the former are smaller and more stable, and can provide reference for the performance evaluation of the energy meter under complex conditions.

Abstract:A large number of electri c vehicles connected to charging stations will increase the peak-valley difference and affect the safe and stable operation of the electric vehicle charging stations. Thus a coordinated charging strategy for plug-in electric vehicle (PEV) charging stations based on Mind Evolutionary Algorithm (MEA) is proposed. The strategy set minimum customer charging costs and minimum peak-valley difference as objective function. The optimal charging period of electric vehicles is calculated dynamically by using MEA. Customers decide whether or not to respond to peak-valley prices and to delay their charging to lower price periods by themselves. The charging coordination of electric vehicles is then realized. In order to verify the effectiveness of the proposed strategy, the Monte Carlo simulation method was utilized to generate the charging needs of customers based on actual customer charging behaviors. The distribution transformer load profiles, customer charging costs were simulated under uncoordinated and coordinated charging scenarios correspondingly. Simulation results indicate that under the proposed coordinated charging control strategy, customer charging costs can be greatly reduced and the peak shaving of distribution transformer loading profile can also be achieved; compared with genetic algorithm, the effect of MEA is better.

Abstract:Due to serious corrosion of ground water in saline soil area, the durability of pile foundation is seriously reduced in transmission line towers. Prestressed cast-in-place pile, which was reinforced with prestressing tendon in pile body and applied prestress by the post tension method, provides significant improvement in construction durability. Through numerical examples, it is found the additional prestressing tendon can effectively increase pile body crack-control level and reduce material dosage in foundations. The advantage of GFRP guard barrel replacing steel guard barrel are narrated with the reduction of the construction costs and the local workload. The design method of prestressed cast-in-place pile, construction process and manufacture method of prestressed steel cage with tensioning and anchoring constructions control points are recommend in the paper.

Abstract:Aiming at the problems such as weak system processing capability and insufficient stability in online monitoring of circuit breakers, the ARM, DSP and FPGA three-core platform are used to realize the on-line monitoring of the circuit breaker. The on-line monitoring function of circuit breaker is divided into 3 parts: data acquisition, data operation and human-computer interaction. Data acquisition is completed by FPGA control ADS8568. The circuit breaker state variables are passed into the system by sensors. The DSP performs wavelet decomposition five times on the signal collected by FPGA using db2 wavelet. Processed data is transmitted to the ARM through the dual-core communication mechanism based on Syslink heterogeneous, and finally the human-computer interaction is completed by the ARM. The scheme gives full play to the advantages of three control cores, so that it has better data processing ability. Through testing, the on-line monitoring system of circuit breaker based on three-core structure has a better performance than the original system.

Abstract:Aiming at fault point locating problem of the line protection multiplexing optical channels, the digital multiplexing device and protection device detect the channel fault flags by the validity of physical layer encoding, generate a status stamp at reserved field by expanding communication message, and use heartbeat frame mechanism of digital multiplexing device to solve the problem of exchanging status stamp when error occurs in channel. The fault point location of the channel can be detected on the protection device directly. Fault self-diagnosis mechanism is implemented for multiplexing optical channels.

Abstract:DC magnetic bias current will be caused in transformers when HVDC systems operating in mono-pole situation. The combined influence on DC magnetic bias of 500 kV transformers is researched, taking ±800 kV Jinbei-Nanjing, Ximeng-Taizhou and Longbin-Xuzhou in northern Jiangsu for example. A comprehensive horizontal multilayer soil model is adopted, considering different soil conditions adjacent to different ground electrodes, based on which the DC system model of northern Jiangsu is built. The DC magnetic bias currents in substations nearby are analyzed when one or more in three HVDC power transmission lines are operated in monopole operation mode. Simulation results show that the greater the soil resistivity, the higher the earth surface potential; when multi HVDC lines are operated in monopole mode simultaneously, the value of DC current is equal to algebraic sum of the DC current of each HVDC line solely operated in monopole mode; the restraining measures of adjacent transformers should be considered comprehensively.

Abstract:Three-phase pulse width modulation (PWM) rectifier is widely used in motor control, wind power generation, flexible HVDC and micro grid due to the controllable power factor, sinusoidal grid side three-phase current waveform, stable DC side voltage and so on.In order to improve the reliability of three-phase PWM rectifier, a PWM fault-tolerant control system based on NCAV fault detection method is proposed in this paper.The control system can implement fault-tolerant control in a short time in the case of an open circuit fault has occurred on a single power switch, reduce the impact to the system caused by the single open circuit fault.This system can effectively improve the three-phase current waveform, reduce the output voltage ripple and enhance the overall system performance and reliability when an open circuit fault has occurred on a single power switch.The usefulness of this paper is verified through simulation results.

Abstract:Due to the factors such as weak fault-induced signals, change of neutral grounding mode, and complicated fault conditions, fault line selection in non-effectively grounded system has been a technical challenge in actual field. Based on data fusion technology, the information of fault-generated zero-sequence voltages and currents is fully analyzed by means of colony amplitude comparison-based, the fifth harmonics-based and wavelet analysis-based methods. Fuzzy theory is employed to create membership functions of the criteria and weights of each method, which improves the adaptive ability and success rate. A single-terminal radial distribution grid model is constructed in PSCAD/EMTDC to test the performance of the presented method and the calculation results demonstrate the high reliability and applicability of the method.

Abstract:To solve the problem of power system data coming from multiple sources, huge amount of on-site operation and maintenance workload and high manual verification error rate, a fuzzy matching technique is introduced, which fuzzy matching variety sources of data as a reference value for comparison. Regular inspection value is compared with reference value, inspection information is automatically sorted and intelligently analyzed. A variety of inspection reports are produced and displayed by Web. This technique has been successfully applied in Guangdong Power Grid with the characteristics of fast matching speed, high accuracy and low confusion rate. It can effectively replace the regular, daily and annual inspection of operation and maintenance personnel to power grid safety and stability devices, which can reduce human participation, workload of manual verification and error rate and improve work efficiency.

Abstract:In order to provide a good man-machine interface for electric power control operation running, to achieve unattended or less intervention graphics maintenance work, the concept of automatic mapping is proposed. This paper mainly introduces the methods and effect of automatic mapping. Firstly, the overall framework of the system is given, and then the basic process of three automatic mapping models, which are model extraction, node layout and graph routing are introduced. At the same time, this paper makes a description of various types of automatic mapping, and taking the single line diagram and the system diagram as an example, the paper describes the application of the tree level layout, the boundary layer layout algorithm and the channel routing algorithm. Finally, the application effect of the grid automatic mapping will be showed in the paper.

Abstract:In recent years, the transmission line tripping accidents caused by lightning activity occur frequently.The corresponding research work is carried out aiming at the transmission line lightning protection technology. Based on the analysis of the lightning activity in Jiangsu, the tripping reasons and lightning characteristics are analyzed in many aspects including the style, height, circuit number and span of tower. The statistics of tripping times of Jiangsu power gird transmission lines from 2012 to 2016 are completed. Then, in combination with the actual production of power grid, the rationalization of lightning protection measures and suggestions are proposed from the aspects of transmission line differential evaluation, operation and maintenance and new technology.

Abstract:A two-layer detailed optimization method is proposed for the allocation of energy storage capacity and location, combining the distribution network operation and planning. A two-layer planning model is established and the corresponding solution method is proposed. The configuration results are obtained by optimizing the solution. The allocation model takes the cost of active distribution network as the goal. Different cost-economic models were made for different energy storage investors, realizing differentiation goal optimization allocation. As for the distribution network with high penetration of distributed power, the proposed method can solve problems of low qualified rate of distribution network voltages and waste of renewable resources. Therefore, the reliability and power quality of the distribution network can be improved effectively.

Abstract:As the necessary supporting facilities for electric vehicle operation, the construction time, location and scale of electric car charging stations are of great significance to the promotion of electric vehicles. The existing research takes the location planning of electric car charging stations as a static problem, ignoring construction time. Therefore, a multi-stage planning model of charging station location is proposed, and the model is solved by the idea of pseudo-dynamic planning. Firstly, a multi-stage programming model is proposed, which takes into account the investment cost, operation and maintenance cost and user charge loss expense. Secondly, based on the accurate prediction of the charging needs of each stage, the genetic algorithm is used to determine the planning scheme at the end of the planning period. Finally, the planning scheme of each stage is obtained by dynamic planning reverse solution. A case study proves the superiority of the scheme.

Abstract:Tree-related failure is a typical non lightning fault on transmission lines. Current researches mainly focus on the diagnosis and treatment, while the mechanism study is seldom reported. Firstly, the formation process of tree-related failure and the typical discharge characteristics in different stages of tree height are analyzed, and then different phases of tree-wire gap discharge process are simulated in the lab environment. The discharge current is monitored, and the characteristics of the waveform and the frequency spectrum are analyzed. Characteristics and rules of tree-wire discharge at different stages are obtained, and the mechanism of transmission line tree-related failures is further expounded.

Abstract:As an effective partial discharge detection technology, UHF detection technology has been widely used in GIS detection. In the live detection process, the UHF abnormal signal is detected on a 252 kV GIS basin-type insulator. An X-ray detection was performed to the basin-type insulator, and several centimeters long pores are found inside. The results are consistent with the detection and positing of UHF method.However, the power frequency withstand voltage test and partial discharge test by pulsed current method to the basin-type insulator can meet the requirement of the factory test，indicating that the traditional detection method has its own limitations.In view of this situation, some suggestions are put forward, such as the extra high frequency partial discharge detection of basin-type insulators before leaving the factory, so as to improve the outgoing quality of the basin-type insulators.

Abstract:As afull-featured power electronic equipment, unified power flow controller (UPFC) need fault ride-through ability. UPFC series and parallel inverter parts will withstand the impact of failure duringAC line fault.And for instantaneous fault of the line, theUPFC needstocontinue to run after theline fault is cleared.Based on the structure and fault characteristics of UPFC，the processing strategy of UPFC in the case of AC system failure is put forward, so that it has the fault ride-through ability.The UPFC parallel side can run continuously during the fault by use optimization control strategy. And the serial side can exit and restart quickly, with the coordination of UPFC control and protection strategy, line protection and reclosing logic.The rationality of the strategy is verified by manual short circuit test and the actual system fault test during the operation of Nanjing UPFC demonstration project.

Abstract:The combined cooling, heating and power (CCHP) microgrid is a kind of distributed power system with the cogeneration plant as the core part, existing three kinds of energy balance, including various distributed micro-sources. The CCHP micro-grid has a lot of advantages such as high energy utilization ratio, strong power supply reliability, low environmental pollution and flexible dispatching. Models of mixed integer programming (MIP) composed by a variety of power mathematical models and constraints are established, so the system can better accord with the actual situation. Considering the economic dispatching of micro-grid, this paper simulates the optimization of typical day of each month for the minimum cost of overall system using CPLEX and the result should meet the needs of electrical-cold-heat load in this micro-grid. Simulation of optimal sizing and the optimized operation of typical daily load of different seasons can learn from the simulation results, so the powers can work economically. Meanwhile, sensitivity analysis of natural gas’s price was established to evaluate the impact on the operation of the system.

Abstract:For the application requirements of power system stabilizer for generator excitation system, the functional requirements of PSS devices are analyzed. And a new external power system stabilizer device based on PowerPC + DSP as the control core is proposed. The hardware and software design of the device is described, and a real-time measurement method of the generator rotor speed is proposed. The efficiency and applicability of this device are demonstrated by dynamic simulation test. The device provides a way to realize the transformation and upgrading of PSS for excitation system through the external device, which can enhance the effect of the generator on suppressing the low frequency oscillation of the power system and improve the stability margin of the power grid.