The development of interstate electric ties ISETs and grids(ISGs)is a global process; recently, countries of Northeast Asia(NEA)that were previously very poorly connected have started to study the possibility of constructing ISETs and ISGs.This paper describes the current state of the interstate transmissions in the NEA region, considering the prospective projects of ISETs in NEA.The results of the system optimization study on prospective NEA ISGs are provided.The proposals on the development of electric power cooperation in NEA are formulated.

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As the proportion of renewable energy increases,the interaction between renewable energy devices and the grid continues to enhance.Therefore,the renewable energy dynamic test in a power system has become more and more important.Traditional dynamic simulation systems and digital-analog hybrid simulation systems are difficult to compromise on the economy, flexibility and accuracy.A multi-time scale test system of doubly fed induction generator based on FPGA+ CPU heterogeneous calculation is proposed in this paper.The proposed test system is based on the ADPSS simulation platform.The power circuit part of the test system is setup up using the EMT(electromagnetic transient simulation)simulation,and the control part uses the actual physical devices.In order to realize the close-loop testing for the physical devices,the power circuit must be simulated in real-time.This paper proposes a multi-time scale simulation algorithm,in which the decoupling component divides the power circuit into a large time scale system and a small time scale system in order to reduce computing effort.This paper also proposes the FPGA+CPU heterogeneous computing architecture for implementing this multitime scale simulation.In FPGA, there is a complete small time-scale EMT engine, which support the flexibly circuit modeling with any topology.Finally, the test system is connected to an DFIG controller based on Labview to verify the feasibility of the test system.

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Recently,with increasing improvements in the penetration of wind power and photovoltaic power in the world,probabilistic small signal stability analysis(PSSSA)of a power system consisting of multiple types of renewable energy has become a key problem.To address this problem,this study proposes a probabilistic collocation method(PCM)-based PSSSA for a power system consisting of wind farms and photovoltaic farms.Compared with the conventional Monte Carlo method, the proposed method meets the accuracy and precision requirements and greatly reduces the computation; therefore, it is suitable for the PSSSA of this power system.Case studies are conducted based on a 4-machine 2-area and New England systems,respectively.The simulation results show that,by reducing synchronous generator output to improve the penetration of renewable energy,the probabilistic small signal stability(PSSS)of the system is enhanced.Conversely,by removing part of the synchronous generators to improve the penetration of renewable energy,the PSSS of the system may be either enhanced or deteriorated.

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For building Global Energy Interconnection(GEI), it is necessary to implement new breakthroughs on largepower system simulation.Key routes for implementing full electromagnetic transient simulation of large-power systems are described in this paper,and a top framework is designed.A combination of the new large time step algorithm and the traditional small-time step algorithm is proposed where both parts A and B are calculated independently.The method for integrating the Norton equivalence of the power electronic system to the entire power grid is proposed.A two-level gird division structure is proposed,which executes a multi-rate parallel calculation among subsystems and element parallel calculation in each subsystem.The initialization method of combining load flow derivation and automatic trial-and-error launching is introduced.The feasibility of the method is demonstrated through a practical power grid example,which lays a foundation for further research.

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For demonstrating a multiterminal voltage-source converter(VSC)-based high-voltage DC(HVDC)(VSCHVDC)project,this study puts forward a technical route for calculating the power flow in a 500-kV VSC-HVDC power grid in comparison with that of an AC power grid.The Jacobian matrix used in the power-flow calculation was deduced through methods such as Newton-Laphson iteration and Taylor series expansion.Further,the operation effect of powerflow calculation on a true bipolar VSC-HVDC power grid was analyzed briefly.The elements of the Jacobian matrix corresponding to VSC were studied under the mode of droop control and the control strategy of VSC-HVDC power grid was analyzed in detail.The power-flow calculation model for VSC-HVDC power grid of the master-slave control mode was simplified using the PQ decomposition method of the power-flow calculation of an AC power grid.Moreover,a four-terminal model of the Zhangbei VSC-HVDC demonstration project was established and tested on MATLAB.The simulation results under two kinds of operating conditions were analyzed and compared to the results of BPA; the deviation between the power-flow results was studied.The results show that the proposed calculation method can provide a feasible support for calculating the power flow in VSC-HVDC grids.

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In a power system,power generation and load have frequency response characteristics,which randomly fluctuate with changes in operating status.This study investigates a probabilistic power flow method that considers the unit and load uncertainty of the static frequency characteristic.Firstly,a calculation model is established on the basis of the characteristics of the frequency modulation performance of the unit and load.Then a calculation method is developed using the concept of dynamic power flow in order to determine the probability distribution of the active power flow of each line under the occurrence of a fault in the system.In the method,Monte Carlo sampling with the semi-invariant method is applied for analysis and calculation.The IEEE-30-buses system is taken as an example to analyze the impact of different responses of units on the power flow distribution of various branches.The method discussed herein is compared with the Monte Carlo simulation method to verify its effectiveness.

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Inter-regional and transnational grid interconnection is necessary for energy development.Xinjiang, which is rich in renewable energy resources, is adjacent to countries in Central Asia and has great potential for interconnection with its neighbors.This paper outlines China’s relevant policies for transnational power interconnection, and introduces the energy structure, load demand endowments, and power supply status of Xinjiang, Pakistan, and five Central Asian countries.Further, it analyzes the advantages of the multinational power interconnection from the aspects of power supply and load complementation.Finally, from the perspective of technical support and practical basis, the feasibility of interconnection between Xinjiang, Pakistan, and five Central Asian countries have been analyzed.This paper provides a theoretical basis for promoting and implementing China’s “Belt and Road” power transnational interconnected development strategy.

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This study investigated the feasibility of distance protection in extra-high voltage(EHV)networks.In long-distance transmission lines, the distributed parameter characteristic of the EHV network is obvious.When a fault occurs far away from the measurement site, the measured impedance might not be directly proportional to the fault distance, and the protection domain of distance protection will be decreased.The detailed theory inferred and proven in this paper reveals that this phenomenon is widespread in EHV transmission lines.The results indicate that the protection domain error is greatly reduced by the application of the shunt reactor.Overall, simulation results show that the proposed method is effective for impedance relay, considering different characteristics, different lengths of lines, and compensation degrees.

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Spacer insulators are important insulating component of gas insulated switchgear(GIS).In order to analyze the influence of spacer insulator materials temperature characteristics on the electric performance, we tested the temperature distribution under work condition and the temperature characteristics of the material’s relative permittivity.Then established a spacer insulator simulation model in finite element numerical simulation software to calculate its temperature and electric field.Using the temperature test results as a reference to verify the temperature calculation, and in order to analyze changes of the electric field along the surface of the spacer insulator, the temperature characteristics of relative permittivity have to be considered.Through the experimental research and simulation analysis, we found that the temperature characteristics of the spacer insulator materials have great impacts on the spacer insulator performance.When the temperature increases, the material relative permittivity also increases.In the low-temperature region of spacer insulator, the electric field intensity along the surface increases, so the electrical performance deteriorates.The conclusion of this paper can provide an important reference for further research about spacer insulator’s working performance analysis.

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With the development of information technology, the amount of power grid topology data has gradually increased.Therefore, accurate querying of this data has become particularly important.Several researchers have chosen different indexing methods in the filtering stage to obtain more optimized query results because currently there is no uniform and efficient indexing mechanism that achieves good query results.In the traditional algorithm, the hash table for index storage is prone to “collision” problems, which decrease the index construction efficiency.Aiming at the problem of quick index entry, based on the construction of frequent subgraph indexes, a method of serialized storage optimization based on multiple hash tables is proposed.This method mainly uses the exploration sequence to make the keywords evenly distributed; it avoids conflicts of the stored procedure and performs a quick search of the index.The proposed algorithm mainly adopts the “filterverify” mechanism; in the filtering stage, the index is first established offline, and then the frequent subgraphs are found using the “contains logic” rule to obtain the candidate set.Experimental results show that this method can reduce the time and scale of candidate set generation and improve query efficiency.

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Wide area measurement system(WAMS), which is based on synchronization data from phasor measurement units(PMU)and EMS SCADA, is implemented to establish a system model that can handle certain functions such as realtime power system monitoring, oscillation mode analysis, accident analysis and decision-making assistance for emergency control.The Brazilian Interconnected Power System(BIPS)is a large system covering an extensive geographical region, which faces certain risks and challenges.It has several main transmission corridors associated with large power plants and interconnection between the northern and southeastern regions.Mismatch between the energy base and load pool also exists in Brazil as energy resources are not well-distributed; therefore, the use of large-capacity, long-distance transmission technique to transmit remote power is unescapable.On the other hand, there are many types of voltage levels and multiple entangled electromagnetic loops owing to historical reasons.Then, for insufficient power reservation and defective grid body in load pools, once the external power is cut, it’s easy to raise a blackout.The infrastructure is old and the power system operates close to the upper limit.All these represent risks and challenges to BIPS.Through WAMS technology research method in this project, the electrical power system function of monitoring, analysis, and control improved from the static state to the dynamic state.WAMS enhances data integration and real-time analysis capabilities, and can provide dispatchers with high quality real-time dynamic information and decision-making support information, enhance monitoring of auxiliary services in the electricity market, enable operators to improve the accuracy of power network analysis, thereby increasing power grid monitoring and operation, and improve the transmission capacity and reliability of the power grid operation [1].

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