National and international policies encourage increased penetration of solar and wind energy into electrical networks in order to reduce greenhouse gas emission. Solar radiation and wind speed variations complicate the integration of wind and solar generation into power systems and delay the transition of these sources from centralized to distributed energy sources. The increased penetration of nontraditional energy sources into the electric grid stimulates the demand for large capacities in the field of energy storage. A mathematical model, which describes the operation of a proposed hybrid system, including solar PV, wind energy, and a pumped storage hydroelectric power plant is developed in this paper. This hydropower plant utilizes seawater as a lower reservoir, and only a tank has to be built in order to reduce the installation cost of the storing system. The pumped storage power plant used for compensation of the variation of the output energy from the PV and wind power plants by discharging water from the upper reservoir, which is previously pumped in the case of surplus energy from PV and wind turbine power plants. The impact of the proposed system on the grid utility is investigated in accordance with the values of energy exchange (deficits and surpluses of energy) between the considered hybrid system and the grid. The optimum design is determined by the pump and turbine capacities, upper reservoir volume, and the volume of water left in the tank for emergencies. Different scenarios of the optimum operations are presented for analysis. The results obtained from the examined scenarios indicate the ability of such a hybrid energy system to reduce the exchange of energy with the grid. This paper indicates the technical feasibility of seawater pumpedstorage hydropower plant for increasing the Egyptian national grid’s ability to accept high integration of renewable energy sources.

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Global Energy Interconnection(hereafter GEI) is not only connectivity of power grid, but also a series of methodical innovations for energy transition towards sustainable and resilient societies,which is different from the traditional energy development mode in the past. This paper seeks to summarize the key features about the abovementioned innovations, as Green & Clean, Balanced & Reciprocal, Efficient & Intelligent and Vitality & Business opportunity. Finally it puts forward some reflections on the future development of GEI based on ASEAN practice cases.

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Construction of Global Energy Interconnection (GEI) is regarded as an effective way to utilize clean energy and it has been a hot research topic in recent years. As one of the enabling technologies for GEI, big data is accompanied with the sharing, fusion and comprehensive application of energy related data all over the world. The paper analyzes the technology innovation direction of GEI and the advantages of big data technologies in supporting GEI development, and then gives some typical application scenarios to illustrate the application value of big data. Finally, the architecture for applying random matrix theory in GEI is presented.

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The Ethiopian Electric Power (EEP) has been operating and managing the national interconnected power system with dispersed and geographically isolated generators, a complex transmission system and loads. In recent years, with an increasing load demand due to rural electrification and industrialization, the Ethiopian power system has faced more frequent, widely spread and long lasting blackouts. To slash the occurrence of such incidents, identifying the system vulnerabilities is the first step in this direction. In this paper, the vulnerability assessment is performed using indices called active power performance index (PIp) and voltage performance index (PIv). These indices provide a direct means of comparing the relative severity of the different line outages on the system loads and voltage profiles. Accordingly, it is found that the most severe line outages are those lines that interconnect the high load centered (Addis Ababa and Central regions) with the rest of the regional power systems. In addition, the most vulnerable buses of the network in respect of voltage limit violations are mainly found at the high load centers.

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The scenarios of a half wavelength transmission line (HWTL) connected to the original DC asynchronous interconnection system are established based on the quasi-steady state model of HWTL, which include single or double loops of single channel and multi-channel scenarios with different starting and landing points. Firstly, the steady state power flow characters of multi-scenario transmission schemes are studied. The voltage distribution characters of HWTL are analyzed when its transmission power and power factor vary, and the influence of the DC power variation on voltage of HWTL is discussed. Then the transient characters of HWDHTS are explored. The DC commutation failure caused by the fault of HWTL is simulated and the power transfer capacity of HWTL while DC blocking is calculated in this paper.

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Seamless switching is an important guarantee for the inverter to work continuously without stopping when gridconnected power generation system is the transient process from grid-connected to isolated island and from isolated island reclosing. Based on the principle of pre-synchronous operation of traditional synchronous generators, this paper analyzes the principle of pre-synchronous process and its effect on the steady-state of micro grid with multiple virtual synchronous generators. At the same time, the paper analyzes the transient influence of the closed pre-synchronous switch on the power distribution of the micro grid under different phase modes. This paper proposes a pre-synchronous control strategy based on phase recognition. MATLAB/Simulink simulation software is used to verify the correctness and validity of the proposed method.

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Running composite insulators are prone to failure due to their harsh surrounding work environment, which directly affects the safe operation of transmission lines. This paper puts forward the method of using fiber Bragg grating (FBG) as the monitors to parameters correlated with thermal and stress of the composite insulators in transmission lines at working status. Firstly, monitoring points are found out by the mechanical test on composite insulator samples. Secondly, based on the monitoring theory, this paper introduces the feasibility design frame of the composite insulator with FBG implanted in the rod and the online monitor system. At last, it describes applications of this monitor system in the field of transmission lines.

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This paper introduces the implementation and data analysis associated with a state-wide power quality monitoring and analysis system in China. Corporation specifications on power quality monitors as well as on communication protocols are formulated for data transmission. Big data platform and related technologies are utilized for data storage and computation. Compliance verification analysis and a power quality performance assessment are conducted, and a visualization tool for result presentation is finally presented.

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The AC/DC hybrid distribution network is one of the trends in distribution network development, which poses great challenges to the traditional distribution transformer. In this paper, a new topology suitable for AC/DC hybrid distribution network is put forward according to the demands of power grid, with advantages of accepting DG and DC loads, while clearing DC fault by blocking the clamping double sub-module (CDSM) of input stage. Then, this paper shows the typical structure of AC/DC distribution network that is hand in hand. Based on the new topology, this paper designs the control and modulation strategies of each stage, where the outer loop controller of input stage is emphasized for its twocontrol mode. At last, the rationality of new topology and the validity of control strategies are verified by the steady and dynamic state simulation. At the same time, the simulation results highlight the role of PET in energy regulation.

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