The interconnections of electric power systems are developed for the economic benefits and in order to increase the overall power supply reliability and quality level. Development of power industry shows the positive effects in operation of the country-wide electric power systems and international interconnections. Creation of World Energy System or, by the other words, Global Energy Interconnection is objective trend on the way of expansion of international and intercontinental electric power interconnections. Several important aspects of above mentioned problems are discussed in this paper.

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In 2011, a large scale earthquake and tsunami hit the northeastern coast of Japan, and nuclear plants were damaged to a large extent. Before the Tsunami, 54 nuclear plants were operated, however presently, only three nuclear plants are in operation. Therefore, Japan is suffering from high price of electricity and low supply reliability. In generation mix, nuclear plants generate only one percent and 87 percent of electricity is generated by fossil energy.This is not preferable for Japan from the viewpoints of energy security and stable electricity supply. Therefore, it is mandatory to increase sustainable energy and to decrease consumption of fossil fuel. International grid connection and the Global Energy Interconnection will be one of countermeasures against these problems existing in Japan. In this paper, international grid connection initiatives proposed in Asia are described and features and issues of electric power grids in Japan are discussed to implement the international grid connection. As the key technology for implementing the international grid connection, the present status of DC superconducting power transmission lines and power converters for long-distance power transmission lines are presented. In conclusion, conditions and legal frameworks for realizing the international grid connection are described.

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With the change of energy structure in Europe and the trend of diversification of energy supply, the interconnection of the power grid in the Mediterranean region has gradually become a hotspot in European energy research. This paper introduces the power supply, load demand, power grid construction and the present situation of multinational interregional interconnection in the Iberian Peninsula of the Tour of Mediterranean in Europe (Portugal and Spain) and the Western Maghreb countries (Morocco and Algeria). And the driving force and influence factors of regional power grid interconnection are also analyzed. According to the MEDGRID project aimed at realizing the Mediterranean power grid interconnection, this paper presents the interconnection schemes of the Iberian Peninsula and the Western Maghreb. Furthermore, the subsequent technical problems need to be solved are also expounded.

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Firstly, relevant stress properties of millisecond level breaking process and microsecond level commutation process of hybrid HVDC circuit breaker are studied in detail on the basis of the analysis for the application environment and topological structure and operating principles of hybrid circuit breakers, and key stress parameters in transient state process of two time dimensions are extracted. The established digital simulation circuit for PSCAD/EMTDC device-level operation of the circuit breaker has verified the stress properties of millisecond level breaking process and microsecond level commutation process. Then, equivalent test method, circuits and parameters based on LC power supply are proposed on the basis of stress extraction. Finally, the results of implemented breaking tests for complete 200kV circuit breaker, 100kV and 50kV circuit breaker units, as well as single power electronic module have verified the accuracy of the simulation circuit and mathematical analysis. The result of this paper can be a guide to electrical structure and test system design of hybrid HVDC circuit breaker.

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The increasing penetration of renewable energy on the transmission and distribution power network is driving the adoption of two-way power flow control, data and communications needed to meet the dependency of balancing generation and load. Thus, creating an environment where power and information flow seamlessly in real time to enable reliable and economically viable energy delivery, the advent of Internet of Energy (IoE) as well as the rising of Internet of Things (IoT) based smart systems.

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Dramatic fall in costs of renewable energy in the last 24 months has not only accelerated the replacement of fossil fuels by renewable energy in electricity generation. The low cost renewable electricity is now starting to replace fossil fuels in other sectors.

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The economic analysis of solar energy development is the basis of promoting the solar energy planning in north Africa and realizing the clean energy power transmission among continents. In this paper, the cost development trend of photovoltaic(PV) power and concentrating solar power(CSP) generation is analyzed, and the levelized cost of energy (LCOE) of solar power generation is forecasted. Then, taking the development of Tunisian solar energy as an example in the context of transcontinental transmission, PV power with energy storage and PV-CSP power generation are given as two kinds of development plan respectively. The installed capacity configurations of the two schemes are given with production simulation method, and comprehensive LCOE are calculated. The studies show that based on the LCOE forecast value, the LCOE of PV-CSP combined power generation will decrease when the annual utilization hours of transmission channel is increased. It can be chosen as one of important mode of the North Africa solar energy development.

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Nowadays, the technology of renewable sources grid-connection and DC transmission has a rapid development.And phasor measurement units (PMUs) become more notable in power grids, due to the necessary of real time monitoring and close-loop control applications. However, the PMUs data quality issue affects applications based on PMUs a lot. This paper proposes a simple yet effective method for recovering PMU data. To simply the issue, two different scenarios of PMUs data loss are first defined. Then a key combination of preferred selection strategies is introduced. And the missing data is recovered by the function of spline interpolation. This method has been tested by artificial data and field data obtained from on-site PMUs. The results demonstrate that the proposed method recovers the missing PMU data quickly and accurately. And it is much better than other methods when missing data are massive and continuous. This paper also presents the interesting direction for future work.

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The world is witnessing increasing frequency of extreme events. The power system is the backbone critical infrastructure of our economy and is under treat of such events. The resilient power system is intended to cope with low probability, high risk extreme events including extreme natural disasters and man-made attacks. Realizing resilience in the power system has been an unprecedented mission. Equipped with today’s smart grid technologies, power system can be rendered more resilient by the strategies taken before, during and after a disruptive event erupts. Based on a thorough review of existing works, we present the most-investigated problems and solving measures according to their application stage. In the preparation stage, innovative planning frameworks considering disaster scenarios are discussed; after the event, the system can alter the topology and integrate resource allocation to alleviate load shedding. The characteristics of different disasters are investigated to facilitate enhancing resilience. The review provides a summary of resilience strategies in the power system and can shed light to future research and application.

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In the context of constructing Global Energy Interconnection (GEI), energy storage technology, as one of the important basic supporting technologies in power system, will play an important role in the energy configuration and optimization. Based on the most promising battery energy storage technology, this paper introduces the current status of the grid technology, the application of large-scale energy storage technology and the supporting role of battery energy storage for GEI. Based on several key technologies of large-scale battery energy storage system, preliminary analysis of the standard system construction of energy storage system is made, and the future prospect is put forward.

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Energy crisis and climate change have become two seriously concerned issues universally. As a feasible solution, Global Energy Interconnection (GEI) has been highly praised and positively responded by the international community once proposed by China. From strategic conception to implementation, GEI development has entered a new phase of joint action now. Gathering and building a global grid database is a prerequisite for conducting research on GEI. Based on the requirement of global grid data management and application, combining with big data and geographic information technology, this paper studies the global grid data acquisition and analysis process, sorts out and designs the global grid database structure supporting GEI research, and builds a global grid database system.

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The necessity of large-scale and long-distance power transmission in future energy development is analyzed and some application scenarios of ultra-high voltage (UHV) half-wavelength transmission (HWLT) system are presented in the paper. Steady state and transient characteristics of half-wavelength transmission lines are reviewed in detail.The characteristics of UHV HWLT are very different from those of conventional UHV transmission mode, especially the overvoltage problem. To analyze the particularity and key techniques of UHV HWLT, current research results are summarized from simulation method, steady-state voltage control, relay protection, tuning network, secondary arc and overvoltage suppression, economic evaluation and engineering design. Some future research directions are also briefly addressed.

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