Current Issue

  • Characteristic Analysis of UHVAC/DC Hybrid Power Grids and Construction of Power System Protection

    Abstract

      2017-12-25

    Strong DC coupling with weak AC and large-scalerenewable energy integration are the two significant characteristicsof ultra-high-voltage AC/DC (UHVAC/DC) hybrid powergrids in China. Strong coupling between AC and DC gridsand the different integration performance of renewable energysources have profoundly changed the stability characteristicsof the power system. The traditional stability control systemis inadequate for the stability control of UHVAC/DC powergrids. This paper analyzes the requirements for constructingan integrated defense system in a UHVAC/DC hybrid powergrid (i.e. power system protection). The definition, connotation,and designing principles of power system protection are putforward. The relationship between the power system protectionand the traditional three-defense lines is investigated. The designprinciples, general hardware structure and main functions ofa power system protection are presented. Key problems andtechnologies are specified in the construction of the power systemprotection.

  • Analysis and Recommendations for the Adaptability of China’s Power System Security and Stability Relevant Standards

    Abstract

      2017-12-25

    In developing power grids, setting standards is criticalto its success. The development of China’s power industry hasproposed new requirements for power systems to ensure secureand stable operations. The principal standards for the securityand stability of China’s current power systems are analyzed interms of operational control, generator-grid coordination andsimulation. The shortcomings are pointed out and the directionsof future development are discussed. In the end, the study highlightedthe following key areas that require further research andimprovement: the evaluation criteria of power system securityand stability should be improved to ensure the secure and stableoperation of China’s power systems; the operational controlstandards should be constantly enhanced to increase the reliabilityand flexibility of operational control strategies; generatorgridcoordination standards should be upgraded to improve thecoordination between the generator control protection system andthe grid; and the simulation methodology should be standardizedin future power system security and stability research.

  • Modeling, Control, and Protection of Modular Multilevel Converter-based Multi-terminal HVDC Systems: A Review

    Abstract

      2017-12-25

    Multi-terminal direct current (MTDC) grids providethe possibility of meshed interconnections between regionalpower systems and various renewable energy resources to boostsupply reliability and economy. The modular multilevel converter(MMC) has become the basic building block for MTDCand DC grids due to its salient features, i.e., modularity andscalability. Therefore, the MMC-based MTDC systems shouldbe pervasively embedded into the present power system to improvesystem performance. However, several technical challengeshamper their practical applications and deployment, includingmodeling, control, and protection of the MMC-MTDC grids. Thispaper presents a comprehensive investigation and reference inmodeling, control, and protection of the MMC-MTDC grids. Ageneral overview of state-of-the-art modeling techniques of theMMC along with their performance in simulation analysis forMTDC applications is provided. A review of control strategiesof the MMC-MTDC grids which provide AC system support ispresented. State-of-the art protection techniques of the MMCMTDCsystems are also investigated. Finally, the associatedresearch challenges and trends are highlighted.

  • Renewable Energy Transmission by HVDC Across the Continent: System Challenges and Opportunities

    Abstract

      2017-12-25

    Rapid development of renewable energy in Chinais driving a major shift in the characteristics and controlrequirements of the electricity grid. Since the best renewableenergy resources are far away from load centers in the east andsoutheast, transmission over long distances is required. Over 20high-voltage DC (HVDC) transmission lines, with a combinedcapacity exceeding 150 GW, are in operation or are currentlyunder construction. This rapid expansion of new generationand transmission capacities based on power electronics starts tochange the characteristics of the grid, especially in areas wherethey concentrate, creating new stability problems and operationalchallenges. New system theories and technologies are requiredto support the development and operation of a future grid thatrelies more and more on power electronics. This paper highlightsthe characteristics of power electronics as used in renewableenergy generation and HVDC transmission systems, discusses theimpacts of these power-electronics-based assets on grid stabilityand operational requirements, and identifies opportunities for thedevelopment of both new system theories and system technologiesto support a national energy policy that emphasizes the use ofclean energy.

  • Protection Challenges Under Bulk Penetration of Renewable Energy Resources in Power Systems: A Review

    Abstract

      2017-12-25

    Among different sources of alternate energy, windand solar are two prominent and promising alternatives tomeet the future electricity needs for mankind. Generally, thesesources are integrated at the distribution utilities to supplythe local distribution customers. If the power generated bythese sources is bulk, then they are either integrated at thedistribution/transmission level or may be operated in an islandmode if feasible. The integration of these renewables inthe power network will change the fault level and networktopologies. These fault levels are intermittent in nature andexisting protection schemes may fail to operate because oftheir pre-set condition. Therefore, the design and selection ofa proper protection scheme is very much essential for reliablecontrol and operation of renewable integrated power systems.Depending upon the level of infeed and location of the renewableintegration, the protection requirements are different. For lowrenewable infeed at the distribution level, the existing relaysettings are immune from any small change in the networkfault current from new incoming renewables. However, bulkrenewable infeed requires modification in the existing protectionschemes to accommodate the fault current variation from theincoming renewables. For bulk penetration of the renewable,the requirement of modified/additional protection schemes is unavoidable.Adaptive relaying and non-adaptive relaying schemesare discussed in the literature for protection of power networks,which are experiencing dynamic fault currents and frequentchanging network topologies. This article presents a detailedreview of protection schemes for renewable integrated powernetworks which includes distribution, transmission and microgridsystems. The merits and demerits of these protection schemesare also identified in this article for the added interest of thereaders. The visible scope of advance protection schemes whichmay be suitable for providing reliable protection for dynamicfault current networks is also explored.

Introduction

CSEEJPESThe articles published in this journal will focus on advanced concepts, technologies, methodologies and practices associated with all aspects concerning power and energy systems...
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