Prospect and key techniques of Global Energy Interconnection Zhangjiakou Innovation Demonstration Zone

In the Background of implementing innovation-driven development strategy and building Global Energy Interconnection, the necessity of building Global Energy Interconnection Zhangjiakou Innovation Demonstration Zone for stimulating economic growth, promoting social development and supporting 2022 Winter Olympics are discussed by analyzing the location advantages of Zhangjiakou and the characteristics of renewable energy in Zhangjiakou. Solutions are put forward in aspects of renewable energy integration in National Wind/Solar/Storage/Transmission Pilot Project, VSC-HVDC transmission of renewable energy and demonstration utilization of renewable energy in the Olympics zone, which could be a reference for problems of large-scale renewable energy in secure integration, outgoing transmission and flexible consumption. And replicable experience for building Global Energy Interconnection will be provided by conducting ± 500kV VSC-HVDC Power Grid Demonstration Project, Virtual Synchronous Generator Demonstration Project, Flexible Substation and AC/DC Power Distribution Network Demonstration Project, EV Battery Secondary Utilization Energy Storage Demonstration Project, Smart Grid Demonstration Project of Low Carbon Winter Olympics and other demonstration projects.     

RES support in Russia: Impact on capacity and electricity market prices

Russian renewable energy policy has undergone changes following an establishment of targets for installed capacity and power production using renewable energy sources and the introduction of new capacity based support scheme for renewable energy. The forecasted amount of future renewable power will not provide enough power production to meet growing demand for renewable energy; although, it will help with modernization of the energy sector and development of renewable technology and innovation. At the same time, the capacity support scheme for renewable energy may adversely affect capacity prices and become an additional burden for industrial consumers, who are already paying the cost of capacity support for conventional power plants, so-called Capacity Delivery Agreements (CDAs). This work assesses the impact of the new capacity based support scheme on capacity and electricity price formation. Modeling results show that the impact of capacity support for renewable energy is small compared to that of capacity support for conventional energy, suggesting that the Russian energy production mix will continue to be dominated by fossil fuel based generation.     

Grid integrated renewable DG systems: A review of power quality challenges and state-of-the-art mitigation techniques

Increased energy demands due to rapid industrialization, environmental concerns with fossil fuel–based generation, diminishing fossil energy resources, transmission network congestion, and technical performance deterioration are the motivations behind the integration of small renewable distributed generation (DG) units and turning the existing power systems into a restructured one. Optimizing the technical benefits offered by DG placement is a well-known challenge for distribution network operators (DNOs) for both fossil and renewable energy resource–based DGs, but renewable DG systems have several power quality (PQ) challenges associated additionally. Power quality is a very significant characteristic of renewable DG systems because today's loads are more sensitive to PQ disturbances and penetration of renewable energy as well as nonlinear loads is proliferating in distribution power networks. So the need for innovative power quality improvement (PQI) techniques becomes inevitable due to ongoing reformation in traditional distribution networks by the integration of renewable energy. This article presents a comprehensive analysis of power quality challenges with grid integration of renewable DG systems and current research status of associated mitigation techniques. Firstly, this paper puts emphasis on theoretically illustrating all the crucial power quality challenges associated with grid integration of renewable energy, and secondly, a thorough survey, of all PQI techniques introduced till date, is elaborated along with highlighting the opportunities for future research. Furthermore, all the crucial power quality issues, the impact of high penetration of renewable energy and mitigation techniques on power quality, are demonstrated also by simulating a grid integrated PV-based DG system in MATLAB/Simulink. This article is believed to be very beneficial for academics as well as industry professionals to understand existing PQ challenges, PQI techniques, and future research directions for renewable energy technologies.     

从标准看智能电网的发展

目前世界各国在什么是智能电网、如何推进智能电网的发展等方面并没有达成一致意见。美国设想的未来电力系统是一个完全自动化的电力传输网络,能够保证从电厂到终端用户整个输配电过程中所有节点之间的信息和电能的双向流动。欧洲智能电网技术平台的目标是提高输配电系统的效率、安全性和可靠性,消除大规模集成配网与可再生能源的障碍。日本将主要以大规模开发太阳能等新能源、确保电网系统稳定作为智能电网建设的主要思路。结合中国的实际情况,我国智能电网业务框架应包含发电、输变电、配电、用户、运行、服务提供者、电力市场及统一信息平台等8个领域。现有标准与智能电网之间存在差距,主要体现在需求响应和电力市场、广域状态测量、电力存储、电力传输、AMI系统、配网管理等6个方面。其中,一部分差距已经有了清晰的发展方向和解决思路;而另一部分的具体发展方向和解决思路尚不明确。智能电网相关标准的开发需要以具体项目实施为载体,标准体系是否完备需要通过具体项目检验和修订,同时具体项目的顺利实施也有赖于标准体系的约束和规范。针对中国某省级电网的特殊性和典型性,建议其智能电网的发展,一是应重点关注标准研究方向,二是由此引出的示范工程项目。     

SmartGrid: Future networks for New Zealand power systems incorporating distributed generation

The concept of intelligent electricity grids, which primarily involves the integration of new information and communication technologies with power transmission lines and distribution cables, is being actively explored in the European Union and the United States. Both developments share common technological developmental goals but also differ distinctly towards the role of distributed generation for their future electrical energy security. This paper looks at options that could find relevance to New Zealand (NZ), in the context of its aspiration of achieving 90% renewable energy electricity generation portfolio by 2025. It also identifies developments in technical standardization and industry investments that facilitate a pathway towards an intelligent or smart grid development for NZ. Some areas where policy can support research in NZ being a “fast adapter” to future grid development are also listed.This paper will help policy makers quickly review developments surrounding SmartGrid and also identify its potential to support NZ Energy Strategy in the electricity infrastructure. This paper will also help researchers and power system stakeholders for identifying international standardization, projects and potential partners in the area of future grid technologies.     

城市电网柔性分区互联方案研究

目的  柔性直流技术由于其灵活性、快速的控制能力,可应用在异步电网互联、可再生能源并网、城市电网供电等。文章提出城市电网柔性分区互联紧凑型方案以实现城市电网分区间的互联、互济,提高电网安全稳定水平。 方法  根据电网现状,考虑到城区新建输电通道的实施难度以及建设工期难以控制等因素,利用已有的交流互联通道进行布点,将交流弱互联改为柔性强互联,互联端数及规模结合系统需求、原有线路的输送能力、增容改造的可行性等综合确定。由于城市用地紧张,选用紧凑型设备,采用户内紧凑布置。 结果  采用柔性直流背靠背实现城市电网分区间互联、互济,可显著降低系统短路电流水平,提高电网互济能力和安全稳定水平;采用户内紧凑布置,可节省约40%的空间,满足缓解城市土地资源稀缺的需求。 结论  提出的柔性分区互联紧凑型设计方案对柔性直流技术在城市互联的应用中起到很好的指导作用,具有较高的参考价值。     

Adaptive intelligent power systems: Active distribution networks

Electricity networks are extensive and well established. They form a key part of the infrastructure that supports industrialised society. These networks are moving from a period of stability to a time of potentially major transition, driven by a need for old equipment to be replaced, by government policy commitments to cleaner and renewable sources of electricity generation, and by change in the power industry. This paper looks at moves towards active distribution networks. The novel transmission and distribution systems of the future will challenge today's system designs. They will cope with variable voltages and frequencies, and will offer more flexible, sustainable options. Intelligent power networks will need innovation in several key areas of information technology. Active control of flexible, large-scale electrical power systems is required. Protection and control systems will have to react to faults and unusual transient behaviour and ensure recovery after such events. Real-time network simulation and performance analysis will be needed to provide decision support for system operators, and the inputs to energy and distribution management systems. Advanced sensors and measurement will be used to achieve higher degrees of network automation and better system control, while pervasive communications will allow networks to be reconfigured by intelligent systems.     

Index system and methods for comprehensive assessment of cross-border power grid interconnection projects

With the global economy integration and progress in energy transformation, it has become a general trend to surpass national boundaries to achieve wider and optimal energy resource allocations. Consequently, there is a critical need to adopt scientific approaches in assessing cross-border power grid interconnection projects. First, considering the promotion of large-scale renewable energy resources and improvements in system adequacy, a comprehensive assessment index system, including costs, socio-economic benefits, environmental benefits, and technical benefits, is established in this study. Second, a synthetic assessment framework is proposed for cross-border power grid interconnection projects based on the index system comprising cost–benefit analysis, with market and network simulations, iterative methods for indicator weight evaluation, and technique for order preference by similarity to an ideal solution (TOPSIS) method for the project rankings. Finally, by assessing and comparing three cross-border projects between Europe and Asia, the proposed index system and assessment framework have been proved to be effective and feasible; the results of this system can thus support investment decision-making related to such projects in the future.     

Application analysis and prospect of electrochemical energy storage in power grid

为促进能源产业的优化升级,可再生能源的开发利用力度不断加大,电网的规划运行和调度管理将面临重大变革,亟需先进的大规模储能技术来改善可再生能源发电特性。本文从电化学储能技术在电网系统应用进行探讨,从各种电化学储能安全性、成本、技术特点等进行深入解析,归纳各种类型电化学储能的优势与不足,并对未来电化学储能在电网系统的应用前景做出展望。     

海上平台柔性直流换流站工程应用方案研究

随着柔性直流输电技术的不断发展,至今已经成为主流的直流输电技术,在海岛供电、风电接入、电网互连等方面已经有了大量的应用,积累了充足的工程经验。由于柔性直流输电技术的自身特点,用于海上平台供电有着先天的优势。基于陆上柔性直流换流站的技术基础,从拓扑结构、主要电气设备选型、电气平面布置以及二次系统等方面论述了海上平台换流站的工程应用方案,对柔性直流输电技术的在海上平台供电领域的应用以及发展方向提出了一些具有积极意义的设想和建议。     

多端柔性直流输电系统的阻抗建模及稳定性分析

与两端柔性直流输电(VSC-HVDC)系统相比,多端柔性直流输电(VSC-MTDC)系统更具灵活性和经济性,且有助于电力系统接纳新能源,在VSC-MTDC系统中,换流器需兼备整流器和逆变器的功能,其控制器参数会对系统的稳定性造成较大的影响,阻抗分析法可直接用于指导控制器的参数整定。为此,以一个三端系统为例,提出了适用于VSC-MTDC系统的阻抗稳定性分析方法,建立了系统的等效小信号阻抗模型,根据Nyquist判据判稳,并结合时域仿真,对直流电压控制器参数进行了分析和整定。仿真分析结果验证了所提阻抗模型和判稳方法有效、精确。     

世界促进风电产业发展最新动向

近年来可再生能源发电发展迅速,其中风力发电表现尤为突出.在一些风电先行国家的推动下,风电机组大型化取得长足进展,单机容量从亚兆瓦级迅速提升到兆瓦级,研制中的10MW级风电机组即将问世.机组的大型化提高了风电的经济性和竞争力.风机设备利用率将由目前的25％左右提高至2015年的28％,同时投资成本将大幅下降,按照GWEC的高增长方案预测,投资成本将由2009年的1350欧元/kW降至2030年的1093欧元/kW.鉴于风力发电的间歇性和随机性,蓄电技术成为大量引入可再生能源的有效手段,美欧日等都投入专项经费支持蓄电技术的研究开发.IEA最近在报告中指出,与热电联产组合的方式可大幅扩大可再生能源的利用,其重点在于热供应.智能电网将成为解决风电大规模接入和输送问题的根本途径,它将使电力系统整体利用效率大大提高,有利于抑制发电厂的化石燃料消费.我国在智能电网方面已取得了一定成果,但仍面临许多问题.各国政府的可再生能源电力收购政策促进了风电产业的发展,其中德国的风电收购政策值得我国借鉴.     

Hydrogen-based systems for integration of renewable energy in power systems: Achievements and perspectives

This paper is a critical review of selected real-world energy storage systems based on hydrogen, ranging from lab-scale systems to full-scale systems in continuous operation. 15 projects are presented with a critical overview of their concept and performance. A review of research related to power electronics, control systems and energy management strategies has been added to integrate the findings with outlooks usually described in separate literature. Results show that while hydrogen energy storage systems are technically feasible, they still require large cost reductions to become commercially attractive. A challenge that affects the cost per unit of energy is the low energy efficiency of some of the system components in real-world operating conditions. Due to losses in the conversion and storage processes, hydrogen energy storage systems lose anywhere between 60 and 85% of the incoming electricity with current technology. However, there are currently very few alternatives for long-term storage of electricity in power systems so the interest in hydrogen for this application remains high from both industry and academia. Additionally, it is expected that the share of intermittent renewable energy in power systems will increase in the coming decades. This could lead to technology development and cost reductions within hydrogen technology if this technology is needed to store excess renewable energy. Results from the reviewed projects indicate that the best solution from a technical viewpoint consists in hybrid systems where hydrogen is combined with short-term energy storage technologies like batteries and supercapacitors. In these hybrid systems the advantages with each storage technology can be fully exploited to maximize efficiency if the system is specifically tailored to the given situation. The disadvantage is that this will obviously increase the complexity and total cost of the energy system. Therefore, control systems and energy management strategies are important factors to achieve optimal results, both in terms of efficiency and cost. By considering the reviewed projects and evaluating operation modes and control systems, new hybrid energy systems could be tailored to fit each situation and to reduce energy losses.     

Recent developments in HVDC transmission systems to support renewable energy integration

The demands for massive renewable energy integration, passive network power supply, and global energy interconnection have all gradually increased, posing new challenges for high voltage direct current (HVDC) power transmission systems, including more complex topology and increased diversity of bipolar HVDC transmission. This study proposes that these two factors have led to new requirements for HVDC control strategies. Moreover, due to the diverse applications of HVDC transmission technology, each station in the system has different requirements. Furthermore, the topology of the AC-DC converter is being continuously developed, revealing a trend towards hybrid converter stations.     

Current facts about offshore wind farms

This paper reviews offshore wind projects with a wide perspective. The current situation of the offshore wind market is presented, pointing out the countries leading the process in terms of installed capacity and in terms of technological leadership. Feasibility studies of alternative offshore wind farms (OWFs) are interesting not only in relation to the business but in relation to the techno-economical analyses that engineering researchers need to do. Details about the average energy yield assessment, the costs and the price for the purchased energy are commented on, as key elements of those feasibility studies. The higher cost of renewable energy sources of electricity (RESE) when compared with conventional sources, demands appropriate policy support. The European regulatory framework and the support schemes established by European Member States are presented, as well as the role that different transmission system operators (TSOs) are playing at the moment. Finally, most of the OWFs currently operating are presented, analysing the technical characteristics of their electric subsystems: the wind energy conversion systems (WECSs) transforming the kinetic energy of the wind into electricity, the collector system (CS) gathering the power output of all the turbines to a central collection point (CCP) and the transmission system (TS) taking that power to the onshore main grid.     

集约式海上换流站电气应用技术研究

  目的  深远海大规模海上风电送出会选用大容量风机和66 kV集电系统,风机具备直接接入海上换流站的条件,从而可以取消海上升压站,实现集约式设计。针对集约式海上换流站需要关注的电气关键技术点开展初步研究。  方法  在现有海上风电柔性直流输电技术的基础上,通过研究集约式海上换流站的主回路拓扑结构、核心电气设备选择和平台布置方案优化,对电气关键技术点给出了切实可行的技术方案。  结果  随着海上风电66 kV集电系统的逐渐普及,集约式海上风电柔直送出将成为以后的主流设计方案。针对集约式海上换流站的电气关键技术点给出了具有指导意义的研究结论。  结论  集约式海上换流站相比传统海上换流站具有明显的技术优势,形成的研究结论可以为后续深远海大规模海上风电送出项目的方案设计和实施提供技术支持,具有很好的示范应用前景。     

Cooperation mechanisms to achieve EU renewable targets

There are considerable benefits from cooperating among member states on meeting the 2020 renewable energy sources (RES) targets. Today countries are supporting investments in renewable energy by many different types of support schemes and with different levels of support. The EU has opened for cooperation mechanisms such as joint support schemes for promoting renewable energy to meet the 2020 targets. The potential coordination benefits, with more efficient localisation and composition of renewable investment, can be achieved by creating new areas/sub-segments of renewable technologies where support costs are shared and credits are transferred between countries.Countries that are not coordinating support for renewable energy might induce inefficient investment in new capacity that would have been more beneficial elsewhere and still have provided the same contribution to meeting the 2020 RES targets. Furthermore, countries might find themselves competing for investment in a market with limited capital available. In both cases, the cost-efficiency of the renewable support policies is reduced compared to a coordinated solution.Barriers for joint support such as network regulation regarding connection of new capacity to the electricity grid and cost sharing rules for electricity transmission expansion are examined and examples given. The influence of additional renewable capacity on domestic/regional power market prices can be a barrier. The market will be influenced by for example an expansion of the wind capacity resulting in lower prices, which will affect existing conventional producers. This development will be opposed by conventional producers, whereas consumers will support such a strategy.A major barrier is the timing of RES targets and the uncertainty regarding future targets. We illustrate the importance of different assumptions on future targets and the implied value of RES credits. The effect on the credit price for 2020 is presented in an exemplary case study of 200 MW wind capacity.     

基于改进支持向量机的多能源电力系统中储能容量规划及运行模型

研究多能源电力系统中储能装置的定容及运行,有利于减小功率波动,降低对电网的冲击,提高电能质量。以青海省海西千万瓦级可再生能源基地为例,首先根据光伏电站和风电场的历史数据分析了两种新能源发电系统的出力特性,在此基础上建立了支持向量机模型,对新能源电站的输出功率进行了短期预测。根据光伏电站和风电场的出力预测误差,建立了ARMA误差预测模型,进一步修正了光伏电站和风电场的预测曲线,最后根据出力预测曲线的功率谱确定了储能系统的容量及出力曲线。研究成果可为新能源并网提供技术支持。     

Alleviating freshwater shortages with combined desert-based large-scale renewable energy and coastal desalination plants supported by Global Energy Interconnection

Under the background of sustainable energy transition and environmental protection, Global Energy Interconnection (GEI), which features an innovative combination of clean energy (e.g., solar power) and ultra-high voltage (UHV) transmission technologies, provides a means to realize global climate governance. China is a large country with unevenly distributed water resources, energy production, and energy consumption, and the large areas of desert in northern and western China have the potential for installing large-scale solar power plants. This study analyzed the potential of using large-scale solar power from deserts to coastal seawater desalination plants, which could alleviate the freshwater crisis and control desertification in China. First, the measurement data from NASA were used to estimate the potential exploitable amount of solar energy in desert areas. A macro idea was proposed for the transmission of electrical power from inland integrated energy bases to coastal seawater desalination and pumping of freshwater to western China to combat desertification and alleviate the freshwater crisis. Based on this, the electricity demands for desalination and water redistribution were estimated. As a huge interruptible load, desalination and pumping systems could be used to suppress power fluctuations of the integrated energy bases. Finally, the fundamental support roles of UHV grids in large-scale renewable energy allocation and utilization were discussed. This analysis offers a theoretical framework to help realize efficient renewable energy generation and consumption and alleviate freshwater shortage.     

State-of-the-art in the industrial implementation of protective relay functions,communication mechanism and synchronized phasor capabilities for electric power systems protection

Protective systems in electricity delivery networks have a major role to play in the increasing of renewable energy systems, and a broad understanding of their current a future application can aid into better taking them into account for achieving future energy networks that adapt for the incorporation of renewable energy generation sources. This paper provides a survey in the state of the art of protective relaying technology and its associated communications technology used in today's power transmission systems. The paper also provides the fundamental knowledge concerned with power system relaying communications. The unifying theme of this paper is to highlight that the future potential of these devices lies in realizing the possibility of going beyond their traditional application as stand-alone equipments with the single role of acting “the last line of defense” so that they can be handled with the increment of renewable energy power delivery systems in near future.