Abstract China has set a new goal of reaching carbon peak by 2030 and becoming carbon neutralization by 2060. To achieve this goal as well as provide a strong and reliable energy supply for comprehensive revitalization of Northeast China, special action is planning by Northeast China power grid (NCPG). Current situation of renewable energy in NCPG is introduced at first. As the primary method for renewable energy accommodation in Northeast China, the existing rules of ancillary services (AS) market are then analyzed. However, considering the rapid growth of renewable energy installed capacity, the existing market has some limitations. In this paper, we take the structural reform on generation side as thread and market demand as guidance. Initiatives and suggestions for high quality development of renewable energy in Northeast China are then proposed for each implementation stage. Through the improving of market rules, expansion of market scale and cultivation of new market entities, NCPG may realize full consumption of the generated renewable energy. The transition from generation side upgrade to the aggregation of source and storage and finally to the cooperation of source-grid-load-storage will be facilitated and accelerated.

特高压±800千伏直流输电技术作为世界上电压最高、容量最高(可达1000万千瓦级)、经济输电距离最远(可达2000公里级)的直流输电技术,可以跨越千里之外,将集中了80％以上能源分布的中西部和北部地区的电力,传输到集中了70％以上电力消费的东部和中部地区.该技术之所以具备这样的优势,是因为直流电压的提高可以大幅降低输电损耗,进而提升经济输电距离和输电走廊利用效率.但这也带来了相当大的挑战:电压和电流的提升使得外绝缘设计、电磁环境控制以及装备研制的难度大幅提升.

Based on completely mastering ±800 kV transmission technologies, the first ±1100 kV direct current (DC) transmission demonstration project is being constructed in China. Combining theoretical analysis and a large number of experiments, the margin of switching overvoltage in converter stations, the configuration scheme and performance of lightning arresters, the shielding angles of ground lines under different geographical conditions, and the maximum air gap of lines have been determined. The switching impulse flashover characteristics of equipotential sphere and typical rod-plane air gaps are also provided. The external insulation is designed differently for light, medium, and heavy pollution areas. For the ±1100 kV project, if the 8 × 1250 mm2 conductors are applied, the pole gap is 26 m and the height of the line is 25 m, all the electromagnetic parameters will meet the requirement of international electromagnetic standards. The key design points of ±1100 kV converter transformers, smoothing reactors, converter valves, and wall bushings are researched and the 75 mH smoothing reactors, ±1100 kV/5000 A converter valves, and ±1100 kV/5523 A wall bushings are successfully made. The optimised hierarchical connection modes and coordination control measure of the ±1100 kV project are studied and the results can provide sufficient technical support for the demonstration project.

在中国的"西电东送"输电工程中,±1100千伏直流输电以其输电距离远、输送容量大、输电损耗低等突出优点,成为支撑更远距离、更大规模输电的核心技术.以中国正在建设的昌吉—古泉±1100千伏特高压直流输电工程为例,其双极运行输送容量达1200万千瓦,输电距离长达3284公里.在这类工程中, ±1100 千伏直流穿墙套管是连接换流站阀厅内部和外部高电压大容量电气装备的唯一电气贯通设备,单体承载着全系统的电压和电流,输送容量达600万千瓦(约相当于北京市总用电负荷的1/3),堪称直流输电系统的"咽喉",具有复杂度高、可靠性要求高等技术特点.

This paper reviews the applications of line commutated converter based high voltage direct current transmission (LCC-HVDC) technologies in China, with a special focus on UHVDC technology developed in the last 10 years. The paper examines six specific aspects of areas-voltage increase, capacity upgrade, reliability improvement, engineering design innovation, equipment and materials innovation, and the R&D of next step. Subsequent advances in LCC-HVDC technologies in recent years are also discussed.

The successful construction and reliable operation of Xiangjiaba-Shanghai project fully proved the performance of ±800kV UHVDC technology. Considering the huge power export of Sinkiang and Tibet area, SGCC (State Grid Corporation of China) started R&D of higher voltage level UHVDC technology on 2008. Considering the capacity and distance of power transmission, the economics of different voltage level development were evaluated as well as the feasibility of key equipments. On the end of 2010, several key parameters are decided. For the 10,000MW power transmission over 2350kM or longer, the selected rated voltage is ±1100kV, and rated current is 4750A with capacity 10,450MW. In addition, the R&D schedule is presented. In this paper, the current R&D progress and the scheduled study of ±1100kV UHVDC are presented. The content is organized into six parts. In part I, the basics and operation status of Xiangjiaba-Shanghai project is given. Then, the demand of ±1100kV project is introduced, as well as pilot project. In part II, the R&D progress of key technology is given. Main circuit scheme and the technical specification of equipments are introduced. The main circuit configuration is same with Xiangjiaba project. The two series converter scheme is connected with equivalent voltage distribution in one pole. By optimizing the configuration and parameters of surge arresters, the over-voltage level is suppressed deeply including AC side and valve side of transformer, critical points in DC circuit, etc. The insulation level is also proposed. The study of external insulation and electromagnetic environment, are presented, which have significant impact on the project construction cost. The length of insulators and air clearance are proposed., In third part, the R&D progress of key equipment is introduced. Firstly, the crucial points of all DC equipments are reviewed, and give possible solution. Secondly, the roadmap and technical solution of converter transformer and wall bushing is discussed, In part IV, the scheme of converter transformer on-site assembling is proposed. Due to the transportation limit, it is impossible to transport the whole transformer to Sinkiang area by railway or road. Then, the on-site assembling idea is proposed and studied. In the scheme, the high-end valve hall of pole II is used for transformer assembling. The current technical solutions are introduced including manufacture, fault treatment and test. In addition, the preliminary manufacture and test equipment layout in valve hall is also given. Then, this paper discusses the key points in the solution, and ideas. In part V, the R&D of next step is presented.

Two-circuit ±800 kV DC transmission lines in the same corridor will be applied in China in the near future, so the total electric field at the ground level under lines of this type needs to be studied to provide technical support for project design and environmental protection. Through the simulation tests on the total electric field at the ground level under two circuit DC transmission lines in the same corridor with different pole arrangement schemes, the lateral distribution regulation was obtained. A calculation method for this total electric field was proposed with the consideration of various important affecting factors, and its validity was proved by simulation tests. The distribution characteristics of the total electric field at the ground level under two circuit ±800 kV DC transmission lines in the same corridor were analyzed by using the method proposed in this paper. Analytical results showed that different pole arrangement schemes for two circuit DC transmission lines in the same corridor will not notably influence the magnitude of the maximum total electric field at the ground level, but will influence its distribution location. The absolute value of the maximum total electric field of this kind is not greatly different from that of a single circuit in normal operation. The parallel adjacent erection for two-circuit DC transmission lines in the same corridor, compared with the far-away erection, can greatly reduce the corridor width and the project removal expense.

The lightning protection in the DC yard is a key problem of the ±800 kV UHVDC power transmission systems.Since the lightning rods in the DC yard can not meet the demands of lightning protection,the densely packed shield wires are proposed,showing a better effect than the lightning rods.The numerical method is applied to analyze the parameters of the shied wires.The safety clearance between the shield wire and the bus or apparatus is considered for the parameter selection of the shield wire.In addition,the surface electric field of the shield wire should also be small enough to avoid the corona discharge.As a conclusion,the duplex shield wires surpass the single shield wire due to the relatively low surface electric field and the robustness against the wire breaking.Finally,the diameter and the height of the shield wire above the bus or apparatus are provided,which had been adopted in the shield wire designs of Xiangjiaba-Shanghai and Jinping-Sunan ±800 kV UHVDC yards.

The equipment in ultra-high voltage(UHV) DC yard have a low lightning withstand level to direct striking lightning,much stricter protection measures than those for AC substations should be adopted when designing the protection system of UHV DC yard against direct lightning strike.We analyzed the protection range of the lighting rod on the basis of the fractal model of the lightning channel.Due to the lower probability of lightnings with lightning current directly striking the DC yard,densely packed shielding wires were suggested to be used to protect electrical equipment in the UHV DC yard.According to the lightning withstand level of different devices in the DC yard,the polyline method,rolling-sphere method,leader progression model,and fractal model were applied to analyze the spacing distances in different regions of UHV DC yard.The results from different methods are compared,and the recommended values of shielding wire spacing distances in different regions of UHV DC yard are suggested,which have been applied in the shield wire designs of Xiangjiaba-Shanghai and Jinping-Sunan ±800 kV UHVDC yards.

±1 000 kV ultra high voltage direct current(UHVDC)transmission technology can realize the optimal allocation of energy resources over a large area,and is suitable for the extra long-distance and super-capacity electrical power transmission.In this paper,the research and development(R&D)thought and plan of ±1000kV UHVDC transmission technology are presented.They are organized into five parts.In the first part,the necessity to carry out ±1000kV UHVDC projects and the necessity to conduct the corresponding R&D are analyzed.In part two,the system adaptability of ±1000kV UHVDC transmission is discussed,and the key points of researches are presented.Part three analyzes the technical feasibility of the transmission line and apparatus in converter stations.The key technical difficulties and R&D roadmap are discussed.In part four,a new thought to analyze economic advantages of ±1000kV UHVDC transmission technology from the perspective of converter station cost,transmission line cost and energy price is put forward.Part five introduces the R&D plan of ±1000kV UHVDC transmission technology of the State Grid.

±1000 ultra high voltage direct current (UHVDC) transmission technology can realize the optimal allocation of energy resources over a large area, and is suitable for the extra long-distance and super-capacity electrical power transmission. In this paper, the research and development (R and D) thought and plan of ±1000 kV UHVDC transmission technology are presented. They are organized into five parts. In the first part, the necessity to carry out ±1000 kV UHVDC projects and the necessity to conduct the corresponding R and D are analyzed. In part two, the system adaptability of ±1000 kV UHVDC transmission is discussed, and the key points of researches are presented. Part three analyzes the technical feasibility of the transmission line and apparatus in converter stations. The key technical difficulties and R and D roadmap are discussed. In part four, a new thought to analyze economic advantages of ±1000 kV UHVDC transmission technology from the perspective of converter station cost, transmission line cost and energy price is put forward. Part five introduces the R and D plan of ±1000 kV UHVDC transmission technology of the State Grid. © 2009 Chin. Soc. for Elec. Eng.

It is planed that total 38GW of Jinshajiang hydropower will be transmitted to east China and central China by several HVDC links.There could be several kinds of combination of HVDC voltage and transmitting capacity for each bipole.The destination of this paper is to give the best combination for this project.First,three preliminary power transmission schemes are proposed in this paper.Then the optimal voltage level and conductor size are given through comparing the cost-effectiveness at different voltage,analyzing its sensitivity,and considering the impact on environment.By detailed comparison on average power transmission cost,average power selling price,investment and annual cost,and the needed corridor width among three schemes,it is shown that scheme 1,3 bipolar HVDC links and each rated at 800 kV and 6.4GW,has the obvious advantage over the others because of a lower cost and significant reduction of land occupation.The technical feasibility and power grid stability of scheme 1 are then analyzed in this paper.By investigation on the development of HVDC equipment,it is shown that although lots of subjects are required to be investigated further,UHVDC transmission rated on 800 kV and 6400MW is technically feasible and engineering practical.The system stability of scheme 1 is also analyzed.It is shown that the system can remain stable after any monopole fault and can recover by tripping several units in sending end after any bipole fault,both in year 2020 and 2015.So,it is concluded that the best scheme for power transmission of Jinshajiang I hydro power plant is 3 bipolar HVDC links and each rated at ±800 kV and 6.4GW.