现有试验技术在输出功率及能量方面不能满足张北工程对柔性直流换流阀(MMC换流阀)和直流断路器提出的短时电流耐受要求.为了解决该问题,对MMC换流阀和直流断路器的短时电流应力进行了分析,提出了基于超级电容储能和功率变换的试验方法.设计的试验电路采用超级电容储能降低了对试验电源容量的需求,采用基于Buck变换器实现高功率输出,采用交错并联调制方式降低功率模块的电流应力.搭建了PSCAD电磁暂态仿真模型和试验平台对丰宁站关键设备进行了短时电流耐受试验仿真,仿真和试验结果表明试验电路所输出的试验电流可有效跟踪电流指令变化,具有试验要求的输出电流等价性.

大容量新能源电能采用孤岛方式通过双极柔性直流系统送出具有广阔的应用前景.文中对存在的非故障极过负荷和直流过电压情况下的功率盈余特性进行了分析,提出了分组交流耗能电阻方案,分别设计了送端换流器故障和直流过压下的功率盈余控制策略,通过分组交流耗能电阻的精确投切避免功率盈余引起双极柔性直流系统停运.通过四端柔性直流电网实时数字仿真器(RTDS)和EMTDC仿真系统,对提出的2种功率盈余控制策略进行验证.仿真结果表明,所提策略能够实现功率盈余工况下的故障穿越,避免故障范围扩大.

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.

With the rapid construction of UHV grid and the progress of construction technology and equipment of power transmission towers,some problems appear in the current technical standard system for assembly and erection construction of steel towers of overhead transmission line with the standard "Construction technology guidance for the assembling and erection of the steel towers of 750 kV overhead transmission line" (Q/GDW 112-2004)as the core,which include contents repetition,poor connection and poor applicability to the practical engineering.Therefore,in order to provide a technical support for assembling and erecting steel towers,it is necessary to further optimize the framework structure of existing China's electric power industry technical standard system for assembly and erection construction of steel towers of overhead transmission line,which should be carried out based on an analysis of the constitutions and problems of current standard system,and with a consideration of the features of tower types,the tower construction technology and the equipment for erecting steel tower.

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.

As the highest DC transmission voltage level over the world,±1100kV DC transmission line will be built in China soon. Electric field strength in surrounding space of ±1100kV DC line is much stronger than that of±800kV and lower voltage level line. To ensure safety of hot-line work on ±1100kV DC lines, its safety protection should be researched. Firstly, based on proposed screening clothes, test results of hot-line work shield protection on±1100kV DC line were given, including measurements of characteristics of screening clothes, their inside and outside electrical field strengths, flowing through current of hot-line work screening clothes, discharge arc current and audible noise. Then, safety control level of±1100kV DC hot-line work shield protection was analyzed. Finally, based on the test results, precautions for shielding protection in± 1100kV hot-line work were summarized. The results show that it is feasible to hot-line work on± 1100kV DC transmission lines with high quality screening clothes.

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.

For UHVDC project,corona discharge may start if the maximum electric field of electrode surface reaches corona electric field.The shape and structure of different equipment are having large difference for ±1100kV UHVDC project DC yard,and the zero potential wall and roof are presented and increase the surface electrical field,thus the all domain 3D electric field simulation of indoor DC yard is necessary for repeated optimization of electrode shape.In this paper,the electric field simulation study and test were carried out to state the permitted electrical filed of electrode with different diameter.By 3D simulation and continuously optimizing the electrode shape of the critical equipment in 1100kV indoor DC yard,the maximum electric field of electrode surface meets the permitted value requirement finally.

Considering mutual inductance between bipolar DC transmission lines in ultra-high voltage direct current (UHVDC) projects, bipolar characteristics during restarting of one pole after line fault occurring were analyzed and researched. According to voltage calculation formula for transient fault on transmission line, several improved control strategies were proposed on basis of the control measures that voltage dependent current limit (VDCL) function of the non-fault pole was blocked shortly. Comparative study of the strategies was presented based on close-loop simulation of a UHVDC system consisting of real-time digital simulator (RTDS) and control and protection equipment. Effectiveness of the two control methods adopting constant DC voltage control at rectifier side and changed parameters of current controller was confirmed. Then suggestion on project application was put forward.