State of the art from State Grid Corporation of China (SGCC) on Thyristor-based HVDC

source: http://www.sgcc.com.cn/ywlm/mediacenter/inspotlight/10/297984.shtml

I thought this press release from State Grid Corporation of China was excellent, and really laid out their future vision for HVDC upgrades. I have reproduced the cited press release below. I have interspersed my own comments as well, identified clearly by RWF. It is clear from this, I think, that State Grid holds firm to the course of pushing line commutated converters (LCCs) based on thyristors to higher currents and higher voltage. This is not very compatible with the supergrid concept, I think, though all the innovations developed by State Grid will still be useful in a supergrid, regardless of the concept they were pursuing when the innovations were made. The key difference is that a supergrid requires multi-terminal HVDC and bi-directional energy flow; (but not necessarily EVERY energy flow needs to be bi-directional).

China Energy News: China Ready for Large-scale Construction of UHV
Released on:2013-10-23         
    The test run meeting of the Xiangjiaba - Shanghai ±800kV UHV DC project was held in Beijing on 9th November. Deputy Director of Electric Power Department of National Energy Administration, Qin Zhijun pointed out that in spite of large capacity and technological difficulty of UHV DC projects, with independent innovation, SGCC successfully tackled a series of worldwide technological problems through comprehensive and solid scientific research and cooperation. National Energy Administration supports the development of UHV DC technology and hopes that SGCC can summarize its past experience so as to better push forward UHV DC technology.

  Not only the Xiangjiaba – Shanghai UHV DC project, projects including 1000kV Jindongnan-Nanyang-Jingmen UHV AC project, Jinping-Sunan ±800kV UHV DC project, 1000kV Huainan-Zhebei-Shanghai UHV AC project, and Southern Hami-Zhengzhou ±800kV UHV DC project in adjustment as well as the East Shore of Xiluodu -Jinhua ±800kV UHV DC project and 1000kV Zhebei-Fuzhou UHV AC project that are under construction, are the results of scientific innovations as SGCC has tackled down problems that the world is now facing.

RWF: State Grid relies on the AC grid for redundancy
UHV DC realized domestic production

  It is learned that SGCC first invented the 6-inch thyristor and applied it in the Xiangjiaba - Shanghai project. The 800kV, 4500A, 1.8GW thyristor valves that SGCC made updated the world record in voltage, current, and capacity. The DC technology can now transmit in 8GW-level over 200km instead of 3GW-level within 1000km. Meanwhile SGCC created the first UHV converter transformer of the highest voltage and largest capacity but with the same transmission constraints as a 500kV converter transformer.

RWF: not sure what this means "The 800kV, 4500A, 1.8GW thyristor valves that SGCC made updated the world record in voltage, current, and capacity." I understand that SGCC increased the ampacity of the thyristor to 4500 amps by increasing its diameter; at the +/-800kV voltage level (which requires multiple series-connected thyristors), this corresponds to 7.2GW, the current best proven transmission capacity. I do not know what is meant by the "1.8 GW thyristor valves?" This appears to reference the 400kV modules that are used to form the converter. It would be more useful to know the voltage step per thyristor: is it still 8kV as is used by ABB, or have they advanced to the 12kV per thyristor step that was achieved in the USSR before their research was shut down by the collapse of the Soviet Union?
  Experts of the test run said that the technology of the UHV was successful and could be popularized in application. The project has maintained a stable operation since its launch 3 years ago, transmitting 47.3TWh of power in total, which provided a solid foundation for transmitting excessive hydropower from Xiangjiaba power station and the Southwest to other places, especially during summer peak time in 2013 when the machines were running overtime and with overload. The project greatly eased the pressure of power demand from East China such as Jiangsu, Zhejiang and Shanghai that suffered high temperature.

  In technology innovation, SGCC was never satisfied. It accelerated the development of UHV technology on the basis of the stable operation of Xiangjiaba–Shanghai project. Deputy Director of Department of DC Construction, Gao Liying introduced that with self-innovation, the company had another breakthrough in Jinping-Sunan project. The UHV DC system was completely domestically designed and the low-end converter transformer was also domestically researched and developed. China-made converter bushing was applied for the first time. Polar low-end stations also used independently developed UHV converter valves and control software for the first time. DC equipment was supplied by domestic manufacturers in set. All these signified that China was ready for systematic and domestic construction of ±800kV UHV projects.

RWF: Watch out, ABB, Siemens, and Alstom Grid! From SGCC's perspective it might look like the push towards multi-terminal HVDC, and voltage-source converters by the Western "Majors" is more about changing the game to their advantage than anything else. They may be right, but my reasons for advocating a supergrid are not influenced by those considerations.
  In addition, the Southern Hami-Zhengzhou ±800kV UHV DC project to be put into operation at the end of this year and the East Shore of Xiluodu -Jinhua ±800kV UHV DC project under construction have larger transmission capacity, more advanced technology and are more domesticized. They will further validate the advantages of UHV AC transmission with high capacity and high efficiency over long distances.

  Equip China with strong DC technology instead of just large DC capacity  

  “While bringing the economic and social benefits of UHV into play, SGCC also made a breakthrough in the core technology of high-end products based on construction of UHV  projects which helped to realize leapfrog development of manufacturing power transmission equipment. The most representative example is the research and application of UHV converter valve,”said Tang Guangfu, Director of the DC Department of the Institution of Smart Grid Research of SGCC and the general manager of CLP Power Engineering CO., Ltd, Purell, “A sophisticated system based on power electronic devices which combines knowledge of different sciences is difficult to control. To a certain extent, it represents the level in equipment manufacturing as well as scientific and technological innovation ability of a nation. So developing the UHV converter valve with full independent intellectual property rights is a strategic demand to construct the Strong and Smart Grid.”

  It is known that UHV converter valve is the core equipment of a UHV DC project, the electric power equipment that realizes large-capacity electricity transformation. But the manufacturing of the equipment used to be monopolized by multinationals like ABB and Siemens for a long time. In order to tackle this problem, SGCC developed the valve prototype with full independent intellectual property rights with reference to the experience in major DC projects, cooperation and collaboration, and solid scientific research. Now a test platform for converter valve with the highest test parameters in the world has been established.

  The prototype has a rated voltage level of ±800kV, a rated flow of 4500-5000A, and a fault current of 50kA. All these core technical parameters excel similar products from home and abroad while the cost was 20% less than that of the foreign ones. The demonstration devices of the valve has the highest test voltage of 80kV,
RWF: that answers my earlier question. An 80kV test voltage for an individual thyristor could potentially mean 24kV per series-connected thyristor in use (current ABB thyristors are used at 8kV per step; that implies one third as many thyristors! per 400kV converter module. If I have interpreted correctly, that is the biggest bit of news here!).
the highest steady-state DC test current of 6kA and the maximum fault current of 55kA, all representing the highest level in the world. The successful test of the converter valve can save 2 million yuan for each DC project in our country.

RWF: This is huge, potentially. What if Chinese Foreign Aid starts funding 800kV HVDC lines around the world?
  Tang Guangfu pointed out that the research and application of UHV converter valve made China the third country to master the core technology of UHV DC converter valve following Sweden and Germany, which altered the pattern in the international DC market and realized three transformations of China’s DC industry. 
RWF: Mitsubishi is also a technology leader.

Now equipment was not just made in China, but created by China. And the country is now leading in the industry instead of learning from other countries. The industrial pattern has changed from large DC capacity to strong DC technology.

RWF: Congratulations! SGCC can supply the current state of the art highest capacity HVDC line. The highest capacity on one set of towers is a double-circuit overhead powerline based on 800kV with SGCC valves @ 800kV: 7.2 GW/circuit times 2 circuits. This sets a very specific alternative product to compare elpipes against.

I would also like to publically disclose, and thus make this concept non-patentable (if it is not already): 
one can also have elevated, air insulated pipes (busbars that go many kilometers); that must also be considered as an alternative technology.
  Domestic UHV equipment realized mass production

  While continuing making progress in solving the problems in UHV DC technology, the development of UHV AC technology attracts worldwide attention.

  The 1000kV Jingdongnan-Nanyang-Jingmen AC transmission project is the first commercially operated 1000kV line in the world, which was commissioned five years ago. Before that, countries like the former Soviet Union, the United States, Italy and Japan have tried to develop such technology but failed to form mature technology and standards, not to mention system electrical equipment. However, this project conquered worldwide challenges in high voltage, strong current electromagnetism and insulation technology, breaking new records in six aspects including voltage control, external insulation technology, system equipment manufacturing, electromagnetic environment management, construction of demonstration projects, and experimental capability.

  Chen Weijiang, Deputy Director of AC Construction of SGCC, said that the project greatly enhanced China’s  scientific technology in electric power, upgraded power transmission and transformation equipment manufacturing industry, gained bigger voice for China on the international arena in the electrical technology industry, and established China’s leading role in world’s UHV industry.

  On 25th September, 1000kV Huainan-Zhebei-Shanghai UHV AC project was put into operation, establishing a milestone in the world’s UHV history. It is introduced that the project is the first commercially operated double-circuit UHV AC transmission project on same tower, whose transmission capacity per corridor is doubled than single-circuit technology. It represents the highest level in UHV AC transmission technology, equipment manufacturing and engineering application in the world.

  Chen Weijiang introduced that facing the challenges, SGCC organized people from over 100 organizations from the electric power industry and the mechanical industry to tackle a series of worldwide problems in areas of system design, equipment manufacturing, installation, testing and readjustment of the double-circuit UHV AC transmission system on the same tower through domestic research and independent innovation. It can be said that Huainan-Zhebei-Shanghai UHV AC project not only broke new records in UHV AC technology but also upgraded the electric equipment manufacturing industry.

  For example, the project first invented the loaded voltage-regulating UHV transformer and single-column UHV shunt reactor with a rated capacity of 240MW. The manufacturing quality and reliability of domestic UHV equipment has been systematically enhanced, able for mass production. In addition, based on the innovative experience, China has made leapfrog progress in the organization, management, S&T, manufacturing, construction and operation in the transmission and transformation projects, laying a solid foundation for large-scale construction of UHV grids.

  Adhere to independent innovation to command new height in S&T 

  SGCC never stops moving forward and innovating, which is the only way for eternal brightness. The company is now aiming at higher objectives after realizing the system design of  ±800kV UHV DC project and the domestication of overall construction.

  Gao Liying introduced that based on the research results of the ±800kV/5000A UHV converter valve, SGCC also successfully installed the world’s first valve tower prototype with ±1100kV/5000A UHV DC converter valve of independent property rights of China, a remarkable accomplishment in the high-end products of UHV industry. Its operational test was successfully conducted at the same time. This can play as a pillar to the demand from constructing higher-grade UHV DC projects, and enrich and improve the UHV theology.

  It is known that this scientific program carried out a series of scientific researches such as research on steady-state electromagnetic disturbance characteristics of large capacity UHV converter valve and research on upgrading the anti-electromagnetic ability of valve monitoring equipment in unfavorable electromagnetic conditions for the ±1100kV Zhundong-Sichuan UHV DC project. At the same time, the project put forward new design theories such as optimized design of grading and shielding system, light thyristor installation structure, and compacted triggering monitor system.

RWF: I think higher voltage than 800kV in a supergrid is not needed. If we go with the low cost conductor sodium, sealed in high strength alloy shells, then the lowest total cost for conductor + insulator occurs around 400-600kV...more on that below the SGCC document end.
  SGCC Chairman Liu Zhengya also introduced in the recently held International Smart Grid Forum that the transmission capacity for ±1100kV UHV DC technology and equipment could reach 13.75GW with an economic transmission distance of 5000km, providing the foundation for cross-regional, cross-national and cross-continental power transmission lines. With that Africa and the Middle East can be linked together, and there can be a big grid in South America.

  President of IEC, Dr. Klaus Wucherer pointed out resource was distributed unevenly in many countries. Since UHV can reduce the loss in long-distance transmission, it will have a bright future in other places of the world, too. Right now, China is leading in the technology of UHV transmission. The UHV AC voltage in China is promoted in the world as the international standard.  

  Source: China Energy News

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