电气设备：当前时点，怎么看待柔直技术的发展趋势？

Investment Rating - The report maintains a "Positive" investment rating for the flexible direct current (DC) transmission technology sector [7]. Core Insights - The report highlights that China has reached a historical turning point for the large-scale application of direct current technology, with various levels of DC projects emerging. The flexible DC transmission technology is being widely applied, although there are still differing opinions on its future application prospects [3][7]. - The necessity of flexible DC technology is emphasized due to its ability to address the major drawback of conventional DC transmission, which is the risk of commutation failure. Statistics from the State Grid Corporation indicate that there were 1,353 commutation failures from 2004 to the end of 2018, averaging 9.1 failures per year [7][41]. - The economic viability of ultra-high voltage flexible DC technology is discussed, showing that the cost increase for flexible DC stations is relatively modest compared to conventional stations, with a total cost increase of approximately 11.38 billion yuan [8][70]. - The report identifies multiple application scenarios for flexible DC technology, including long-distance transmission, offshore wind power delivery, and interconnection between regions [9][82]. - Various flexible DC transmission technologies are expected to coexist, with options like HCC, CLCC, SLCC, and IGCT-MMC showing potential for future applications [10]. Summary by Sections Necessity of Flexible DC Technology - Flexible DC transmission technology, based on Voltage Source Converters (VSC), is essential due to its advantages over conventional DC technology, particularly in preventing commutation failures [7][41][67]. - The report cites that conventional DC systems are prone to failures due to reliance on stable AC voltage, which can lead to significant operational risks [41][67]. Economic Aspects of Ultra-High Voltage Flexible DC - The report analyzes the cost structure of flexible DC projects, indicating that the increase in costs is manageable and that the technology has reached an economically viable stage [8][70][80]. - The estimated transmission price for the Gansu-Zhejiang project is around 8.706 cents/kWh, which is only slightly higher than other existing projects, indicating a reasonable pricing level [80][81]. Application Scenarios for Flexible DC Technology - Flexible DC technology is applicable across all voltage levels and can be used in various scenarios, including offshore wind power and multi-terminal networks [9][82]. - The report highlights ongoing projects, such as the Yangjiang Sanshan Island offshore wind power project, which aims to utilize flexible DC technology for efficient power delivery [86][92]. Various "Flexible" DC Transmission Technologies - The report anticipates that multiple flexible DC technologies will be developed, with a focus on balancing cost and performance [10].