HV and LV Converter Station Segmentation for UHVDC Grid Stability
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Solution Overview
Problem
The existing UHVDC transmission systems face challenges such as high transmission costs and losses due to multiple AC loops, difficulty in transporting large HV transformers, and poor reliability and stability caused by over-strong short circuit currents, especially when power sources are located at remote distances from the converter stations.
Innovation Solution
The proposed solution involves setting UHV HV and LV converter stations at different physical locations, allowing for separate input and conversion of AC and DC powers, reducing the number of AC loops, and enabling direct power transmission to multiple load centers, thereby reducing construction and transportation costs and improving grid reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple power sources are converged via multi-path AC transmission to a single UHV converter station, then the power transmission capacity is improved, but the transmission cost and losses increase due to too many AC loops
Solution Approach 1:
The patent divides the converter station into separate HV and LV valve halls located at different physical positions. Each valve hall independently converts AC to DC, eliminating the need for multiple AC loops to converge at a single station. This segmentation reduces transmission losses while maintaining the ability to transmit large power capacities through parallel DC paths.
2Power
If HV transformers with large power capacity are installed in a single UHV converter station, then the power transmission capability is improved, but the transportation and construction difficulty increase due to their large dimension volume
Solution Approach 1:
The patent segments the converter station into separate HV and LV valve halls, each with its own transformers. This allows transformers to be installed at different locations optimized for their specific requirements, making transportation and construction easier while maintaining overall high power transmission capability through the combined system.
3Device complexity
If a single receiving end is used at the inversion side, then the converter station structure is simplified, but the grid reliability and stability deteriorate due to over-strong short circuit currents
Solution Approach 1:
The patent implements separate HV and LV valve halls at the inversion side, each capable of independent operation. This segmentation distributes the power reception points, reducing short circuit currents at any single point while maintaining a relatively simple overall structure. The modular design improves reliability without significantly increasing complexity.
4Adaptability or versatility
If power sources are located at remote areas, then the resource utilization is improved, but the construction cost and transportation difficulty increase due to the distance from the converter station
Solution Approach 1:
The patent allows different valve halls to be located at different positions, enabling the system to accept power from multiple remote sources more efficiently. Each valve hall can be optimally positioned relative to its power sources, reducing construction and transportation costs while maintaining the ability to utilize remote resources.
Data Source
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AI summary
Present invention discloses a connection method for UHVDC transmission, an UHV converter station and an UHVDC transmission system. An UHV LV converter station at rectification side converts a first AC power into a first low voltage DC power and transmits it to an UHV HV converter station at rectification side. The UHV HV converter station at rectification side converts a second AC power into DC power and superimposes it with the first low voltage DC power to generate a first UHV DC power and transmits it to an UHV HV converter station at inversion side. The UHV HV converter station at inversion side outputs a third AC power and a second low voltage DC power, supplies the third AC power to a first load area, and transmits the second low voltage DC power to an UHV LV converter station at inversion side, at which the second low voltage DC power is converted into a fourth AC power, which is supplied to a second load area. One or more UHV MV converter stations can be set between the HV and LV converter stations at both rectification side and inversion side. The respective UHV MV converter stations are cascaded via DC transmission line. The present invention employs a manner of multiple drop points to solve the problem of poor security stability of electric grid caused by feeding a large amount of power via one point.