Bipole Converter Station Layout for Transient Fault Reliability
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Solution Overview
Problem
High voltage direct current (HVDC) power transmission networks face challenges in cost-effectiveness and reliability due to the need for extensive converter stations, particularly in bipole power transmission schemes, where existing methods do not adequately address transient fault conditions and capital costs.
Innovation Solution
The design incorporates a bipole power transmission scheme with voltage source converters featuring chain-link converters, where the number of series-connected chain-link modules is optimized to balance energy storage and reduce capital costs, footprint, and maintenance burdens, while ensuring reliability through controlled stepped variable voltage sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the number of series-connected chain-link modules is increased to withstand transient fault conditions, then reliability is improved, but capital cost and device complexity increase
Solution Approach 1:
The patent applies local quality by differentiating the number of chain-link modules in specific converter limbs (first and fourth) versus others (second and third). The first and fourth limb portions have a greater number of series-connected chain-link modules to handle transient fault conditions, while the second and third have fewer modules. This localized differentiation optimizes reliability where needed without unnecessarily increasing complexity system-wide.
Solution Approach 2:
The patent implements partial action by providing the greater number of chain-link modules only in specific limb portions (first and fourth) rather than uniformly across all converters. This selective approach provides sufficient protection against transient faults in critical areas while avoiding excessive complexity and cost in non-critical areas.
2Reliability
If the number of series-connected chain-link modules is increased to withstand transient fault conditions, then reliability is improved, but capital cost increases
Solution Approach 1:
The patent applies local quality by differentiating the number of chain-link modules in specific converter limbs (first and fourth) versus others (second and third). The first and fourth limb portions have a greater number of series-connected chain-link modules to handle transient fault conditions, while the second and third have fewer modules. This localized differentiation optimizes reliability where needed without unnecessarily increasing complexity system-wide.
3Device complexity
If the number of chain-link modules is reduced to lower capital cost, then capital cost is reduced, but reliability under transient fault conditions deteriorates
Solution Approach 1:
The patent applies local quality by differentiating the number of chain-link modules in specific converter limbs (first and fourth) versus others (second and third). The first and fourth limb portions have a greater number of series-connected chain-link modules to handle transient fault conditions, while the second and third have fewer modules. This localized differentiation optimizes reliability where needed without unnecessarily increasing complexity system-wide.
4Area of stationary object
If the number of chain-link modules is reduced to minimize footprint, then area is reduced, but cooling requirements and operational complexity increase
Solution Approach 1:
The patent applies local quality by differentiating the number of chain-link modules in specific converter limbs (first and fourth) versus others (second and third). The first and fourth limb portions have a greater number of series-connected chain-link modules to handle transient fault conditions, while the second and third have fewer modules. This localized differentiation optimizes reliability where needed without unnecessarily increasing complexity system-wide.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enhances the reliability of HVDC power transmission networks by reducing capital costs, minimizing the overall structure and cooling requirements, and simplifying control systems, thereby improving operational efficiency and cost-effectiveness.
Implementation Method 1
each chain-link module including a first pair of switching elements connected in parallel with an energy storage device
Data Source
Figure 1
Figure 2
AI summary
In the field of bipole power transmission schemes there is a need for an improved converter station. A converter station (10), for a bipole power transmission scheme, comprises a first voltage source converter (12) which has a first terminal (14), for connection to a first transmission conduit, and a second terminal (16) for connection to a return conduit. The first voltage source converter (12) also includes at least one converter limb (18A, 18B, 18C) which extends between the first and second terminals (14, 16). The or each converter limb (18A, 18B, 18C) includes first and second limb portions (20A, 20B, 20C, 22A, 22B, 22C) that are separated by a corresponding first AC terminal (24A, 24B, 24C) which is for connection to a respective phase (A, B, C) of a first AC network. The or each first limb portion (20A, 20B, 20C) includes a first chain-link converter (26) that extends between the associated first AC terminal (24A, 24B, 24C) and the first terminal (14), and the or each second limb portion (22A, 22B, 22C) includes a second chain-link converter (28) which extends between the associated first AC terminal (24A, 24B, 24C) and the second terminal (16). Each chain-link converter (26, 28) includes a plurality of series connected chain-link modules (30), each of which has a plurality of switching elements connected in parallel with an energy storage device, whereby each chain-link converter (26, 28) is controllable to provide a stepped variable voltage source. The converter station (10) additionally includes a second voltage source converter (32) which has a third terminal (34), for connection to a second transmission conduit, and a fourth terminal (36), for connection to the return conduit. The second voltage source converter (32) also includes at least one converter limb (18A, 18B, 18C) which extends between the third and fourth terminals (34, 36). The or each converter limb (18A, 18B, 18C) includes third and fourth limb portions (38A, 38B, 38C, 40A, 40B, 40C) which are separated by a corresponding second AC terminal (42A, 42B, 42C), for connection to a respective phase (A, B, C) of a second AC network. The or each third limb portion (38A, 38B, 38C) includes a third chain-link converter (44) that extends between the associated second AC terminal (42A, 42B, 42C) and the third terminal (34), and the or each fourth limb portion (40A, 40B, 40C) includes a fourth chain-link converter (46) which extends between the associated second AC terminal (42A, 42B, 42C) and the fourth terminal (36). Each chain-link converter (44, 46) includes a plurality of series connected chain-link modules (30), each of which has a plurality of switching elements connected in parallel with an energy storage device, whereby each chain-link converter (44, 46) is controllable to provide a stepped variable voltage source. Also, each of the second and third chain-link converters (28, 44) includes a first number (58) of series-connected chain-link modules (30), and each of the first and fourth chain-link converters (26, 46) includes a second number (52) of series-connected chain-link modules (30), the second number (52) being greater than the first number (58).