HVDC Electronic Valve Parallel Chains for Thermal Load Sharing
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Solution Overview
Problem
The high thermal duty on safety valves in HVDC power transmission systems leads to decreased lifespan and increased cooling needs, posing a challenge in maintaining system reliability and efficiency.
Innovation Solution
Implementing a plurality of parallel chains of devices with asymmetric transfer functions, each chain having controllable switching devices and energy storage, to distribute the load and facilitate fault detection by applying reverse voltage for testing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single safety valve is used to block reverse current in HVDC transmission, then the system structure is simple, but the thermal stress on the valve is excessive leading to decreased lifespan
Solution Approach 1:
The patent divides the single safety valve into multiple parallel chains of devices (e.g., multiple diodes or thyristors in parallel). Each chain carries a portion of the forward current, distributing the thermal load and reducing stress on individual devices. This segmentation allows the system to maintain the same overall blocking capability while improving reliability and reducing thermal stress on each component.
2Reliability
If multiple parallel chains of devices are implemented to reduce thermal stress, then the lifespan and reliability improve, but the device complexity increases
Solution Approach 1:
The safety valve is segmented into multiple identical or similar parallel chains, each with the same structural configuration. This modular approach allows for standardized design and manufacturing, reducing the overall complexity despite the increased number of components. Each chain can be designed and tested independently, simplifying the development process.
Solution Approach 2:
Multiple parallel chains are combined to work together as a unified safety valve system. The chains are connected in parallel between the same input and output nodes, creating a redundant structure that maintains the same external interface while improving internal reliability. This merging approach allows the system to achieve enhanced performance without requiring fundamentally new design concepts.
3Difficulty of detecting and measuring
If controllable switching devices are added to each chain for fault detection, then the fault detection capability is enhanced, but the device complexity and cost increase
Solution Approach 1:
Controllable switching devices (such as thyristors or IGBTs) are integrated into each chain to enable active testing of the asymmetric devices. By preliminarily establishing the capability to apply reverse voltage through these switches, the system can detect faults in the diodes or thyristors before they lead to system failure. This preliminary action allows for proactive maintenance and improves system reliability.
Solution Approach 2:
The controllable switching devices enable feedback mechanisms for monitoring the health of each chain. By applying reverse voltage through the switches and monitoring the response, the system can detect degraded performance or failures in the asymmetric devices. This feedback capability allows for real-time assessment of system health and triggers appropriate maintenance actions.
Data Source
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AI summary
The present disclosure relates to an electronic valve apparatus for a high voltage direct current, HVDC, power transmission system. The electronic valve apparatus comprises a first device chain (301) including a plurality of first devices (302, 303) connected in series between an input node (330) and an output node (332) of the electronic valve apparatus (300, 400, 500). Each of the plurality of first devices (302, 303) has an asymmetric transfer function configured substantially to block current flow through the device in a first direction, and the plurality of first devices (302, 303) are connected such that they all block current flow in the same direction. The electronic valve apparatus also includes a second device chain (311) including a plurality of second devices (312, 313) connected in series between the input node (330) and the output node (332). Each of the plurality of second devices (312, 313) has an asymmetric transfer function configured substantially to block current flow through the device in a first direction, and the plurality of second devices (312, 313) are connected such that they all block current flow in the same direction. The second device chain (311) is connected in parallel with the first device chain (301).