Bipole HVDC Power Feed Balancing During Return Conduit Faults
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Solution Overview
Problem
In high voltage direct current (HVDC) power transmission networks, the absence of a functional return conduit leads to current imbalances between transmission conduits, causing undesirable current flow through the ground, which can harm marine life and corrode pipes, and requires expensive telecommunications for external input to maintain power transmission.
Innovation Solution
A bipole power transmission scheme with converter controllers that monitor and adjust power infeeds from independent power sources to match power feeds in each conduit, reducing imbalances and allowing continued power transmission without a return conduit, using frequency modifications and excess power absorbers to manage imbalances during faults.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If the return conduit is faulty and unable to provide a return current path, then power transmission can continue through the ground, but current imbalances cause harmful effects such as marine life damage and pipe corrosion
Solution Approach 1:
The converter controllers continuously monitor the power feeds from both transmission conduits and use this feedback to detect imbalances. When a return conduit fault is detected, the controllers adjust the power infeeds to maintain balance, preventing harmful ground currents while ensuring continuous power transmission
Solution Approach 2:
The system dynamically changes the power infeed parameters from independent variable values to balanced values when a return conduit fault occurs. The converter controllers modify the power transmission parameters to equalize the currents in both conduits, eliminating ground current flow while maintaining power delivery
2Object-affected harmful factors
If converter controllers monitor and adjust power infeeds to match, then current imbalances are reduced, but device complexity increases due to additional control mechanisms
Solution Approach 1:
The converter controllers perform multiple functions: normal power conversion, fault detection, imbalance monitoring, and automatic power infeed adjustment. By making the controllers multi-functional, the patent avoids adding separate dedicated devices for each function, thereby reducing overall system complexity while still achieving current balance
Solution Approach 2:
The converter controllers automatically detect imbalances and adjust power infeeds without external intervention. The system serves itself by using its own monitoring capabilities to maintain current balance, eliminating the need for complex external control systems or manual adjustment mechanisms
3Reliability
If independent power sources are used at each converter station, then system reliability is improved, but maintaining power transmission without a return conduit becomes difficult due to current imbalances
Solution Approach 1:
The independent power sources feed into converters with controllers that continuously monitor the power feeds. When a return conduit fault occurs, the feedback mechanism enables the controllers to detect and correct imbalances, allowing reliable operation with independent power sources even without a functional return conduit
Solution Approach 2:
The system dynamically changes the operating parameters of the independent power sources through the converter controllers. By adjusting the power infeed parameters to match between conduits, the system maintains ease of operation and reliable power transmission despite the absence of a return conduit
Data Source
AI summary
A bipole power transmission scheme with two independent converts, two power feed and one return conduit. During operation of the bipole power transmission scheme under abnormal conditions, when a return conduit is faulty and unable to provide a return current path, each converter controller is programmed to monitor the first power feed in the first transmission conduit and the second power feed in the second transmission conduit and, if the first power feed in the first transmission conduit and the second power feed in the second transmission conduit differ from one another, at least one converter controller modifies the power infeed from its corresponding power source to reduce the difference between the first power feed and the second power feed.