Power Converter Protection via Segmented AC DC Fault Detection
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Solution Overview
Problem
In DC power transmission systems, existing protection devices using Rogowski coils struggle to accurately detect faults due to the presence of both DC and AC components, leading to potential damage from fault currents in power converters.
Innovation Solution
A protection device that includes a current input unit for AC currents, a current change rate input unit using an air core Rogowski coil for DC currents, and a fault determination unit to assess fault occurrence based on both AC current values and DC change rates, enabling timely and accurate fault detection and protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a Rogowski coil is used to detect current temporal change for power converter protection, then the protection response speed is improved, but the fault detection accuracy deteriorates due to the presence of both DC and AC components in the current
Solution Approach 1:
The patent segments the fault detection function into two independent parts: a Rogowski coil for detecting AC component temporal changes (providing fast response) and a DC current detector for detecting DC component changes (providing accurate fault determination). Each detector handles a specific current component, allowing both speed and accuracy requirements to be met simultaneously without interference between the AC and DC detection functions.
2Device complexity
If only a Rogowski coil is used for fault detection, then the device complexity is reduced, but the reliability of fault determination deteriorates due to inability to accurately distinguish faults from normal AC component variations
Solution Approach 1:
The protection device is segmented into specialized detection units: a Rogowski coil unit for AC component detection and a DC current detector unit for DC component detection. This segmentation allows each unit to be optimized for its specific function, improving reliability while keeping each individual unit relatively simple in structure.
Solution Approach 2:
The patent introduces an intermediary processing unit that receives signals from both the Rogowski coil and DC current detector, processes these signals according to predetermined criteria, and generates the final protection command. This intermediary unit acts as a mediator that combines information from both detectors to make reliable fault determination, distinguishing actual faults from normal operational variations.
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 solution allows for swift and precise fault detection and disconnection of power converters, preventing damage from fault currents and minimizing disruptions in the DC power transmission system.
Implementation Method 1
a Rogowski coil configured to detect a temporal change in a main circuit current flowing through the switching element
Data Source
AI summary
A protection device for a power converter provided between an AC system and a DC power transmission system is configured to: receive an input of an AC current value obtained between a transformer connected to the AC system and the power converter capable of converting AC power into DC power; receive an input of a change rate of a direct current detected by a Rogowski coil provided between a DC line and the power converter, the DC line receiving DC power from the power converter; determine based on the AC current value and the change rate whether a fault occurs or not in one of the power converter and the DC line; and output information for protecting the power converter based on a determination result.