Selective Tripping in Redundant UPS Systems via d-q Power Analysis
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Solution Overview
Problem
Existing parallel redundant power systems face challenges in selective tripping, where a faulty UPS can cause disturbances on the critical bus, leading to potential loss of redundancy due to slow response times and reliance on external signaling, which can be unreliable and memory-intensive.
Innovation Solution
The use of a d-q component transformer to generate voltage and current values, combined with filtering and power value generation to detect faults, allows for efficient characterization of fault conditions and control of power systems, enabling selective tripping without inter-unit signaling by determining the direction of power flow changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Difficulty of detecting and measuring
If inter-unit signaling is used for selective tripping, then fault detection capability is improved, but system reliability deteriorates due to single failure points in signaling circuits
Solution Approach 1:
Each UPS unit independently monitors its own output current and compares it against a reference current to detect faults, eliminating the need for inter-unit signaling. The system serves itself by using locally available measurements rather than external signals, thereby removing single failure points in signaling circuits while maintaining fault detection capability.
2Measurement precision
If vector addition of difference from average current signal is used, then fault characterization is improved, but response time deteriorates due to signal comparison and logical processing requirements
Solution Approach 1:
The patent extracts only the essential fault detection function by directly comparing instantaneous current measurements against a reference, eliminating the complex vector addition and signal comparison processes. This extraction of the core functionality achieves fast response times while maintaining adequate fault characterization through the simplified comparison operation.
3Reliability
If redundant inter-unit signaling is implemented, then selective tripping robustness is improved, but device complexity increases due to additional signaling circuits
Solution Approach 1:
The system achieves robust selective tripping without additional signaling circuits by having each unit independently perform fault detection using its own current measurements. This self-service approach eliminates the need for redundant inter-unit signaling infrastructure, thereby reducing device complexity while maintaining or improving selective tripping robustness through decentralized fault detection.
Data Source
AI summary
An apparatus can include a fault condition detector configured to detect a fault condition in an electrical system, a delta d-q power value generator configured to generate a delta d-q power value temporally corresponding to the detected fault condition, and a characterizer circuit configured to characterize the fault condition relative to the apparatus responsive to the delta d-q power value. Methods can include detecting a fault condition in an electrical system and determining changes in d-q component voltage and current temporally corresponding to the detected fault condition. Such methods can further include characterizing the fault condition responsive to the determined first and second changes and controlling an apparatus based on characterizing the fault condition.