Open Phase Detection Using Reactor Capacitor Current Differences
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Solution Overview
Problem
Existing open phase detection systems in power conversion systems, which rely solely on current amplitudes, often erroneously detect an open phase, especially during low output conditions, due to detection errors and impedance variations, leading to incorrect shutdowns.
Innovation Solution
An open phase detection system that utilizes both current amplitude and phase differences between the reactor and capacitor currents, with threshold-based abnormality detection units to accurately determine an open phase, reducing erroneous detections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If open phase detection is performed using only current amplitude, then the detection system is simple, but erroneous detection occurs during low output conditions
Solution Approach 1:
The patent transitions from one-dimensional amplitude-only detection to two-dimensional detection by incorporating both amplitude and phase difference parameters. The phase difference abnormality detection unit and amplitude difference abnormality detection unit work together to evaluate open phase conditions from multiple dimensions, preventing erroneous detections during low output conditions while maintaining system reliability.
2Reliability
If both amplitude and phase detection are used, then detection accuracy is improved, but device complexity increases
Solution Approach 1:
The detection system is segmented into distinct functional units: a phase difference abnormality detection unit that evaluates phase differences between reactor and capacitor currents, and an amplitude difference abnormality detection unit that evaluates amplitude differences. This segmentation allows complex detection logic to be divided into manageable modules, improving accuracy while organizing system complexity into structured, maintainable components.
3Ease of operation
If current amplitude only is used for detection, then the detection method is simple, but false positives occur during low output operation
Solution Approach 1:
The patent introduces phase difference as an intermediary parameter that mediates between the simple amplitude measurement and the accurate open phase detection. By evaluating both the phase difference between reactor and capacitor currents and the amplitude difference, the system achieves precise detection without sacrificing operational simplicity, as the additional phase evaluation provides a reliable discriminator against false positives during low output operation.
Data Source
AI summary
An open phase detection system for a power conversion system includes a phase difference abnormality detection unit, an amplitude difference abnormality detection unit, and an open phase determination unit. The phase difference abnormality detection unit outputs a phase difference abnormality signal when an absolute value of a phase difference between a current flowing through a reactor and a current flowing through a capacitor is equal to or smaller than a phase threshold value. The amplitude difference abnormality detection unit outputs an amplitude difference abnormality signal when an absolute value of a value based on an amplitude difference between the current flowing through the reactor and the current flowing through the capacitor is equal to or smaller than an amplitude threshold value. The open phase determination unit outputs an open phase signal when receiving inputs of both the phase difference abnormality signal and amplitude difference abnormality signal.