Flying Capacitor Converter Fault Detection Using Current Gradients
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Solution Overview
Problem
High-voltage flying capacitor converters require expensive switches, and existing fault detection methods are inadequate for real-world operation, particularly for short circuit detection.
Innovation Solution
A method and apparatus for detecting faults in flying capacitor converters by measuring currents and current gradients using multiple sensors, allowing for the detection of short circuits, other faults, and ground faults, and enabling disconnection of faulty switches to prevent damage, using a configuration of cells with flying capacitors and MOSFET transistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If expensive high-voltage converter switches are used, then the converter can operate at high voltages, but the cost increases significantly
Solution Approach 1:
The patent divides the high-voltage converter into multiple cells, each operating at a lower voltage level. By segmenting the overall voltage into smaller portions handled by individual cells with low-voltage switches, the system achieves high-voltage operation through series connection of cells while using affordable low-voltage switching components throughout.
2Measurement precision
If multiple current sensors are used for comprehensive fault detection, then detection accuracy improves, but device complexity increases
Solution Approach 1:
The patent makes the current sensors serve multiple functions: they detect both overcurrent conditions and overvoltage conditions on the flying capacitors. By analyzing current magnitude and rate of change (di/dt) with intelligent processing, a single sensor setup provides comprehensive protection against multiple fault types, eliminating the need for separate voltage sensors on each capacitor.
Solution Approach 2:
The patent replaces physical voltage sensing components (voltage sensors) with an electrical measurement approach using current sensors combined with di/dt analysis. This substitution reduces hardware complexity while maintaining comprehensive fault detection capability through mathematical processing of current waveforms.
Data Source
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AI summary
The invention relates to the field of flying capacitor converters, particularly for high voltages. The flying capacitor converter (10) comprises a converter input comprising a positive pole (PP) and a negative pole (NP), an output terminal (OT), and a plurality of cells, each comprising two switches (Si, S3, S2, S4) and a flying capacitor (Cfc1, Cfc2) arranged between each cell. The invention further relates to a method for detecting a plurality of faults in the converter, the method comprising the steps of: measuring, by a second current sensor (CT2) arranged at the positive pole (PP), a second current (cu2); measuring, by a third current sensor (CT3) arranged at the negative pole (NP), a third current (cu3); and detecting a first fault in the flying capacitor DC/AC converter (10), if the second current (cu2) or if the third current (cu3) exceeds a first current threshold, and/or if a gradient of the second current (cu2) or a gradient of the third current (cu3) exceeds a first gradient threshold.