Parallel Converter AC Switch Detection Using Pre-Charge Voltage
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Solution Overview
Problem
Detecting stuck AC switches in converters with multiple parallel arrangements is cumbersome and costly, especially in high-power converter systems, as standard testing methods can trigger overcurrent protections and degrade system performance.
Innovation Solution
A method involving sequential closure and voltage measurement of AC switches, utilizing a pre-charge unit and decoupling switches to identify stuck AC switches without disrupting the operational converters, thereby allowing for safe and efficient detection before system startup or during service routines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If standard testing methods are used to detect stuck AC switches in converters with multiple parallel arrangements, then detection capability is achieved, but system performance degrades and overcurrent protections are triggered
Solution Approach 1:
The patent applies preliminary action by performing the stuck switch detection before the converter is switched on or during service routines when the converter is not operating. This allows detection to be performed without interfering with normal operation, thus maintaining system performance while achieving detection capability.
Solution Approach 2:
The patent introduces an intermediary measurement approach by using voltage measurements across AC legs instead of direct current-based testing. This intermediary method allows detection of stuck switches through voltage differences without triggering overcurrent protections, resolving the contradiction between detection capability and system performance.
2Measurement precision
If each single AC switch is switched on and off for testing, then detection accuracy is improved, but service effort becomes prohibitive
Solution Approach 1:
The patent segments the detection process by focusing measurements only on the neutral point connections of parallel converter arrangements rather than testing each AC switch individually. This segmentation maintains detection accuracy for stuck switches while dramatically reducing service effort by measuring voltage at strategic points rather than manipulating each switch.
Solution Approach 2:
The patent enables the system to perform self-diagnosis by automatically measuring voltages and determining stuck switches without requiring manual switching operations. The converter arrangement itself provides the measurement signals needed for detection, eliminating the need for service personnel to manually test each switch.
3Adaptability or versatility
If multiple power converters are connected in parallel for redundancy, then system flexibility and reliability are improved, but detection complexity increases
Solution Approach 1:
The patent exploits the equipotential relationship at the neutral points of parallel converter arrangements. By measuring voltages relative to the neutral point, the method simplifies detection across multiple parallel converters, as all neutral points should be at the same potential. This approach maintains system flexibility while reducing detection complexity by providing a common reference point.
Solution Approach 2:
The patent creates a universal detection method that works for any number of parallel converter arrangements by measuring voltages at the neutral point. This single measurement approach serves multiple functions: detecting stuck switches, verifying parallel connection integrity, and working with any converter configuration, thus reducing detection complexity while maintaining adaptability.
Data Source
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AI summary
The invention relates to the field of converters, e.g. DC/AC or AC/DC converters, and particularly to a method for detecting a stuck AC switch (Sa1, Sb1, Sc1, San, Sbn, Scn) in a converter with a plurality of converter arrangements (10.1, 10.n), arranged in parallel. Each of the converter arrangements (10.1, 10.n) is configured for connecting to a DC source or DC load (20), and to a plurality of AC terminals (30). Each converter arrangement (10.1, 10.n) comprises a DC part (14.1, 14.n), with two capacitors (Cp1, Cn1), arranged in parallel to the DC source or DC load (20), and a neutral DC point (O1, On) between them. Further, each converter arrangement (10.1, 10.n) comprises a converter unit (12.1, 12.n) and at least one AC leg (a.1, b.1, c.1, a.n, b.n, c.n), each AC leg connected to a neutral AC point (N1, Nn) via an AC leg capacitor (Cfa1, Cfb1, Cfc1, Cfan, Cfbn, Cfcn). A pre-charge unit (40), arranged at each leg of the AC terminal (30). Between the neutral DC point (O1, On) and the neutral AC point (N1, Nn), a decoupling switch (So1, Son) is arranged. The method comprising the steps of: opening the second decoupling switch (Son) and all second AC switches (San, Sbn, Scn) of the second converter arrangement (10.n); loading the pre-charge unit (40); sequentially closing each second AC switch (San, Sbn, Scn) of the second converter arrangement (10.n); measuring, at each closing step, a voltage (Vabn, Vbcn, Vcan) between each AC leg (a.n, b.n, c.n) of the second converter arrangement (10.n); and determining the stuck AC switch (San, Sbn, Scn) of the second converter arrangement (10.n) based on the measured voltage (Vabn, Vbcn, Vcan).