AC Switch Stuck Detection in Parallel Converter Legs
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Solution Overview
Problem
Detecting stuck AC switches in converters with multiple parallel arrangements is cumbersome and inefficient, especially in high-power converter systems, as it requires significant effort and can lead to prohibitive costs and performance degradation due to homopolar current circulation.
Innovation Solution
A method involving sequential closure of AC switches and voltage measurement across AC legs, using a pre-charge unit and decoupling switches to identify stuck AC switches, allowing for efficient detection without disrupting the entire system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If each single AC switch is switched on and off for testing, then the stuck AC switch can be detected, but the effort for service personnel becomes considerable and prohibitive for high numbers of AC switches
Solution Approach 1:
The converter is divided into multiple converter arrangements arranged in parallel, each with its own DC part, converter unit, and AC part. This segmentation allows individual testing of each arrangement without affecting others, reducing overall testing complexity while maintaining detection accuracy for stuck AC switches.
Solution Approach 2:
A decoupling switch is introduced as an intermediary component between the DC part and AC part of each converter arrangement. This decoupling switch enables isolated testing of individual arrangements by disconnecting them from the parallel system during testing, significantly reducing the effort required compared to testing all switches in the complete system.
2Adaptability or versatility
If multiple power converters are connected in parallel to build modular systems, then flexibility and redundancy are improved, but detecting stuck AC switches becomes more complex and costly
Solution Approach 1:
The parallel converter system is segmented into independent converter arrangements, each with identical functional modules (DC part, converter unit, AC part). This modular segmentation maintains system flexibility and redundancy while simplifying detection procedures, as each module can be tested independently using the same methodology.
Solution Approach 2:
The decoupling switch is configured to enable preliminary isolation of individual converter arrangements before testing. By opening the decoupling switch, a specific arrangement can be disconnected from the parallel system and tested in isolation, preventing detection complexity from scaling with the number of parallel converters.
3Loss of time
If sequential closure and voltage measurement method is used, then detection effort is minimized, but the system requires additional decoupling switches and pre-charge units
Solution Approach 1:
A decoupling switch serves as an intermediary that enables rapid isolation of individual converter arrangements. This single component allows the sequential closure and voltage measurement method to be applied efficiently to each arrangement without requiring complex testing equipment or procedures, minimizing detection time despite the added component.
Solution Approach 2:
The decoupling switch and pre-charge unit serve multiple functions: they enable isolated testing of individual arrangements, protect the system during testing, and maintain normal operation when closed. This multi-functionality justifies the additional components by eliminating the need for separate testing equipment and procedures for each converter arrangement.
Data Source
AI summary
A converter arrangement connects to a DC source or load and to a plurality of AC terminals. Each converter arrangement includes a DC part with two capacitors arranged in parallel to the DC source or DC load and a neutral DC point between them. At least one AC leg is connected to a neutral AC point via an AC leg capacitor. A pre-charge unit is arranged at each leg of the AC terminal. The method includes opening a decoupling switch and all second AC switches; loading the pre-charge unit; sequentially closing each second AC switch; measuring at each closing step a voltage between each AC leg of the second converter arrangement; and determining the stuck AC switch of the second converter arrangement based on the measured voltage.