Grid-Forming Converter Fault Control via Selective Switch Blocking
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Solution Overview
Problem
Grid-forming converters, such as Smart Transformers, face challenges in handling faults due to their low overload capability, which can lead to premature intervention and loss of selectivity in grid-breakers, causing unintended power supply disruptions.
Innovation Solution
A method that detects faults and switches the converter to a fault operating mode, blocking semiconductor switches to protect the converter while maintaining grid-breaker selectivity by gradually increasing output voltage and potentially switching to a square-wave mode to manage high short circuit currents, thereby integrating with existing protection systems without changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the converter blocks semiconductor switches rapidly to protect itself from high current, then converter protection is improved, but grid-breaker selectivity is lost
Solution Approach 1:
The converter detects fault conditions and blocks semiconductor switches in advance before the grid-breaker would naturally trip, preventing converter damage while allowing the grid-breaker selectivity to be maintained through controlled timing
Solution Approach 2:
The converter dynamically adjusts its response to fault conditions by implementing a staged blocking strategy that adapts to the severity and type of fault, balancing self-protection needs with grid-breaker selectivity requirements
2Reliability
If the converter interrupts short circuit current before the breaker, then converter safety is improved, but power supply to the distribution network is interrupted
Solution Approach 1:
The converter implements selective blocking of only the affected phase or phases during fault conditions, maintaining power supply continuity for healthy phases while protecting itself from damage in the faulty phase
Solution Approach 2:
The converter applies partial blocking action by selectively interrupting current in only the faulty phase rather than completely shutting down all phases, thus providing adequate protection while minimizing impact on overall power supply
Data Source
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AI summary
The invention relates to a method for controlling a grid-forming converter, the converter comprising semiconductor switches and a control unit which controls the semiconductor switches. The invention further relates to a computer program for computer controlled execution of such a method and a grid-forming converter which is arranged for executing such a method.