Grid-Forming Power Converter Current Limiting During Voltage Transients
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Solution Overview
Problem
Grid-forming power converters face challenges in maintaining voltage support and overcurrent capability during transient states, leading to potential overheating, failure, or explosion due to poor overcurrent handling.
Innovation Solution
A power converter with a controller that switches between steady-state, transient voltage stabilization, and transient voltage regulation modes to manage current output and virtual impedance, adjusting the ratio of active to reactive current to stabilize voltage and limit current, enhancing grid-forming capability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the power converter operates in grid-forming mode during transient states, then voltage support capability is improved, but overcurrent risk increases leading to potential device failure
Solution Approach 1:
The patent implements dynamic current threshold adjustment based on real-time voltage detection. When voltage exceeds the preset range during transient states, the controller dynamically switches from a first current threshold to a second current threshold, enabling adaptive current limiting that maintains voltage support while preventing overcurrent damage
Solution Approach 2:
The controller changes the current threshold parameter from the first current threshold to the second current threshold based on voltage conditions. This parameter change allows the system to tolerate higher currents during transient voltage fluctuations while still providing voltage support, effectively resolving the contradiction between reliability and overcurrent risk
2Object-affected harmful factors
If current limiting is performed by switching to grid following mode, then overcurrent risk is reduced, but grid-forming capability is lost
Solution Approach 1:
The patent maintains grid-forming capability dynamically during transient states by detecting voltage conditions and adjusting current thresholds accordingly. The system remains in grid-forming mode throughout transient events, switching only the current threshold parameter rather than the operational mode, thus preserving voltage support and frequency regulation capabilities while managing overcurrent risk
3Reliability
If the power converter withholds current margin for safety, then device protection is improved, but overcurrent capability utilization decreases
Solution Approach 1:
The patent changes the current threshold parameter dynamically based on voltage conditions. During normal operation, the first current threshold provides adequate protection margin. During transient voltage fluctuations, the second current threshold is applied, which is higher than the first threshold, allowing full utilization of the semiconductor device's overcurrent capability while still maintaining device protection through controlled current limiting
Data Source
AI summary
A power converter and a method. When the voltage at the grid connection point exceeds the preset voltage range and an amplitude of a voltage output by the power conversion circuit is not greater than a voltage threshold, embodiments can control the amplitude of the current output by the power conversion circuit to be not greater than a second current threshold, where the second current threshold is greater than the first current threshold, and a ratio of an active current to a reactive current output by the power conversion circuit is constant or changes; or, when the amplitude of the voltage output by the power conversion circuit is greater than the voltage threshold, embodiments can control the amplitude of the current output by the power conversion circuit to be equal to the second current threshold, where the ratio of the active current to the reactive current changes.