PCC Voltage Feedback for Inverter Stability in Weak Grids
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Solution Overview
Problem
Existing control systems for inverter-based resources (IBRs) in weak grids face challenges in maintaining stability due to high grid impedance and low grid short-circuit strength, leading to oscillations and instability.
Innovation Solution
Implementing a high-pass filter and feedback control system to modulate the q-axis current order of IBRs, coordinating reactive current control among multiple IBRs to mitigate low-frequency oscillations and enhance stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If inverter-based resources are deployed in weak grid conditions, then power delivery capability is improved, but system stability deteriorates due to high grid impedance and low short-circuit strength
Solution Approach 1:
The patent implements a voltage feedback control system where the controller receives voltage feedback from the point of common coupling and uses it to regulate the q-axis current order of the inverter. This feedback mechanism enables the system to automatically adjust reactive current in response to voltage variations, thereby maintaining stability while delivering power in weak grid conditions.
Solution Approach 2:
The patent dynamically adjusts the q-axis current parameter based on voltage feedback to counteract the adverse effects of high grid impedance. By changing the reactive current parameter in response to grid conditions, the system maintains stability margins while preserving power delivery capability in weak grids.
2Device complexity
If conventional control systems are used in weak grids, then device simplicity is maintained, but oscillations and instability occur due to high grid impedance
Solution Approach 1:
The patent introduces a voltage feedback loop that connects the point of common coupling back to the controller. This feedback path enables the controller to sense voltage variations and adjust the q-axis current accordingly, providing a simple yet effective mechanism to dampen oscillations and enhance stability without requiring complex control architecture.
3Reliability
If reactive current control is coordinated among multiple IBRs, then stability margins are enhanced, but control coordination complexity increases
Solution Approach 1:
The patent implements a universal voltage feedback control scheme that can be applied to multiple inverter-based resources connected at the same point of common coupling. Each inverter uses the same control strategy based on local voltage feedback, enabling coordinated reactive current control across multiple IBRs without requiring complex inter-inverter communication or coordination protocols.
Data Source
AI summary
An example supplementary control for existing inverter control systems uses the PCC voltage as an input and outputs a signal to modulate the q-axis current order. The supplementary control can mitigate low-frequency oscillations in voltage through reactive current regulation.