Inverter Reactive Power Control for Grid-Weakness Stability
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Solution Overview
Problem
Wind farms face instability in reactive power command due to high gains in farm-level controllers, which can lead to unstable operation when grid strength reduces, especially during contingencies.
Innovation Solution
A system and method that monitors reactive power commands for oscillatory behavior, reducing gains of the volt-var regulator to stabilize the farm-level controller, using filters and algorithms to detect and mitigate instability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If high gains are used in the farm-level controller to meet fast voltage regulation requirements, then voltage regulation speed is improved, but system stability deteriorates when grid strength is reduced
Solution Approach 1:
The controller dynamically adjusts the gain of the volt/VAR regulator based on real-time detection of oscillatory behavior in reactive power commands. When oscillations are detected indicating instability, the gain is reduced to stabilize the system. This dynamic adjustment allows the system to maintain high voltage regulation speed under normal conditions while preventing instability when grid strength reduces, effectively resolving the contradiction between speed and stability.
2Loss of time
If high gains are maintained to ensure fast response, then response time is improved, but oscillatory behavior and instability increase under reduced grid strength
Solution Approach 1:
The system implements a feedback mechanism that continuously monitors the reactive power command signal for oscillatory behavior. When oscillations exceeding a threshold are detected, the system feeds back a signal to reduce the volt/VAR regulator gain, thereby eliminating the oscillatory behavior and ensuring stable operation. This feedback approach maintains fast response capability while preventing instability under varying grid conditions.
Data Source
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AI summary
A method for controlling a power system having at least one inverter-based resource connected to an electrical grid includes monitoring, via at least one controller of the at least one inverter-based resource, one or more command signals issued by a system-level controller. The method also includes determining, via the at least one controller of the at least one inverter-based resource, whether the one or more command signals issued by the system-level controller includes oscillatory behavior characteristic of an instability. In response to determining that the one or more command signals issued by the system-level controller includes oscillatory behavior characteristic of the instability, the method includes reducing one or more gains of a volt-var regulator of the system-level controller to reduce the instability.