Wind Turbine Reactive Current Pulse Control for Grid Fault Response
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Solution Overview
Problem
Wind turbines often face challenges in meeting grid code requirements for reactive current response time during low-voltage events, as their current regulators may not respond quickly enough to maintain connection and supply energy during grid faults.
Innovation Solution
A method and system that utilize a controller to generate a reactive current pulse command, combining it with the existing reactive current reference command to achieve a transiently higher total reactive current command, improving response time while preventing excessive current levels by determining the pulse's magnitude and duration based on grid voltage deviations and system capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the wind turbine uses the fastest current regulators available, then the current response speed is improved, but it still cannot meet the grid code requirements for reactive current response time during low-voltage events
Solution Approach 1:
The controller issues a pre-calculated reactive current reference command that anticipates the required response magnitude and timing. This preliminary action ensures the power converter is prepared to deliver the exact current needed to meet grid code requirements during low-voltage events, resolving the contradiction between available regulator speed and required response performance.
Solution Approach 2:
The system dynamically adjusts the reactive current reference command parameters based on grid conditions. By changing the current reference magnitude and timing parameters in response to detected voltage sags, the system optimizes the response to meet grid code requirements while utilizing the capabilities of the existing current regulators.
2Loss of time
If the wind turbine increases the reactive current magnitude beyond grid code requirements to speed up response time, then the response time is improved, but excessive current may surpass system capabilities
Solution Approach 1:
The controller implements a two-stage reactive current response: an initial higher magnitude current pulse that exceeds the minimum grid code requirement to achieve faster response time, followed by a reduction to the sustained grid code-required level. This partial excessive action provides the speed benefit while limiting the duration of high current to prevent system overload.
Solution Approach 2:
The reactive current reference command is made dynamic, with the controller continuously adjusting the current magnitude based on real-time system conditions and the evolving grid fault characteristics. This dynamic adjustment allows the system to temporarily exceed rated current when necessary for fast response while automatically reducing current when system limits are approached, resolving the contradiction between response speed and system safety.
Data Source
AI summary
The present disclosure is directed to a system and method for improving reactive current response time in a renewable energy power system connected to a power grid. The method includes providing, via a controller of the power system, a permissive logic relating to the power grid. Another step includes determining, via a controller of the renewable energy power system, a reactive current reference command for the renewable energy power system in response to the permissive logic being satisfied. The method also includes generating, via the controller, a reactive current pulse command for the renewable energy power system. Thus, the controller is configured to determine a total reactive current command by combining the reactive current reference command and the reactive current pulse command. Further, the method includes operating the renewable energy power system based on the total reactive current command so as to improve the current response time.