Wind Plant Reactive Power Control Using Tap Changer and Converter Overload
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Solution Overview
Problem
Existing wind power plants face challenges in efficiently controlling reactive power exchange between a power grid and a wind power plant during sudden changes in voltage, often requiring over-dimensioning with costly compensation equipment.
Innovation Solution
A method that combines the use of a power plant transformer's on-load tap changer with the short-term overload capability of power converters in wind turbine generators to rapidly adjust reactive power exchange, thereby meeting grid code requirements without over-dimensioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If compensation equipment such as capacitor banks, STATCOM or SVC is installed to meet reactive power requirements during voltage changes, then reactive power delivery capability is improved, but investment costs increase due to over-dimensioning
Solution Approach 1:
The power converters in wind turbine generators are designed to perform multiple functions: their primary function is active power generation, but they are also configured to provide reactive power support during voltage disturbances. By utilizing the existing power converters for both active and reactive power delivery, the invention eliminates the need for separate compensation equipment, thereby reducing investment costs while maintaining adequate reactive power delivery capability
Solution Approach 2:
The wind power plant uses its own internal resources (the power converters already present in each wind turbine generator) to provide reactive power support during voltage changes. Instead of relying on external compensation equipment, the system serves itself by enabling the power converters to operate in a mode that delivers both active and reactive power, thus avoiding additional investment in separate compensation devices
2Power
If tap-changing transformer is used to maximize reactive power capability, then reactive power delivery is improved, but response time is too slow to meet TSO requirements during sudden voltage changes
Solution Approach 1:
The invention replaces the mechanical tap-changing transformer system with an electronic control approach using power converters. Instead of relying on the slow mechanical movement of tap changers to adjust reactive power capability, the system uses electronic modulation of the power converters to rapidly change reactive power output, achieving response times that meet TSO requirements for voltage disturbance mitigation
3Power
If wind power plant is over-dimensioned to provide power and reactive power above nominal level, then reactive power delivery during voltage changes is improved, but nominal power production capability is not increased and investment costs rise
Solution Approach 1:
The power converters are designed to operate beyond their steady-state ratings for short durations during voltage disturbances. By allowing temporary excessive reactive power delivery (partial overload) during critical events like voltage sags or swings, the system achieves the required reactive power support without needing to be permanently over-dimensioned, thus avoiding increased investment costs while maintaining adequate capability during emergencies
Data Source
AI summary
The invention relates to wind turbines, particularly to controlling reactive power exchange between a power grid and a wind power plant. The wind power plant has a plurality of wind turbine generators each having a corresponding power converter with a converter controller. Further, the wind power plant has a power plant transformer with an on load tap changer coupled between the wind power plant and the power grid. The power plant controller is regulating the on load tap changer and is generating reactive component setpoints for the wind turbine generators, when determining a need for production of short-term reactive power due to a sudden change in reactive power measured at the point of common coupling.