Wind Turbine Feed-In Filtering for Fast Frequency Response
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Solution Overview
Problem
Existing converter-based feed-in technologies in wind turbines and wind farms experience delays and limited dynamics, leading to delayed active power responses that cause frequency oscillations in weakly damped electrical grids, and low-pass filters can exacerbate these issues during grid faults.
Innovation Solution
A method involving a filter device with two low-pass filters having different time constants, allowing switching between them using weighting factors to quickly respond to frequency changes while damping oscillations, ensuring rapid frequency-dependent power adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a single low-pass filter is used to determine frequency-dependent active power setpoint, then frequency oscillations are damped in weakly damped grids, but the response to frequency events (especially grid faults) becomes excessively delayed
Solution Approach 1:
The filter device dynamically switches between two low-pass filter functions with different time constants based on grid conditions. During normal operation, the first filter function with smaller time constant provides fast response. During detected oscillations, the second filter function with larger time constant provides strong damping. This dynamic adaptation resolves the contradiction between fast response and oscillation damping.
Solution Approach 2:
The system changes the time constant parameter of the low-pass filter based on detected grid oscillations. When oscillations are detected, the time constant is increased (switching to second filter function) to enhance damping. When no oscillations are present, the time constant is decreased (switching to first filter function) to improve response speed. This parameter adaptation resolves the trade-off between response delay and oscillation damping.
2Speed
If no low-pass filter is used to enable rapid response to frequency events, then response speed is improved, but frequency oscillations are excited in weakly damped grids
Solution Approach 1:
The filter device dynamically adjusts its damping characteristics based on grid conditions. During normal operation without oscillations, the system uses the first filter function with smaller time constant that provides minimal damping, enabling fast response. When oscillations are detected, the system switches to the second filter function with larger time constant that provides strong damping to suppress oscillations. This dynamic behavior resolves the contradiction between response speed and oscillation excitation.
Solution Approach 2:
The system converts the potentially harmful effect of low-pass filtering (which can delay response) into a beneficial effect by selectively applying strong filtering only when oscillations are detected. During normal operation, minimal filtering is applied to maintain fast response. The harmful delay effect is transformed into a beneficial oscillation-damping effect only when needed, resolving the contradiction between response speed and oscillation suppression.
3Reliability
If grid-following feed-in technologies are used to support the grid, then grid support function is achieved, but delayed active power response causes frequency oscillations in weakly damped grids
Solution Approach 1:
The feed-in unit dynamically adapts its frequency response characteristics by switching between two filter functions. During normal grid support operation, the first filter function provides appropriate damping while maintaining responsive active power adjustment. When frequency oscillations are detected, the system switches to the second filter function with enhanced damping to suppress oscillations. This dynamic adaptation maintains grid support capability while preventing frequency instability.
Solution Approach 2:
The system uses feedback from frequency measurements to detect oscillations and adjust the filter characteristics accordingly. The frequency measurement signal is continuously monitored, and when oscillations are detected, the feedback triggers switching to the second filter function with larger time constant to dampen oscillations. This feedback mechanism ensures that grid support function is maintained while preventing frequency instability caused by delayed responses.
Data Source
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AI summary
The invention relates to a method for feeding electrical power into an electrical supply network having a mains voltage with a mains frequency, by means of a feed-in unit, in particular by means of a wind turbine or a wind farm, comprising the steps of detecting the mains frequency and forwarding the detected mains frequency as a frequency measurement signal, filtering the frequency measurement signal by means of a filter device with low-pass behavior into a frequency filter signal, determining a frequency-dependent power setpoint component as a function of the frequency filter signal, and feeding electrical power as a function of the frequency-dependent power setpoint component, wherein for filtering the frequency measurement signal by means of the filter device with low-pass behavior at least a first and a second filter function with low-pass behavior with characteristic first and secondsecond low-pass time constants are used, and it is possible to switch completely or partially between the first and second filter functions, in particular by means of a first and/or second weighting factor.