Wind Turbine Active Power Control to Prevent Frequency Event Wind-Up
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Solution Overview
Problem
Wind turbines experience a phenomenon known as 'wind-up' due to mismatches between set point and output active power values during frequency deviations, leading to delays in ramping back to normal levels, which can result in under- or over-generation of active power and penalties from transmission system operators.
Innovation Solution
A method for controlling wind turbine generators that sets active power references equal to or within upper and lower limits during frequency events, ensuring that the active power output matches the reference throughout the deviation and immediately after, allowing for immediate ramping back to baseline levels without delay by determining active power values based on measured frequency and adjusting them according to predefined limits and ramp rate limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If active power references are determined based on predefined curves during frequency events, then frequency support is provided, but wind-up occurs causing delays in ramping back to normal levels
Solution Approach 1:
The system continuously monitors the actual active power output and compares it with the limit level. When the determined active power value from predefined curves exceeds the limit, feedback mechanisms detect this discrepancy and adjust the active power reference to be equal to the limit, preventing wind-up and ensuring immediate ramping capability when frequency events end.
Solution Approach 2:
The control system dynamically adjusts the active power reference based on real-time conditions. During frequency events, if the determined active power value is outside limits, the reference is set equal to the limit; otherwise, it follows the determined value from predefined curves. This dynamic adjustment eliminates the static mismatch that causes wind-up delays.
2Adaptability or versatility
If active power output is limited based on available wind or user-implemented limits, then physical constraints are respected, but controllers may issue commands outside limits causing wind-up
Solution Approach 1:
Before issuing active power commands during frequency events, the system preliminarily checks whether the determined active power value from predefined curves is within the applicable limits (available wind or user-implemented). If the determined value exceeds the limit, the active power reference is pre-adjusted to equal the limit, preventing the controller from issuing commands outside limits and avoiding subsequent wind-up corrections.
3Loss of time
If active power references are set equal to limits during frequency events, then wind-up is prevented, but normal frequency support control may be compromised
Solution Approach 1:
The system applies partial frequency support control by setting the active power reference equal to the limit only when the determined value from predefined curves exceeds the limit. When the determined value is within limits, the system uses the full predefined curve control. This partial application of limit-based control prevents wind-up in critical cases while maintaining normal frequency support control in non-critical cases, achieving a balance between preventing wind-up and maintaining frequency support effectiveness.
Data Source
AI summary
Aspects of the present invention relate to methods for controlling active power output of a wind turbine generator in response to a frequency event on a power network to which the wind turbine generator is connected, wherein the active power output of the wind turbine generator is limited to be below an upper active power limit and/or above a lower active power limit. The methods comprise determining and dispatching active power references to a controller of the wind turbine generator for controlling the wind turbine generator. The methods operate to ensure that the value of the active power reference immediately after the frequency event is within the allowable active power range, thereby avoiding any mismatch between the reference and the output that may cause a delay in returning to normal operation.