Wind Turbine Speed Control via Grid Frequency Curves
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Solution Overview
Problem
Double-fed asynchronous generators in wind turbines are sensitive to grid frequency fluctuations, leading to reduced power yield due to fixed speed parameters that provide tolerance to maintain converter safety, but this reduces efficiency.
Innovation Solution
Implementing variable speed parameters based on mains frequency, with characteristic curves determining minimum, maximum, and nominal speeds in relation to grid frequency, allowing dynamic adjustment to maintain optimal power output and prevent converter damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fixed speed parameters with tolerances are used to protect the converter from damage due to grid frequency fluctuations, then the reliability of the converter is improved, but the power yield and operational efficiency deteriorate
Solution Approach 1:
The patent applies dynamics by transitioning from fixed speed parameters to dynamically adjustable speed parameters. The controller continuously adapts minimum speed, maximum speed, and nominal speed based on actual grid frequency measurements, allowing the system to respond to changing grid conditions while maintaining converter protection. This dynamic adjustment resolves the contradiction by enabling both reliability (through protective tolerances) and productivity (through optimized speed settings at each frequency level).
Solution Approach 2:
The patent implements parameter changes by modifying speed parameters (minimum speed, maximum speed, nominal speed) as a function of grid frequency. Different speed parameter sets are stored in memory for different frequency ranges, and the controller selects the appropriate set based on current grid conditions. This allows the system to maintain converter safety across varying frequencies while optimizing power yield for each specific frequency condition.
2Device complexity
If fixed speed parameters are used to simplify control, then the device complexity is reduced, but the adaptability to grid frequency changes deteriorates
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing multiple sets of speed parameters in memory, each optimized for specific grid frequency ranges. The controller simply needs to measure the current frequency and select the corresponding pre-prepared parameter set, avoiding complex real-time calculations. This approach maintains control system simplicity while achieving high adaptability to grid frequency variations.
3Stability of the object's composition
If speed parameters are kept fixed to ensure stable operation, then the stability of operation is improved, but the power distribution optimization between stator and rotor deteriorates
Solution Approach 1:
The patent implements feedback by continuously measuring grid frequency and using this information to adjust speed parameters. The controller creates a closed-loop system where grid frequency measurements feed back into the speed parameter selection process. This ensures stable operation through systematic parameter management while optimizing power distribution between stator and rotor for each frequency condition, resolving the contradiction between stability and efficiency.
Data Source
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AI summary
The invention relates to a method for controlling a wind turbine with a wind rotor (2), a doubly fed asynchronous generator (1) driven therein, and a converter (4) which is electrically connected to feed electrical energy into an electrical network (8) with at least one network parameter, and a control unit with a memory in which speed parameters are stored, characterized in that at least one variable characteristic curve is determined between at least one of the speed parameters and the at least one network parameter, the at least one characteristic curve is stored in the memory in which at least one network parameter is measured, the network parameter measurement values are supplied to the control unit, which activates the values of the at least one speed parameter assigned to the network parameter measurement values via the at least one characteristic curve.