DFIG Wind Turbine Control for Low-Wind Reactive Power
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Solution Overview
Problem
Wind turbines with doubly-fed induction generators face challenges in providing reactive power, especially at low wind speeds, which can lead to grid disconnection due to reduced reactive power capability, and existing solutions like full converter topologies increase costs and complexity.
Innovation Solution
A method that operates wind turbines in two modes: a first mode for maximum power generation and a second mode where the rotor speed is increased at the expense of active power to enhance reactive power capability, allowing the turbine to maintain reactive power provision across a wider range without additional compensation equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a doubly-fed induction generator is used to reduce converter size and costs, then the power converter handles only a fraction of produced electrical power, but the capability to provide reactive power is significantly reduced at low wind speeds
Solution Approach 1:
The patent implements dynamic operational mode switching based on real-time wind speed conditions. The control system automatically transitions between first operational mode (maximum power extraction) and second operational mode (enhanced reactive power capability) as wind speed varies, optimizing both active and reactive power delivery dynamically
Solution Approach 2:
The patent changes the operational parameters of the DFIG by adjusting the rotor speed and generator slip. In the second operational mode, the rotor speed is increased and slip is reduced to improve reactive power capability, demonstrating parameter adjustment to resolve the contradiction between converter size and reactive power capability
2Productivity
If the wind turbine operates at maximum power point to maximize electrical power production, then the rotor speed is optimized for active power, but the reactive power capability is reduced
Solution Approach 1:
The control system dynamically adjusts operational modes based on grid requirements and wind conditions. When reactive power support is needed, the system transitions from maximum power point tracking to a mode that prioritizes reactive power capability, enabling flexible response to grid needs
Solution Approach 2:
The patent implements periodic monitoring of wind speed and grid conditions to determine when to switch between operational modes. The control system continuously evaluates whether to operate in first or second mode based on current conditions, creating a periodic decision cycle that optimizes both active and reactive power delivery
3Reliability
If additional compensation equipment is added to improve reactive power capability, then reactive power provision is enhanced, but costs and system complexity increase
Solution Approach 1:
The patent enables the wind turbine itself to provide reactive power support through intelligent control of the DFIG, eliminating the need for external compensation equipment. The turbine's own generator and converter are utilized to deliver reactive power, making the system self-sufficient and avoiding additional complexity
Solution Approach 2:
The DFIG and its associated converter are designed to perform multiple functions: active power generation, reactive power compensation, and voltage support. This multi-functionality eliminates the need for separate compensation devices, reducing overall system complexity while maintaining enhanced reactive power capability
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables wind turbines to meet stringent grid code requirements for reactive power while reducing costs and complexity, maintaining efficiency by minimizing the use of converters and avoiding the need for additional reactive power compensation systems.
Implementation Method 1
a power generating system including a doubly-fed induction generator (DFIG) that converts rotational mechanical power to electrical power
Implementation Method 2
a generator that converts mechanical power provided by the rotating shaft of the wind turbine into electrical power, the frequency of which is adjusted to the grid frequency by means of a power converter
Data Source
AI summary
A method of operating a wind turbine wherein the wind turbine includes a doubly-fed induction generator that converts rotational mechanical power to electrical power. The method includes operating the wind turbine in a first operational mode in which a speed of a rotor of the wind turbine is controlled to maximize the power generation by the wind turbine. Upon a monitored parameter reaching or dropping below a respective threshold, the wind turbine is operated in a second operational mode. The monitored parameter may include at least one of the rotational speed of the rotor, the rotational speed of the doubly-fed induction generator, a wind speed, an active electrical power, or generator torque. Operating the wind turbine in the second operational mode may include increasing the rotational speed of the doubly-fed induction generator at the expense of the generation of active electrical power by the power generating system.