Wind Turbine Tap Changer Current Control
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Solution Overview
Problem
Existing wind turbine systems with on-load tap changer transformers face limitations in adjusting the transformer's turns ratio when the primary or secondary side current exceeds the switching current threshold, leading to inefficiencies and potential tripping of power converters during network voltage fluctuations.
Innovation Solution
Implementing a control system that temporarily reduces the primary or secondary side current below the switching current threshold to allow changes in the transformer's turns ratio, using a variable time delay to manage current reductions across multiple wind turbines and enabling efficient voltage regulation during network faults or imbalances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the transformer is designed with a high switching current threshold to allow tap position changes during high current operation, then the adaptability and reliability of voltage regulation is improved, but the cost and complexity of the on-load tap changer transformer increases
Solution Approach 1:
The control system proactively detects voltage conditions and triggers tap position changes before critical voltage deviations occur. By predicting voltage trends and initiating tap changes in advance, the system maintains reliable voltage regulation without requiring the transformer to handle extreme switching currents, thus avoiding the need for an oversized expensive transformer.
Solution Approach 2:
The system dynamically adjusts the switching current threshold based on real-time operating conditions such as load level, voltage deviation magnitude, and rate of change. This adaptive parameter adjustment allows the transformer to operate efficiently across different conditions without requiring a consistently high switching current threshold, reducing overall system cost and complexity while maintaining reliability.
2Ease of operation
If the wind turbine reduces primary or secondary side current below the switching current threshold to enable turns ratio adjustment, then the ease of operation for tap position changes is improved, but the power output and current injection capability deteriorates temporarily
Solution Approach 1:
The control system implements periodic monitoring of voltage conditions and initiates current reduction and tap position changes only when necessary. By using periodic detection and control rather than continuous operation at reduced current, the system minimizes the duration and frequency of power output reductions while ensuring timely voltage regulation when grid conditions require it.
Solution Approach 2:
The system dynamically adjusts the current reduction strategy based on real-time grid conditions, load demands, and voltage deviation severity. Rather than applying a fixed current reduction, the control system optimizes the reduction magnitude and duration to achieve successful tap position changes while minimizing impact on power output, adapting continuously to changing operating conditions.
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
The invention relates to a method for controlling a wind turbine which comprises a transformer has a variable turns ratio such as an on load tap changer transformer. The adjustment of the turns ratio is possible when a primary side current or a secondary side current of the transformer is less than a switching current threshold. The method comprises operating the wind turbine so that the primary or secondary side current is above the switching current threshold. In response to obtaining a condition for changing the turns ratio of the transformer, the wind turbine is operated so that the primary or secondary side current is reduced below the switching current threshold so that the turns ratio can be changed during the temporary current reduction.