DFIG Rotor Current Control for High-Voltage Grid Ride-Through
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Solution Overview
Problem
Wind turbines equipped with doubly fed induction generators (DFIGs) face damage risks due to high-voltage grid events, which can cause voltage and frequency deviations, leading to potential equipment failure and operational disruptions.
Innovation Solution
A control system and method that utilize a controller to detect high-voltage grid events, adjust rotor torque and converter operations, and manage DC link voltage to prevent overvoltage, allowing the DFIG to ride through high-voltage conditions and safely shut down when necessary, thereby protecting the electrical system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the DFIG continues operating during high-voltage grid events, then productivity is maintained, but equipment reliability deteriorates due to voltage and frequency deviations exceeding equipment capability
Solution Approach 1:
The control system performs preliminary detection of high-voltage conditions and preemptively adjusts converter operations and rotor torque before damage can occur. The system monitors grid voltage continuously and prepares shutdown procedures in advance when threshold violations are detected, preventing equipment damage while maintaining operational continuity during normal conditions
Solution Approach 2:
The system implements closed-loop feedback control by continuously monitoring grid voltage and frequency, comparing them against safe operating thresholds, and automatically adjusting converter operations or initiating shutdown based on real-time conditions. This feedback mechanism ensures equipment protection while maximizing operational continuity during recoverable events
2Reliability
If the controller adjusts rotor torque and converter operations to mitigate high-voltage effects, then equipment reliability is improved, but device complexity increases due to additional control mechanisms
Solution Approach 1:
The control system integrates multiple functions into the existing DFIG control architecture, using the same power electronics converters for both normal power regulation and high-voltage mitigation. The controller performs both standard maximum power point tracking and protective response to grid events, eliminating the need for separate dedicated protection equipment and reducing overall system complexity
Solution Approach 2:
The system protects against high-voltage events by dynamically changing operational parameters such as rotor torque, converter switching frequencies, and reactive power injection. These parameter adjustments are achieved through software control of existing hardware, avoiding the need for additional physical protection devices and maintaining system simplicity
3Reliability
If the DFIG shuts down immediately upon detecting high-voltage conditions, then equipment reliability is improved, but productivity is reduced due to operational disruptions
Solution Approach 1:
Instead of immediate complete shutdown, the system applies partial protective actions by adjusting converter operations and rotor torque to mitigate high-voltage effects. This partial action allows the turbine to continue generating reduced power during moderate events, maximizing energy capture while providing sufficient protection. Complete shutdown is reserved only for severe conditions where equipment safety is at risk
Data Source
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Figure 3A
AI summary
In one aspect, a method for controlling a dual-fed induction generator (DFIG) 118 during a high-voltage grid event is provided. The method includes setting, by a controller 202, an output of a closed-loop portion of a rotor current regulator to a fixed value such that a predictive feed-forward path sets an internal voltage for the DFIG 118; and detecting, by the controller 202, a condition of high dc voltage on a dc link 224 or a condition predictive of high dc voltage on the dc link 224, and in response reduce a rotor torque producing current command to approximately zero, wherein the dc link 224 connects a line-side converter 222 connected to a system bus 216 and a rotor-side converter 220 connected to a rotor of the DFIG 118.