Wind Turbine Power Converter Control for SSCI Damping
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Solution Overview
Problem
Wind turbines with doubly fed induction generators (DFIGs) experience subsynchronous control interaction (SSCI) instability due to negative resistance in the subsynchronous frequency range, which can lead to faults and component damage when connected to series-compensated transmission lines, as these systems amplify instability rather than dampen it.
Innovation Solution
A control system for the power converter in a wind turbine system that determines the flux magnitude between the rotor and stator, calculates an orientation adjustment reference signal based on this magnitude, and adjusts the power converter's operation to exhibit a positive damping characteristic in the subsynchronous frequency range, thereby stabilizing the system without the need for hardware damping circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If wind turbines are electrically coupled to series-compensated transmission lines, then power transmission efficiency is improved, but subsynchronous resonance currents increase in amplitude causing instability and potential damage
Solution Approach 1:
The patent converts the harmful subsynchronous resonance currents into a beneficial effect by using them as feedback signals for the control system. The control system processes these currents and generates compensating control signals that actively counteract the resonance, transforming the harmful oscillations into useful information for stabilization.
Solution Approach 2:
The patent implements a feedback mechanism where subsynchronous current components are detected, processed through a control algorithm, and used to generate compensating control signals. This closed-loop feedback system continuously monitors and adjusts the power converter output to maintain system stability despite the presence of series compensation.
2Reliability
If hardware damping circuits are installed to reduce subsynchronous resonance, then system stability is improved, but device complexity and cost increase
Solution Approach 1:
The patent replaces physical hardware damping circuits with a software-based control system. Instead of using additional electrical components and circuits to dampen resonance, the invention uses digital signal processing and control algorithms to achieve the same stabilization effect, eliminating the need for complex hardware modifications.
Solution Approach 2:
The power converter's existing control system is enhanced to perform self-stabilization by processing its own output current signals. The control system uses the subsynchronous current components generated by the converter itself as feedback, allowing the system to self-regulate and dampen resonance without requiring external damping devices.
3Device complexity
If conventional power converter control is used, then system simplicity is maintained, but subsynchronous control interaction instability occurs
Solution Approach 1:
The patent introduces dynamic adaptability into the control system by implementing flux magnitude-dependent orientation adjustment. The control parameters are not fixed but dynamically adjusted based on real-time flux conditions, allowing the system to adapt its damping characteristics to varying operating conditions while maintaining overall simplicity.
Solution Approach 2:
The patent changes the control parameter orientation based on flux magnitude to achieve positive damping in the subsynchronous frequency range. By adjusting the orientation angle as a function of flux magnitude, the system modifies its electrical characteristics to counteract subsynchronous resonance without requiring complex additional hardware.
Data Source
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AI summary
Systems and methods for controlling a power converter in a wind turbine system are provided. The wind turbine system can include a generator and a power converter. The power converter can include a plurality of switching devices and a current damping module. A method can include determining, by a control device, a flux magnitude of an air-gap between a rotor and a stator in the generator. The method can further include determining, by the control device, an orientation adjustment reference signal for the current damping module based at least in part on the flux magnitude. The method can further include controlling, by the control device, the power converter based at least in part on the orientation adjustment reference signal.