Stationary Frame P+Resonant Controller for Wind Turbine Power Converters
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Solution Overview
Problem
Current methods for controlling power converters in wind turbine generators are complex and inefficient, particularly in handling negative sequence voltages and varying grid frequencies, leading to potential grid code incompliance and system instability.
Innovation Solution
A method that controls power converters in a stationary coordinate frame, using a P+Resonant current controller with a varying resonant frequency, eliminates the need for coordinate transformation and sequence separation, allowing for efficient operation under unbalanced supply conditions and frequency variations, thereby simplifying the control system and improving stability margins.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional current control methods are used with coordinate transformation and sequence separation, then control performance under balanced conditions is improved, but device complexity increases and stability margins deteriorate under unbalanced supply conditions
Solution Approach 1:
The patent extracts and eliminates the coordinate transformation and sequence separation components from the control system. By operating directly in the stationary coordinate frame without transforming to rotating d-q frames or separating positive/negative sequence components, the invention removes unnecessary complexity while maintaining control effectiveness under both balanced and unbalanced supply conditions.
Solution Approach 2:
The control method achieves universal applicability across different operating conditions (balanced and unbalanced supply, varying frequencies) using a single unified controller structure. The P+Resonant controller in stationary frame simultaneously handles all sequence components and frequency variations without requiring separate control paths or transformations, making the system multi-functional without increasing complexity.
2Manufacturing precision
If four PI controllers with feed forward and decoupling elements are implemented to regulate positive and negative sequence currents, then current control performance is improved, but device complexity and hardware requirements increase
Solution Approach 1:
The patent merges the functionality of multiple separate controllers (positive sequence PI, negative sequence PI, feed forward elements, decoupling elements) into a single unified P+Resonant controller operating in stationary coordinate frame. This consolidation achieves the same current control precision while eliminating the need for multiple separate control paths and reducing overall device complexity.
Solution Approach 2:
The invention changes the control approach from using multiple PI controllers with complex feed forward and decoupling parameters to a single P+Resonant controller with simplified parameters. The resonant controller structure inherently provides the necessary control action for both sequence components without requiring separate tuning of multiple controllers or complex parameter sets.
3Measurement precision
If sequence component extracting filters are employed to separate positive and negative sequence voltages, then control accuracy is improved, but overall regulator bandwidths and stability margins are undermined
Solution Approach 1:
The patent removes the sequence component extracting filters from the control system. By eliminating these filters, the invention avoids the bandwidth limitations and stability margin reductions they introduce, while still achieving accurate control through direct stationary frame processing that inherently handles both sequence components without requiring explicit separation.
4Device complexity
If the control system is designed for operation at a fixed frequency, then control simplicity is maintained, but adaptability to frequency variations deteriorates
Solution Approach 1:
The patent implements a dynamic resonant frequency parameter that automatically adapts to grid frequency variations. The P+Resonant controller is designed with a varying resonant frequency that tracks the grid frequency, enabling the system to maintain high control performance across a wide frequency range (47-53 Hz for 50 Hz grids, 57-61.7 Hz for 60 Hz grids) without requiring complex retuning or redesign.
Data Source
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AI summary
A method for controlling a power converter in a wind turbine generator, the power converter being connected to a power grid, the method comprising obtaining an alternating current (AC) line voltage at a connection point between the power converter and the power grid, obtaining a frequency of the power grid based on the AC line voltage, dynamically adapting the AC line voltage to the frequency of the power grid, generating a reference signal based on at least the frequency-adapted AC line voltage, and determining a converter control signal to be provided to the power converter based on the reference signal and the grid frequency in order to generate a power at the frequency of the power grid. Further, a wind turbine generator implementing the method is provided.