Power Converter Phase-Locked Loop Control for Grid Stability
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Solution Overview
Problem
Wind turbine generators face instability and phase tracking errors during grid contingency events, particularly in weak AC transmission grids, leading to fluctuations in grid voltage and frequency, which affect the performance and stability of power converters.
Innovation Solution
A synchronizing system that includes a phase-locked loop (PLL) to generate a line converter angle reference signal, aligning the power converter output with the electrical grid phase, and reducing system oscillations by using a PLL error signal to adjust the line converter angle, thereby stabilizing the power generation system and grid connectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a power converter operates during grid contingency events in weak AC transmission grids, then power delivery capability is maintained, but phase tracking errors and system oscillations increase
Solution Approach 1:
The patent implements a phase-locked loop (PLL) control system that continuously monitors the phase difference between the power converter output and the electrical grid, and dynamically adjusts the converter's output phase to maintain synchronization. This feedback mechanism enables the system to maintain reliable power delivery while compensating for phase tracking errors and reducing oscillations during grid contingency events.
2Productivity
If variable speed operation is used to enhance energy capture, then productivity increases, but voltage and frequency variations increase
Solution Approach 1:
The patent introduces a power converter as an intermediary device between the variable speed wind turbine generator and the electrical grid. This intermediary converts the variable frequency and voltage output from the turbine into stable grid-compatible electrical parameters, thereby enabling variable speed operation for enhanced energy capture while maintaining voltage and frequency stability for grid delivery.
3Reliability
If grid connectivity is maintained during transient events, then reliability is improved, but system oscillations and instability increase
Solution Approach 1:
The patent employs dynamic control strategies that adapt the power converter's operating parameters in real-time during grid transient events. The system dynamically adjusts impedance, phase angle, and power injection levels based on grid conditions, enabling maintained grid connectivity while actively damping oscillations and preserving system stability through continuous adaptation.
Data Source
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AI summary
A controller for use with a power generation system (150) coupled to an electrical grid (136) is provided. The controller includes a circuit (172) configured to receive a phase locked loop (PLL) error signal (190) representative of a difference between a phase angle of the power generation system and a phase angle of the electrical grid. The circuit is further configured to generate a PLL shift signal (210) based at least partially on the PLL error signal and a threshold phase.