Grid Converter Control via Voltage Feedback Damping
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Solution Overview
Problem
Conventional vector control methods for voltage-source converters face instability and difficulty in controlling converters connected to weak grids due to varying grid impedance, requiring re-tuning of controllers and phase-locked loops, which is impractical without knowing the grid impedance.
Innovation Solution
The method modifies current references using feedback from the output voltage, specifically by high-pass filtering the output voltage and adjusting active and reactive power references, allowing robust control without needing grid impedance information or re-tuning of controllers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional vector control methods are used in weak grid conditions, then the converter can operate, but the system becomes unstable due to strong coupling between active and reactive power
Solution Approach 1:
The patent introduces a feedback mechanism where the measured PCC voltage magnitude is fed back to dynamically adjust the PLL bandwidth and outer loop controller gains. This closed-loop adaptation allows the system to maintain stability across varying grid conditions without requiring manual re-tuning, directly resolving the contradiction between reliability and adaptability.
Solution Approach 2:
The control parameters (PLL bandwidth, controller gains) are made dynamic rather than fixed. The system automatically adjusts these parameters based on real-time grid strength detection, enabling the same controller to perform optimally across weak, medium, and strong grid conditions, thus achieving both reliability and versatility.
2Reliability
If re-tuning of PLL and outer loop controllers is performed to improve stability, then system performance improves, but the method requires knowledge of grid impedance which is typically unknown and time-varying
Solution Approach 1:
The control system performs self-tuning by automatically detecting grid strength from measured PCC voltage and adjusting its own parameters accordingly. This eliminates the need for external grid impedance information or manual configuration, making the system both simpler to deploy and more reliable in unknown grid conditions.
Solution Approach 2:
The patent changes the control parameters (PLL bandwidth, controller gains) dynamically based on detected grid conditions rather than using fixed parameters. This allows the system to adapt to varying grid impedance without requiring prior knowledge or complex configuration procedures.
3Device complexity
If the same controller tuning is used irrespective of grid strength, then device complexity is reduced, but the system becomes less stable in weak grid conditions
Solution Approach 1:
The controller uses dynamic parameter adjustment based on real-time grid strength detection. The same physical controller hardware is used across all grid conditions, maintaining simplicity, while its internal parameters adapt automatically to ensure stability in weak grids and optimal performance in strong grids.
Solution Approach 2:
The control system is designed to be universal, working across weak, medium, and strong grid conditions without requiring different controller hardware or manual reconfiguration. The automatic adaptation mechanism enables one controller design to serve multiple grid strength scenarios, maintaining both simplicity and reliability.
Data Source
Figure 1~2
AI summary
A method in connection with control of a grid connected converter and a converter. The control comprising forming a current reference for the converter, feeding the current reference to a current controller for producing a voltage reference for the converter. The method comprises high-pass filtering the produced voltage reference or measured output voltage of the converter and modifying the current reference with the high-pass filtered voltage reference or measured output voltage of the converter.