Dual-Mode Converter Control for Seamless Grid Following and Forming
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Solution Overview
Problem
Existing converters in high-voltage applications face challenges in seamlessly integrating renewable energy sources like wind and solar plants, particularly in transitioning between grid following and grid forming modes, which affects stability and dynamics in varying network conditions.
Innovation Solution
A converter system with both grid following and grid forming controllers sharing an underlying current controller, allowing for seamless mode transitions and improved dynamics, enabling effective integration of renewable energy sources by compensating operating point deviations and enhancing power transmission capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a converter operates in grid following mode to maintain stability in strong networks, then performance and reliability are preserved, but adaptability to weak networks and renewable energy integration is limited
Solution Approach 1:
The converter control system is designed to dynamically switch between grid following mode and grid forming mode based on network conditions. The system can adapt its control strategy in real-time, transitioning from passive grid following in strong networks to active grid forming in weak networks or when integrating renewable energy sources, thus resolving the contradiction between maintaining reliability and achieving adaptability
Solution Approach 2:
The converter is designed with multi-functionality to operate in both grid following mode and grid forming mode. By incorporating dual control capabilities, the single converter can serve multiple functions: maintaining stability in strong networks through grid following while also supporting weak networks and renewable energy integration through grid forming, thus achieving both reliability and adaptability
2Adaptability or versatility
If a converter operates in grid forming mode to support weak networks and renewable energy integration, then adaptability and stability in varying conditions are improved, but control complexity increases
Solution Approach 1:
The control system is segmented into distinct grid following controller and grid forming controller modules, each handling specific control functions. This modular segmentation allows the complex control tasks to be divided into manageable segments, reducing overall control complexity while maintaining adaptability across different network conditions
3Reliability
If seamless transition between grid following and grid forming modes is implemented, then reliability and dynamics are improved, but control complexity increases
Solution Approach 1:
The grid following controller and grid forming controller are merged into a unified control architecture that shares common components and coordination mechanisms. This merging allows seamless transition between modes by coordinating the controllers within a single integrated system, improving reliability while managing complexity through unified design rather than separate independent systems
Data Source
AI summary
A converter includes an AC side to be connected to an AC network at a connecting point, a grid following controller configured to control a steady state current at the connecting point, and a grid forming controller configured to actively control frequency and voltage at the connecting point. The grid following controller and the grid forming controller share an underlying current controller. A method for operating the converter is also provided.