Medium-High Voltage Energy Conversion System Mode Switching
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional power electronic transformers face challenges in providing adequate support during faults in direct current microgrids or grids, such as voltage fluctuations, which can lead to undervoltage or overvoltage conditions, potentially causing device burnout or failing to support the grid effectively.
Innovation Solution
A control method and controller for medium-high voltage energy conversion systems that dynamically switch between direct-current current source and voltage source modes based on grid voltage thresholds, utilizing a DC/DC isolation circuit and grid-connected circuit to maintain stability and support the grid during faults.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the power electronic transformer operates in direct-current current source mode to support the grid, then grid support capability is improved, but the ability to maintain constant voltage during normal operation deteriorates
Solution Approach 1:
The system dynamically switches between direct-current current source mode and voltage source mode based on grid fault conditions. During normal operation, it operates in voltage source mode to maintain constant voltage. When grid faults occur (voltage drops below threshold), it switches to current source mode to provide grid support, and switches back when voltage recovers. This dynamic mode switching resolves the contradiction by allowing the system to optimize for different operational conditions.
2Stability of the object's composition
If the power electronic transformer operates in direct current voltage source mode to maintain constant voltage, then voltage stability is improved, but the ability to provide support during grid faults deteriorates
Solution Approach 1:
The system employs dynamic mode switching between voltage source mode and current source mode based on real-time grid voltage monitoring. When grid voltage is normal, the system operates in voltage source mode to maintain constant voltage. When grid voltage drops below a predetermined threshold indicating fault conditions, the system switches to current source mode to provide grid support, and switches back to voltage source mode when voltage recovers. This dynamic adaptation resolves the contradiction by allowing the system to prioritize voltage stability during normal operation while providing grid support capability during faults.
3Adaptability or versatility
If the system switches between different operational modes based on voltage thresholds, then adaptability to fault conditions is improved, but system complexity increases
Solution Approach 1:
The control system dynamically switches between operational modes based on real-time voltage threshold comparisons. The system monitors grid voltage and automatically transitions between voltage source mode and current source mode when voltage drops below or recovers above predetermined thresholds, enabling adaptive response to fault conditions without requiring complex predictive algorithms.
Solution Approach 2:
The system employs feedback control by continuously monitoring grid voltage and comparing it against predetermined thresholds. When voltage drops below the lower threshold, the system receives feedback to switch to current source mode. When voltage recovers above the upper threshold, feedback triggers a switch back to voltage source mode. This feedback mechanism provides simple yet effective adaptability to changing grid conditions.
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
A medium-high voltage energy conversion system, and a control method and a controller therefor are provided. In the control method, an operation state of the medium-high voltage energy conversion system is acquired. In a case that the system is in a normal operation state, the system is controlled to operate in a first direct circuit current source mode. In a case that the system is in a first fault state in which a direct current grid voltage drops, the system is controlled to operate in a direct current voltage source mode. In a case that the system is in a second fault state in which a direct current grid voltage is in an overvoltage state, the system is controlled to operate in a second direct circuit current source mode.