Dual-Converter UPS Switching for Grid Fault Ride-Through
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Solution Overview
Problem
Existing uninterruptible power supply (UPS) systems are often complex and expensive, with certain architectures not providing high-quality power continuously during grid disturbances, and battery-energy-storage systems (BESS) may not be configured to offer continuous high-quality power immediately after a fault, making them less desirable for critical loads.
Innovation Solution
A UPS system with a first and second power converter, each with a power rating less than the load, and a controller that switches between them to provide fault-ride-through protection by disconnecting from the grid fault, allowing the UPS to remain connected and provide power to critical loads during faults, then reconnecting when the fault is resolved.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional UPS systems are used to provide continuous high-quality power during grid faults, then power quality is maintained, but system complexity and cost increase
Solution Approach 1:
The system divides the power conversion function into two separate converters: a first power converter that interfaces with the grid and a second power converter that interfaces with the load. Each converter is independently controlled and can operate autonomously, allowing the system to maintain power quality without requiring a single complex converter design.
Solution Approach 2:
The first and second power converters are designed with dual functionality - they can operate in parallel during normal conditions and also function as standalone units during grid faults. This multi-functionality eliminates the need for separate backup systems, reducing overall system complexity while maintaining reliability.
2Speed
If battery-energy-storage systems are configured to provide immediate power after faults, then response speed improves, but system complexity increases
Solution Approach 1:
The first power converter remains connected to and synchronized with the grid during normal operation, maintaining readiness to detect faults. When a grid fault occurs, the controller immediately detects the fault condition and switches to the second power converter, providing immediate response without requiring battery-energy-storage systems or complex switching arrangements.
3Device complexity
If a single power converter is used to handle full load power, then system simplicity is maintained, but fault protection capability is reduced
Solution Approach 1:
The power conversion function is segmented into two converters, each with power rating less than the full load power. This segmentation allows the system to isolate the load from grid faults by switching to the second converter, providing fault protection while keeping individual converter designs simpler and more manageable.
Solution Approach 2:
The controller acts as an intermediary that monitors grid conditions and manages the switching between the first and second power converters. This intermediary control mechanism provides intelligent fault protection without requiring each converter to be overly complex, as the controller handles the decision-making logic.
Data Source
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AI summary
Aspects of the disclosure include a system comprising at least one energy-storage-device connection, a first output connection to be coupled to a main power source providing main power, a second output connection to be coupled to at least one load, a first and second power converter coupled to the at least one energy-storage-device connection, and at least one controller coupled to the power converters and being configured to control the system to connect the power converters to the output connections, control the system to disconnect the first power converter from the second output connection responsive to detecting a fault in the main power, control the first power converter to provide power to the first output connection responsive to detecting the fault in the main power, and control the system to disconnect the second power converter from the first output connection responsive to detecting the fault in the main power.