Multi-UPS Frequency Synchronization During Mode Transitions
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Solution Overview
Problem
Conventional UPS systems with multiple units experience inconsistencies during mode transitions due to differing decision-making and synchronization initiation times, leading to operational issues.
Innovation Solution
A method involving controllers in each UPS unit to broadcast and determine a major synchronization direction based on grid frequency, adjusting frequencies via communication links to achieve synchronization among multiple UPS units, using an angle inhibit band to resolve ambiguities near 180 degrees.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If each UPS unit operates independently with local decision-making, then each unit can autonomously transition between modes, but synchronization inconsistencies occur among UPS units
Solution Approach 1:
The patent introduces a master-slave architecture where one UPS unit is designated as master and others as slaves. The master unit coordinates mode transitions and frequency regulation for all units, eliminating independent decision-making conflicts while maintaining autonomous operation capabilities. This intermediary control structure ensures all units synchronize their transitions simultaneously, resolving the contradiction between operational autonomy and synchronization consistency.
2Adaptability or versatility
If UPS units transition at different instants based on local information, then each unit can respond to local conditions, but frequency discrepancies and power imbalances arise
Solution Approach 1:
The patent implements a feedback mechanism where the master unit continuously monitors the operational state of all UPS units and broadcasts synchronization commands. When transitioning from island mode to power conditioning mode, the master unit coordinates the timing based on grid frequency recovery detection, ensuring all units transition at the same instant. This feedback loop maintains frequency consistency while allowing the system to adapt to local grid conditions.
3Device complexity
If no coordination mechanism is implemented, then system complexity is reduced, but phase angle inconsistencies and unsafe synchronization scenarios occur
Solution Approach 1:
The patent segments the control function into two distinct roles: master unit responsible for coordination and synchronization commands, and slave units responsible for executing commands and providing status feedback. This segmentation introduces a coordination mechanism that ensures safe synchronization without requiring complex peer-to-peer communication among all units. The master-slave division maintains manageable system complexity while guaranteeing synchronization safety through centralized coordination.
Data Source
AI summary
A method of regulating frequency of plurality of uninterruptible power supply units and corresponding uninterruptible power supply (UPS) unit. The method includes broadcasting, to a controller of a UPS unit, an expected synchronization direction to other UPS units via a communication link, the expected synchronization direction being determined based on a frequency of the corresponding UPS units and a frequency of a grid. The method includes obtaining the expected synchronization directions of other UPS units via the communication link; determining a major synchronization direction based on the expected synchronization direction of each UPS unit; and regulating a frequency of each UPS unit based on the major synchronization direction.