Phase Angle Adjustment for Power Balancing in Parallel UPS Converters
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Solution Overview
Problem
In modular uninterruptible power supply (UPS) systems, identical building blocks with manufacturing tolerances in components like inductors and capacitors lead to unequal power sharing when using a centralized controller, resulting in inefficiencies and increased costs due to the need for oversized components.
Innovation Solution
A method involving a centralized controller that applies a common control signal to power converters, adjusts the phase angle of the voltage applied to each converter based on current measurements, using a derived relationship between phase angle adjustments and current changes, to balance power sharing among modules, with adjustments made through closed-loop feedback control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the same control signal is applied to each building block from a centralized controller, then the control system is simplified and cost is reduced, but the power through each building block becomes different due to component mismatch
Solution Approach 1:
The patent applies local quality by introducing individual phase angle adjustments for each building block's control signal. While the base control signal remains common to all modules (maintaining simplicity), each module receives a customized phase shift tailored to its specific component characteristics, thereby achieving balanced power sharing without increasing overall system complexity
Solution Approach 2:
The patent changes the parameter of phase angle for each building block's control signal. By dynamically adjusting the phase angle of individual control signals based on measured power output and component variations, the system compensates for manufacturing tolerances in inductors and capacitors, achieving equal power distribution across all modules
2Manufacturing precision
If inductors, capacitors and other building block power components are oversized to account for mismatch, then power sharing balance is improved, but cost increases
Solution Approach 1:
Instead of increasing component sizes, the patent changes the operational parameter of phase angle for each building block. By adjusting the phase angle of control signals, the system achieves balanced power sharing with nominally sized components, avoiding the cost and size penalties of oversized design
3Manufacturing precision
If phase angle adjustments are made to balance power amongst converters, then power sharing is improved, but control signal complexity increases
Solution Approach 1:
The patent implements feedback by measuring the actual current or power output from each building block and using this information to dynamically adjust the phase angle of control signals. This closed-loop approach automatically compensates for component variations without requiring complex open-loop calculations or manual tuning
Solution Approach 2:
The patent changes the phase angle parameter of control signals in a systematic manner based on measured power output. The phase adjustment is calculated to be proportional to the power imbalance, providing a simple and elegant solution that balances power without requiring complex control algorithms
Data Source
AI summary
A method is provided for balancing power amongst parallel connected power converters in an uninterruptible power supply (UPS). The method includes: applying a control signal to each of the parallel connected power converters, where the control signals applied to the parallel connected power converters are derived from a common control signal output by a centralized controller; receiving measurements of current being supplied by each power converter to the load; and adjusting phase of voltage applied to at least one of the power converters based on the received current measurements, such that the phase adjustment causes same magnitude of current to flow though each filter. Advancing phase angle of the voltage increases current supplied by the at least one power converter while retarding phase angle of the voltage decreases current supplied by the at least one power converter.