Static UPS Inverter Partial Current Limiting Control
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Solution Overview
Problem
In ring bus architectures, static UPS systems face challenges in sizing chokes to handle breaker failures effectively, impacting cost, feasibility, and reliability, as they require additional time to deal with faults without increasing choke size.
Innovation Solution
Implementing a current limiting algorithm that controls bridge currents to operate inverters in a partial current limiting regime between full current limiting and linear modes, allowing for extended operation time during faults and reducing choke size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If choke size is increased to handle breaker failures effectively, then reliability is improved, but cost and device complexity increase
Solution Approach 1:
The patent implements dynamic current limiting control that adjusts the inverter's current output in real-time based on fault conditions. The controller monitors bridge currents and dynamically switches between full current limiting regime and linear mode, creating a time-varying current profile that extends the effective time available to handle breaker failures without requiring larger chokes. This dynamic adaptation resolves the contradiction by making the system's protective capability temporally flexible rather than relying on fixed, oversized hardware components.
Solution Approach 2:
The patent changes the operational parameters of the inverter by controlling bridge currents to operate between full current limiting and linear mode. This parameter adjustment creates a partial current limiting regime that extends the duration the inverter can safely operate during fault conditions. By modifying the current waveform characteristics and timing, the system achieves enhanced breaker failure handling capability without increasing choke size, thus resolving the technical contradiction between reliability and device complexity.
2Reliability
If full current limiting regime is used to protect against faults, then reliability is improved, but the time available to handle faults is reduced
Solution Approach 1:
The patent applies partial current limiting rather than full current limiting by controlling the inverter to operate in an intermediate regime between full current limiting and linear mode. This partial action approach provides sufficient fault protection while avoiding the excessive current suppression that would prematurely terminate operation. The controller selectively applies current limiting only when necessary and at controlled levels, extending the operational time during faults while maintaining adequate protection, thus resolving the contradiction between reliability and duration of action.
Solution Approach 2:
The system dynamically adjusts the current limiting level based on real-time monitoring of bridge currents and fault conditions. Rather than maintaining constant full current limiting, the controller adapts the limiting degree to extend safe operation time while preserving fault protection capability. This dynamic modulation of protective action resolves the contradiction by making protection intensity variable rather than fixed.
Data Source
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AI summary
A system (300) is provided. The system includes a plurality of uninterruptible power supplies (UPSs) (302), each UPS of the plurality of UPSs including an inverter (330), a ring bus (306), and at least one controller (309) communicatively coupled to the plurality of UPSs, the at least one controller configured to control at least one bridge current in each UPS, the at least one bridge current controlled such that the inverter of each UPS operates in a partial current limiting regime between a full current limiting regime and a linear mode.