UPS Battery Load Allocation via Inverter Phase Control
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Solution Overview
Problem
In parallel UPS systems, the runtime available to power a load is constrained by the capacity of the weakest battery, leading to potential shutdowns due to overload when one UPS determines its battery has low voltage, causing other UPSs to shut down.
Innovation Solution
A method and system where a difference in battery capacity between individual UPSs and the average capacity of multiple UPSs is determined, allowing for controlled power flow adjustments, including inverter phase control, to equalize power distribution and prevent overloading, using a controller that adjusts power flow based on battery voltage differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If parallel UPSs operate with independent battery capacity management, then each UPS can operate autonomously, but the system runtime is constrained by the weakest battery causing potential overload shutdowns
Solution Approach 1:
The patent merges the battery capacity management of multiple UPSs into a coordinated system. The controller receives battery status information from all UPSs and calculates average battery voltage, then adjusts power flow distribution based on individual battery capacity differences. This combining approach allows the system to operate as a unified entity that optimizes runtime by compensating for weaker batteries through stronger ones, rather than being constrained by the weakest link.
Solution Approach 2:
The system dynamically changes the power flow parameter based on battery capacity variations. When a battery has lower capacity (indicated by lower voltage), the controller reduces its power flow contribution and compensates by increasing power flow from UPSs with higher capacity batteries. This parameter adjustment resolves the contradiction by allowing the system to maintain reliable operation while extending overall runtime beyond what any single battery could provide independently.
2Duration of action of moving object
If power flow is adjusted based on battery capacity differences, then runtime is extended by utilizing stronger batteries, but system complexity increases due to coordination requirements
Solution Approach 1:
The controller implements a feedback mechanism where it continuously receives battery status information (voltage levels) from all UPSs in the parallel system. Based on this feedback, the controller calculates the average battery voltage and determines power flow adjustments needed for each UPS. This feedback loop enables the system to automatically adapt power distribution to current battery conditions, extending runtime while keeping control complexity manageable through algorithmic rather than hardware-based coordination.
Solution Approach 2:
The controller acts as an intermediary between the individual UPSs and the load. It receives information from all UPSs, processes the battery capacity data, and distributes power flow commands accordingly. This intermediary approach simplifies the coordination complexity by centralizing the decision-making logic in a single controller rather than requiring direct peer-to-peer communication and coordination between all UPS units, thus extending runtime without proportionally increasing system complexity.
3Reliability
If a UPS with low battery voltage shuts off to protect itself, then battery damage is prevented, but the remaining UPSs may overload and shut down, reducing system availability
Solution Approach 1:
The system transitions from static, independent UPS operation to dynamic, coordinated power flow management. Instead of each UPS operating independently with fixed shutdown thresholds, the controller dynamically adjusts power flow distribution based on real-time battery capacity differences. This dynamic approach allows UPSs with stronger batteries to compensate for weaker ones, preventing the cascade shutdown effect while still protecting batteries from damage, thus maintaining both battery reliability and system availability.
Solution Approach 2:
The controller implements preliminary anti-action by proactively adjusting power flow before a battery reaches its shutdown threshold. Rather than allowing a battery to discharge to critical levels and then shutting off (which causes overload of remaining UPSs), the system preemptively reduces power flow from weaker batteries and redistributes load to stronger ones. This prevents the harmful cascade effect before it occurs, maintaining both battery protection and continuous system availability.
Data Source
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AI summary
An uninterruptible power supply (UPS) system including a plurality of UPSs (110) connected in parallel at a load bus (35) and configured to provide power thereto from respective batteries of a plurality of batteries (20) is operated such that a difference between a variable, for example, battery voltage, indicative of battery capacity for a battery (20) associated with the subject UPS (110) and an average value of the variable for the plurality of batteries (20) is determined and a power flow between the subject UPS (110) and the load bus (35) is controlled responsive to the determined difference. Controlling a power flow between the subject UPS (110) and the load bus (35) responsive to the determined difference may include, for example, controlling a phase of an inverter (112) of the subject UPS (110) responsive to the determined difference.