Battery Stack Current Balancing to Prevent Power Foldback
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Solution Overview
Problem
Conventional battery systems, such as multi-stack redox flow battery systems, are limited by underperforming stacks, which constrain overall power output and can lead to power foldback, as they evenly distribute power demand without accounting for individual stack performance, resulting in reduced efficiency and capacity.
Innovation Solution
A method that adjusts discharging and charging currents of each battery stack in real-time based on estimated overpotential, allowing higher performing stacks to compensate for underperforming ones, thereby optimizing power output and preventing power foldback, while also preventing overplating in plating redox flow battery systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If power demand is evenly distributed across all battery stacks, then system simplicity is maintained, but overall power output is constrained by underperforming stacks
Solution Approach 1:
The patent implements individualized current setpoints for each battery stack based on their specific performance characteristics. The controller determines a current setpoint for each stack according to its state of charge, temperature, and health status, rather than applying a uniform distribution. This local optimization allows high-performing stacks to contribute more power while underperforming stacks operate within their capabilities, thereby increasing overall system power output without significantly increasing control complexity.
2Power
If higher current is applied to maximize power output, then power delivery is improved, but overplating occurs during charging
Solution Approach 1:
The patent employs continuous monitoring of battery stack parameters including state of charge, temperature, and current. The controller uses this feedback information to dynamically adjust current setpoints for each stack. During charging, when metal plating is involved, the system monitors the charging current and stack conditions to prevent excessive current that would cause overplating. This feedback mechanism allows the system to maximize power delivery while preventing harmful overplating effects.
Solution Approach 2:
The patent implements dynamic current setpoint adjustment based on real-time battery conditions. Rather than using fixed current limits, the system continuously adapts the current applied to each stack according to its instantaneous state of charge, temperature, and performance characteristics. This dynamic approach enables higher current delivery when conditions permit, maximizing power output, while automatically reducing current when conditions indicate risk of overplating or other degradation.
3Ease of operation
If uniform current setpoints are used for all stacks, then control simplicity is maintained, but system efficiency is reduced due to underutilization of high-performing stacks
Solution Approach 1:
The patent changes the control parameter from a single uniform current setpoint applied to all stacks to individualized current setpoints for each stack. The controller determines specific current values for each stack based on their state of charge, temperature, and health status. This parameter differentiation allows high-performing stacks to operate at higher efficiency points while maintaining simple overall control architecture through automated determination of appropriate setpoints for each unit.
Data Source
AI summary
Systems and methods are provided for operating a battery power module. In one example, the method may include constraining an electrical parameter of the battery power module to be constant among a plurality of battery stacks of the battery power module and determining current setpoints for each of the plurality of battery stacks of the battery power module based on an estimated overpotential of each of the plurality of battery stacks of the battery power module.