Redox Flow Battery SOC Balancing for High-Voltage Series Modules
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Solution Overview
Problem
Existing redox flow batteries face challenges in achieving high voltage output while minimizing leakage current and maintaining State of Charge (SOC) uniformity between modules, leading to increased system costs and reduced efficiency due to the use of high-power DC/DC converters and decreased discharge capacity.
Innovation Solution
A high voltage-type redox flow battery system with an SOC balancing device and battery management system (BMS) that connects multiple modules in series, utilizing passive and active balancing methods to equalize SOC across modules, and employs parallel DC/DC converters to optimize power conversion efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple modules are connected in series to increase output voltage, then power conversion efficiency increases and system costs decrease, but leakage current increases and voltage deviation between cells occurs
Solution Approach 1:
The system is divided into multiple independent modules, each with its own electrolyte circulation system. Modules are connected in series electrically but remain physically independent with separate tanks and flow paths. This segmentation prevents leakage current from propagating across the entire system while maintaining high voltage through series connection.
Solution Approach 2:
DC/DC converters are introduced as intermediary devices between modules to manage voltage and current distribution. These converters act as mediators that balance the electrical parameters across series-connected modules, preventing voltage deviation and ensuring uniform SOC while allowing high voltage output.
2Power
If different modules that do not share electrolyte are connected in series, then leakage current between modules is eliminated and high voltage is achieved, but discharge capacity decreases due to uneven SOC between modules
Solution Approach 1:
The BMS continuously monitors SOC of each module and uses this feedback information to control the DC/DC converters. Based on real-time SOC data, the system dynamically adjusts current distribution to balance charges between modules, ensuring uniform SOC and maximizing discharge capacity while maintaining high voltage output.
Solution Approach 2:
The system dynamically adjusts operating parameters during charging and discharging cycles. The DC/DC converters modify their conversion ratios and current outputs in real-time based on SOC differences, enabling flexible adaptation to maintain balance across modules and optimize overall system performance.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system increases output voltage, reduces power conversion device costs, and enhances system efficiency by minimizing leakage current and maintaining uniform SOC, thereby improving discharge capacity and reducing the need for high-power DC/DC converters.
Implementation Method 1
RFB (redox flow battery) has a structure in which electrolytes are stored in separate tanks 30a, 30b, and liquid electrolytes stored in the tanks circulate inside cells 9 which make up the stacks 10a, 10b, 10c to perform charging and discharging
Implementation Method 2
since cells in the stack sharing the same tank are connected by a common flow path and the electrolyte acts as a conductor, an undesired current called a leakage current flows through the electrolyte
Data Source
AI summary
The present invention relates to a high voltage-type redox flow battery comprising: a plurality of modules (1001, 1002, 1003, . . . , 100n) which are serially connected; and a battery management system (BMS) for monitoring a state-of-charge (SOC) of each of the plurality of modules (1001, 1002, 1003, . . . , 100n), wherein each of the modules (1001) includes an SOC balancing device comprising a stack (10), a positive electrode electrolyte tank (30a), a positive electrode pump (20a) for providing a positive electrode electrolyte of the positive electrode electrolyte tank (30a) to the stack (10), a positive electrode inlet pipe (21a) connecting the positive electrode electrolyte pump (20a) to the stack (10), a positive electrode outlet pipe (11a) connecting the stack (10) to the positive electrode electrolyte tank (30a), a positive electrode tank outlet pipe (31a) connecting the positive electrode electrolyte tank (30a) to the positive electrode electrolyte pump (20a), a negative electrode electrolyte tank (30b), a negative electrode pump (20b) for providing a negative electrode electrolyte of the negative electrode electrolyte tank (30b) to the stack (10), a negative electrode inlet pipe (21b) connecting the negative electrode electrolyte pump (20b) to the stack (10), a negative electrode outlet pipe (11b) connecting the stack (10) to the negative electrode electrolyte tank (30b), and a negative electrode tank outlet pipe (31b) connecting the negative electrode electrolyte tank (30b) to the negative electrode electrolyte pump (20b).