Control of DC-DC Power Converters with Battery Cell Inputs and Series and Parallel Outputs
Electrical & Computer Engineering
Abstract
USU researchers have developed a control scheme that eliminates the drawbacks of conventional control architectures in battery packs. One aspect of the invention permits stable operation of the battery pack in both charging and discharging conditions. Another aspect of the invention allows cell-level control to force the degradation of individual cells. This technology allows for hot swapping of battery cells to increase modularity and flexibility regardless of battery chemistry.
Problem
Lithium-ion batteries, common in grid applications, produce a relatively low voltage limited to parallel operation of battery packs or cells. A high voltage must come from a lithium-ion battery series, which can be difficult to regulate.
Solution
This technology regulates the input and output voltages to bring the same charge across each battery cell. This creates the necessary voltage for the batteries through what is called a variable droop.
Value Proposition
This invention permits stable operation of a battery pack in both charging and discharging conditions, provides modularity and scalability, and allows cell-level control of battery cells for life extension and balancing.
Benefit
USU researchers have developed a control scheme that eliminates the drawbacks of conventional control architectures in battery packs, specifically related to output voltage sharing among series-connected battery modules in a plug-and-play (PnP) DC microgrid. Traditional voltage regulation approaches are not suitable for PnP systems due to their variable output voltages. Instead, USU researchers provide a current regulation strategy that utilizes existing cell current sensors to improve modularity and eliminate the need for additional output current sensors. Research introduces an I-V droop control method to address asymmetries between charging and discharging modes, ensuring effective voltage sharing across modules. Experimental validation on a 1.5 kW system demonstrates successful voltage and power sharing, with minimal voltage differences among modules during operation. This invention aims to improve the modularity and scalability of battery systems by regulating input current rather than output voltage, while addressing stability concerns in series-connected converters.
This allows for improved performance in high-capacity applications while minimizing complexity and cost. Experimental results confirm its effectiveness in maintaining balanced charge levels across different battery configurations.
Market Application
Businesses that work with large scale battery management systems, switches for battery packs, and lithium battery manufacturing will benefit from functionalities offered by this technology.
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Inventors
Regan A Zane, Ph.D.
USU ASPIRE Engineering Research Center
Dragan Maksimovic, Ph.D.
USU ASPIRE Engineering Research Center
Mohamed Ahmed Kamel Ahmed, Ph.D.
University of Colorado Boulder Department of Electrical, Computer and Energy Engineering
Developed in cooperation with:
University of Colorado Boulder
Funding
This invention was made with government support under contract #N00014-16-1-2986 awarded by the Office of Naval Research. The government has certain rights in this invention.
USU Reference No. C20022
Priority Date: June 17, 2020