Parallel Battery SOC Balancing via DC-DC Converter Voltage Control
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Solution Overview
Problem
In parallel battery systems, the charging and discharging process is often halted when one battery reaches 0% or 100% state of charge (SOC), leading to uneven SOC balances and wasted residual energy due to differences in SOC among batteries, resulting in suboptimal battery capacity utilization.
Innovation Solution
A method and apparatus for controlling the SOC of batteries connected in parallel by calculating and adjusting the output voltage command values of DC-DC converters to perform SOC average control, excess component output, and SOC limit value control, ensuring balanced SOC across batteries through amplification and subtraction of differences, thereby minimizing residual energy waste.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If parallel battery system charges or discharges when one battery reaches 0% or 100% SOC first, then system operation is simple and fast, but SOC balance becomes uneven and residual energy is wasted
Solution Approach 1:
The patent changes the control parameter from simple charge/discharge termination to active SOC balancing control. By continuously monitoring and adjusting the SOC of each battery through DC-DC converters, the system maintains all batteries within optimal charge ranges, preventing residual energy waste while preserving fast charging/discharging capability
Solution Approach 2:
The patent implements feedback control by continuously measuring the SOC of each battery and using this information to adjust the output voltage command values of DC-DC converters. This closed-loop control ensures that SOC differences between batteries are actively corrected, preventing energy waste while maintaining system productivity
2Device complexity
If SOC balance control is not performed, then system control is simple, but battery capacity is not fully utilized due to uneven SOC distribution
Solution Approach 1:
The patent introduces dynamic SOC balancing control that adapts to the real-time state of batteries. The control system dynamically adjusts output voltage command values based on current SOC levels, enabling the system to respond to changing battery states and maximize capacity utilization without requiring overly complex static control structures
Solution Approach 2:
The patent segments the control of each battery individually through separate DC-DC converters, allowing independent SOC management for each battery unit. This segmentation enables precise control of each battery's charge state while maintaining overall system coordination, improving capacity utilization without excessive complexity
3Reliability
If DC-DC converter output voltage command values are adjusted based on SOC differences, then SOC balance is improved, but control algorithm complexity increases
Solution Approach 1:
The patent uses DC-DC converters as intermediary devices between the control algorithm and the batteries. These converters translate complex SOC balancing requirements into simple voltage command adjustments, isolating the complexity of the control logic from the battery management system while maintaining reliable SOC balance
Data Source
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AI summary
A method of controlling state of charge (SOC) of a first battery and a second battery that are connected in parallel with each other, includes: calculating the SOC of the first battery and the SOC of the second battery; controlling output voltage command values of a first direct current (DC-DC) converter and a second DC-DC converter based on the SOC of the first battery and the SOC of the second battery, the first DC-DC converter and the second DC-DC converter being connected to ends of the first battery and the second battery, respectively; and controlling the SOC of the first battery and the SOC of the second battery based on the controlling of the output voltage command values of the first DC-DC converter and the second DC-DC converter.