Adaptive Power Limiting for Multi-Battery Electric Vehicles
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Solution Overview
Problem
Electric vehicles equipped with multiple power storage devices face challenges in limiting electric power to prevent overdischarging and overcharging, leading to inefficient power distribution and potential shortages, especially due to varying internal resistances among devices.
Innovation Solution
A power limiting apparatus that calculates and applies limit values for each power storage device, allowing for compatible electric power management by limiting the sum of power in driving conditions and individual device power in braking conditions, ensuring sufficient power for the vehicle while protecting devices from overcharging and overdischarging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electric power is limited in accordance with the state of each power storage device, then electric power can be effectively protected from overdischarging and overcharging, but electric power shortage occurs reducing the driving force of the vehicle
Solution Approach 1:
The patent applies dynamics by making the power limitation strategy adaptive based on operating conditions. The control device dynamically switches between two limitation modes: (1) limiting each power storage device individually based on its state of charge when protection is prioritized, and (2) limiting the total power based on the sum of individual limit values when driving force is prioritized. This dynamic adjustment resolves the contradiction by allowing the system to achieve both protection and sufficient driving force under different conditions.
2Device complexity
If total charging power or discharging power into/from the plurality of power storage devices is limited, then power management is simplified, but charging power or discharging power into/from each individual device is not necessarily limited to a limit value
Solution Approach 1:
The patent applies segmentation by dividing the power limitation control into two hierarchical levels: (1) individual device level, where each power storage device has its own limit value calculated based on its state of charge, and (2) system level, where the total power is limited based on the sum of individual limit values. The control device segments the limitation strategy by first determining individual device limits and then aggregating them for total system limitation, ensuring both individual protection and simplified overall management.
3Quantity of substance
If a plurality of power storage devices are connected in parallel, then total capacity is increased, but charging current or discharging current into/from each device varies when internal resistance varies
Solution Approach 1:
The patent applies local quality by recognizing that each power storage device has different internal resistance characteristics and treating them individually rather than uniformly. The control device calculates a specific limit value for each device based on its state of charge and internal resistance, then applies individualized power limitation to each device. This ensures that devices with different internal resistances receive appropriate power distribution, preventing excessive current to devices with low internal resistance while maintaining total system capacity.
Data Source
AI summary
In a first condition, the sum of discharging power from a first battery stack and discharging power from a second battery stack is limited in accordance with the sum of a limit value of discharging power from the first battery stack and a limit value of discharging power from the second battery stack. In a second condition, electric power of the battery stacks is limited in accordance with either the limit value of discharging power from the first battery stack or the limit value of discharging power from the second battery stack.