Dynamic Battery Charge Discharge Control for Hybrid Vehicles
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Solution Overview
Problem
Existing secondary battery charge/discharge control systems fail to reliably prevent overcharge and overdischarge, leading to reduced battery performance and shortened lifespan, especially in hybrid vehicles where precise SOC control is crucial.
Innovation Solution
A charge/discharge control device equipped with a battery state estimation portion, input/output-allowed time prediction, and load control, which dynamically estimates the battery's internal state using a battery model to predict allowed charge/discharge times and power limits, preventing overcharge and overdischarge by generating operation commands based on real-time conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If charge/discharge control is performed by setting inputtable/outputtable power limits according to battery state, then battery lifetime is protected, but maximum battery performance cannot be achieved
Solution Approach 1:
The patent applies dynamics by transitioning from static power limits to dynamic power limits that adapt in real-time to battery state. The ECU continuously calculates allowable charge/discharge power based on current SOC, temperature, and battery characteristics, enabling the power limits to change dynamically throughout the battery's operational life and charge cycles, thus maximizing performance while protecting lifetime
Solution Approach 2:
The patent implements parameter changes by adjusting power limits based on varying battery parameters such as SOC, temperature, and aging characteristics. The system modifies the allowable charge/discharge power parameters according to the actual battery state, enabling optimal performance extraction at each moment while maintaining protection against degradation
2Reliability
If SOC control is maintained at midpoint (50-60%) to enable regenerative power reception, then battery can receive regenerative power and supply power immediately, but charge/discharge flexibility is restricted
Solution Approach 1:
The system dynamically adjusts SOC targets and power limits based on real-time conditions rather than maintaining a fixed midpoint SOC. The ECU calculates optimal charge/discharge strategies adaptively, allowing the SOC to vary dynamically while ensuring power availability when needed, thus providing both reliability and flexibility
3Duration of action of stationary object
If regenerative braking charge is restricted based on predicted deterioration, then battery lifetime is prolonged, but energy recovery efficiency is reduced
Solution Approach 1:
The system changes the approach from binary restriction to continuous parameter adjustment. Instead of simply restricting regenerative charging when deterioration is predicted, the ECU calculates the optimal charge power parameter that balances energy recovery with lifetime protection, allowing partial charging based on current battery state and deterioration risk
Data Source
AI summary
A state estimation value indicating a battery state is successively calculated from time to time according to a battery model capable of dynamically estimating the internal state of the secondary battery by using an inspection value of a sensor group indicating the secondary battery behavior. By using the sate estimation value at each moment estimated by the battery model expression at each predetermined cycle, an I/O-enabled time is predicted when a predetermined power is continuously inputted (charged) or outputted (discharged) from the current moment. A load operation instruction of the secondary battery is set so as to avoid overcharge and over-discharge of the secondary battery according to the operation request to the load and by considering the predicted characteristics between input/output power and input/output-allowed time.