Hybrid Vehicle Battery SOC Control for Driveability
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Solution Overview
Problem
The performance of secondary batteries in electrically powered vehicles is temperature-dependent and deteriorates over time, leading to decreased output and compromised driveability if not properly managed in charging and discharging control systems.
Innovation Solution
A hybrid vehicle control method that monitors battery temperature, voltage, and current to adjust the state of charge (SOC) control range, setting higher lower limits for SOC to ensure sufficient output power and prevent engine starting failures, using a system with sensors, converters, and a control device to dynamically manage charging and discharging based on battery health and temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the SOC control range is maintained at standard levels regardless of battery condition, then the control system remains simple, but the vehicle driveability deteriorates when battery performance decreases
Solution Approach 1:
The SOC control range is made dynamic rather than fixed. The control device adjusts the SOC control range based on real-time battery temperature and battery deterioration degree, allowing the system to adapt to changing battery conditions and maintain optimal performance across different operational states.
Solution Approach 2:
The system changes the SOC control parameter (SOC control range) based on battery condition parameters (temperature and deterioration degree). By adjusting the SOC control range according to battery state, the system maintains reliable vehicle operation without requiring complete redesign of the control architecture.
2Power
If the SOC control range is adjusted based on battery temperature and deterioration, then sufficient output power is ensured, but the control system becomes more complex
Solution Approach 1:
The control device determines the battery deterioration degree in advance by comparing actual battery characteristics with standard characteristics. This preliminary assessment allows the system to proactively adjust the SOC control range before performance issues arise, ensuring sufficient output power is maintained throughout battery operation.
Solution Approach 2:
The system implements feedback control by continuously monitoring battery temperature and deterioration degree, then adjusting the SOC control range accordingly. The control device uses feedback from battery state measurements to dynamically optimize the SOC control range, ensuring adequate power output while adapting to battery degradation.
3Use of energy by moving object
If the lower limit of SOC is allowed to decrease to maximize energy utilization, then energy efficiency improves, but output power becomes insufficient when battery deteriorates
Solution Approach 1:
The lower limit of the SOC control range is made dynamic based on battery condition. Instead of using a fixed lower limit, the system adjusts it according to battery temperature and deterioration degree, allowing maximum energy utilization when battery performance is good while maintaining sufficient output power when battery deteriorates.
Data Source
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AI summary
The SOC of a power storage device provided in an electrically powered vehicle is controlled not to fall out of a SOC control range (151, 152). When a SOC estimate value reaches a control lower limit value (SOCl) during vehicle traveling, a power generating structure provided in the vehicle starts to charge the power storage device. In the case of low temperature and/or deterioration of the power storage device, i.e., in the case where decrease of performance of the power storage device is concerned, the control lower limit value (SOCl) is increased as compared with that in a normal state. As a result, decrease of driveability and decrease of startability of an engine in the hybrid vehicle, both otherwise caused by insufficient output electric power from the power storage device, can be avoided.