Battery Charging Current Control for Cold-Weather Overvoltage
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional high voltage battery charging systems in electrified vehicles fail to communicate charging current limitations effectively, leading to overvoltage malfunctions, particularly at cold ambient temperatures and high state of charge conditions, due to the slower operating speed of the supervisory controller compared to the on-board charging module.
Innovation Solution
A charging control system that includes a supervisory controller performing closed-loop control based on error accumulation, temporarily suspending and decrementing the error, and updating the charging current to compensate for lesser loads, preventing overvoltage by modifying the closed-loop control when the OBCM fails to meet the requested current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the supervisory controller uses closed-loop control with error accumulation to manage charging current requests, then the charging control precision is improved, but the system reliability deteriorates due to overvoltage malfunctions when the OBCM cannot meet the requested current under cold and high SOC conditions
Solution Approach 1:
The supervisory controller applies preliminary anti-action by detecting when the OBCM is operating at speed limits or reporting overvoltage conditions, and proactively adjusting the charging current request downward before an overvoltage malfunction occurs. This prevents the windup effect by counteracting the error accumulation that would otherwise cause the charging current request to exceed safe limits.
Solution Approach 2:
The system uses feedback from the OBCM regarding its operating status (speed limits, overvoltage conditions, actual charging current delivery) to dynamically adjust the supervisory controller's charging current requests. This closed-loop feedback mechanism allows the supervisory controller to recognize when the OBCM cannot meet requested currents and modify its control strategy accordingly, preventing overvoltage malfunctions while maintaining charging precision.
2Device complexity
If the supervisory controller operates at slower speed compared to the OBCM, then the device complexity is reduced, but the productivity deteriorates due to delayed response and error accumulation windup
Solution Approach 1:
The supervisory controller performs preliminary action by calculating and adjusting the charging current request based on predicted OBCM capabilities and system conditions before the OBCM executes the charging cycle. By anticipating the OBCM's response limitations and pre-adjusting requests, the supervisory controller compensates for its slower operating speed and prevents error accumulation windup without requiring increased controller complexity.
3Reliability
If the OBCM limits charging current to protect the battery from overcharging, then the battery safety is improved, but the loss of information occurs as the OBCM does not communicate this limitation to the supervisory controller, causing charging current request windup
Solution Approach 1:
The OBCM provides feedback to the supervisory controller about its operating status, including when it is operating at speed limits or encountering conditions that prevent it from meeting requested charging currents. This feedback mechanism ensures the supervisory controller is informed of charging limitations, preventing error accumulation windup while maintaining battery safety through coordinated control.
Data Source
AI summary
A charging control system for a high voltage battery system of an electrified vehicle includes an on-board charging module (OBCM) configured to control a charging current provided to the high voltage battery system and a supervisory controller configured to perform closed-loop control of a requested charging current provided to the OBCM based on feedback from the OBCM including a commanded charging current, wherein the closed-loop control is based on an accumulation of an error between the requested and commanded charging currents and, when the accumulated error exceeds a threshold, temporarily adjust the closed-loop control of the commanded charging current request to the OBCM to prevent an overvoltage malfunction of the high voltage battery system by (i) suspending the accumulation of the error, (ii) decrementing the accumulated error, and (iii) updating the requested charging current to compensate for a lesser load than a total load on the electrified vehicle.