Battery SoP Prediction With Nested Loops for Power Limit Accuracy
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing battery management systems (BMS) face inaccuracies in predicting battery State-of-Power (SoP), leading to potential overestimation of current and/or voltage, which can cause additional wear and limit battery performance.
Innovation Solution
Implementing nested control loops with an inner and outer control loop to update an equivalent circuit model (ECM) based on voltage and current errors, ensuring accurate maximum current and power predictions within predefined limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conservative power limits are set for the BMS to operate within, then the risk of cell current and voltage limit violations is reduced, but the battery power output and vehicle capabilities are limited
Solution Approach 1:
The patent implements a feedback mechanism where the BMS continuously monitors actual cell voltage and current, compares them against predicted values from the ECM, and uses the resulting errors to update the model parameters. This closed-loop feedback enables the system to adapt to actual battery behavior, allowing more accurate and higher power limits to be set while maintaining reliability by detecting and correcting prediction deviations in real-time
Solution Approach 2:
The patent dynamically changes the parameters of the equivalent circuit model based on operating conditions and error feedback. By adjusting model parameters such as resistance and capacitance values according to actual battery performance, the system can accurately predict voltage and current behavior under varying loads, enabling higher power output while maintaining safety margins
2Measurement precision
If adaptive SoP-prediction algorithms are used to minimize predicted cell voltage error, then more accurate maximum current prediction is achieved, but current and voltage overshoot may still occur due to overestimation
Solution Approach 1:
The patent uses feedback to continuously monitor the difference between predicted and actual voltage and current values. When overshoot or deviation is detected, the system updates the ECM parameters to correct the prediction error, thereby eliminating current and voltage overshoot while maintaining accurate maximum current prediction capability
Solution Approach 2:
The patent applies beforehand cushioning by maintaining a safety margin in the voltage prediction model. The BMS predicts future voltage with built-in conservatism and adjusts the maximum current limit accordingly, preventing overshoot before it occurs while still allowing the battery to operate near its true capacity limits
Data Source
Figure 1~3
Figure 4A~5
Figure 6A
AI summary
A device (100) for State-of-Power (SoP) prediction is provided. The device implements an inner (110) and outer (120) control loop. In the inner loop, an equivalent circuit model (ECM, 130) is used to predict a maximum allowed current ( lmax') so as not to go beyond a predefined voltage limit (Vlim) at an end of a predefined time period/interval. A voltage error (Verr) between the predefined voltage limit and an actual voltage (Vt) at the end of the time interval is used to update the ECM. In the outer loop, a current error (Ierr) between the maximum allowed current and an actual current (I) at the end of the interval is used to update the same ECM. The ECM is used to predict future voltage (Vtp), that together with the maximum allowed current is used to determine a maximum power (Pmax) for the interval. A corresponding method is also provided.