DC/DC Converter Current Control for mHEV Battery Thermal Management
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Solution Overview
Problem
Mild hybrid electric vehicles (mHEVs) with 48V battery packs experience rapid temperature increases during operation, particularly during regenerative braking, limiting vehicle performance and fuel economy due to higher per-cell root mean square current (IRMS) leading to heat generation issues.
Innovation Solution
A hybrid vehicle system incorporating a DC/DC converter that dynamically adjusts electrical communication between high-voltage and low-voltage bus networks based on battery temperature and current thresholds, using a controller to manage thermal properties by altering charging and discharging currents to maintain optimal temperatures, and employing a cooling system for thermal regulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the DC/DC converter operates at high current during regenerative braking to maximize energy recovery, then energy efficiency is improved, but battery temperature increases rapidly exceeding thermal thresholds
Solution Approach 1:
The DC/DC converter dynamically adjusts its operating current based on real-time battery temperature conditions. During regenerative braking, the controller monitors battery temperature and automatically reduces the current acceptance rate when thermal thresholds are approached, transforming the static converter into a dynamic thermal-management device that adapts its energy recovery rate to prevent overheating while maximizing efficiency within safe thermal limits
Solution Approach 2:
The system changes the electrical parameters (current, voltage, power) of the DC/DC converter based on battery temperature feedback. When battery temperature exceeds predetermined thresholds, the controller modifies the converter's operating parameters to reduce charging current, thereby controlling heat generation while maintaining optimal energy recovery within thermal safety boundaries
2Temperature
If the DC/DC converter limits current to maintain battery temperature below thresholds, then thermal management is improved, but energy recovery and fuel economy deteriorate
Solution Approach 1:
The controller performs preliminary thermal assessment before full energy recovery operation. By predicting battery temperature rise based on current thermal conditions and anticipated regenerative braking events, the system proactively adjusts DC/DC converter current limits in advance, preventing thermal excursions while maximizing energy recovery opportunity without sacrificing fuel economy
Solution Approach 2:
The system applies partial current limiting only when and where thermal thresholds are approached, rather than uniformly restricting all current flow. This selective partial action allows the DC/DC converter to operate at full capacity during cool conditions, recovering maximum energy, while applying minimal necessary current reduction only when thermal management becomes critical, thereby preserving fuel economy
3Reliability
If the controller continuously monitors and adjusts DC/DC converter current based on multiple battery parameters, then battery life is extended, but system complexity increases
Solution Approach 1:
The battery management system performs self-service thermal management by autonomously monitoring its own temperature, state of charge, and current flow, then automatically adjusting DC/DC converter operation accordingly. This self-regulating capability extends battery life through continuous optimal condition maintenance without requiring complex external control systems or manual intervention
Solution Approach 2:
The DC/DC converter is designed with multi-functionality, serving both as an energy recovery device during regenerative braking and as a thermal management device through its controllable current regulation. This universal design allows a single component to perform multiple functions (energy conversion and thermal control), reducing overall system complexity while extending battery life through integrated thermal management
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system effectively manages thermal properties by reducing battery temperatures and optimizing power capabilities, thereby enhancing vehicle performance, fuel economy, and extending battery life by dynamically adjusting electrical communication and utilizing thermal management strategies.
Implementation Method 1
a direct current to direct current electrical converter configured to selectively permit electrical communication of either a predetermined first current value and a second predetermined current value between a first electrical bus network and a second electrical bus network
Implementation Method 2
The internal combustion engine may be in mechanical communication with the generator such that torque produced by the engine is converted into electrical energy and supplied to the first electrical bus network
Implementation Method 3
employing a cooling system for thermal regulation
Implementation Method 4
employing a cooling system for thermal regulation
Implementation Method 5
higher per-cell root mean square current (IRMS) leading to heat generation issues
Data Source
AI summary
A power system includes a primary bus connected to a traction battery, a secondary bus connected to an auxiliary battery, a power converter between the traction and auxiliary batteries, and a controller. The controller commands the power converter to increase a magnitude of current output to the secondary bus when an amount of charge current received by the traction battery exceeds a first amount threshold and commands the power converter to decrease the magnitude when an amount of charge current received by the auxiliary battery exceeds a second amount threshold.