AC Motor Battery Heating With Zero-Torque d-Axis Injection
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Solution Overview
Problem
Lithium batteries in electric vehicles experience reduced discharge performance and are prone to damage at low temperatures, limiting charging and discharge capabilities until they reach a certain temperature, especially at sub-zero temperatures, which affects performance and longevity.
Innovation Solution
The method involves using a field-oriented controller to inject an AC signal onto the d-axis of an AC motor coupled to the battery pack, controlling the rotor to achieve maximum heating efficiency, thereby maintaining the battery temperature within optimal ranges for charging and discharging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lithium battery operates at low temperatures, then discharge performance is reduced and battery is prone to damage, but adding heating mechanisms increases device complexity
Solution Approach 1:
The motor controller is designed to perform multiple functions: normal motor control and battery heating. By utilizing the existing inverter and motor as heating elements, the system avoids adding separate heating devices, thus reducing overall system complexity while maintaining battery reliability
Solution Approach 2:
The battery heating is achieved using the motor and inverter components that are already part of the vehicle's propulsion system. The system uses its own existing components (motor windings and inverter switches) to generate heat for the battery, eliminating the need for external heating devices and reducing device complexity
2Temperature
If AC signal is injected onto d-axis for battery heating, then battery temperature is maintained within optimal ranges, but torque ripple and vibration increase
Solution Approach 1:
An AC signal is injected onto the d-axis to produce periodic heating effect in the battery. The periodic nature of the AC signal allows for controlled heat generation while the amplitude and frequency can be adjusted to minimize harmful torque ripple and vibration effects
Solution Approach 2:
The amplitude and frequency of the injected AC signal are optimized to achieve effective battery heating while minimizing torque ripple and vibration. By adjusting these parameters, the system balances thermal management effectiveness with mechanical stability
3Temperature
If discharge current self-heating is used, then battery temperature increases, but charging capability at low temperatures remains limited due to anode plating
Solution Approach 1:
The system performs preliminary heating of the battery using the motor and inverter before charging operations. By pre-heating the battery to optimal temperature ranges, the system eliminates the anode plating issue that occurs at low temperatures, thereby enabling effective charging
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
This approach effectively improves battery performance and extends its lifespan by maintaining optimal temperature ranges during charging and discharging, reducing charge time and minimizing damage from low-temperature aggressive discharge.
Implementation Method 1
an alternating current (AC) motor coupled to the battery pack through a power inverter module
Implementation Method 2
Lithium batteries may be preferred in many applications, including propulsion systems, due to their high energy density
Data Source
AI summary
A method and apparatus for heating a battery pack in an electrified vehicle provides a zero d-axis current command and a zero q-axis current command to a field-oriented controller for an alternating current (AC) motor coupled to the battery pack through a power inverter module controlled by the field-oriented controller. An AC signal is injected onto the d-axis of the field-oriented controller resulting in an AC current through the battery pack effecting AC resistance heating.