Induction Motor Slip Frequency Control for Electric Vehicle Battery Heating
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Solution Overview
Problem
In electrically-driven vehicles, low battery temperatures lead to reduced operability and fuel efficiency due to limited charge and discharge power, necessitating a method to accelerate battery temperature rise without additional heating apparatus.
Innovation Solution
The vehicle employs an electronic control unit to adjust the slip frequency command of the induction motor, increasing the amplitude of battery current fluctuation, thereby accelerating battery temperature rise by optimizing the frequency of current ripple components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the battery temperature is low, then the battery protection is ensured by limiting charge and discharge electric power, but the operability deteriorates due to reduction in regenerative torque and fuel efficiency deteriorates due to reduction in regenerative power
Solution Approach 1:
The invention changes the operating parameters of the induction motor (slip frequency) to increase current fluctuation amplitude, which generates heat in the battery through increased I²R losses. This parameter change allows the battery temperature to rise without modifying the battery itself or adding heating apparatus, thereby resolving the contradiction between protecting the battery and maintaining operability.
2Reliability
If the battery temperature is low, then the battery protection is ensured by limiting charge and discharge electric power, but the fuel efficiency deteriorates due to enlargement of engine drive zone
Solution Approach 1:
The invention utilizes the induction motor's own operational characteristics to generate heat within the battery. By adjusting the slip frequency to increase current fluctuations, the battery heats itself through increased resistive losses, eliminating the need for external heating systems and the associated energy losses, thus improving fuel efficiency while maintaining battery protection.
3Temperature
If additional heating apparatus is used to raise battery temperature, then the battery temperature rise is accelerated, but the device complexity and cost increase
Solution Approach 1:
The invention makes the battery heat itself by utilizing the induction motor's current fluctuations. The battery's internal resistance converts the increased current fluctuations directly into heat within the battery, eliminating the need for external heating apparatus and reducing system complexity and cost.
Solution Approach 2:
The invention converts what would normally be considered harmful effects (current fluctuations and I²R losses) into a beneficial outcome (battery heating). By intentionally increasing the current fluctuation amplitude through slip frequency adjustment, the previously wasted energy dissipation becomes a useful heating mechanism.
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 raises battery temperature, enhances operability, and improves fuel efficiency by increasing charge and discharge power limits at low temperatures, while reducing costs by eliminating the need for dedicated heating systems.
Implementation Method 1
increasing the amplitude of the current fluctuation... accelerate the temperature rise of the battery
Data Source
AI summary
An electrically-driven vehicle includes: a battery; an induction motor connected to the battery; a synchronous motor connected to the battery that is connected to the induction motor; and at least one electronic control unit configured to change a slip frequency command of the induction motor based on a predetermined frequency of current fluctuation when a temperature of the battery is low such that an amplitude of the current fluctuation increases, the current fluctuation being any one of current fluctuation of a battery current or current fluctuation of a battery-related current that relates to the battery current.