Battery Heating via Motor Inverter AC Injection
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Solution Overview
Problem
Lithium-ion batteries in eco-friendly vehicles face decreased capacity and efficiency at low temperatures due to uneven lithium ion deposition, requiring additional heating devices that increase cost and volume, and existing methods for generating heat inside the battery complicate maintenance.
Innovation Solution
A battery-heating system using a motor-driving system with an inverter and motor that injects AC current into the battery through complementary on-off control of switching elements, minimizing torque pulsation and eliminating the need for a separate heater.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a conventional heater (e.g., PTC heater) is added to the battery to heat it, then the battery temperature can be increased, but the cost and total volume increase
Solution Approach 1:
The inverter's switching elements are controlled to serve dual purposes: motor driving and battery heating. By utilizing the existing inverter components for heating function, the system avoids adding separate heating devices, thereby maintaining cost-effectiveness and compactness while achieving the heating objective
Solution Approach 2:
The battery heating is achieved by utilizing the battery's own internal resistance to generate heat through AC current injection. This self-heating mechanism eliminates the need for external heating devices, reducing system complexity and cost while effectively increasing battery temperature
2Temperature
If a separate dedicated circuit is added to pass current to the battery for heating, then the battery temperature can be increased uniformly, but the volume and cost increase due to additional components
Solution Approach 1:
The inverter's switching elements are controlled to serve dual purposes: motor driving and battery heating. By utilizing the existing inverter components for heating function, the system avoids adding separate heating devices, thereby maintaining cost-effectiveness and compactness while achieving the heating objective
Solution Approach 2:
The battery heating function is merged with the motor driving system by using the same inverter and switching elements. This consolidation eliminates the need for separate heating circuits and components, reducing overall system volume and cost while achieving uniform battery heating through AC current injection
3Temperature
If a separate dedicated circuit is added to pass current to the battery for heating, then the battery temperature can be increased, but the maintenance complexity increases
Solution Approach 1:
The inverter's switching elements are controlled to serve dual purposes: motor driving and battery heating. By utilizing the existing inverter components for heating function, the system avoids adding separate heating devices, thereby maintaining cost-effectiveness and compactness while achieving the heating objective
Solution Approach 2:
The battery heating function is merged with the motor driving system by using the same inverter and switching elements. This consolidation eliminates the need for separate heating circuits and components, reducing overall system volume and cost while achieving uniform battery heating through AC current injection
4Temperature
If AC current is injected into the battery to repeatedly charge and discharge it for heating, then the battery temperature increases efficiently, but torque pulsation may occur
Solution Approach 1:
The switching elements are controlled with periodic on-off patterns to generate AC current for battery heating. The periodic switching creates the necessary alternating current while allowing control over the heating intensity and duration, balancing temperature increase with motor performance
Solution Approach 2:
The control unit monitors motor torque and adjusts the switching element control accordingly. When torque pulsation is detected or anticipated during battery heating, the control unit modifies the switching patterns to minimize torque variation, thereby maintaining motor stability while continuing the heating process
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
Efficiently increases battery temperature without additional costs or volume, promoting vehicle stability by suppressing torque pulsation and preventing lithium precipitation, thus extending battery lifespan.
Implementation Method 1
a method of generating heat inside the battery using electricity has been studied. In this method, the internal resistance of the battery is used, and the loss generated in proportion to the amount of current flowing through the battery is used as heat
Data Source
AI summary
A battery-heating system and method using a motor-driving system is provided. The battery-heating system includes an inverter having legs respectively including a pair of switching elements connected in series between the ends of a battery and corresponding to a plurality of phases. A motor of the system includes coils each having one end connected to a connection end between a pair of switching elements of the legs, other ends of the plurality of coils being connected together. A controller determines one of the plurality of phases as a reference phase, and alternately controls the on-off states of the switching elements so that the on-off state of the switching element included in the leg corresponding to the reference phase and the switching element included in the other leg are mutually complementary, thereby generating AC current to be injected into the battery.