Inverter Battery Heating via AC Current
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Solution Overview
Problem
Lithium ion batteries used in eco-friendly vehicles face reduced capacity and efficiency at low temperatures, leading to premature degradation due to irregular lithium ion deposition, and existing temperature increase methods, such as separate heaters or electrical heating, incur additional costs and complexity.
Innovation Solution
A system and method utilizing an inverter with switching devices and a controller to generate alternating current (AC) at a preset frequency, which alternately controls the on/off state of switching devices in the inverter legs to efficiently increase battery temperature without a separate heating device, using the internal resistance to generate heat while minimizing torque generation in the motor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a separate heater is installed in the battery to increase temperature, then the battery temperature can be increased, but the additional costs and volume of the battery increase
Solution Approach 1:
The inverter legs are designed to perform dual functions: motor driving during normal operation and battery heating during low-temperature conditions. By controlling the switching devices in the inverter legs, the system can generate AC current that flows through the battery to produce heat via internal resistance, eliminating the need for a separate heater
Solution Approach 2:
The battery's own internal resistance is utilized as the heating element. By circulating AC current through the battery using the inverter, the battery generates heat internally through resistive heating, serving its own heating needs without external heating components
2Temperature
If electrical heating method is used by enabling current to flow in the battery, then the battery temperature can be increased uniformly, but a separate dedicated circuit is needed which increases volume, costs, and maintenance complexity
Solution Approach 1:
The existing inverter circuit is made multi-functional by enabling it to perform both motor control and battery heating operations. The same switching devices and control circuitry used for motor driving are repurposed to generate heating current, eliminating the need for a separate dedicated heating circuit
Solution Approach 2:
The motor driving function and battery heating function are merged into a single inverter system. By controlling the switching devices appropriately, the system can switch between motor operation mode and battery heating mode, combining two functions into one integrated system
3Temperature
If conventional heater is installed to increase battery temperature, then the battery temperature can be increased, but the additional costs increase
Solution Approach 1:
The battery system uses its own internal resistance as the heating element, converting electrical energy directly into thermal energy within the battery. This self-heating approach eliminates the need for external heaters and associated manufacturing costs
Solution Approach 2:
The mechanical/electrical heating system (separate heater) is replaced with an electrical field-based heating method. By controlling the flow of AC current through the battery using the inverter, heat is generated electronically through resistive heating, replacing the need for physical heating components
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
Effectively increases battery temperature without additional costs or complexity, inhibiting lithium precipitation and enhancing energy efficiency, thus extending battery lifespan and maintaining vehicle stability.
Implementation Method 1
the internal resistance of a battery is used to enable current to flow in the battery, and loss generated in proportion to the amount of flowing current is used as heat
Data Source
AI summary
A system for increasing a temperature of a battery includes an inverter including a plurality of legs each including one pair of switching devices connected in series to each other between opposite ends of the battery and corresponding to a plurality of phases, respectively, a motor including a plurality of coils corresponding to the plurality of phases, respectively, where one end of each of the plurality of coils is connected to a connection node between one pair of switching devices included in a corresponding leg and other ends of the coils are connected to each other, and a controller configured to select two phases of the plurality of phases, and to alternately control an on/off state of switching devices included in two legs in the inverter, corresponding to the two selected phases, at a preset switching frequency to generate alternating current (AC) supplied to the battery.