WRSM Current Control for Battery Heating in Cold EVs
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Solution Overview
Problem
Electrified vehicles face challenges in maintaining battery performance in cold temperatures due to insufficient waste heat generation, leading to reduced efficiency and vehicle range, and existing auxiliary heaters increase complexity and reduce efficiency.
Innovation Solution
A wound rotor synchronous electric machine (WRSM) is controlled to generate heat by adjusting rotor and stator currents, transferring heat to the battery and other components through a closed-loop system, eliminating the need for auxiliary heaters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If auxiliary electric heaters are provided to heat the battery in cold temperatures, then battery temperature is improved, but device complexity and system complexity increase
Solution Approach 1:
The electric machine is designed to perform multiple functions: propulsion and heating. By controlling the electric machine to operate in a high-loss mode, it generates heat that is transferred to the battery through the cooling system, eliminating the need for separate auxiliary heaters and reducing system complexity.
Solution Approach 2:
The electric machine serves itself by generating its own waste heat during normal operation and redirecting this heat to the battery when needed. The cooling system, already present for thermal management, is repurposed to transfer heat from the electric machine to the battery, creating a self-sufficient heating solution.
2Temperature
If auxiliary electric heaters are provided to heat the battery, then battery temperature is improved, but overall efficiency and vehicle electric range are reduced
Solution Approach 1:
The high electrical losses in the electric machine, which are normally wasted energy reducing vehicle range, are converted into a beneficial heat source for the battery. By intentionally operating the electric machine in a high-loss mode and transferring this waste heat to the battery, the system turns an energy liability into a useful thermal resource, eliminating the need for additional heating energy.
3Temperature
If rotor current is reduced and stator current is increased for heating, then heat generation is improved, but electric machine efficiency is reduced
Solution Approach 1:
The electric machine operates in different modes depending on thermal requirements. During normal propulsion, it operates efficiently. When heating is needed, the controller dynamically adjusts the operating point by reducing rotor current and increasing stator current, accepting temporary efficiency reduction to generate the necessary heat for battery 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 WRSM provides efficient heating of vehicle components, maintaining battery performance in cold conditions while enhancing vehicle range and reducing system complexity.
Implementation Method 1
a cooling system arranged to circulate a cooling fluid that transfers heat from the electric machine to the battery
Implementation Method 2
control rotor current to the rotor windings and control stator current to the stator windings in response to temperature of the cooling fluid
Data Source
AI summary
An electrified vehicle includes a wound rotor synchronous electric machine configured to provide propulsive torque to wheels of the electrified vehicle and having a rotor with rotor windings and a stator with stator windings, a battery electrically coupled to the electric machine, a cooling system arranged to circulate a cooling fluid that transfers heat from the electric machine to the battery, and a controller programmed to, for a specified electric machine torque, control rotor current to the rotor windings and control stator current to the stator windings to operate the machine at an inefficient operating point that increases stator power losses to generate heat transferred to the cooling fluid to heat the battery, cabin, and/or other components. The controller performs closed-loop feedback control of stator winding current and rotor winding current based on a target machine output torque and target stator power loss to control the amount of heat generated.