Motor Torque Control Using Battery SOC Power Limits
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Solution Overview
Problem
Conventional electric motor power control systems in hybrid or fully electric vehicles face shutdowns due to battery voltage drops when high torque demands are made at low battery states of charge, limiting operational time and reliability.
Innovation Solution
A control system that determines the battery's capability to supply commanded power or torque based on its state of charge, outputting either the commanded or a reduced power/torque command to prevent voltage drops, using a comparison module and battery model to assess available power and adjust motor control accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If high torque demand is applied to the motor at low battery state of charge, then the motor can provide required power output, but the battery voltage drops below the minimum operating level causing system shutdown
Solution Approach 1:
The control system performs preliminary assessment of battery capability before allowing high torque demand. By evaluating state of charge and predicting available power in advance, the system prevents voltage drops that would cause shutdown, thereby maintaining reliability while enabling power output when safe
Solution Approach 2:
The system continuously monitors battery state of charge and uses this feedback to dynamically adjust the maximum allowed torque command. This closed-loop control ensures that power demands never exceed what the battery can safely supply, preventing voltage collapse and system shutdown
2Reliability
If the motor controller limits power output at low battery state of charge to prevent voltage drops, then system reliability is maintained, but the operational time of the propulsion system is decreased
Solution Approach 1:
The system dynamically adjusts the maximum allowed torque command based on real-time battery state of charge rather than using fixed limits. This allows the system to maximize operational time by permitting higher power output when battery conditions allow, while maintaining reliability when voltage drops are detected
3Power
If the motor controller outputs high torque command at low battery state of charge, then the commanded power is delivered, but the battery voltage becomes too low for the motor controller to function
Solution Approach 1:
The control system applies preliminary anti-action by preemptively limiting the torque command to levels that will not cause voltage drops below the motor controller's minimum operating threshold. This prevents the harmful effect of controller malfunction before it can occur
Data Source
AI summary
A control system for an electric motor powered by a battery can be configured to receive an input instantaneous power or torque command corresponding to a commanded instantaneous power or torque. The control system can be configured to determine if the battery is capable of supplying the commanded instantaneous power or torque based on a state of charge (SOC) of the battery. The control system can be configured such that if the battery is capable of supplying the commanded instantaneous power or torque, the control system outputs the input instantaneous power or torque command, and such that if the battery is not capable of supplying the commanded instantaneous power or torque, the control system outputs an available maximum instantaneous power or torque command corresponding to an available maximum instantaneous power or torque that is less than the commanded instantaneous power or torque.