Multi-Motor EV Power Management for Partial-Load Efficiency
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Solution Overview
Problem
Existing power management systems in electric vehicles with multiple motors inefficiently distribute power among motors, leading to reduced efficiency and shortened motor lifetimes during partial loads.
Innovation Solution
A power management system that selectively activates or deactivates individual electric motors based on mechanical power demand, using a mechanical power demand indicator and electrical power demand estimator to optimize torque control and electrical power demand.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If all e-motors with inverters are always active and torque demand is equally split over all e-motors, then the requested power can be delivered reliably, but the efficiency and lifetime of the e-motors are reduced during partial load operation
Solution Approach 1:
The system dynamically adjusts the number of active e-motors based on real-time power demand. The controller continuously monitors the mechanical power demand indicator and electrical power demand estimator, and selectively activates or deactivates e-motors to match the required power level, transitioning from static all-motors-always-on operation to dynamic adaptive motor activation
Solution Approach 2:
The powertrain is segmented into multiple independently controllable e-motor units, each capable of being activated or deactivated. This segmentation allows the system to operate with different numbers of motors depending on load requirements, enabling partial load operation with fewer motors while maintaining the capability for full power delivery when needed
2Adaptability or versatility
If multiple smaller e-motors are installed instead of one large e-motor, then the powertrain can be adapted to different payload requirements, but the system complexity increases with multiple inverters and control systems
Solution Approach 1:
Multiple e-motors are designed with identical or similar specifications and control architecture, allowing them to perform interchangeable functions. Each motor-inverter unit serves as a universal module that can be activated based on power demand, simplifying the control logic despite the presence of multiple components
Solution Approach 2:
The control functions for multiple e-motors are merged into a single centralized controller that manages all motor units through a unified control algorithm. This merging of control functions reduces the overall system complexity compared to having separate control systems for each motor
3Power
If e-motors operate at partial load with equal torque distribution, then the power demand is met, but drag and cogging losses increase and motor lifetime decreases
Solution Approach 1:
Instead of operating all e-motors at partial load, the system applies partial action by activating only the necessary number of motors to meet the current power demand. This ensures that active motors operate at higher load levels with better efficiency, while inactive motors contribute zero losses
Data Source
AI summary
A power management system is disclosed for an electrically driven vehicle, comprising a powertrain of at least two electric motors that can be selectively geared into the powertrain. The power management system is configured to indicate a level of mechanical power demanded from the powertrain, to estimate an electrical power demand from a respective one of the at least two electric motors as a function of the demanded mechanical power, and to activate or deactivate the respective electric motor in response to the mechanical power demand indicator. The power management system is further configured to (a) deactivate the respective electric motor when (1) the demanded mechanical power does not exceed a maximum value with the respective electric motor deactivated, and (2) the estimated electric power with the respective electric motor deactivated is lower than that with the respective electric motor activated; or otherwise (b) activate the respective electric motor.