Inverter Shutdown Control for Electric Vehicle Energy Efficiency
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Solution Overview
Problem
Existing electrically-powered vehicles face limitations in improving fuel efficiency due to losses in the inverter used for controlling and driving the motor generator, particularly when the inverter is shut down, which can affect vehicle running performance.
Innovation Solution
An electrically-powered vehicle with an electric motor, a first power converter, and a control device that estimates drag torque based on rotation speed and stops the power converter when the difference between estimated drag torque and torque command value is met, allowing the inverter to operate only when necessary to maintain vehicle performance and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the inverter is continuously operated to control the motor generator, then the vehicle running performance is maintained, but the energy loss increases and fuel efficiency deteriorates
Solution Approach 1:
The inverter is operated periodically rather than continuously. The control device determines whether to operate the inverter based on whether torque conversion is actually needed, creating an on-demand operational pattern that reduces energy loss while maintaining vehicle performance when required
Solution Approach 2:
The patent extracts the essential function of the inverter (torque control) from its continuous operation state. By separating the inverter operation from continuous running and activating it only when torque conversion is needed, the system reduces energy loss while preserving necessary vehicle performance
2Loss of energy
If the inverter is shut down to reduce energy loss, then fuel efficiency improves, but the motor generator cannot be controlled and vehicle running performance deteriorates
Solution Approach 1:
The inverter operation state is made dynamic rather than static. The control device continuously evaluates whether torque conversion is needed and adjusts the inverter operation state accordingly, allowing the system to switch between operated and shut-down states based on real-time vehicle conditions
3Reliability
If the torque command value is increased to compensate for drag torque, then the vehicle running performance is maintained, but the energy consumption increases
Solution Approach 1:
The patent converts the harmful drag torque into a beneficial condition for inverter shutdown. By estimating drag torque and comparing it with the torque command value, the system identifies conditions where the drag torque is sufficient to meet vehicle needs, allowing the inverter to be shut down and turning the previously harmful energy loss into a benefit for fuel efficiency
Data Source
AI summary
An inverter performs bidirectional DC/AC power conversion between a power line and a second MG so as to control an output torque of the second MG for generating vehicle driving force. A PM-ECU sets a torque command value of the second MG such that requested driving force for an entire vehicle is exerted on a drive shaft. An MG-ECU estimates, based on a rotation speed of the second MG, a magnitude of a drag torque acting as rotational resistance when the second MG rotates at zero torque, and stops the inverter in accordance with a difference between the estimated drag torque and the torque command value.