Motor Generator Current Control for Full-Charge Regeneration
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Solution Overview
Problem
Current methods for consuming surplus power in hybrid vehicles during regenerative braking are inefficient, particularly when the battery is fully charged, leading to potential battery deterioration.
Innovation Solution
A motor generator control system that includes a motor generator capable of performing power running using electric power from a capacitor, with a drive current control unit, current coordinate control unit, and strong field control unit to manage d-axis and q-axis current values, allowing for current consumption control during regeneration to limit battery charge when fully charged, by reducing the driving force below the target force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If regenerative braking is performed to consume surplus power when the battery is fully charged, then battery deterioration is prevented, but the charging amount is limited and energy recovery is reduced
Solution Approach 1:
The system changes the motor generator's operating parameters by performing strong field control, which increases the magnetic flux density beyond the optimal point. This causes the motor generator to operate at lower efficiency, intentionally converting regenerative energy into heat through increased copper losses and iron losses, thereby limiting the charge amount to protect the battery while still utilizing the regenerative braking function
2Loss of energy
If strong field control is performed to increase magnetic flux density, then current consumption increases and energy recovery is limited, but the field strength exceeds the optimal efficiency point
Solution Approach 1:
The system intentionally creates energy losses through strong field control by operating the motor generator beyond its optimal efficiency point. The increased copper losses (I²R heating) and iron losses (hysteresis and eddy current losses) are converted from unwanted inefficiencies into a beneficial mechanism for dissipating excess regenerative energy as heat, preventing battery overcharge while maintaining smooth braking operation
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
This approach effectively limits battery charge through regenerative braking, preventing battery deterioration and improving overall system efficiency by reducing drive efficiency and increasing current consumption without complex control requirements.
Implementation Method 1
a motor generator (MG2) configured to perform power running using electric power from a capacitor (BATh), and to regenerate by a driving force input from a drive wheel (W) to charge the capacitor (BATh)
Implementation Method 2
a drive current control unit (3) configured to perform feedback control based on a drive current (Iu, Iv) of the motor generator (MG2) so that the driving force at a time of power running or the driving force (drive torque: Tq) at a time of regeneration of the motor generator (MG2) is a target driving force (target torque: Tq*)
Data Source
AI summary
A motor generator control system includes: a motor generator; a drive current control unit configured to perform feedback control so that a driving force at a time of power running or the driving force at a time of regeneration of the motor generator is a target driving force; a current coordinate control unit configured to output a d-axis current value and a q-axis current value to the drive current control unit; and a strong field control unit configured to perform strong field control of setting a field to be stronger than a field strength at which a maximum efficiency is obtained. When the strong field control is performed during the regeneration, the motor generator control system executes current consumption control of performing the feedback control by changing the d-axis current value and the q-axis current value so that the driving force is smaller than the target driving force.