Motor Neutral-Point Charging Control for Transient Phase Current Stability
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Solution Overview
Problem
Existing electrified vehicles face challenges in maintaining responsiveness during transient states during external charging due to insufficient gain values in feedback control, leading to instability and inability to handle sudden changes or abnormalities.
Innovation Solution
The vehicle employs a control device that adjusts the gain in feedback control based on the phase current state, using larger values during transient states to enhance responsiveness and stability by incorporating a feedforward term and feedback terms for phase current control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a relatively small value is used for the gain in feedback control during external charging, then stability is improved, but responsiveness in transient state deteriorates
Solution Approach 1:
The gain value in feedback control is made dynamic rather than fixed. The control device dynamically adjusts the gain value based on the transient state detection of phase current. When a transient state is detected (such as during startup or abnormality), the gain value is increased to improve responsiveness. When in steady state, the gain value is reduced to maintain stability. This dynamic adjustment resolves the contradiction between stability and responsiveness.
Solution Approach 2:
The control device changes the parameter (gain value) of the feedback control system based on operating conditions. By detecting transient states through monitoring phase current characteristics, the system adjusts the gain parameter appropriately - increasing it during transients for faster response and decreasing it during steady operation for stability. This parameter change strategy effectively resolves the trade-off between stability and responsiveness.
2Speed
If a larger value is used for the gain in feedback control during transient state, then responsiveness is improved, but control stability may deteriorate
Solution Approach 1:
The system employs dynamic gain adjustment where the gain value changes based on the detected transient state. During transient conditions, the gain is temporarily increased to improve responsiveness without causing sustained instability. Once the transient state ends, the gain returns to a lower stable value. This dynamic behavior allows the system to achieve high responsiveness only when needed while maintaining overall stability.
Solution Approach 2:
The control device performs preliminary detection of transient states by monitoring phase current characteristics before implementing control adjustments. By detecting the transient state in advance, the system can proactively adjust the gain value to appropriate levels, ensuring responsiveness is improved before instability can occur, rather than reacting after instability has already manifested.
Data Source
AI summary
An electrified vehicle includes: a motor including three-phase coils connected to each other at a neutral point; a power storage device; an inverter connected to the power storage device and configured to drive the motor; and a control device configured to, during external charging in which electric power supplied from an external power supply to the neutral point is supplied to the power storage device along with voltage conversion, control each phase of the motor and the inverter by setting a duty command using feedback control to cancel out a difference between a phase current and a phase current command based on a current command at the neutral point. The control device is configured to, when the phase current is in a transient state during the external charging, larger value for a gain in the feedback control than when the phase current is not in the transient state.