Motor Rotor Position Control for Zero-Torque Boost Charging
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Solution Overview
Problem
Existing direct-current charging piles with output voltages less than 800 V cannot meet the charging requirements of electric vehicles equipped with 800-V or higher-voltage platforms, leading to inefficient charging.
Innovation Solution
A motor position control method and system that reuses the vehicle's motor and motor drive system for voltage conversion during boost charging, ensuring the motor rotor remains in a zero-torque state by controlling the current distribution in the three-phase winding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the motor rotor is controlled to maintain zero-torque state during boost charging, then charging efficiency is improved, but the rotor becomes unstable due to sampling errors and calibration errors, causing unexpected rotation
Solution Approach 1:
The patent implements real-time monitoring of the rotor's current position and uses feedback control to detect deviations from the initial position. When sampling errors or calibration errors cause the rotor to deviate, the system generates corrective control signals to bring the rotor back to its initial position, thus maintaining stability during boost charging while preserving charging efficiency.
2Power
If equal currents are used in all phases to maintain zero-torque state, then voltage conversion is achieved, but current distribution becomes difficult to control when phases have different characteristics
Solution Approach 1:
The patent applies different control strategies to different phases based on their individual characteristics. Instead of treating all phases uniformly, the system independently controls the current in each phase to ensure that the synthesized current vector remains on the direct axis, accommodating variations in phase characteristics while maintaining voltage conversion capability.
3Device complexity
If the motor and motor drive system are reused for voltage conversion, then device complexity is reduced, but unexpected torque and NVH problems occur due to rotor instability
Solution Approach 1:
The patent takes preliminary action by establishing real-time position monitoring and feedback control mechanisms before unexpected torque and NVH problems can occur. By continuously detecting rotor position deviations and applying corrective control signals in advance, the system prevents the generation of unexpected torque and associated NVH issues, allowing the motor to be safely reused for voltage conversion.
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
The method stabilizes the motor rotor's position near the initial position, preventing unexpected torque and noise, vibration, and harshness (NVH) issues during charging, thus ensuring efficient and stable boost charging.
Implementation Method 1
selecting working windings from a three-phase winding of a stator; obtaining in real time a real-time position angle of the rotor and a sampling current in each phase flowing through the working windings
Data Source
Figure 1
Figure 2A
Figure 2B~3A
AI summary
The disclosure relates to a motor position control method and system. A motor includes a stator and a rotor. The motor position control method includes: obtaining an initial position angle of the rotor; selecting working windings in a three-phase winding of the stator; obtaining in real time a real-time position angle of the rotor and a sampling current in each phase flowing through the working windings; and determining a duty cycle in each phase of working winding based on the initial position angle, the real-time position angle, the sampling current in each phase, and an input current reference value, to substantially stabilize a position angle of the rotor at the initial position angle. The motor position control method in embodiments of the disclosure can resolve the unexpected torque problem caused under a condition that a non-zero direct-axis current vector is used for vehicle charging.