Motor Locked-Rotor Torque Control for EV Charging Safety
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Solution Overview
Problem
Electric vehicles with high-voltage platforms cannot be directly charged by low-voltage charging piles, and existing solutions for boosting voltage result in variable locked-rotor torque affecting vehicle braking systems, leading to safety and applicability issues during charging.
Innovation Solution
A motor locked-rotor torque control method that adjusts the stator magnetic field angle of the motor by connecting first and second phase stator windings in parallel and controlling currents to minimize locked-rotor torque, using a preset mapping relationship between stator and rotor magnetic field angles and locked-rotor torque to ensure consistent and safe charging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the motor is used as a boost loop for charging, then high-voltage charging capability is achieved, but locked-rotor torque varies with rotor position affecting braking system safety
Solution Approach 1:
The patent changes the control parameters of the motor by adjusting the stator magnetic field angle to different predetermined values based on rotor position, thereby minimizing locked-rotor torque while maintaining charging functionality. This resolves the contradiction by modifying operational parameters to eliminate the harmful torque variation.
Solution Approach 2:
The patent converts the potentially harmful locked-rotor torque into a beneficial control variable by establishing a mapping relationship between rotor position and optimal stator magnetic field angles. By pre-calculating and storing these optimal angles, the system transforms the problem of torque variation into a solution that minimizes torque while enabling charging.
2Reliability
If the stator magnetic field angle is adjusted to minimize locked-rotor torque, then braking system safety is improved, but control complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing the mapping relationship between rotor positions and optimal stator magnetic field angles in a lookup table. During charging, the controller simply queries this pre-computed table based on current rotor position, avoiding complex real-time calculations and reducing control system complexity while ensuring safety.
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 effectively reduces locked-rotor torque to minimize its impact on the braking system, enhancing safety and applicability during charging by maintaining a stable stator magnetic field angle, even when the rotor magnetic field angle changes, thereby improving compatibility with different charging systems.
Implementation Method 1
When the motor is in a charging mode, the first phase stator winding and the second phase stator winding are connected in parallel, and then are connected to the third phase stator winding
Implementation Method 2
controlling a first phase current of the first phase stator winding and a second phase current of the second phase stator winding, so that a stator magnetic field angle of the motor is the target stator magnetic field angle
Data Source
Figure 1(a)~1(b)
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AI summary
This application provides a motor locked-rotor torque control method, a motor locked-rotor torque control apparatus, and an electric vehicle. The motor includes a first phase stator winding, a second phase stator winding, and a third phase stator winding, and when the motor is in a charging mode, the first phase stator winding and the second phase stator winding are connected in parallel, and then are connected to the third phase stator winding. The method includes: obtaining a current rotor magnetic field angle of the motor when the motor is in the charging mode; determining a target stator magnetic field angle of the motor based on the current rotor magnetic field angle and a preset mapping relationship between a stator and rotor magnetic field included angle and a locked-rotor torque; and further, controlling a first phase current of the first phase stator winding and a second phase current of the second phase stator winding, so that a stator magnetic field angle of the motor is the target stator magnetic field angle. According to this application, it can be ensured that the stator magnetic field angle of the motor is minimized when the motor is in the charging mode, so that safety during charging is improved and applicability is strong.