Electric Motor Rotation Control via Q-Axis Current Compensation
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Solution Overview
Problem
Conventional methods for controlling the rotation rate of electric motors, such as synchronous electric motors without position sensors, face challenges in responding rapidly and maintaining stability when load or rotation rate variations are large, leading to low response and significant fluctuations.
Innovation Solution
A method that adjusts the q axis current of the electric motor by compensating it according to the difference between the objective and actual rotation rates, using the formula Iq′=Iq−K*Δn, where K is a coefficient, and Δn is the difference in average rotation rates over N cycles, to rapidly adjust the rotation rate and torque, while employing a proportional integral method when the difference is below a predetermined value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If only PI adjustment method is used to control rotation rate, then the rotation rate can respond to normal load variations, but the response becomes slow and fluctuation increases when load or rotation rate variation is large
Solution Approach 1:
The control method dynamically switches between PI adjustment and q-axis current compensation based on the magnitude of rotation rate deviation. When deviation exceeds a threshold, q-axis current compensation is activated to provide rapid response; when deviation is within threshold, PI adjustment maintains stable operation. This dynamic adaptation resolves the contradiction between response speed and stability.
Solution Approach 2:
The invention changes the control parameter from standard PI adjustment to q-axis current compensation when large deviations occur. By modifying the control strategy parameter based on operating conditions, the system achieves both fast response during large variations and stable control during normal operation, resolving the contradiction between response speed and fluctuation.
2Reliability
If PI adjustment is used for large load variations, then torque output remains correct, but response time increases and rotation rate fluctuates significantly
Solution Approach 1:
The system performs preliminary assessment of load variation magnitude by comparing deviation against a threshold before selecting the control strategy. This preliminary action enables proactive switching to q-axis current compensation when large variations are detected, reducing response time while maintaining torque accuracy through appropriate control selection.
Solution Approach 2:
The control system continuously monitors rotation rate deviation and uses this feedback to determine whether to apply PI adjustment or q-axis current compensation. This feedback mechanism ensures torque output accuracy is maintained while minimizing response time by selecting the appropriate control strategy based on real-time conditions.
Data Source
AI summary
A method for controlling a rotation rate of an electric motor includes the s following steps: determining if an absolute value of a difference between an objective rotation rate of the electric motor and an actual rotation rate of the electric motor is greater than or equal to a predetermined value, and if yes, compensating a q axis current of the electric motor to adjust the rotation rate.