Motor Current Control for Sixth-Order Noise Suppression
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Solution Overview
Problem
Existing motor control systems struggle to effectively suppress sixth-order noise in three-phase AC motors, which is generated at a frequency six times the rotational frequency of the motor.
Innovation Solution
A motor control device that includes a current command generation unit, a correction value generation unit, a voltage command generation unit, and a drive signal generation unit, which generate d-axis and q-axis correction values based on the target torque and electrical angle to suppress sixth-order noise by using feedforward and feedback control, with time differentiation to enhance responsiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a torque correction value according to the rotation angle is added to the torque command value, then sixth-order noise is suppressed, but the responsiveness of noise suppression deteriorates at high motor rotation ranges
Solution Approach 1:
The patent changes the parameter representation from torque domain to current domain, using d-axis and q-axis current correction commands instead of torque correction values. This transformation enables the correction to be applied in the current control loop, which has faster response characteristics, thereby maintaining noise suppression effectiveness across wider rotation ranges
Solution Approach 2:
The patent implements feedback control by using the actual d-axis and q-axis currents to generate correction values. The correction amount is determined based on the relationship between actual currents and target currents, creating a closed-loop control mechanism that responds dynamically to noise conditions regardless of motor speed
2Speed
If feedforward control is used for torque following, then responsiveness is improved, but noise suppression precision deteriorates
Solution Approach 1:
The patent merges feedforward control and feedback control into a unified control structure. The feedforward term provides rapid torque response while the feedback term based on actual current measurements ensures precise noise suppression. Both control paths operate simultaneously in the current domain, achieving both responsiveness and precision
Data Source
AI summary
The motor control device includes an inverter that generates a three-phase alternating current for driving the motor, a current command generation unit, a correction value generation unit, a voltage command generation unit, a dq inverse transform unit, and a drive signal generation unit. The current command generation unit generates a d-axis current command value and a q-axis current command value. The correction value generation unit generates a d-axis correction value and a q-axis correction value that suppress sixth-order noise. The voltage command generation unit generates a d-axis voltage command value and a q-axis voltage command value. The dq inverse transform unit generates three-phase voltage command values. The drive signal generation unit generates a drive signal for the inverter.