Motor Control Device Voltage Limit Ellipse Center Correction
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Solution Overview
Problem
Conventional automatic weakening flux control systems face efficiency deterioration due to changes in motor temperature, as the center of the voltage limit ellipse moves, making it difficult to correct current command values optimally, thereby reducing system efficiency in motor and inverter drive systems.
Innovation Solution
A motor control device with a motor temperature sensor, magnet magnetic flux calculation section, current combination candidate calculating section, and d-q axis current search section that adjusts the current command values to minimize inverter input current within the voltage limit ellipse, improving robustness and alleviating efficiency reduction by updating the voltage limit ellipse center based on calculated magnet magnetic flux.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If automatic weakening flux control is performed using conventional methods, then high-speed operation is enabled, but system efficiency deteriorates due to temperature-induced shifts in the voltage limit ellipse center
Solution Approach 1:
The control device calculates the actual center position of the voltage limit ellipse based on measured or estimated magnetic flux values, and uses this feedback to dynamically adjust the d-q axis current command values. This closed-loop feedback mechanism compensates for temperature-induced shifts in the voltage limit ellipse center, maintaining optimal operating points and preventing efficiency deterioration during high-speed weakening flux control operation
Solution Approach 2:
The invention dynamically changes the parameters (d-q axis current command values) based on the calculated center position of the voltage limit ellipse. By adjusting the current command values according to the actual magnetic flux conditions, the system adapts to temperature variations and maintains optimal efficiency across different operating conditions while enabling high-speed operation
2Ease of operation
If the voltage limit ellipse center is not corrected for temperature changes, then control simplicity is maintained, but current command value correction becomes suboptimal
Solution Approach 1:
The control device performs self-correction by automatically calculating the center position of the voltage limit ellipse based on measured magnetic flux values and using this information to adjust the current command values. This self-service mechanism eliminates the need for external calibration or complex manual adjustments, maintaining control simplicity while achieving accurate current command value correction across varying temperature conditions
Data Source
AI summary
A motor control device having a motor temperature sensor for detecting a magnet temperature of the motor, a magnet magnetic flux calculation section that calculates a magnet magnetic flux of the motor corresponding to the magnet temperature of the motor, a current combination candidate calculating section that calculates a d-q axis current combination candidate that minimizes the input current of the inverter within a voltage limit ellipse determined by a value that can be output by a voltage of a power supply of the motor, and a d-q axis current search section that searches the d-q axis current that minimizes the input current of the inverter within the range of the combination candidate of the d-q axis currents when the d-q axis current of the motor moves on a voltage limiting ellipse by automatic weakening flux control.