Asynchronous Motor Control via Flux Reference Adaptation
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Solution Overview
Problem
Conventional control methods for asynchronous-type electric motors face dynamic disturbances during transitions to a 'defluxed' region, leading to instability and torque fluctuations when the voltage reference exceeds the available voltage limit.
Innovation Solution
A method implemented in a processing unit that generates a speed trajectory and determines corresponding flux values to maintain motor voltage within a threshold, avoiding voltage limitations by adapting the flux reference in real-time using stored values from an identification phase.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the flux reference is reduced to generate a voltage within the inverter's capability, then the voltage compatibility is improved, but the motor enters a defluxing zone causing transient dynamic disturbances on torque and mechanical quantities
Solution Approach 1:
The system performs preliminary identification to determine the maximum voltage for each speed reference before actual operation. This pre-characterization allows the control to anticipate voltage limitations and adjust flux references proactively, avoiding sudden defluxing transitions that cause torque disturbances.
Solution Approach 2:
The control system uses feedback from the identified voltage characteristics to dynamically adjust the flux reference. When the calculated voltage exceeds the maximum available voltage for the current speed reference, the system feeds back the appropriate flux correction to maintain voltage compatibility without entering the defluxing zone.
2Reliability
If the flux reference is dynamically corrected to maintain voltage within limits, then the voltage limitation is avoided, but the current references are not dynamically corrected leading to instability in the voltage limitation zone
Solution Approach 1:
The system changes the flux reference parameter dynamically based on the identified voltage characteristics and current operating conditions. By adjusting the flux reference in real-time according to the pre-identified maximum voltage envelope, the system maintains optimal operation without entering voltage limitation zones.
3Speed
If the speed reference is increased beyond nominal speed with constant flux reference, then the speed performance is improved, but the calculated voltage becomes incompatible with the available voltage
Solution Approach 1:
The system makes the flux reference dynamic rather than constant, allowing it to adapt to different speed references. The flux reference is continuously adjusted based on the pre-identified voltage characteristics at each speed point, enabling the motor to operate at speeds beyond nominal while maintaining voltage compatibility through real-time flux optimization.
Data Source
Figure 1~2
Figure 3A~3C
Figure 3D~4
AI summary
The invention relates to a method for controlling an asynchronous electric motor (M), implemented in a processing unit associated with a power converter connected to said electric motor (M), said method comprising an identification phase which consists of: - Generating a speed trajectory as input to a motor control law so as to make the speed reference take several successive determined values, - For each value taken by the speed reference, determining the voltage (Um) across the terminals of the electric motor (M), - For each value taken by the speed reference, determining and storing the flux value for which the voltage across the terminals of the electric motor is equal to a determined threshold value (Umax).