Switched Reluctance Motor Current Control for High Speed and Low Ripple
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Solution Overview
Problem
Existing control methods for switched reluctance motors (SRMs) struggle with achieving high-speed operation and low torque ripple due to their simplicity and inability to accurately control drive currents.
Innovation Solution
A digital closed-loop control method for SRMs that involves converting measured drive currents into reference current values in a rotating reference frame, generating updated reference voltage values based on target data and inductance values, and controlling the inverter to set the voltages of the phase outputs accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If simple control methods are used for SRMs, then device complexity is reduced, but motor performance (high speed operation and low torque ripple) cannot be achieved
Solution Approach 1:
The patent implements a digital closed-loop control system that continuously measures drive currents, transforms them to a rotating reference frame, compares them with target currents, and adjusts voltage outputs accordingly. This feedback mechanism enables high-speed operation and low torque ripple by dynamically correcting current deviations from desired values.
Solution Approach 2:
The patent transforms control parameters from a stationary reference frame to a rotating reference frame synchronized with the motor's electrical angular speed. This parameter transformation simplifies the control of high-speed operation by converting time-varying parameters into steady-state equivalents in the rotating frame, enabling effective high-speed control.
2Device complexity
If simple control methods are used for SRMs, then device complexity is reduced, but torque ripple is increased
Solution Approach 1:
The closed-loop control system continuously monitors drive currents and adjusts voltage outputs to maintain currents at target values. This feedback control suppresses current fluctuations that cause torque ripple, enabling smooth motor operation even with the inherent non-linearities of SRMs.
Solution Approach 2:
The patent employs dynamic voltage adjustment based on real-time current measurements and target current discrepancies. The control system adapts voltage outputs moment-by-moment to compensate for inductance variations and maintain constant torque production, thereby reducing torque ripple through dynamic rather than static control.
3Speed
If digital closed-loop control with reference frame transformation is implemented, then motor performance (high speed and low torque ripple) is improved, but device complexity increases
Solution Approach 1:
The patent introduces a rotating reference frame as an intermediary coordinate system between the stationary measurement frame and the control output frame. This intermediary transformation simplifies the control of high-speed operation by converting complex time-varying parameters into steady-state parameters in the rotating frame, making high-speed control more manageable despite increased computational requirements.
4Productivity
If digital closed-loop control with reference frame transformation is implemented, then motor performance (high speed and low torque ripple) is improved, but control calculation complexity increases
Solution Approach 1:
The patent changes the reference frame parameters from stationary to rotating coordinates synchronized with the motor's electrical angular speed. This parameter transformation converts complex time-varying control problems into steady-state control problems in the rotating frame, improving motor efficiency through better current control despite increased computational complexity.
Data Source
AI summary
In one embodiment, the method includes i) obtaining target data specifying desired operating parameters of a switched reluctance motor, ii) obtaining data indicative of a value of a measured drive current for each of the phase outputs of an associated inverter, iii) converting the measured drive current values from a stationary reference frame into reference current values in a rotating reference frame, iv) generating, based on the reference current values and the target data and the set of inductance values, updated reference voltage values in the rotating reference frame, v) converting the updated reference voltage values from the rotating reference frame into updated voltage values in the stationary reference frame, and vi) controlling the inverter to set the voltages of the phase outputs to the updated voltage values.