SRM Torque Harmonic Reduction via Position-Dependent Current Shaping
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Solution Overview
Problem
Switched reluctance machines (SRMs) experience significant torque harmonic pulsations during normal operation due to conventional excitation schemes, which existing technologies have not effectively mitigated.
Innovation Solution
A controller system that estimates torque based on monitored phase currents and rotor position, adjusts current commands to minimize torque harmonics, and applies a position-dependent multiplier to ensure smooth phase-to-phase transitions, reducing torque pulsations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If conventional excitation schemes are used in SRMs, then the machine structure remains simple and energy-efficient, but significant torque harmonic pulsations occur during normal operation
Solution Approach 1:
The control scheme employs feedback by continuously monitoring phase currents and rotor position, estimating instantaneous torque, and comparing it with commanded torque to generate error signals that adjust current commands in real-time, thereby reducing torque harmonics while maintaining operational simplicity
Solution Approach 2:
The invention applies dynamic current shaping by varying the current command waveform based on rotor position and torque error signals, using time-varying multipliers that change with rotor position to smooth phase transitions and minimize torque pulsations throughout the operational cycle
2Object-generated harmful factors
If sophisticated control schemes are used to shape current profiles, then torque pulsations are reduced, but the control system complexity increases
Solution Approach 1:
The control scheme changes parameters by dynamically adjusting current waveform shape, amplitude, and timing based on rotor position and torque requirements, using variable multipliers that modulate the current command to achieve smooth phase transitions and reduced torque harmonics
Solution Approach 2:
The system performs preliminary action by pre-shaping the current command waveform before phase switching occurs, using estimated torque and position information to prepare optimal current profiles that prevent torque pulsations rather than correcting them after occurrence
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The controller significantly decreases torque harmonics in SRMs by accurately modifying current commands and smoothing transitions between stator coil energization phases, resulting in more stable torque delivery.
Implementation Method 1
The stator coils are selectively energized to attract the nearest rotor pole (i.e., bring the rotor pole into alignment with the energized stator coil). By energizing the field coils in sequence, the rotation of the rotor can be selectively controlled.
Implementation Method 2
A multiplier that varies with the monitored rotor position is applied to the modified current command to provide a smooth phase-to-phase transition.
Data Source
AI summary
A controller for a switched reluctance machine (SRM) generates current commands that reduce torque harmonics generated by the SRM. The controller monitors the phase currents and rotor position of the SRM to estimate torque generated by the SRM. The current command signal is modified based on the difference between the torque command and the estimated torque. A multiplier that varies with the monitored torque command is applied to the modified current command to provide a smooth phase-to-phase transition.