Rotary Electric Machine Control Reducing Torque Pulsation
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Solution Overview
Problem
Existing methods for reducing torque pulsation in permanent magnet dynamo-electric machines, such as superimposing harmonic currents, often lead to increased oscillations and noise, and higher current amplitudes, making them impractical for practical implementation.
Innovation Solution
A control device for rotary electric machines that periodically changes the phase of sinusoidal current based on the magnetic pole position and rotation frequency, reducing torque pulsation without relying on salient poles or permanent magnet structures, and allowing the current phase to be adjusted within specific ranges to maintain optimal voltage levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If harmonic current is superimposed on fundamental current to reduce torque pulsation, then torque pulsation is reduced, but current amplitude increases and new oscillations and noises are generated
Solution Approach 1:
The invention changes the timing parameter (phase) of the fundamental current periodically according to the rotor position, rather than superimposing harmonic currents. This parameter change allows torque pulsation reduction while maintaining the same current amplitude, avoiding the worsening of current magnitude and new oscillations.
Solution Approach 2:
The invention applies periodic phase adjustment of the fundamental current based on rotor position feedback. The phase is periodically changed in synchronization with the rotor rotation, creating a periodic control action that reduces torque pulsation without requiring harmonic current superposition.
2Object-generated harmful factors
If harmonic current is superimposed on fundamental current to reduce torque pulsation, then torque pulsation is reduced, but new oscillations and noises are generated
Solution Approach 1:
By changing the phase parameter of the fundamental current periodically according to rotor position, the invention reduces torque pulsation without introducing new frequency components that would cause oscillations and noises. This approach avoids the harmful side effects of harmonic superposition.
Solution Approach 2:
The invention replaces the mechanical approach of harmonic current superposition with a control system approach that adjusts the fundamental current phase electronically. This substitution eliminates the need for additional current components that would generate new oscillations and noises.
3Force
If current phase is periodically changed to reduce torque pulsation, then torque pulsation is reduced without increasing current amplitude, but control complexity increases
Solution Approach 1:
The invention uses rotor position feedback to determine the appropriate phase adjustment at each instant. By continuously monitoring rotor position and adjusting current phase accordingly, the system achieves torque pulsation reduction with simple control logic based on position-dependent phase modulation.
Solution Approach 2:
The invention makes the current phase dynamic rather than fixed, adjusting it periodically according to rotor position. This dynamic phase adjustment simplifies the control approach compared to harmonic superposition, as it uses a single fundamental current with variable phase rather than multiple current components.
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
This approach effectively reduces torque pulsation without exceeding maximum current values, minimizing oscillations and noise, and can be tailored to specific rotation frequencies and torque levels, enhancing the operational stability of the machine.
Implementation Method 1
A magnetomotive force distribution of the stator winding becomes a distribution where spatial harmonics are superimposed on a sinusoidal wave (fundamental wave) and varies with time in proportion to the winding current of the stator
Implementation Method 2
the magnetic flux density formed in the air gap by the rotor also contains ripples similarly, and varies with time due to a rotation movement
Implementation Method 3
Since a torque operating on the rotor is an angular differential of magnetic energy stored in the air gap, a torque pulsation is generated when there are ripples in the magnetic flux density of the air gap
Data Source
AI summary
An object of the invention is to reduce a torque pulsation. A control device of a rotary electric machine according to the invention includes a sinusoidal wave generation circuit which generates a sinusoidal wave signal according to a magnetic pole position of a rotor of the rotary electric machine, a current command circuit which generates a speed command, a torque command based on actual speed information, and a current command on the basis of the sinusoidal wave signal, and a current control circuit which controls an inverter circuit interposed between a stator winding and a DC power source to make a sinusoidal current flow to the stator winding on the basis of the current command and a current detection signal of the stator winding of the rotary electric machine, wherein the current control circuit periodically changes a current phase of the sinusoidal current when the rotary electric machine is driven by a predetermined torque and a predetermined rotation frequency.