Multi-phase Motor Control via Virtual Neutral Point
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Solution Overview
Problem
Existing multi-phase motor control methods experience noise and vibration issues due to transient imbalances during phase switching, as they rely on sensing zero-crossing points between floating phases and back electromotive force (BEMF), which are not sinusoidal, leading to inefficient torque generation and noise in quiet environments.
Innovation Solution
A multi-phase motor control method that senses current signals, determines phase differences with reference phases, and adjusts phase switching frequencies to synchronize zero-crossing points, eliminating the need for floating phases and ensuring sinusoidal current waveforms, thereby reducing noise and improving torque balance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If zero-crossing points are sensed between floating phases and BEMF to determine phase switching timing, then phase switching control is achieved, but phase current cannot be sinusoidal and transient imbalance occurs causing noise and vibration
Solution Approach 1:
The patent extracts the harmful floating phase operation from the system by introducing a virtual neutral point. Instead of actually floating phases to sense zero-crossing points, the invention creates a virtual reference point through coordinate transformation of three-phase currents, eliminating the source of transient imbalance while maintaining the ability to determine phase switching timing.
Solution Approach 2:
The patent introduces a virtual neutral point as an intermediary element. This virtual point serves as a reference for determining zero-crossing points without requiring actual floating phase operation. The virtual neutral point is generated through mathematical transformation of phase currents, acting as a mediator between the need for zero-crossing detection and the requirement to maintain sinusoidal phase currents.
2Loss of time
If floating phases are used to sense zero-crossing points with BEMF, then phase switching timing is determined, but torque generation becomes unbalanced during phase switching
Solution Approach 1:
The patent removes the problematic floating phase mechanism while preserving its functional benefit. By using virtual neutral point and coordinate transformation, the system can determine zero-crossing points and phase switching timing without extracting current from any phase, thereby maintaining continuous sinusoidal phase currents and balanced torque generation.
Solution Approach 2:
The patent replaces the mechanical/electrical floating phase switching mechanism with a mathematical computation approach. Instead of physically floating phases to sense zero-crossing points, the invention uses coordinate transformation of current signals to virtually determine switching timing, substituting a computational system for the mechanical switching approach.
3Use of energy by moving object
If phase current is forced to be sinusoidal for optimal efficiency, then torque generation is optimized, but zero-crossing point sensing becomes difficult without floating phases
Solution Approach 1:
The patent introduces a virtual neutral point as an intermediary that enables zero-crossing point detection without disrupting phase current sinusoidal waveforms. This virtual reference point is generated through mathematical transformation and serves as a basis for sensing zero-crossing points while all phases remain connected and carrying sinusoidal currents.
Solution Approach 2:
The patent replaces the physical floating phase sensing mechanism with a computational approach using coordinate transformation. Instead of mechanically floating a phase to access BEMF for zero-crossing detection, the invention transforms three-phase current measurements into a reference frame where zero-crossing points can be determined mathematically, maintaining continuous sinusoidal phase currents.
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 method effectively reduces noise and vibration by synchronizing phase switching frequencies with desired target current signals, enhancing motor efficiency and operation in quiet environments by maintaining sinusoidal current waveforms and optimal torque generation.
Implementation Method 1
The rotation of the motor is generated by a torque and the torque is generated by an interaction between the electromagnetic field of the stator and the permanent magnetic field of the rotor
Data Source
AI summary
A multi-phase motor control method controls a multi-phase motor which includes multiple nodes respectively receiving a corresponding number of driving voltage signals to control a rotation of a rotor. The motor control method includes: sensing a signal phase of a current signal corresponding to at least one node, for example by sensing a zero-crossing point of the current signal; determining a reference phase for the current signal; calculating a phase difference between the signal phase and the reference phase; and controlling a phase switching frequency of the stator according to the phase difference, such that the signal phase is close to or in phase with the reference phase, to thereby obtain an optimum rotation speed of the rotor corresponding to a given driving voltage. The present invention also provides a multi-phase motor control device using the motor control method.