Rotary Electric Machine Control Using PLL Position Estimation
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Solution Overview
Problem
Existing control methods for rotating electrical machines suffer from harmonic contamination in position and velocity signals, leading to torque vibrations, iron and copper losses, and stability issues due to the use of digital low-pass filters that attenuate velocity information and introduce phase shifts.
Innovation Solution
A method and system that utilize a fictitious two-phase reference frame and a phase-locked loop to determine control parameters, eliminating harmonics and phase shifts by constructing two-phase signals from mechanical position measurements, applying selective bandpass filtering, and using a phase-locked loop to generate precise electrical position and speed estimates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a three-phase alternating voltage is applied to a permanent magnet synchronous motor, then the motor can be driven, but torque ripple and vibration occur due to harmonic components in the back electromotive force
Solution Approach 1:
The control device measures the actual three-phase currents flowing through the motor windings and uses this feedback information to calculate and generate compensation currents. This closed-loop feedback mechanism enables real-time correction of harmonic components, reducing torque ripple and vibration while maintaining motor driving capability.
Solution Approach 2:
A compensation current is introduced as an intermediary element between the power supply and the motor. This compensation current contains harmonic components that are opposite in phase to the back electromotive force harmonics, thereby canceling out the harmful effects through electromagnetic interaction without requiring mechanical modifications to the motor.
2Device complexity
If conventional control methods are used, then the control system is simple, but accurate current control is difficult due to coupling between three-phase currents
Solution Approach 1:
The patent transforms the electrical control problem into a mathematical transformation problem by applying Clarke and Park transformations. This substitution converts the complex coupled three-phase current control into independent direct-axis and quadrature-axis current control, enabling precise control through standard PI controllers without requiring complex mechanical or electrical coupling mechanisms.
Solution Approach 2:
The control system dynamically changes reference current parameters based on operating conditions (acceleration, deceleration, constant speed). During acceleration and deceleration, reference currents are set to zero to prevent overcurrent; during constant speed operation, reference currents are adjusted to maintain optimal torque while minimizing losses. This parameter adaptation enables accurate current control across different operating modes.
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
Enables high-precision, harmonic-free electrical position and speed determination without phase shift, ensuring stable and reliable control of electrical machines by filtering out low-frequency harmonics and maintaining signal integrity.
Implementation Method 1
a three-phase alternating voltage is applied to a permanent magnet synchronous motor, a three-phase alternating current flows through an armature
Implementation Method 2
the rotor is rotated by an electromagnetic force generated between the stator and the rotor
Implementation Method 3
a rotor magnetic field generated by a permanent magnet is rotated at a synchronous speed
Data Source
Figure 1
Figure 2
Figure 3A~3C
AI summary
The invention relates to a method and system for determining control parameters for a rotary electric machine, comprising: - a two-phase imaginary reference module (17) configured to construct two imaginary two-phase signals (x_α, x_β) on the basis of a measurement of the mechanical position θmeca of the shaft of a rotor of the rotary machine received from a position sensor; - an open-loop module (19) configured to determine an open-loop estimate of the electrical speed, referred to as the electrical speed open-loop estimate ω_estflt, using the imaginary two-phase signals; - a phase-locked loop module (21) configured to generate the actual electrical position θ of the rotary machine on the basis of the two imaginary two-phase signals (x_α, x_β) and using the electrical speed open-loop estimate ω_estflt received from the open-loop module.