Rotating Electric Machine Control Using Harmonic-Free PLL Estimation
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Solution Overview
Problem
Conventional methods for determining control parameters of rotating electric machines suffer from harmonics in position and speed signals, leading to torque vibrations and signal attenuation, compromising stability and accuracy.
Innovation Solution
A method involving a two-phase imaginary reference frame and phase-locked loop to generate harmonic-free electrical position and speed estimates, using digital processing to filter low-frequency harmonics without introducing phase shifts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If digital low-pass filters are used to attenuate harmonic content of position and speed signals, then harmonic vibrations are reduced, but the cut-off frequency must be close to zero which attenuates speed information and introduces phase delay
Solution Approach 1:
The patent segments the filtering process into two independent parts: a digital low-pass filter that removes high-frequency harmonics from position signals, and a separate harmonic generator that creates compensation signals specifically targeted at low-frequency harmonics. This segmentation allows each filter to operate with optimized parameters without compromising the other, resolving the contradiction between harmonic attenuation and control stability.
Solution Approach 2:
The patent introduces an intermediary harmonic generator that creates compensation signals based on the relationship between position and speed harmonics. This intermediary component generates anti-phase signals that cancel out low-frequency harmonics without requiring aggressive filtering of the original position and speed signals, thus maintaining signal integrity and control stability while eliminating vibrations.
2Speed
If derivative is used to estimate mechanical speed from mechanical position, then speed information is obtained, but the same harmonics are present causing torque vibrations and additional losses
Solution Approach 1:
The patent converts the harmful harmonics present in the derivative-based speed estimation into a beneficial compensation mechanism. By analyzing the harmonic content of the position signal and generating corresponding anti-phase compensation signals, the system transforms the problematic harmonic information into useful cancellation signals that eliminate torque vibrations while preserving accurate speed estimation.
Solution Approach 2:
The patent changes the parameter approach by not directly filtering the speed signal derived from differentiation, but instead modifying the position signal parameters to generate harmonic compensation. This parameter transformation allows speed estimation to retain its responsiveness while the harmonic content is eliminated through the compensation mechanism, resolving the contradiction between speed accuracy and vibration elimination.
Data Source
AI summary
A method and a system for determining control parameters of a rotating electric machine, including: a two-phase imaginary reference frame module configured to construct two imaginary two-phase signals (xα, xβ) based on a measurement of the mechanical position θmeca of the axis of a rotor of the rotating machine received from a position sensor, an open-loop module configured to determine in open loop an estimate of the electrical speed, so-called the open-loop estimated electrical speed ωest<sub2>flt</sub2>, using the imaginary two-phase signals, a phase-locked loop module configured to generate the actual electrical position θ of the rotating machine from the two imaginary two-phase signals (xα, xβ) and using the open-loop estimated electrical speed ωest<sub2>flt </sub2>received from the open-loop module.