Electric Motor Torque Compensation for Compressor Speed Ripple
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Solution Overview
Problem
Electric motor control systems face challenges in suppressing speed fluctuations and resulting vibrations and noise when used in applications with periodic load fluctuations, such as compressors, as existing methods are inadequate in effectively managing torque variations.
Innovation Solution
An electric motor control apparatus that includes a speed ripple component extraction unit, a phase locked loop circuit, a torque compensation value generation unit, and a current control unit to generate and apply a torque compensation value, thereby stabilizing the motor's speed and reducing vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If conventional speed control methods are used in electric motors with periodic load fluctuations, then the motor can operate at the commanded speed, but speed fluctuations and vibrations occur due to load variations
Solution Approach 1:
The invention extracts speed ripple components from the difference between commanded and feedback angular frequencies, generates a phase signal through PLL, and creates torque compensation values in advance based on the periodic nature of load fluctuations. This preliminary action allows the system to counteract speed variations before they manifest as vibrations, improving speed stability while reducing harmful vibrations and noise
Solution Approach 2:
The system continuously monitors the difference between commanded angular frequency and speed feedback angular frequency, extracts ripple components from this feedback signal, and uses the extracted information to generate compensating torque values. This closed-loop feedback mechanism enables real-time correction of speed fluctuations, addressing both speed stability and vibration reduction
2Stability of the object's composition
If torque compensation is applied to suppress speed fluctuations, then speed stability improves, but control system complexity increases
Solution Approach 1:
The invention replaces complex mechanical position measurement systems with an electrical signal processing approach. By extracting speed ripple components from electrical frequency signals and using PLL to generate phase information, the system achieves torque compensation without mechanical sensors or complex position detection mechanisms, improving speed stability while keeping the control system relatively simple
Solution Approach 2:
The system transforms the speed control problem by changing parameters: it extracts frequency ripple components from the error signal, converts them to phase information through PLL, and generates torque compensation values based on these transformed parameters. This parameter transformation simplifies the control approach compared to direct mechanical measurement methods
3Stability of the object's composition
If existing torque correction methods are used, then some speed fluctuation suppression is achieved, but the methods are inadequate for effectively managing torque variations in compressors
Solution Approach 1:
The invention segments the torque control into distinct components: it separates the speed ripple extraction, phase generation, and torque compensation value calculation into distinct processing stages. By segmenting the control function and applying targeted compensation based on extracted ripple characteristics, the system achieves more effective torque management for compressor applications compared to conventional unified control approaches
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 solution effectively suppresses speed fluctuations and vibrations in electric motors by generating a torque compensation value based on the phase and amplitude of speed ripple components, enhancing motor stability without requiring mechanical position measurement or feedback loops.
Implementation Method 1
a phase locked loop circuit configured to generate a phase of the speed ripple component from the speed ripple component
Data Source
AI summary
Provided is an electric motor control apparatus (1) configured to extract a speed ripple component from a difference between an angular frequency command and an angular frequency feedback, configured to generate a phase of the speed ripple component from the speed ripple component, configured to multiply a value of a periodic function corresponding to the phase and a given amplitude by each other, to thereby generate a torque compensation value, configured to calculate a torque command value from the difference between the angular frequency command and the angular frequency feedback, and configured to control a current to be output to an electric motor based on a compensated torque command obtained by adding the torque compensation value to the torque command value.