Inverter Motor Resonance Control via Comparative Voltage
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Solution Overview
Problem
Conventional inverter systems face challenges in avoiding resonance frequencies, leading to over-current issues and potential motor damage, as existing methods like frequency jump methods are inefficient in preventing current hunting and extending acceleration time.
Innovation Solution
An apparatus and method that include a current detector, d axis/q axis current converter, subtracter, comparative controller, and adder to detect and convert currents, calculate differences, and generate a comparative control voltage to adjust the driving voltage of the motor, effectively managing resonance frequencies by adding a comparative control voltage to the torque portion voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the frequency jump method is used to avoid resonance frequency band, then the motor is made not to operate in resonance frequency, but the acceleration time is lengthened and current hunting continues if motor operates in resonance frequency band
Solution Approach 1:
The patent converts the harmful resonance frequency into a beneficial control signal by detecting the resonance frequency and adding it to the torque portion voltage through the adder. This transforms the harmful vibration into a useful control mechanism that actively suppresses current hunting while allowing the motor to operate through the resonance frequency band without extending acceleration time.
Solution Approach 2:
The patent implements a feedback mechanism where the current detector continuously monitors the motor current, the d axis/q axis current converter processes the current signals, and the subtractor compares the actual d axis current with the pre-sampled d axis current. This feedback loop enables real-time detection and suppression of resonance effects, preventing over-current while maintaining normal acceleration performance.
2Reliability
If the resonance frequency band is avoided by not setting target frequency in the band, then current hunting is reduced, but it is very difficult to prevent the motor from passing the resonance frequency band
Solution Approach 1:
The patent replaces the mechanical frequency jump method with an electrical control solution. Instead of mechanically avoiding the resonance frequency band by setting target frequencies outside the band, the system uses electrical signals (comparative control voltage) to actively suppress current hunting. This substitution enables precise frequency control while eliminating current hunting through electronic feedback rather than mechanical frequency avoidance.
Solution Approach 2:
The patent changes the control parameter from frequency avoidance to voltage compensation. By detecting the resonance frequency and dynamically adjusting the torque portion voltage through the adder, the system transforms the control strategy from passive frequency avoidance to active parameter compensation, enabling precise operation through the resonance frequency band without current hunting.
3Duration of action of stationary object
If conventional inverter system operates in resonance frequency, then the motor can operate continuously, but over-current is generated causing potential motor damage and shaft twisting
Solution Approach 1:
The patent applies preliminary action by pre-sampling the d axis current and using it in the subtractor to generate the comparative control voltage before the resonance condition fully develops. This anticipatory control mechanism prevents over-current from occurring in the first place, allowing continuous operation through the resonance frequency band without damaging the motor or shaft.
Data Source
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AI summary
An apparatus for controlling operation of inverter system configured to drive a motor by using an inverter, and to normally operate the motor in a resonance-generated frequency band if the resonance occurs, and a method thereof are disclosed, wherein the method includes detecting a current outputted by an inverter system to a motor, if an operation frequency of the motor is in a resonance frequency band, converting the detected current to a d axis current and a q axis current, calculating a difference between the converted d axis current and pre-sampled d axis current (magnetic flux portion), multiplying the calculated difference by a preset comparative control gain to calculate a comparative control voltage, and adding the calculated comparative control voltage to a torque portion voltage responsive to an operation frequency of the motor to generate a driving voltage of the motor.