Plant Control Device for Harmonic Current Tracking
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Solution Overview
Problem
Conventional feedback control methods struggle to accurately track harmonic currents in motor systems due to inherent model errors, which persist even after correcting time-domain model errors, leading to suboptimal vibration reduction and noise suppression.
Innovation Solution
A control device that combines feedback control, feedforward control using an inverse plant model, a feedforward voltage corrector to address modeling errors, and a repetitive controller to learn and correct periodic disturbances, enabling precise tracking of harmonic current commands by generating a command voltage value through a combination of feedback and feedforward voltage components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional feedback control is used to track harmonic currents, then the control system is simple to implement, but the tracking precision is insufficient due to model errors
Solution Approach 1:
The control system is segmented into multiple functional modules: feedback controller, feedforward controller using inverse plant model, feedforward voltage corrector for modeling errors, and repetitive controller for periodic disturbances. Each module handles specific aspects of the control task, allowing high precision tracking while maintaining manageable system complexity through modular architecture
Solution Approach 2:
An inverse plant model is introduced as an intermediary component to generate feedforward control signals that anticipate system behavior. This intermediary allows the system to compensate for model errors before they affect tracking precision, resolving the contradiction between simplicity and precision
2Measurement precision
If time-domain model error correction is applied to PTC, then some harmonic currents are suppressed, but residual model errors remain that prevent perfect tracking
Solution Approach 1:
The solution moves from single-domain correction to multi-dimensional correction by addressing model errors in both time domain (through PTC improvement) and frequency domain (through repetitive controller). This dimensional expansion allows comprehensive suppression of residual errors that single-domain approaches cannot eliminate
Solution Approach 2:
A repetitive controller is implemented to learn periodic current disturbances and feed back correction signals. This feedback mechanism continuously refines the control accuracy by compensating for residual model errors that persist after time-domain correction, achieving reliable high-precision tracking
3Measurement precision
If multiple controllers are combined to improve tracking precision, then model errors are better corrected, but the device complexity increases
Solution Approach 1:
Multiple controllers (feedback, feedforward with inverse model, feedforward corrector, and repetitive controller) are merged into a unified control architecture. This combination allows each controller to address specific limitations of the others, achieving high tracking precision while the integrated structure manages complexity through coordinated operation rather than isolated complex systems
Data Source
AI summary
A control device to perform feedback control based on a current value, and output a first voltage value includes a feedforward controller using an inverse model of a plant; a feedforward voltage corrector to correct a voltage disturbance due to a modeling error between the plant and a model of the plant; a repetitive controller to learn periodic current disturbances; and a switch. The switch is ON when the current response is in a steady state, and the repetitive controller learns the disturbances and corrects a command current value. A feedback controller outputs the first voltage value by performing the feedback control based on a current value from the corrected command current value, and inputs the command current value to the inverse model to generate a second voltage value. The control device outputs a sum of the first and the second voltage value as a command voltage value.