Induction Motor Inverter Control for Output Current Minimization
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Solution Overview
Problem
Existing methods for controlling induction motors do not effectively minimize output current, particularly in general-purpose inverters, leading to inefficiencies.
Innovation Solution
A power conversion device that includes a voltage command correction computation unit to adjust torque and magnetic flux axis current detection values using a magnetic flux saturation coefficient, minimizing output current by correcting the q-axis voltage command based on the deviation between detected currents and the saturation coefficient.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional magnetic flux command methods are used, then control simplicity is maintained, but output current cannot be minimized in general-purpose inverters
Solution Approach 1:
The invention changes the parameter of magnetic flux command values by computing correction values based on saturation current limits. The magnetic flux command is adjusted using correction values that depend on the excitation current command relative to the saturation current limit, transforming the control approach to achieve current minimization without requiring complex hardware modifications.
Solution Approach 2:
The invention implements feedback by computing voltage command correction values based on the deviation between actual current detection values and corrected torque current. The system continuously monitors current detection values, compares them with target values, and adjusts voltage commands accordingly, creating a closed-loop control system that minimizes output current while maintaining operational requirements.
2Productivity
If two-point approximation method is used, then computation is simplified, but output current minimization fails for different motor models
Solution Approach 1:
The invention makes the control system dynamic by using a magnetic flux saturation coefficient that changes according to the excitation current. Instead of fixed two-point approximation values, the system dynamically adjusts the saturation coefficient based on real-time excitation current levels, enabling adaptation to different motor models and operating conditions while maintaining output current minimization.
3Productivity
If excitation current command exceeds saturation current limit, then magnetic flux command slope changes, but output current is not minimized
Solution Approach 1:
The invention performs preliminary action by pre-computing voltage command correction values based on the deviation between current detection values and corrected torque current. The system calculates correction values in advance using the saturation coefficient and excitation current relationship, then applies these corrections to minimize output current before saturation effects become problematic, ensuring both current reduction and control precision.
Data Source
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AI summary
Provided is a power conversion device that has reduced output current and is capable of realizing highly efficient output current properties. The present invention is a power conversion device that controls driving of an induction motor, the power conversion device comprising a voltage command correction computation unit that computes a voltage command correction value for correcting a voltage command for a torque axis on the basis of a current detection value for the torque axis and a current detection value for a magnetic flux axis. The voltage command correction computation unit computes the voltage command correction value on the basis of the deviation between the current detection value for the magnetic flux axis and a corrected torque current obtained by multiplying the absolute value of the current detection value for the torque axis and a magnetic flux saturation coefficient that varies according to excitation current.