Motor Control Switching Boundaries for Stable Five-Pulse Transition
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Solution Overview
Problem
The challenge in controlling rotating electrical machines is the potential for voltage and current distortion when switching between asynchronous pulse-width modulation control and synchronous five-pulse control, particularly due to changes in rotational speed, leading to overcurrent thresholds being exceeded.
Innovation Solution
A rotating electrical machine control device that incorporates asynchronous pulse-width modulation and synchronous five-pulse control, with region boundaries set to manage the transition between these controls based on torque and rotational speed, ensuring hysteresis to stabilize the number of switching pulses and minimize distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If voltage commands are saturated to prevent overvoltage, then overvoltage is prevented, but current continuity deteriorates and torque ripple increases
Solution Approach 1:
The system performs preliminary saturation determination before voltage saturation occurs by comparing predicted q-axis current values against current limits. This advance detection allows the control system to adjust voltage commands proactively, preventing both overvoltage and current discontinuity by modifying control actions before the problematic state is reached.
Solution Approach 2:
The system implements feedback by continuously monitoring actual current values and comparing them against target values. When deviations are detected, the saturation determination unit adjusts voltage saturation strategies in real-time, and the voltage command generation unit modifies commands based on this feedback, creating a closed-loop control system that maintains current continuity while preventing overvoltage.
2Reliability
If voltage saturation is applied to prevent overvoltage, then overvoltage is prevented, but torque ripple increases
Solution Approach 1:
The system determines voltage saturation requirements in advance by predicting q-axis current behavior before voltage saturation occurs. This preliminary determination allows for smooth transition strategies that maintain torque continuity, preventing the abrupt torque changes that cause ripple while still preventing overvoltage conditions.
Solution Approach 2:
The system dynamically adjusts voltage saturation strategies based on real-time operating conditions. The saturation determination unit continuously evaluates whether saturation is needed and adjusts the degree of saturation dynamically, allowing the system to maintain optimal torque production while preventing overvoltage, rather than applying fixed saturation thresholds that cause torque ripple.
3Adaptability or versatility
If d-axis current is increased to improve power factor, then power factor improves, but flux weakening control effectiveness deteriorates
Solution Approach 1:
The system determines d-axis current saturation requirements in advance based on predicted operating conditions and flux weakening needs. By proactively setting appropriate saturation thresholds before operation enters critical regions, the system can maintain improved power factor through controlled d-axis current while preventing degradation of flux weakening control effectiveness.
Solution Approach 2:
The system dynamically changes d-axis current saturation parameters based on operating conditions. The saturation determination unit adjusts d-axis current limits according to the degree of flux weakening required, allowing the system to optimize power factor improvement while maintaining flux weakening effectiveness through adaptive parameter adjustment rather than fixed parameter settings.
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
This approach stabilizes the switching process, reducing voltage and current distortions, preventing overcurrent, and ensuring smooth transitions between control systems, particularly in high-speed and high-torque operations.
Implementation Method 1
a converter that transforms a power supplied from a power supply to the motor to be controlled, into a control signal for the motor to be controlled
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
A rotating electrical machine control device shifts a control system to synchronous five-pulse control when an operating point crosses a second boundary K22 from a state in which asynchronous pulse-width modulation control is being executed, and shifts the control system to the asynchronous pulse-width modulation control when the operating point crosses a first boundary K21 from a state in which the synchronous five-pulse control is being executed. The first boundary K21 is set such that the number of switching pulses per unit rotational speed by the synchronous five-pulse control immediately before the operating point crosses the first boundary K21 is smaller than the number of the switching pulses per unit rotational speed by the asynchronous pulse-width modulation control immediately after the operating point crosses the first boundary K21.