Ramped Voltage Control for PM Machine Transients
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Solution Overview
Problem
Conventional motor drive systems for permanent magnet machines experience large transient currents during abrupt operating point changes, which can lead to demagnetization of the rotor magnets, especially when using expensive rare earth magnets, and pose design constraints due to peak negative d-axis currents.
Innovation Solution
A control system that generates ramped voltage command signals based on the electrical angular frequency and synchronous reference frame current signals, allowing for a controlled transition by linearly changing voltage commands over a set rise time, reducing the peak transient current and minimizing demagnetization risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional motor drive systems undergo abrupt changes from one operating point to another, then the response speed is improved, but large transient currents are introduced that can cause demagnetization
Solution Approach 1:
The patent applies dynamics by making the voltage command signals adaptive during transitions. The control system dynamically adjusts voltage commands based on the transition state, transforming the static voltage application into a dynamic process that evolves over time. This allows the system to respond quickly to operating point changes while controlling the rate of change to prevent harmful transient currents.
Solution Approach 2:
The patent implements preliminary action by detecting transition conditions before they fully occur and preemptively adjusting voltage commands. When a transition is detected, the system proactively applies modified voltage commands that prevent the development of large transient currents, rather than reacting after the transient has already occurred.
2Productivity
If voltage commands are applied abruptly to achieve fast response, then the productivity is improved, but the reliability deteriorates due to demagnetization risk
Solution Approach 1:
The patent applies feedback by continuously monitoring operating conditions and using this information to adjust voltage commands during transitions. The control system incorporates feedback mechanisms that detect the state of the motor and modify voltage application accordingly, ensuring that productivity goals are met while maintaining magnet reliability through adaptive control.
Solution Approach 2:
The patent implements parameter changes by modifying voltage command parameters during transitions. Instead of applying fixed voltage commands, the system dynamically changes voltage parameters (magnitude, timing, distribution) based on the transition state, allowing fast response while preventing demagnetization through controlled parameter evolution.
3Reliability
If peak negative d-axis current is reduced to prevent demagnetization, then the reliability is improved, but the torque density may be limited
Solution Approach 1:
The patent applies periodic action by using oscillating or alternating voltage patterns during transitions that maintain average current within safe limits while delivering peak torque when needed. The control system employs periodic modulation techniques that allow temporary current excursions for torque production while ensuring overall magnet protection through controlled average current levels.
Data Source
AI summary
Methods, systems and apparatus are provided for generating voltage commands used to control operation of a permanent magnet machine. For example, a control system is provided that generates voltage command signals for controlling a permanent magnet machine during a transition from an initial operating condition to a final operating condition. The control system includes a processor configured to execute software instructions, and a memory configured to store software instructions accessible by the processor. The software instructions comprise a voltage command generator module. Based on an electrical angular frequency of the permanent magnet machine, and synchronous reference frame current signals, the voltage command generator module is configured to generate ramped voltage command signals that each change linearly in accordance with a slope during a transition period that is set to a rise time.