Motor PWM Control With Adaptive Carrier Frequency and Modulation
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Solution Overview
Problem
Existing motor control methods face challenges in providing temperature protection to power converters while maintaining efficiency, as they often result in voltage ripple and sound vibration, and struggle to switch the carrier frequency to a low frequency except at low motor rotation speeds.
Innovation Solution
A motor control method that adjusts the carrier frequency and modulation method of PWM signals based on a characteristic coordinate of motor rotation speed and torque, allowing for temperature protection without efficiency loss, by setting the carrier frequency to a reference or low frequency depending on the operating point and applying two-phase or three-phase modulation accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the carrier frequency is switched to a lower frequency for temperature protection or efficiency improvement, then energy loss is reduced, but voltage ripple and sound vibration deteriorate
Solution Approach 1:
The patent dynamically switches between high-frequency and low-frequency carrier waves based on the motor's rotation speed. At high rotation speeds, a high-frequency carrier wave is used to minimize voltage ripple and sound vibration. At low rotation speeds, a low-frequency carrier wave is used to reduce switching losses and improve efficiency. This dynamic adaptation resolves the contradiction by optimizing the carrier frequency according to operating conditions.
Solution Approach 2:
The patent changes the carrier frequency parameter based on the motor's rotation speed. When the rotation speed exceeds a predetermined threshold, the carrier frequency is set to a high frequency; otherwise, it is set to a low frequency. This parameter change strategy allows the system to achieve both low energy loss and acceptable voltage ripple/sound vibration characteristics across different operating ranges.
2Temperature
If the carrier frequency is switched to a lower frequency for temperature protection, then temperature protection is achieved, but efficiency improvement is limited unless current reduction is applied
Solution Approach 1:
The patent implements dynamic carrier frequency switching based on rotation speed to protect the power converter from overheating while maintaining efficiency. By using low-frequency carrier waves at low rotation speeds, the patent reduces switching losses without requiring current reduction, thus avoiding torque limitation and maintaining productivity. At high rotation speeds, high-frequency carrier waves are used which naturally produce less heat, eliminating the need for frequency switching.
Solution Approach 2:
The patent changes the carrier frequency parameter according to rotation speed conditions. When rotation speed is low, a low-frequency carrier wave is selected to reduce switching losses and prevent overheating. When rotation speed is high, a high-frequency carrier wave is selected which inherently produces less heat. This parameter adaptation achieves temperature protection without sacrificing PWM control efficiency.
3Object-generated harmful factors
If a high carrier frequency is used to reduce voltage ripple and sound vibration, then output quality is improved, but switching losses increase reducing efficiency
Solution Approach 1:
The patent dynamically adjusts the carrier frequency based on the motor's rotation speed. At high rotation speeds where voltage ripple and sound vibration are more critical, a high-frequency carrier wave is used to ensure output quality. At low rotation speeds where efficiency is more important, a low-frequency carrier wave is used to minimize switching losses. This dynamic strategy resolves the contradiction by matching the carrier frequency to the prevailing operational requirements.
Solution Approach 2:
The patent changes the carrier frequency parameter according to rotation speed thresholds. When the rotation speed exceeds a predetermined value, the carrier frequency is set high to reduce voltage ripple and sound vibration. When the rotation speed is below the threshold, the carrier frequency is set low to reduce switching losses. This conditional parameter change optimizes both output quality and efficiency across different operating conditions.
Data Source
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AI summary
A motor control method for controlling a motor by transmitting a PWM signal at a predetermined carrier frequency to a power converter configured to supply power to the motor and performing switching control on the power converter, the method including, in a characteristic coordinate having a rotation speed of the motor and a torque of the motor as axes, the characteristic coordinate including a first region representing a region where the rotation speed is higher than a first predetermined rotation speed, a second region representing a region where the rotation speed is equal to or lower than the first predetermined rotation speed and the torque is higher than a predetermined torque, and a third region representing a region where the rotation speed is equal to or lower than the first predetermined rotation speed and the torque is equal to or lower than the predetermined torque, setting the carrier frequency to be a reference frequency when an operating point representing a current rotation speed and torque is included in the first region, selecting and setting the carrier frequency to be either the reference frequency or a low frequency lower than the reference frequency when the operating point is included in the second region, setting the carrier frequency to be the low frequency when the operating point is included in the third region, setting a modulation method of the PWM signal to be three-phase modulation when the operating point is included in a region other than a specific region disposed inside the third region, and setting the modulation method of the PWM signal to be two-phase modulation when the operating point is included in the specific region.