Motor Control Device Harmonic Loss Reduction
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Solution Overview
Problem
Existing motor drive systems using PWM control face challenges in reducing harmonic loss, particularly in the over-modulation region, and are limited by low carrier frequency and asynchronous PWM control, which restricts the drive range and efficiency.
Innovation Solution
A motor control device that switches to a synchronous correction signal and fixed amplitude when the modulation rate reaches a certain value, optimizing the carrier frequency and pulse pattern to minimize harmonic loss, allowing for higher carrier frequencies and broader drive ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If synchronous PWM control is used to reduce harmonic loss in the over-modulation region, then harmonic loss is reduced, but the technique is limited to railway systems with low carrier frequency upper limits and narrow drive region
Solution Approach 1:
The patent creates a universal PWM control method that can be applied to both synchronous and asynchronous PWM controls across different system types and carrier frequency ranges. By using asynchronous PWM control with dynamic carrier frequency adjustment, the invention extends the applicability beyond railway systems to general motor drive systems with radio frequency carrier capabilities, significantly widening the drive region.
Solution Approach 2:
The patent employs dynamic carrier frequency adjustment based on modulation rate to maintain effectiveness across a wide drive region. This dynamic approach allows the system to adapt to different operating conditions and motor types, making the harmonic loss reduction technique universally applicable rather than limited to specific railway system constraints.
2Adaptability or versatility
If asynchronous PWM control is used to widen drive range and increase carrier frequency to radio frequency, then adaptability is improved, but harmonic loss in the over-modulation region increases
Solution Approach 1:
The patent dynamically adjusts the carrier frequency based on the modulation rate in asynchronous PWM control. When the modulation rate is below the predetermined threshold, a higher carrier frequency is used to reduce harmonic loss. When the modulation rate reaches or exceeds the threshold, the carrier frequency is adjusted to optimize performance. This dynamic adjustment enables asynchronous PWM control to achieve both wide drive range and reduced harmonic loss.
Solution Approach 2:
The patent changes the carrier frequency parameter in response to modulation rate changes, enabling asynchronous PWM control to maintain low harmonic loss across the entire drive range including the over-modulation region. This parameter adjustment resolves the contradiction between wide adaptability and harmonic loss reduction.
Data Source
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AI summary
An object of the invention is to reduce or minimize a harmonic loss which is generated when an alternating-current motor is driven in an over-modulation region. In a case where a modulation rate reaches a predetermined value equal to or greater than one, a final correction signal wave is switched from zero to the synchronous correction signal. In a case where the modulation rate reaches a predetermined value equal to or greater than one, a final amplitude is switched from the first amplitude to a fixed amplitude.