Air Conditioner Motor PWM Control for Low-Loss Stable Operation
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Solution Overview
Problem
Partial two-phase current control in air conditioners can lead to step-out due to insufficient torque and vibration and noise due to waveform distortion, despite reducing switching losses.
Innovation Solution
An operation control system that determines whether field weakening control is off for a three-phase AC motor and performs partial two-phase current control by stopping pulse generation during a mask period in a PWM signal, where the mask period is a predetermined angular range including an electrical angle at which the amplitude of the voltage commands becomes zero.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If partial two-phase current control is implemented to reduce switching losses, then switching loss is reduced, but step-out due to insufficient torque and vibration and noise due to waveform distortion occur
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the mask period width based on motor speed and load conditions. At low speeds where torque deficiency causes step-out, the mask period is reduced or eliminated. At high speeds where switching loss is the dominant concern, the full mask period is applied. This speed-dependent parameter adjustment resolves the contradiction by optimizing the balance between switching loss reduction and torque maintenance across different operating ranges.
Solution Approach 2:
The patent implements dynamics by making the mask period width variable rather than fixed. The control system continuously monitors motor speed and adjusts the mask period width accordingly - using a smaller width at low speeds to prevent step-out and a larger width at high speeds to maximize switching loss reduction. This dynamic adaptation allows the system to achieve both reliability and energy efficiency at different operating points.
2Loss of energy
If partial two-phase current control is implemented, then switching loss is reduced, but vibration and noise due to waveform distortion occur
Solution Approach 1:
The patent uses parameter changes by adjusting the mask period width based on operating conditions. At low speeds, the mask period width is reduced to minimize waveform distortion that causes vibration and noise. At high speeds, the full mask period is used to maximize switching loss reduction. This dynamic parameter adjustment resolves the contradiction between energy efficiency and reduction of harmful vibrations and noise.
3Loss of energy
If mask period is applied to stop pulse generation, then switching loss is reduced, but torque becomes insufficient causing step-out
Solution Approach 1:
The patent applies dynamics by making the mask period width variable based on motor speed and load conditions. At low speeds where torque is critical, the mask period width is reduced or eliminated to maintain sufficient torque. At high speeds where switching loss is the primary concern, the full mask period width is applied. This dynamic adjustment resolves the contradiction between torque maintenance and switching loss reduction.
Data Source
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AI summary
An operation control system (10) includes: a field weakening determination unit (51) configured to determine whether a field weakening control is off for a three-phase AC motor (80); and an execution unit (54) configured to perform a partial two-phase current control in a case where the field weakening control is determined to be off, wherein in sine wave voltage commands (vu*, vv*, vw*) correspond to individual phases generated based on a speed command for the three-phase AC motor (80), wherein a mask period is a predetermined angular range including an electrical angle at which the amplitude of the voltage commands becomes zero, and wherein the partial two-phase current control is control to stop pulse generation during the mask period in a case where a pulse-width modulation signal is generated based on the voltage commands (vu*, vv*, vw*).