AC Motor PWM Carrier Control for Harmonic Loss Reduction
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Solution Overview
Problem
Existing AC motor control devices using PWM control generate harmonic components in the current, leading to increased noise and loss due to the high-speed switching of the power conversion device, which existing methods fail to adequately suppress.
Innovation Solution
The AC motor control device employs synchronous PWM control with a carrier wave cycle that is periodically changed to concentrate harmonic components in the d-q orthogonal coordinates on the side of the axis with higher inductance, using a carrier wave generation unit to generate a carrier wave and a PWM pulse generation unit to produce PWM pulses based on the carrier wave and voltage command, thereby suppressing current harmonics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If PWM control is used to convert DC power to AC power, then power conversion efficiency is improved, but harmonic components are generated in the current causing increased noise and loss
Solution Approach 1:
The patent applies periodic action by changing the PWM carrier wave cycle in a periodic manner rather than keeping it constant. The control unit periodically adjusts the carrier wave cycle to concentrate harmonic components on the d-axis or q-axis with larger inductance, thereby reducing current harmonics and energy loss while maintaining power conversion efficiency
Solution Approach 2:
The patent implements parameter changes by dynamically adjusting the PWM carrier wave cycle parameter. The control unit changes the carrier wave cycle based on motor operating conditions, concentrating harmonic components on axes with larger inductance to minimize current harmonics and reduce energy loss in the motor
2Speed
If the switching element is turned on and off at high speed for PWM control, then power conversion capability is improved, but harmonic components are generated causing noise and loss
Solution Approach 1:
The patent uses periodic action by implementing periodic changes in the carrier wave cycle. The control unit periodically adjusts the PWM carrier cycle to concentrate voltage harmonic components on the d-axis or q-axis with larger inductance, which reduces current harmonics and the resulting noise while maintaining high switching speed for effective power conversion
Solution Approach 2:
The patent applies parameter changes by dynamically modifying the PWM carrier wave cycle parameter during operation. The control unit changes the carrier cycle to concentrate harmonic components on axes with larger inductance, thereby reducing current harmonics and noise generation while preserving the high switching speed necessary for PWM control functionality
Data Source
AI summary
An alternating-current (AC) motor control device that is capable of suppressing current harmonic components flowing through an AC motor and reducing a loss generated in the AC motor can be achieved. The AC motor control device 10 includes a power converter 3 that performs power conversion from direct current (DC) power to AC power, and a control unit 2 that performs synchronous PWM control on the AC motor 1. The control unit 2 includes carrier wave generation units 221, 231, and 232 that generate carrier waves, and PWM pulse generation units 22 and 23 that generate PWM pulses based on the carrier waves and a voltage command value 21A. The carrier wave generation units 221, 231, and 232 each change a cycle of the carrier wave so that harmonic components in d-q orthogonal coordinates of the AC motor 1 are concentrated on a side of either a d axis or a q axis having a larger inductance, the harmonic components being included in the PWM pulse.