PWM Phase Correction in Inverter Control Near Zero Crossing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing inverter control devices fail to effectively suppress harmonics and reduce current ripples in the near-zero-cross region, particularly at zero-cross points, leading to noise and vibration issues during overmodulation.
Innovation Solution
An inverter control device with a pulse generation unit that generates PWM pulses based on a modulation factor and a pulse shift unit that corrects the phase of the PWM pulses to align with harmonics of a predetermined order in the near-zero-cross region, thereby reducing current ripples.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If overmodulation mode is used to increase motor rotation speed, then productivity is improved, but harmonics are generated and current ripples increase causing noise and vibration
Solution Approach 1:
The invention changes the phase parameter of PWM pulses in the near-zero-cross region by a predetermined amount, which modifies the timing relationship between PWM pulses and harmonics. This parameter change suppresses harmonics of a predetermined order while maintaining overmodulation operation, thereby reducing current ripples and noise without sacrificing motor rotation speed.
2Object-generated harmful factors
If PWM pulse phase is corrected to suppress harmonics in near-zero-cross region, then current ripples are reduced, but control complexity increases
Solution Approach 1:
The invention applies preliminary phase correction to PWM pulses in the near-zero-cross region before they cause significant harmonic distortion. By pre-adjusting the pulse phase in this critical region, the control system effectively suppresses harmonics with minimal additional complexity, as the correction is applied only where needed rather than throughout the entire modulation cycle.
Data Source
AI summary
An inverter control device 200 includes a current control unit 210 that outputs a voltage commands (Vd*, Vq*), a modulation wave control unit 220 that generates a modulation wave based on the voltage commands (Vd*, Vq*), a pulse generation unit 230 that generates a PWM pulse for controlling an inverter 100 using a modulation wave and a carrier wave of a predetermined frequency, and a pulse shift unit 250 that corrects the phase of the PWM pulse such that the PWM pulse is output in a phase corresponding to a harmonic of a predetermined order of the modulation wave in the near-zero-cross region including the zero-cross point at which the modulation wave changes across 0.