Hysteresis random spread spectrum method in selective harmonic cancellation of inverter random pulse width modulation

Abstract

The present application proposes a hysteresis random spread spectrum method in inverter random pulse width modulation selective harmonic elimination, which belongs to the technical field of inverter pulse width modulation. Average value of inverter switching frequency; set the upper and lower limits of frequency hysteresis; compare the average value of inverter switching frequency with the upper and lower limits of frequency hysteresis to obtain the hysteresis comparison result; determine the average switching frequency according to the hysteresis comparison result error; determine a random number according to the value of the switching frequency error; obtain the sampling period at the next moment based on the random number and the method of selective harmonic elimination; assign a value to the comparison register according to the sampling period at the next moment , to generate the PWM drive signal of the single-phase inverter. The present application can distribute the harmonics concentrated at the switching frequency and its integer multiples in a relatively uniform distribution within the selected frequency range and realize random PWM control, which can selectively reduce the harmonics at a specific frequency.

Description

technical field [0001] The invention belongs to the technical field of inverter pulse width modulation, and in particular relates to a hysteresis random spread spectrum method in the selective harmonic elimination of inverter random pulse width modulation. Background technique [0002] In the traditional Sinusoidal Pulse Width Modulation (SPWM) strategy, the inverter switching frequency is usually fixed. More high-order harmonics will be generated at the switching frequency and its integer multiple frequencies; it is the main reason for electromagnetic vibration and noise of loads such as motors. Although increasing the inverter operating frequency can reduce electromagnetic vibration and noise, it is not suitable for applications where the switching frequency must be limited to a lower value, such as high-power traction drive systems. RPWM can concentrate the original harmonics on the switching frequency and its integer multiple frequencies, and evenly distribute them in a...

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Problems solved by technology

The existing relevant literatures do not consider how to control the instantaneous switching frequency and the average switching frequency of the inverter when realizing selective harmonic elimination; nor do they give general formulas for the switching period, random number and the corresponding upper and lower limits of frequency. Lack of systematic analysis of the elimination mechanism for specific sub-frequency

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