Hysteresis random spectrum spreading method in inverter random pulse width modulation selective resonance elimination

Abstract

The invention provides a hysteresis random spectrum spreading method in inverter random pulse width modulation selective resonance elimination, and belongs to the technical field of inverter pulse width modulation. The method comprises the steps: carrying out the summation based on the frequency of each period of an inverter, and obtaining an average value of the switching frequency of the inverter; setting upper and lower limits of frequency hysteresis; comparing the inverter switching frequency average value with the frequency hysteresis upper and lower limits to obtain a hysteresis comparison result; determining an average switching frequency error according to a hysteresis comparison result; determining a random number according to the value of the switching frequency error; obtaining a sampling period of the next moment based on the random number and a selective harmonic elimination method; and according to the sampling period of the next moment, assigning a value to a comparison register, and generating a PWM driving signal of the single-phase inverter. According to the invention, the harmonic waves which are centrally distributed at the switching frequency and the integral multiple of the switching frequency can be uniformly distributed in the selected frequency range, and random PWM control is realized, so that the harmonic waves at the specific frequency can be selectively reduced.

Description

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

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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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