Selective harmonic eliminated pulse width modulation-based DC bus voltage fluctuation compensation method

Abstract

The invention discloses a selective harmonic eliminated pulse width modulation-based DC bus voltage fluctuation compensation method. The method particularly involves control of a three-phase AC motordriving system and comprises the steps of determining a synchronous processing zone according to selective harmonic eliminated pulse width modulation (SHEPWM) switch angle distribution characteristicat different frequency division parameters; forecasting DC bus voltage waveform in the processing zone; and dividing the zone according to the forecasted waveform, and performing stator magnetic fluxerror accumulation according to switch moment corresponding to the zone. With the method proposed by the invention, the favorable harmonic characteristic of SHEPWM can be maintained, meanwhile, extraoutput voltage harmonic caused by DC bus voltage fluctuation is reduced to minimum, and the low-frequency harmonic current and the output torque fluctuation caused by the bus voltage fluctuation are substantially reduced; and the method can be directly used for an ordinary motor control system, and no extra hardware is needed.

Description

technical field [0001] The invention relates to the technical field of control of three-phase AC motors, more specifically, it relates to a DC bus voltage fluctuation compensation method based on selected harmonic elimination pulse width modulation. Background technique [0002] Harmonic Elimination Pulse Width Modulation (SHEPWM) is selected as one of the synchronous optimization modulation techniques, which can eliminate the lower-order voltage harmonic components as much as possible under a certain number of pulses per cycle, thereby reducing the overall harmonic current consumption . From another point of view, using this technology can achieve a certain limit of the total amount of current harmonics and reduce the number of pulses of each phase in each fundamental wave period as much as possible, thereby reducing the switching frequency of the inverter and reducing switching losses. . Therefore, this technology is widely used in high-power motor drives and other occas...

AI Technical Summary

Problems solved by technology

[0004] The difficulties in using software to realize compensation for SHEPWM mainly include the following three points: 1. Due to the characteristics of the digital control system, the control quantity loaded at the beginning of each control cycle must be calculated in the previous control cycle, and the selection of harmonic elimination pulse When the wide modulation technology is applied, the switching frequency is low, and the control cycle is also long. In this way, if the pulse command calculated based on the DC bus voltage sampled in the current cycle is used to load in the next cycle, a delay equivalent to 1.5 control cycles will be introduced. Therefore, the bus voltage in the next cycle must be known in advance in the previous cycle; 2. There is no concept of carrier in the implementation of SHEPWM, which leads to the traditional duty cycle compensation based on carrier cycle The method is difficult to implement; 3. The generation of the selected harmonic elimination pulse width modulation waveform is synchronized with the phase of the voltage vector, so the phase of the voltage vector output by the current control link must be stable, otherwise it will cause confusion in the pulse output sequence, which brings to the feedback control very difficult

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