Overmodulation method and system for bi-level space vector pulse duration modulation

Abstract

The invention relates to an overmodulation method for double-level space vector pulse width modulation. The method comprises: the modulation ratio is obtained from a reference voltage vector and direct current bus voltage; the modulation ratio is divided into a first setting region and a second setting region; when the modulation ratio is in the first setting region, the acting time of a zero vector and an effective vector is calculated; when the acting time of the zero vector is more than zero, a compensating coefficient is calculated; according to the compensating coefficient, the acting time of the zero vector and the effective vector after being compensated is calculated; when the acting time of the zero vector is less than or equal to zero, the zero vector does not act and the acting time of the effective vector is calculated; when the modulation ratio is in the second setting region, a keeping angle is calculated; the keeping angle is compared with a phase angle of the reference voltage vector, and according to a comparison result, the acting time of the effective vector in different regions is calculated respectively; and according to the acting time, the method carries out overmodulation. The method is simple to calculate and convenient to realize a project and improves precision of SVPWM so as to reduce relative error between the output voltage and the reference voltage vector.

Description

technical field [0001] The invention relates to the technical field of AC drives, in particular to an overmodulation method and system for two-level space vector pulse width modulation. Background technique [0002] Pulse Width Modulation (PWM, Pulse Width Modulation) is an important part of the AC drive control system. The function of this part is to adjust the width of the pulse signal that controls the on-off of the main circuit power semiconductor device according to the input reference voltage vector and the current DC bus voltage, so that the fundamental wave voltage output by the main circuit is equal to the input reference voltage vector. [0003] Space Vector Pulse Width Modulation (SVPWM: Space Vector Pulse Width Modulation) is a PWM method based on the control idea of ​​motor flux trajectory tracking. [0004] According to the different modulation ratios, SVPWM can be divided into linear modulation and over modulation. [0005] see figure 1 , which is a schemat...

AI Technical Summary

Problems solved by technology

[0010] The overmodulation algorithm in the prior art not only needs to calculate the reference angle of the reference voltage vector after compensation according to the modulation ratio, but also corrects the amplitude and phase of the reference voltage vector according to the reference angle, and also needs to adjust the action time of the basic vector Judging and correcting, the calculation steps are cumbersome and occupy more system resources

There is a nonlinear relationship between the reference angle and the modulation ratio that cannot be expressed analytically. In practical applications, the functional relationship between them can only be described by curve fitting or a table, which limits the accuracy of SVPWM overmodulation and makes the output voltage and The relative error of the reference voltage vector is large

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