Optimization control method based on selective harmonic elimination pulse width modulation (SHEPWM)

Abstract

The invention provides an optimization control method based on selective harmonic elimination pulse width modulation (SHEPWM). The optimization control method based on the SHEPWM comprises the following steps: writing amplitude expressions of fundamental waves and controlled harmonic waves of all times in an arraying mode, confirming amplitude of the fundamental waves and the controlled harmonic waves of all times, and obtaining a switch angle. The optimization control method is combined with characteristics of amplitude frequency of a filter, obtains the most advantageous size value of the amplitude of the controlled harmonic waves by optimizing an objective function, improves the harmonic wave distribution condition of an SHEPWM wave form, reduces amplitude of surplus harmonic wave, enables a total harmonic content to reduce, and even removes the big surplus harmonic waves. Small amplitude changes of a controlled harmonic wave component can cause great influence on harmonic wave distribution of output voltage, and suitable changes can reduce amplitude of surplus harmonic wave components of a traditional SHEPWM method.

Description

technical field [0001] The invention belongs to the technical field of flexible power transmission and distribution of power systems, and in particular relates to an optimal control method based on SHEPWM. Background technique [0002] With the vigorous development of smart grid and new energy, the power electronic technology controlled by pulse width modulation has been vigorously developed. In high voltage and high power applications, due to the limitation of heat dissipation of the device itself, the switching frequency of power devices cannot be very high. In these occasions, the efficiency is especially valued, so the output harmonics should not be too large. Therefore, on the one hand, the switching frequency of the individual devices must be reduced, and on the other hand, the harmonic content of the overall output must be reduced. And there are two technologies that can help achieve the above goals: 1) Multi-level technology; 2) SHEPWM (Selective Harmonic Eliminatio...

AI Technical Summary

Problems solved by technology

However, the disadvantage of this PWM technology is that although the specified low-order harmonics are eliminated, the control of the unspecified high-order harmonics is lacking, so that the content of the first few unspecified high-order harmonics becomes very large, while Elimination of these harmonics requires the design of specific filter circuits

[0005] Although the traditional SHEPWM eliminates some harmonic components, it lacks control over the remaining harmonic components, resulting in a large harmonic content, and filtering out such harmonics requires a larger-capacity filter and causes greater harmonic loss

Traditional SHEPWM forces the amplitude of all controlled harmonics to be zero, but makes the amplitude of some components of the remaining harmonics relatively high, resulting in an increase in the capacity, volume and loss of the filter

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