Specific harmonic elimination method for three-level NPC converter

Abstract

The invention discloses a specific harmonic elimination method for a three-level NPC converter, and the method comprises the steps: building a nonlinear transcendental equation set for solving a switching angle according to the input and output signals of the three-level NPC converter, and achieving the equality of an inequality constraint condition in the nonlinear transcendental equation set through coordinate transformation, and solving a switching angle according to the obtained equation nonlinear transcendental equation set, converting the solved switching angle into a pulse signal, and driving a switching tube in the three-level NPC converter to be on and off by utilizing the pulse signal, namely eliminating specific harmonics of the three-level NPC converter. According to the specific harmonic elimination method for the three-level NPC converter, multivariable constraint conditions are simplified into judgment conditions of a single variable through a geometric programming thought, the calculation speed and precision are improved, then the specific harmonic elimination accuracy of the three-level NPC converter is improved, and the method has good application value.

Description

technical field [0001] The invention belongs to the technical field of flexible power transmission and distribution of power systems, and relates to a method for eliminating specific harmonics of a three-level NPC converter. Background technique [0002] In some high-voltage and high-power fields, the self-heating of devices in power converters is a very serious problem. Therefore, the switching frequency of the converter will not be designed to be very high. During the operation of the converter, in order to ensure the quality of the output waveform, it is necessary to design a bulky filter system, which undoubtedly increases the overall system loss and economic cost. To this end, a specific harmonic elimination pulse width modulation (Selective Harmonic Elimination Pulse Width Modulation, SHEPWM) strategy is proposed. SHEPWM can eliminate the selected low-order harmonics by pre-determining the switching angle of the on-off moment, and realize the precise control of the ha...

AI Technical Summary

Problems solved by technology

[0005] The purpose of the present invention is to provide a specific harmonic elimination method for a three-level NPC converter, which solves the problems of cumbersome calculation process of the existing specific harmonic elimination method and low accuracy of converter specific harmonic elimination

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