Overmodulation method implemented based on carrier

Abstract

The invention discloses an overmodulation method implemented based on a carrier. The method includes determining a three-phase original modulated wave U1i according to amplitude and phase of a reference vector in an overmodulation area; superposing a zero-sequence component V0 to the original modulated wave to acquire corresponding three-phase saddle modulated waves U2i, and sorting the three-phase saddle modulated waves U2i; in the overmodulation area, judging whether or not the reference vector is positioned in a linear modulation section, a hexagonal modulation section or a six-pulse wave modulation section according to the magnitude relationship between Umax and 2-|Umid|; correcting the three-phase saddle modulated waves in different modulation sections respectively to acquire a final three-phase modulated wave Ui; comparing the Ui with the triangular carrier to generate PWM (pulse-width modulation) waves, and distributing the PWM waves to corresponding pins. The overmodulation method has the advantages that sector division and vector action time calculation are not needed, so that the overmodulation method is simple to implement, easy to apply to engineering and applicable to overmodulation of any level number converters; accuracy of the overmodulation method is proved by simulation results.

Description

technical field [0001] The invention relates to an overmodulation method for a converter with an arbitrary level number, especially an overmodulation method for an arbitrary level converter based on a carrier wave; it is applicable to the field of photovoltaic power generation grid connection, the field of motor control, and the power system and other converter fields. Background technique [0002] When the converter works at a lower DC voltage or in the field-weakening area of ​​the AC drive system and outputs high torque, the converter is required to have a higher DC voltage utilization rate, and the working state of the converter is also changed from linear to linear. The modulation area enters the over-modulation area. Compared with the linear modulation region, the maximum fundamental voltage amplitude that can be output by the overmodulated multilevel converter can be increased by 9.3%, which can significantly increase the inverter operating range or improve the contr...

AI Technical Summary

Problems solved by technology

[0006] It can be seen that the existing technology needs to calculate the holding angle and the action time of each vector, and then judge the position of the reference vector according to the holding angle and correct the amplitude and phase of the reference voltage. At the same time, the action time of the voltage vector needs to be corrected, and There is a problem of considering sector division, there are a lot of complex mathematical operations, the implementation steps are cumbersome, and it takes up a lot of resources

At the same time, the overmodulation method in the prior art is only for two-level and three-level converters. In practical applications, the overmodulation of multi-level converters will be extremely complicated, which is not conducive to engineering realization.

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