Space vector modulation method based on parallel current source type converter

Abstract

The invention discloses a space vector modulation method based on a parallel current source type converter, which can simultaneously reduce the common mode voltage of the converter and realize the DCbridge arm current sharing. The method comprises: establishing a parallel current source type converter switching state current vector diagram by Clark transform, and classifying current vectors; calculating the common mode voltage corresponding to each current vector, and selecting a current vector with a lower common mode voltage for modulation; analyzing the redundancy state of each type of current vectors to point out a medium vector and a small vector for DC bridge arm current sharing; synthesizing a reference vector from a switching vector according to the principle of ampere-second balance, and selecting a redundant vector according to the bridge arm uneven current condition and the grid voltage state. The method uses a vector with a lower common mode voltage for synthesizing the reference vector, and performs current sharing control with a medium vector and small vector redundant switching state in each sampling period, thereby reducing the common mode voltage of the converterand realizing the DC bridge arm current sharing of the parallel current source type converter.

Description

technical field [0001] The invention relates to space vector modulation of a parallel current source type converter, in particular to a space vector modulation method capable of simultaneously reducing the common-mode voltage of the converter and realizing current sharing of DC bridge arms. Background technique [0002] Converter technology is a technology that converts electrical energy from DC to AC or AC to DC, and plays an important role in today's industrial applications. Parallel current source type three-phase full-bridge inverters are widely used. The principle is to use switching tubes to build the main circuit, and then use the corresponding modulation method to control the switching state of the switching tubes, so that the output current waveform is approximately sinusoidal. The basic principle of the parallel current source converter space vector modulation method is to obtain nineteen kinds of current vectors through the coordinate transformation of nineteen ki...

AI Technical Summary

Problems solved by technology

[0003] Due to the effect of zero vector in the traditional three-level space vector modulation, the peak value of the common mode voltage of the converter is relatively high, which is not conducive to the insulation of the system

The method of adding common-mode reactors can reduce the influence of common-mode voltage to a certain extent, but it will increase the size and cost of the system

On the other hand, for parallel current source converters, due to reasons such as unequal on-state voltage drops of semiconductor devices, different delays of drive signals, and inconsistency of DC bus inductance parameters, the DC bridge will Unbalanced arm currents, resulting in overloading of a converter

However, the two issues of reducing common-mode voltage and achieving DC current balance are coupled with each other, and often cannot meet the two control objectives at the same time.

Images