A three-level inverter midpoint voltage balance and loss reduction control method

Abstract

The present invention relates to a three-level inverter mid-point voltage balance and loss reduction control method based on a new space vector modulation method, and defines a new virtual mid-vector, so that in any area of ​​the new space vector Both contain two pairs of small vectors, and the small vector with a larger value of the midpoint voltage balance coefficient is used to modulate the midpoint voltage balance, which is called the midpoint voltage regulation small vector VSNP; the other pair of small vectors is used to reduce switching losses, It is called the switching loss adjustment small vector VSSL; the reduction of switching loss is realized by minimizing the switching times of the phase with the largest current and reducing the switching frequency. Therefore, under the premise of controlling the midpoint voltage, the corresponding small vectors can be reasonably selected according to the phase current to flexibly form a three-phase switching sequence, thereby reducing the switching loss of the device.

Description

technical field [0001] The invention relates to a three-level inverter control strategy, in particular to a three-level inverter midpoint voltage balance and loss reduction control method. Background technique [0002] In the diode-clamped multi-level inverter, the neutral current flows through the two DC side capacitors, which makes the voltage division of the two capacitors uneven and generates corresponding AC fluctuations. The balance of the midpoint voltage has always been the focus of research and the key to the application of multi-level neutral point clamped inverters. If the midpoint voltage balance of the inverter cannot be guaranteed for a long time, the quality of the output waveform will be seriously affected. impact, and even waveform degeneration in extreme cases. In recent years, the neutral point voltage balance of the diode neutral point clamped inverter has been widely concerned by scholars at home and abroad. The control methods of the neutral point volt...

AI Technical Summary

Problems solved by technology

[0002] In the diode-clamped multi-level inverter, the neutral current flows through the two DC side capacitors, which makes the voltage division of the two capacitors uneven and generates corresponding AC fluctuations.

The balance of the midpoint voltage has always been the focus of research and the key to the application of multi-level neutral point clamped inverters. If the midpoint voltage balance of the inverter cannot be guaranteed for a long time, the quality of the output waveform will be seriously affected. impact, even waveform degeneration in extreme cases

[0003] The switching device loss of multilevel inverter will affect the long-term stable operation and service life of the inverter

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