Three-partition type three-level inverter neutral-point voltage balancing method and system

Abstract

The invention relates to a three-partition type three-level inverter neutral-point voltage balancing method and system. The method comprises the steps: dividing a three-level space vector diagram in athree-partition mode; constructing a virtual space vector in a three-partition type space vector region division result; based on a recent three-virtual-vector synthesis rule, according to the reference voltage vector and a volt-second balance equation, carrying out calculating to obtain action time of a virtual large vector, a virtual middle vector and a virtual zero vector; determining the action time of the positive and negative basic small vectors according to the action time of the virtual middle vector; determining the action time of the switch state corresponding to each virtual spacevector according to the action time of the virtual large vector, the virtual middle vector, the virtual zero vector, and the positive and the negative type basic small vectors; and modulating the three-level inverter according to the action time of the switch state corresponding to each virtual space vector in each cell. According to the invention, the neutral-point voltage oscillation can be weakened, and the output performance of the NPC type inverter is improved.

Description

technical field [0001] The invention relates to the field of midpoint voltage control, in particular to a method and system for balancing the midpoint voltage of a three-level inverter based on a three-division type. Background technique [0002] In response to the actual needs of life and production, and the rapid development of power electronics technology, more high-voltage and high-power inverters have been put into use. The neutral point clamp (NPC) topology is the most used in three-level inverters. Extensive, and its midpoint potential imbalance defect greatly limits its development. The midpoint voltage is one of the important indicators for the efficient and stable operation of the system, and its stability directly affects the waveform quality of the inverter output. If there is a large imbalance in the midpoint voltage, the most direct impact is to increase the distortion rate of the output current, generate more low-order and even-order harmonics, and increase t...

AI Technical Summary

Problems solved by technology

However, the traditional space vector modulation algorithm is prone to serious midpoint voltage oscillation problems under high modulation degree and low power factor conditions, which affects the output performance of NPC inverters.

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