Neutral-point potential balance control system and method for three-level converter

Abstract

The invention relates to a neutral-point potential balance control system and method for a three-level converter. The system comprises an alternating DC / DC main circuit serving as a pre-stage circuit. The neutral-point potential balance control method includes the steps: detecting voltage at a neutral point of the three-level converter in real time to obtain a voltage deviation value; performing proportional-integral control for the voltage deviation value to generate a control quantity; alternately controlling a three-level direct current support capacitor by an alternating DC / DC control method according to the control quantity to control three-level neutral-point potential balance. The three-level direct current support capacitor is alternately controlled by the neutral-point potential balance control method for the three-level converter, voltage deviation of the neutral point of the three-level converter can be rapidly suppressed, and neutral-point balance of the three-level converter is kept, so that stability of a three-level topological circuit is ensured. Both large voltage deviation and small voltage deviation can be rapidly and effectively controlled, and the control method is simple and easy to implement.

Description

technical field [0001] The patent of the invention belongs to the application field of power electronics technology, and proposes a new midpoint potential balance control method of a three-level converter. Background technique [0002] In high-power applications of power electronics, the three-level converter is one of the most commonly used multi-level converters at present. It has the characteristics of low voltage stress for switching devices, high system voltage level, and small output voltage harmonics. The high-power application field has obvious advantages, so it has been more and more widely used. However, since the DC side of the three-level converter is composed of two capacitors in series, it often causes the problem of unbalanced midpoint potential of the three-level converter. [0003] The problem of unbalanced midpoint potential has always been an important problem in three-level converters. The fluctuation of midpoint voltage will cause harm to the system in ...

AI Technical Summary

Problems solved by technology

[0008] Aiming at the above problems, the present invention provides a three-level converter mid-point potential balance control system and method to solve the problem of three-level converter mid-point voltage fluctuations, and provides a new three-level converter mid-point potential balance control system and method. The potential balance control method adopts the circuit topology of adding interleaved DC / DC in the front stage of the three-level converter, and performs a new method of interleaving PI control on the two supporting capacitors on the DC side of the three-level converter according to the situation of the midpoint potential. Effectively reduce or suppress the midpoint voltage fluctuation of the three-level converter, thereby improving the output performance of the system and improving the stability of the three-level topology circuit

Images