Three-level H-bridge five-level inverter direct-current side capacitor voltage balancing method

Abstract

The invention discloses a three-level H-bridge five-level inverter direct-current side capacitor voltage balancing method. According to the method disclosed by the invention, based on the traditional MPC algorithm, tracking of a reference voltage serves as a main objective, and the three-phase direct-current side capacitor voltage is effectively balanced. The method comprises the following steps: establishing corresponding mathematical models for all five-level space voltage vectors, calculating each phase current value of each vector during action, and performing classified analysis on the influence of each voltage vector to a capacitor neutral-point potential; rapidly determining the amplitude and position of the reference voltage in a space vector diagram by utilizing a SVPWM (space vector pulse width modulation) algorithm, and selecting the position and balance vector participating in prediction each time; then establishing a mathematical model of discretized switch, load and direct-current capacitor voltage for the three-level H-bridge five-level inverter; and finally, constructing an appropriate cost function, and optimizing the selected position and balance vector. According to the method disclosed by the invention, real-time balance of the three-phase capacitor neutral-point potential can be realized, and the output performance of the inverter is guaranteed. In addition, because the optimizing vector each time is composed of four balance vectors and three position vectors, the operation amount is small, and the efficiency is high.

Description

technical field [0001] The invention relates to the technical fields of medium and high voltage frequency conversion, flexible AC power transmission and HVDC, in particular to the balance control of DC side capacitor voltage of three-level H-bridge (NPC / H-bridge) cascaded inverters. Background technique [0002] In recent years, multilevel inverters have been widely used in high voltage and high power applications. Compared with the traditional two-level inverter, it has the advantages of improving the application level of voltage and power, reducing the common mode voltage output, and having good harmonic performance at a lower switching frequency. Generally, multilevel inverters mainly have three topologies: diode clamp, flying capacitor clamp, and cascaded H-bridge. Among them, the cascaded H-bridge can be divided into two-level H-bridge cascaded and three-level H-bridge (NPC / H-bridge) cascaded. Compared with diode-clamped and capacitor-clamped topologies, the three-lev...

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Problems solved by technology

[0005] Aiming at the unbalanced capacitor voltage on the DC side in the three-level H-bridge cascaded inverter equipment, and the problems of poor dynamic response capability and reduced output performance in the related solution algorithm, the purpose of the present invention is to provide a three-level H bridge Control method of capacitor voltage balance on DC side of bridge five-level inverter

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