High-modulation-ratio voltage-sharing method for diode-clamped five-level inverter

Abstract

The invention discloses a high-modulation-ratio voltage-sharing method for a diode-clamped five-level inverter. According to the high-modulation-ratio voltage-sharing method for the diode-clamped five-level inverter, twelve peaks of a hexagon of the second layer of a diode-clamped five-level inverter vector diagram are used as centers, the five-level vector diagram is divided into twelve two-level vector diagrams, and 18 triangular areas are obtained through area division. Twelve vector sequences are established in each triangular area, the direct-current side capacitor voltage is controlled to be balanced through combination of the objective function optimization method and the inner hexagon vector decomposition method. Algorithm switching is conducted through the setting of a voltage error hysteresis; the objective function optimization voltage-sharing algorithm is applied when the voltage error is within the hysteresis; the inner hexagon vector decomposition voltage-sharing algorithm is selected so as to enable rapid voltage balance to be achieved when the voltage error exceeds the hysteresis. According to the high-modulation-ratio voltage-sharing method for the diode-clamped five-level inverter, the direct-current side capacitor voltage balance control over the diode-clamped five-level inverter at the high modulation-ratio is achieved, and the inverter has good harmonic characteristics.

Description

technical field [0001] The present invention relates to a method for balancing the capacitor voltage on the DC side of a diode-clamped five-level inverter, in particular to a high modulation ratio voltage equalization method for a diode-clamped five-level inverter, which belongs to the multi-level inverter Transformer technology. Background technique [0002] Multi-level converters use power devices with lower withstand voltage to achieve high-voltage output, and have the advantages of low total harmonic distortion rate of output waveform, small system electromagnetic interference, and small switching loss. High-voltage AC motor speed control and other fields of great concern. There are three basic multi-level topologies: H-bridge cascaded, diode-clamped, and flying-capacitive. Among them, the diode-clamped multilevel inverter has more application prospects because of its simple structure and no need for complex phase-shifting transformers. [0003] The research on the cl...

AI Technical Summary

Problems solved by technology

The traditional three-vector SVM voltage equalization method based on objective function optimization is based on redundant vectors. When the modulation ratio is small, there are many redundant vectors and the corresponding vector sequences are rich. The algorithm has a strong voltage equalization ability. Increase, the number of redundant vectors decreases, and the control of the DC side capacitor voltage by the algorithm becomes worse. The higher the modulation ratio is, the smaller the power factor is. When the modulation ratio is close to 1, the inverter can hardly output active power , which greatly limits the application of diode-clamped five-level inverters

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