A diode-clamped five-level inverter voltage equalization control method

Abstract

The invention discloses a voltage-sharing control method for a diode clamp type five-level inverter. According to the method, by utilizing the adjusting ability of four redundant states of six effective vectors of an internal hexagon to capacitor voltage, a five-level vector diagram is divided into six two-level vector diagram bodies with the six vertexes of the internal hexagon as the center, twelve triangular areas are obtained through area division, then 16 vector sequences are found out in each triangular area and divided into four groups, and finally the optimum vector sequence is selected to control the capacitor voltage of the direct-current side according to the vector sequence selection rule. By the adoption of the method, balance control of the capacitor voltage of the direct-current side when the diode clamp type five-level inverter is high in modulation ratio can be achieved, and an algorithm is not influenced by the power factor of the inverter.

Description

technical field [0001] The invention relates to a voltage equalization control method for a diode-clamped five-level inverter, which belongs to the field of power electronics. Background technique [0002] In terms of high-voltage and large-capacity power electronics applications, compared with two-level converters, multi-level converter technology has the advantages of higher voltage level, low voltage distortion rate, and small switching loss. Compensation, new DC transmission and distributed power generation have good application prospects. 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 main problem of the diode-clamped multi-level is that the capacitor voltage on the DC side is unbalanced. An odd multi-level will gradually degenerate into...

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Problems solved by technology

[0003] The main problem of the diode-clamped multi-level is that the capacitor voltage on the DC side is unbalanced. An odd-numbered multi-level will gradually degenerate into a three-level, while an even-numbered multi-level will degenerate into two levels.

When the modulation ratio is relatively small, the traditional three-vector SVM equalization method based on the objective function optimization uses a large number of redundant vectors in the inner two layers of hexagons for equalization. As the modulation ratio increases, the number of redundant vectors decreases. The control of the capacitor voltage on the DC side by the algorithm becomes worse. The higher the modulation ratio, the smaller the power factor. When the modulation ratio is close to 1, the inverter can hardly output active power, which greatly limits the diode clamping type five Application of Level Inverter

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