Common-mode voltage suppression method for three-phase eight-switch inverter

Abstract

The invention discloses a common-mode voltage suppression method for a three-phase eight-switch inverter. The common-mode voltage suppression method comprises the following steps: determining a space voltage vector of the three-phase eight-switch inverter; determining current partitions of the three-phase eight-switch inverter, and establishing a corresponding relation between each current partition and a space voltage vector; obtaining an included angle between a set current of the three-phase eight-switch inverter in the alpha-axis direction and a set current of the three-phase eight-switch inverter in the beta-axis direction at the k + 1 moment in a two-phase static coordinate system, determining a current partition to which the included angle belongs, and determining a corresponding space voltage vector by combining the corresponding relationship, and recording the space voltage vector as an alternative vector; according to a preset synthesis rule, determining a synthesis vector used for replacing the alternative vector; and inputting the alternative vector and the resultant vector into a preset cost function, determining a vector enabling the cost function to be minimum, and enabling the vector to act on a resistance-inductance load in the three-phase eight-switch inverter. According to the method, common-mode voltage can be reduced, current distortion is obviously improved, the calculation amount is small, and the calculation efficiency is high.

Description

technical field [0001] The invention belongs to the technical field of inverters, and in particular relates to a common-mode voltage suppression method for a three-phase eight-switch inverter. Background technique [0002] Three-level neutral-point clamped (Neutral-Point-Clamped, NPC) inverters are widely used. Compared with two-level output voltage waveform harmonic characteristics, dv / dt is smaller, and switching loss is lower. Small and other advantages, therefore, has been a research hotspot of scholars at home and abroad. However, the three-level NPC inverter has more power switching devices than the traditional two-level inverter, which leads to a higher probability of failure and lower reliability. [0003] A three-phase eight-switch inverter (Eight-Switch Three-Phase Inverter, ESTPI) is a fault-tolerant reconstruction structure of a three-level NPC inverter after a single-phase bridge arm fault. Its structure is as figure 2 As shown (this application takes A-phase...

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Problems solved by technology

[0004] The existence of common-mode voltage will have many adverse effects on the system. It will increase the shaft voltage of the motor and form a shaft current in the motor bearing. Excessive shaft current will damage the insulation performance of the medium on the motor bearing

In addition, the existence of common mode leakage current will also cause electromagnetic interference

In order to reduce the common-mode voltage and reduce its harm, in the prior art, the adjustment of the hardware is added to achieve the suppression of the common-mode voltage, but the above method will increase the size and cost of the system

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