Balance control method for common-mode voltage and neutral point voltage of T-type three-level inverter

Abstract

The invention relates to a balance control method for common-mode voltage and neutral point voltage of a T-type three-level inverter, which comprises the following steps of: firstly, dividing a three-phase space vector of the T-type three-level inverter into six large sectors, and classifying each vector into a large vector, a medium vector, a small vector and a zero vector according to the amplitude; then selecting six medium vectors, one zero vector and six virtual small vectors as basic vectors of a novel virtual vector modulation strategy, dividing a three-phase space vector into twelve sectors again through the novel virtual vectors, adopting five-section symmetrical wave sending, and establishing overall calculation in a 60-degree coordinate system. Compared with the prior art, the method has the advantages that the implementation difficulty of suppressing the common-mode voltage is simplified, the voltage fluctuation of the neutral point is well suppressed, and the overall calculation amount is small.

Description

technical field [0001] The invention relates to the technical field of inverter modulation, in particular to a T-shaped three-level inverter common-mode voltage and neutral point voltage balance control method. Background technique [0002] The T-type three-level inverter is a novel clamp topology, which has the advantages of less components, uniform loss, and high operating efficiency. It is widely used in high-power occasions. However, due to a series of unavoidable problems such as the limited manufacturing process of the capacitor and the fluctuation of the grid voltage, the midpoint voltage fluctuation and the common mode voltage are generated. The fluctuation of the midpoint voltage will cause the waveform of the grid-connected voltage to be distorted, and the harmonic content will increase greatly; if the common-mode voltage is too high, it will easily cause safety incidents. For this reason, whether these two problems can be properly solved is the key to the widesp...

AI Technical Summary

Problems solved by technology

[0004] The traditional SVPWM control strategy uses all the basic vectors, including a large number of high common-mode vectors and neutral point current uncontrollable vectors; the traditional zero-common-mode modulation strategy uses six medium vectors and one zero vector as the basic composite vectors, all of which are There is a problem that the control effect of the midpoint voltage fluctuation is poor

However, other modulation strategies based on virtual synthetic vectors have problems such as complex selection and calculation of basic vectors, and general control effects.

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