Midpoint voltage control and common mode voltage suppression method and system of three-level inverter

A three-level inverter, common-mode voltage technology, applied in electrical components, output power conversion devices, AC power input conversion to DC power output, etc., can solve the malfunction of motor protection circuit, neutral point voltage balance ability Limited, insufficient mid-point voltage regulation ability, etc., to achieve the effect of reducing common-mode voltage and mid-point voltage fluctuation, and improving mid-point voltage balance ability
CN110112945AActive Publication Date: 2019-08-09HUAZHONG UNIV OF SCI & TECH
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Patent Information

Authority / Receiving Office
CN · China
Current Assignee / Owner
HUAZHONG UNIV OF SCI & TECH
Publication Date
2019-08-09

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Abstract

The invention discloses a midpoint voltage control and common mode voltage suppression method and system of a three-level inverter. The method comprises steps that through constructing virtual small vectors and medium vectors reasonably, the amount of change in the midpoint charge of each virtual vector is zero in one control period, and the vectors making the common mode voltage increase are eliminated to guarantee that the common mode voltage of the output voltage is minimized when the virtual vectors are constructed; a midpoint voltage balance factor is added based on the above, the midpoint voltage balance factor is adjusted by detecting voltage difference of upper and lower capacitors and the three-phase current in real time, and thereby the charge is made to flow into or out of the midpoint to adjust the midpoint voltage balance. The method is advantaged in that as the virtual vectors are reasonably constructed, and the midpoint voltage balance factor is further added, the virtual small vectors and the medium vectors are both variable, and the method has the feature of adjusting the midpoint voltage balance in the full modulation ratio range while reducing the common mode voltage.
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Description

technical field

[0001] The invention belongs to the technical field of power electronics, and in particular relates to a method for midpoint voltage control and common mode voltage suppression of a three-level inverter based on a variable virtual vector. Background technique

[0002] Compared with the traditional two-level inverter, the output voltage of the three-level inverter is closer to a sine wave, and the harmonics of the output waveform are small under the same switching frequency. Under the same conditions, the equivalent switching frequency is high and the switching loss Therefore, it is widely used in medium and high voltage high power conversion fields such as medium and high voltage frequency conversion speed regulation, active power filter and power system reactive power compensation. However, there is an inherent midpoint voltage balance problem in a three-level inverter. Inconsistent DC bus capacitor parameters, inconsistent switch parameters, unbalanced loa...

Claims

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