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Abstract

The present invention relates to valve current control method based on modular multi-level converter, this method includes the control of the low frequency oscillations of the current and that of double frequency harmonic component; For said low frequency oscillations of the current, the control method includes some steps as below: first, calculate the half of the sum of the upper arm current and the lower arm current, it is the valve DC current component, said DC current component is arm circulating current; Secondly, comparing the actual value of the arm circulating current to setting value of that, the error is obtained, after some signal processing, additional output set voltage is obtained. For said the double frequency harmonic component of current, the control method includes some steps as below: firstly, figure out capacitor voltage fluctuation prediction value of the sub module; secondly, the output voltage is divided by the sum of the sub module reference voltage and the capacitor voltage fluctuation prediction value, and get the actual output set number of sub module. This method not only can realize stability of the dynamic performance of the system, but also can suppress the arm double frequency harmonic component, at the same time under the abnormal conditions of the AC system; the valve current has good output characteristics.

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