Phase current balancing and amplitude-limiting method for asymmetrical compensation of line current of distribution static compensator (D-STATCOM)

Abstract

The invention relates to a phase current balancing and amplitude-limiting method for the asymmetrical compensation of a line current of a distribution static compensator (D-STATCOM). The method comprises the following steps of: calculating a group of phase current vectors; balancing the absolute value of a three-phase current instantaneous value in the group of phase current vectors as possible when the group of phase current vectors is in accordance with the conditions that the phase current of the D-STATCOM does not exceed a compensation limit, and the phase current and the line current are in accordance with the Kirchhoff current law; performing amplitude-limiting processing on the group of phase current vectors to obtain a vector; after obtaining a deviation value between the obtained vector and the compensation phase current vector actually output by the D-STATCOM, adjusting the deviation value by using a proportional-integral (PI) adjustor and outputting a modulation wave signal; processing the modulation wave signal by adopting a carrier phase-shifting pulse width modulation algorithm to generate a corresponding multi-level pulse-width modulation (PWM) pulse; and controlling a cascaded converter in the D-STATCOM to obtain a corresponding balanced and amplitude-limited phase current.

Description

technical field [0001] The invention relates to the technical field of three-phase full-control rectification, in particular to a D-STATCOM (distribution network static var synchronous generator) phase current balance limiting method for line current asymmetry compensation. Background technique [0002] The grid-connected structure of the three-phase delta-connected cascaded D-STATCOM includes a CPU unit, a main part and a grid-connected part; the main part is composed of a cascaded converter and a connection reactance, and the grid-connected part includes the grid and load. Each phase of the cascaded converter has n power units, namely a1~a n , b1~b n , c1~c n , in the same phase n The power units are connected in series and then connected in series with the connecting reactance, that is, a1~a n and , b1~b n and , c1~c n and in series; and connected to c1, connected to a1, It is connected with b1 to form a three-phase triangle head-to-tail connection. T...

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Problems solved by technology

[0004] In the Chinese invention patent specification CN102222925.A, a D-STATCOM asymmetrical compensation current balance method is disclosed, but the three-phase phase current obtained through the optimal balance algorithm may still exceed the phase current compensation limit of the device, how to adjust the phase current Limiting processing, and the three-phase phase current and line current still need to meet the constraints of Kirchhoff's current law, that is

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