Control method for grid-connected current of three-phase grid-connected inverter

Abstract

The invention discloses a control method for grid-connected current of a three-phase grid-connected inverter, improves the defects of the conventional repetitive control through two disturbance factors of suppressing inverter harmonic generation and resisting power network fluctuation, aims at the problems that the conventional repetitive controller cannot process the aperiodic harmonic and is easily affected by the power network frequency fluctuation based on a principle of adopting last periodic quantity to carry out iteration to cause system instability, provides a multi-target repetitive controller and designs from four aspects of a PI parameter, an internal mode coefficient, a repetitive control coefficient and fractional order phase correction, so that the tracking precision of the grid-connected current about a reference signal is enhanced, the ability of a system to resist power network frequency fluctuation is improved and the steady-state performance of the system is guaranteed.

Description

[0001] 【Technical Field】 [0002] The invention relates to the field of power electronics, in particular to a method for controlling the grid-connected current of a three-phase grid-connected inverter. [0003] 【Background technique】 [0004] The system structure of the existing three-phase grid-connected inverter is as follows figure 1 As shown, the topology of the LCL type grid-connected inverter is adopted, and the grid-connected current control strategy is repeated control in the dq coordinate system. in figure 1 In, the LCL filter includes three parts: the converter side inductor L 1 、Grid-connected inductance L 2 And filter capacitor C. Because the resistance on the circuit and the inductor is very small, its resistance is ignored in the following analysis. [0005] The transfer function of grid-connected current and inverter side voltage is [0006] [0007] The structure diagram of the traditional control system is as figure 2 As shown, traditional repetitive control can suppr...

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Problems solved by technology

[0013] Although the traditional repetitive control can eliminate the periodic harmonic interference very well, because the internal model control is based on the calculation method of the previous cycle iteration, the discrete model contains a cycle delay link, which makes it impossible to suppress the first Periodic and non-periodic harmonics make the dynamic response of the system slow and susceptible to power grid fluctuations

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