Phase angle margin compensation-based system impedance active control method of grid -connected inverter

Abstract

The invention relates to a phase angle margin compensation-based system impedance active control method of a grid-connected inverter. Because the changing impedance exists in a power grid, a dynamic interaction influence exists between the grid-connected inverter and the power grid and thus the grid-connected current waveform quality is influenced, so that the weakening of the impedance interaction influence is crucial to improvement of the grid-connected current quality. According to the invention, the impedance active control method is characterized in that real-time grid impedance information is obtained in real time and thus a phase angle margin at an inverter output impedance amplitude-frequency curve intersection point frequency is solved; a voltage feedforward control method is employed and a phase angle margin of the inverter impedance at the impedance intersection point frequency is compensated in real time; operation is carried out on a voltage feedforward link output and a current ring PI result so as to obtain an SPWM control signal. According to the invention, because the active impedance control method with the phase angle margin compensation function is used, the harmonic resonance generated by the dynamic interaction influence between the inverter and the power grid near the impedance intersection point frequency can be effectively suppressed, so that the rid-connected current waveform quality of the inverter is improved and the grid-connected stability is enhanced.

Description

technical field [0001] The invention relates to a method for actively controlling the impedance of a grid-connected inverter system based on phase angle margin compensation, which belongs to the inverter control technology in the power conversion technology. Background technique [0002] Almost all renewable energy is connected to the AC grid through grid-connected inverters. A dynamic interconnection system is formed between the grid-connected inverters and the grid. However, there may be some Unexpected dynamic interaction effects. [0003] For an ideal grid-connected system, the grid impedance is infinitesimal and the grid voltage harmonics are not considered. At this time, the output current of the system is mainly determined by the output current of the converter, and there is no harmonic oscillation in the grid-connected system. However, in the actual power grid, due to the influence of parameters such as transmission cables, the grid impedance is not zero, so the gri...

AI Technical Summary

Problems solved by technology

However, in the actual power grid, due to the influence of parameters such as transmission cables, the grid impedance is not zero, so the grid impedance and converter impedance will produce an intersection point in the frequency domain

If the grid impedance is too large, or the control parameter design of the converter is unreasonable, it may cause specific sub-harmonic oscillation (near the frequency of the impedance intersection point) due to too small phase angle margin, which will eventually lead to instability of the grid-connected system

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