Output impedance remodeling method for grid-connected inverter parallel system

Abstract

The invention discloses an output impedance remodeling method for a grid-connected inverter parallel system. According to the output impedance remodeling method, the amplitude intersection point of the output admittance Yc (s) and load admittance Yload (s) of a grid-connected inverter is determined through an impedance analysis method, so that possible resonant frequency points between a grid-connected inverter and a power grid are found out; the parameters of a PI controller and a repetitive controller are adjusted, so that the passivity of the output impedance of the grid-connected inverterat the resonant frequency points is remodeled, and therefore, interactive resonance between the grid-connected inverter and the power grid is avoided; the PI controller is designed to ensure the closed-loop stability of the system; the repetitive controller is designed to ensure the stability of the repetitive controller; the output impedance of the grid-connected inverter and the passivity of theimpedance of the power grid are analyzed, so that the possible resonant frequency points can be found out; and the parameters of the controller are corrected, so that the output impedance of the grid-connected inverter is passive at the points.

Description

technical field [0001] The invention belongs to the technical field of current control of grid-connected inverters, and more specifically, relates to a method for reshaping the output impedance of a parallel system of grid-connected inverters. Background technique [0002] Overexploitation of fossil energy and environmental pollution have made countries around the world pay more and more attention to the development and application of renewable energy such as wind energy, solar energy, and biofuels. A research report by the United Nations IPCC shows: By 2050, 50% of the world's energy can be met by renewable energy. China's 13th Five-Year Plan for Renewable Energy Development points out that by 2020, non-fossil energy will account for 15% of primary energy consumption, and the total installed capacity of renewable energy power generation will be 680 million kWh, with a power generation capacity of 1.9 trillion kWh, accounting for all power generation. 27% of the volume. In...

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Problems solved by technology

The traditional design method does not consider the interaction characteristics between the converter and the grid, which may cause the following two situations: under ideal grid conditions, the stand-alone operation is normal, and under non-ideal grid conditions (grid-side impedance is not ignored), mutual resonance with the grid occurs ; A single machine operates stably under non-ideal grid conditions, but the system resonates when multiple machines are running in parallel. At present, there are few ways to reshape the output impedance of inverter parallel systems with repetitive controllers

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