Measuring system and method for self-impedance and mutual impedance of three-phase grid-connected converter

Abstract

The invention provides a measuring system and method for self-impedance and mutual impedance of a three-phase grid-connected converter. The measuring system comprises a disturbance source unit, a volt-ampere characteristic collecting unit, a data processing unit and a data analysis unit; the output end of the disturbance source unit is connected with a common connection point; the input end of thevolt-ampere characteristic collecting unit is connected with common connection points of a disturbance source and the grid-connected converter; the input end of the data processing unit is connectedwith the output end of the volt-ampere characteristic collecting unit; the input end of the data analysis unit is connected with the output end of the data processing unit, and the self-impedance andthe mutual impedance of the three-phase grid-connected converter are calculated based on voltage-current data provided by the data processing unit. According to the measuring system and method, the influence of the frequency coupling effect on impedance measuring of the three-phase converter under the static coordinates is fully considered, when the internal resistance of a power grid is non-negligible, the self-impedance and the mutual impedance of the converter can be accurately measured, and the accuracy of power grid stability analysis based on impedance criteria is improved.

Description

technical field [0001] The invention designs the field of safe and stable operation of power grids, especially designs a self-impedance and mutual-impedance measurement system and method of a three-phase grid-connected converter. Background technique [0002] In recent years, with the rapid development of renewable energy, the distributed power generation mode has been widely used. A large number of renewable energy units are connected to the grid through converters, which makes the application of converters in power systems more and more extensive. The flow converter has strong nonlinear characteristics, which leads to frequent harmonic oscillation and system instability. Impedance criterion is a classic method to analyze the stability of distributed power system. The stability of inverter grid-connected system can be judged by analyzing the ratio of inverter impedance to grid impedance. The existing measurement methods of converter impedance mainly use the traditional mea...

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Problems solved by technology

The existing measurement methods of converter impedance mainly use the traditional measurement method of converter impedance in the stationary coordinate system, but the existing measurement methods of converter impedance do not consider the frequency coupling effect, resulting in the measurement results being insignificant in relatively weak power grids. Inaccurate, the measured converter impedance can only indicate the impedance of the grid under the impedance characteristics of the needle, and cannot characterize the impedance characteristics of the converter under other grid impedance conditions, which leads to low accuracy of grid stability analysis results

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