Grid-connected inverter frequency coupling impedance characteristic extraction method based on multi-sine-wave signal injection

Abstract

The invention discloses a grid-connected inverter frequency coupling impedance characteristic extraction method based on multi-sine-wave signal injection. The method comprises the steps: adopting an impedance measuring device based on a model predictive control method to realize the low-impedance characteristic in a broadband range; decomposing the multi-input and multi-output frequency coupling impedance characteristics of the grid-connected inverter into four single-input and single-output subsystems and performing independent measurement; measuring the broadband frequency coupling impedancecharacteristics of the grid-connected inverter through one-time signal injection, so enough measurement precision and rapidity are ensured. Compared with an existing frequency coupling impedance characteristic extraction method, the frequency coupling impedance characteristic extraction method has the advantages that the impedance characteristic extraction efficiency is remarkably improved whilethe measurement precision is guaranteed, and faster and more efficient frequency coupling impedance characteristic extraction can be achieved.

Description

technical field [0001] The invention belongs to the technical field of grid-connected inverters, in particular to a method for extracting frequency coupling impedance characteristics of grid-connected inverters based on multi-sine wave signal injection. Background technique [0002] With the increasing penetration of new energy power generation, grid-connected inverters, as the main port for output power of new energy equipment, have been widely used in power grids. A large number of grid-connected inverters based on power electronics technology have led to the risk of oscillation and instability in the interconnection system between new energy equipment and the grid. The oscillation phenomenon will lead to a decline in the system's ability to absorb new energy and even a partial grid collapse. The reason for this is The interconnected system formed by the grid-connected inverter and the grid has insufficient stability margin. Therefore, it is necessary to conduct a stabili...

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Problems solved by technology

The problems of the above measurement signals are: (1) the extraction speed of the impedance characteristics of a single sine wave signal is too slow; (2) the binary sequence signal is difficult to avoid the mutual interference of different frequency components under the influence of frequency coupling characteristics, and the measurement results are inaccurate , so it is not suitable for the measurement of frequency coupling impedance characteristics

[0007] In the actual measurement process, the disturbance signal needs to be generated by the disturbance signal generator. For this, the literature "Yu Dezheng, Zhu Dan, Song Fei, etc. Grid Simulator for Grid Adaptability Detection of Distributed Photovoltaic Power Stations [J]. Industrial Control Computer, 2018, 31(10): 150-152" proposed a PI controller-based power grid simulator, which realizes impedance measurement by generating a voltage signal with a specific frequency at the grid-connected point of new energy equipment. However, due to the PI controller's Limited bandwidth, the simulator is not suitable for generating perturbation signals with broadband characteristics

The document "Li Meng, Nian Heng, Chen Liang, etal. Model Predictive Control in Power Grid Simulator for Impedance Measurement [C] / / 22nd International Conference on Electrical Machines and Systems (ICEMS), Harbin, China, 2019" proposed a The grid simulator based on model predictive control can be used for impedance measurement of new energy power generation equipment, but the control strategy uses the current extrapolation formula to realize predictive voltage control, the used predictive model is not accurate enough, and with the increase of frequency, the control error Will gradually increase, so there is room for optimization and improvement

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