Extraction Method of Frequency Coupling Impedance Characteristics of Grid-connected Inverter Based on Multiple Sine Wave Signal Injection

Abstract

The invention discloses a method for extracting frequency-coupled impedance characteristics of grid-connected inverters based on multi-sine wave signal injection. The method adopts an impedance measurement device based on a model predictive control method to realize low-resistance characteristics within a wide frequency range, and integrates The multi-input and multi-output frequency coupling impedance characteristics of the grid inverter are decomposed into four single-input and single-output subsystems and measured independently, and then the broadband frequency coupling impedance characteristics of the grid-connected inverter are measured through one signal injection, ensuring sufficient Measurement accuracy and speed. Compared with the existing frequency coupling impedance characteristic extraction method, the method of the present invention significantly improves the impedance characteristic extraction efficiency while ensuring the measurement accuracy, and can realize faster and more efficient frequency coupling impedance characteristic extraction.

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 rate of new energy power generation, grid-connected inverters have been widely used in the power grid as the main port for the output power of new energy equipment. A large number of grid-connected inverters based on power electronic technology are connected, which leads to the risk of oscillation instability in the interconnection system between new energy equipment and the power grid. The oscillation phenomenon will lead to the decline of the system’s ability to absorb new energy or even local grid collapse. The reason is that The stability margin of the interconnected system formed by the grid-connected inverter and the grid is insufficient. Therefore, it is ne...

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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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