A quasi-passive power grid impedance identification system and method based on goertzel algorithm

Abstract

The invention relates to a pseudo passive power grid impendence recognition system and a method based on a Goertzel algorithm. The system comprises a grid-connected inverter, a sampling module, a control module and a PWM driving module, wherein the grid-connected inverter outputs a current set value into a power grid, the sampling module can sample lineside voltage and current through a voltage sensor and a current sensor, the control module can utilize the Goertzel algorithm to extract harmonic component signals of the sampled lineside voltage and current; finally, the harmonic component signals are utilized to calculate the power grid impendence. The pseudo passive detection method comprises the steps of monitoring power grid impendence and injecting harmonic wave into a power grid to measure power grid impendence when larger change happens. The method has the advantages of higher accuracy and smaller system disturbance. The Goertzel algorithm can effectively reduce a controller calculation amount and storage space and further reduces code complexity. In the occasions when only several frequency points need to be analyzed, the Goertzel algorithm has a higher efficiency than FFT.

Description

technical field [0001] The invention relates to the field of distributed power generation systems, in particular to a quasi-passive grid impedance identification system and method based on Goertzel algorithm. Background technique [0002] Distributed power generation system is a small and medium-sized power conversion and utilization system that fully integrates and utilizes scattered resources to produce and supply energy on site according to user needs. It has multiple functions and can meet multiple goals. [0003] The performance of the power system is closely related to the grid impedance, and the grid impedance changes with time and the operating state of the grid. Therefore, the accurate measurement of the grid impedance is a key technology to realize the high-performance adaptive control of the power system in the case of a weak grid. [0004] Conventional grid impedance measurement methods are: [0005] The passive detection method is to measure the grid impedance ...

AI Technical Summary

Problems solved by technology

Because it needs to repeatedly inject harmonic current into the grid, the quality of incoming current is not high

[0007] Although Fast Fourier Algorithm (FFT) has been widely used in spectrum analysis, its full-band analysis will bring a great burden to the digital controller when it only calculates and extracts the content of some harmonics.

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