General frequency type fundamental wave, harmonic wave, DC component detection method

Abstract

The invention relates to a method for detecting fundamental waves, harmonics, and DC components of a general frequency type, which utilizes the orthogonality characteristics of trigonometric functions and uses the orthogonality factor of the corresponding frequency? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? , extract the projection peak value of the dq axis of the orthogonal coordinate system, and then obtain the signal frequency in real time through the phase-locked loop, solve the actual number of sampling points during work, synthesize the fundamental wave and the DC amount, and finally subtract the fundamental wave from the detection signal, and then subtract the direct current. flow, to obtain harmonic signals. This method can detect DC components, fundamental components and harmonic components in real time; it has high precision, there are no neglected items, and there is no error in theory; due to the use of variable parameters, there is no need to adjust the parameters of the entire algorithm, and it can realize instant Plug and play and modularization, easy to apply, meet the real-time and accurate requirements of the distributed power generation system to obtain the fundamental wave, harmonic wave and DC flow of the public access point.

Description

technical field [0001] The invention relates to a detection method of a power grid, in particular to a detection method of a general-frequency fundamental wave, harmonic wave and direct current component based on the theory of orthogonal transformation. Background technique [0002] In the smart grid and micro grid system, a large number of distributed power generation systems using wind and solar power are connected, especially on the distribution network side, single-phase grid-connected inverters are the core of energy conversion and control in distributed power generation systems , and the interface with the distribution network, its performance directly affects and determines the quality of the entire grid-connected system. However, single-phase grid-connected inverters using full-control devices will generate a large number of harmonic components and a certain amount of DC components, which directly affect the power quality of the distributed system connected to the gr...

AI Technical Summary

Problems solved by technology

It is necessary to filter out the DC component in the detection signal through a power frequency cycle first, and then separate the fundamental wave from the harmonic. The whole process takes one and a half power frequency cycles, which affects the speed of the entire controller.

The harmonic detection method based on the orthogonal transformation theory, if only the normal constant frequency operation is considered, and the sampling point is fixed as a percentage, it will affect the accuracy of the frequency change for this detection method

Once the accuracy of the detected fundamental wave, harmonics, and DC components is insufficient, it is easy to cause deviations in the calculation values ​​of instantaneous active power and instantaneous reactive power, which will further lead to deviations in the output control of single-phase grid-connected inverters, which will affect distributed power generation. accurate output of the system

Using sampling points to set the percentage loses the advantages of ready-to-use products and no need to adjust parameters, making it difficult to meet worldwide use

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