A PLL Based on Adaptive Notch Filter

Abstract

The invention discloses a phase-locked loop based on an adaptive notch filter. The phase-locked loop adopts the adaptive notch filter, eliminates the impact of network voltage distortion on phase lock through reasonable setting of filtering parameters, and solves the problems of time delay and slow dynamic response, which are caused by adoption of manners of discrete fourier transform (DFT) or low pass filtering. The phase-locked loop based on the adaptive notch filter has the beneficial effect of being capable of realizing accurate and fast phase lock of the phase of a micro network voltage under harmonic wave and flicker conditions so as to eliminate the impact of harmonic wave and flicker of the micro network voltage on detection of the phase of a grid connection converter device.

Description

technical field [0001] The invention relates to a phase-locked loop based on an adaptive notch filter. Background technique [0002] The emergence of micro-grid technology provides a solution for the improvement of power quality at the end of the power grid, power supply in areas without power, and the improvement of the ability of large power grids to resist accidents and disasters. Since the capacity of the microgrid is usually limited, the harmonics and flicker of the grid are more obviously affected by the randomness of distributed energy sources (photovoltaic, wind, etc.) and sudden changes in load, which will directly affect the grid-connected converter devices in the microgrid such as The rapidity and accuracy of grid voltage phase detection by key equipment such as photovoltaic inverters, wind turbine converters, and energy storage converters will affect the control performance of equipment and the stability of the entire microgrid system. [0003] In the prior art,...

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Problems solved by technology

[0004] (1) A phase-locked loop based on the voltage zero-crossing point. This method will cause a phase-locking error when the grid voltage waveform is distorted, and the acquisition of the phase difference requires a grid cycle, and the dynamic response is poor;

[0005] (2) The phase-locked loop based on discrete Fourier transform (DFT) has the problems of large amount of calculation and slow dynamic response;

[0006] (3) A phase-locked loop based on coordinate transformation. This method can obtain the phase difference signal in one switching cycle, and has good dynamic performance, but there will be a large phase-locked error when the grid harmonics are large or the three-phase voltage is unbalanced;

[0007] (4) The phase-locked loop based on the low-pass filter method filters out the interference of twice the power frequency when the grid voltage is unbalanced by reducing the bandwidth. However, due to the large delay of the low-pass filter, when the grid voltage is seriously unbalanced can lead to an overcurrent fault in the power device

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