Three-phase power grid phase-locked loop based on fractional order PID control and phase locking method thereof

Abstract

The invention provides a three-phase power grid phase-locked loop based on fractional order PID control and a phase locking method thereof, and the phase locking method comprises the steps: carrying out the calculation of three-phase power phase voltages ua, ub and uc and an electrical angle outputted by an electrical angle conversion module, and obtaining two-phase rotation voltages Ud and Uq; enabling the q-axis MAF module to update the notch frequency according to the output value of the arithmetic mean value filter module and the output value of the d-axis MAF module, and then filtering the input error U * q-Uq; updating the angular frequency variation output by the fractional order PID module according to the output value of the q-axis MAF; 4, enabling an electrical angle conversion module to convert the angular frequency variation output by the fractional order PID module into the electrical angle. The fractional order PID is adopted to compensate the phase lag introduced by the MAF, the open-loop cut-off frequency and the phase margin are improved, and the degree of freedom of a differential link can be increased by a fractional order differential item; therefore, the harmonic suppression effect of the phase-locked loop is ensured to a certain extent.

Description

technical field [0001] The invention relates to the technical field of grid voltage filters, in particular to a three-phase grid phase-locked loop based on fractional-order PID control and a phase-locking method thereof. Background technique [0002] In the application of grid-connected power electronic equipment and renewable energy power generation system, synchronous frame phase-locked loop (SRF-PLL) is the most widely used phase-locking technology. However, the traditional synchronous frame phase-locking technology based on PID control The ring is sensitive to the negative sequence component or harmonic distortion in the grid voltage, and the effect of frequency locking and phase locking is deteriorated. Generally, it is only suitable for phase measurement when the voltage of the three-phase grid is balanced and the harmonics of the grid are relatively small. Since the negative sequence component and grid voltage harmonic component will generate 2 harmonics and ±6k (k=1,...

AI Technical Summary

Problems solved by technology

However, MAF reduces the phase margin of the closed-loop system, limiting its dynamic performance

Using the traditional phase lead link or differential term for phase compensation can improve the dynamic performance of MAF-PLL, but this method will sacrifice the harmonic suppression ability of the phase locked loop

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