Minimum variance filtering-based self-adaptive phase-locked loop method and system

Abstract

The invention provides a minimum variance filtering-based self-adaptive phase-locked loop method and system. The minimum variance filtering-based self-adaptive phase-locked loop method comprises the steps of converting a harmonic-containing power grid voltage to a two-phase static coordinate system from a three-phase static coordinate system so as to obtain voltages v<Alpha> and v<Beta>; and allowing a voltage under the obtained two-phase static coordinate system to pass through a minimum variance filtering module, extracting a fundamental wave component from a voltage containing low-order harmonic, inputting the fundamental wave component to a self-adaptive module with three outputs, obtaining a frequency of the voltage by a self phase-locked loop module, and obtaining a positive sequencecomponent and a negative sequence component of a fundamental wave of the power grid voltage. By the minimum variance filtering-based self-adaptive phase-locked loop method, the amplitude and the phase angle of the power grid voltage can be accurately and rapidly detected when a three-phase unbalanced fault occurs in the power grid voltage, the phase angle and the frequency of the power grid voltage and the amplitudes of the positive sequence component and the negative sequence component which are generated by harmonic also can be accurately and rapidly detected under the condition that harmonic exists in a city power distribution network, the phase-locked loop has rapidness and accuracy, and the grid-connected requirement of a photovoltaic power station can be met.

Description

Technical field [0001] The invention relates to an adaptive phase-locked loop method and system based on minimum variance filtering. Background technique [0002] With the rapid development of new energy, the installed capacity of photovoltaic power plants has increased rapidly, and the proportion of photovoltaic power generation in the power grid is increasing. The stable and reliable operation of grid-connected inverters has become an important guarantee for the safe operation of the power grid. The grid synchronization technology can detect the amplitude of the grid voltage, track the changes in frequency and phase angle, which provides the necessary phase angle information and amplitude information for the realization of inverter low voltage ride through. Phase-locked (frequency) loops are usually divided into single-phase phase-locked loops and three-phase phase-locked loops according to the number of phases, and can be further divided into open-loop phase-locked loops and c...

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Problems solved by technology

[0007] It can be seen from the above that the technology of phase-locked loop plays a key role in the new energy grid connection, but the operation of the grid is complex and real-time, and the grid voltage will be affected by disturbance; the above phase-locked loop technology is mainly for phase-locked Fast and accurate, but they are not able to suppress the low-order harmonics that exist in large numbers in the distribution network, and these harmonics will also affect the performance of the phase-locked loop

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