Novel soft phase-locked loop

Abstract

The invention mainly provides a novel soft phase-locked loop, which is an improved soft phase-locked loop based on a wave trap and a low-pass filter. The novel soft phase-locked loop can accurately and quickly detect the amplitude and the phase of a positive-sequence component of power network voltage when a power network has an unsymmetrical fault, so the novel soft phase-locked loop not only can effectively inhibit phase 100 Hz disturbances, but also has a quick response speed, has high stability and high disturbance resisting capacity, is helpful for improving the dynamic control performance of a network-side converter when the power network has the unsymmetrical fault, and provides a guarantee for a low-voltage traversing technique of a wind power generation system.

Description

technical field [0001] The invention relates to the field of wind power generation, in particular to a novel soft phase-locked loop based on a filter with notch and low-pass filtering functions. Background technique [0002] Wind power generation is the power generation form with the most mature technology, the largest development scale and commercial development prospects in the development and utilization of renewable energy in the world today. Accurate acquisition of grid synchronization information is the key to power control of wind turbines. The vector control strategy of the converter is oriented based on the fundamental positive sequence voltage of the power grid. When the power grid is in normal operation, the soft phase-locked loop can be applied to the observation of the phase of the fundamental positive sequence voltage of the power grid. It has smooth, fast and flexible phase tracking. better features. With the continuous increase of wind power generation scale...

AI Technical Summary

Problems solved by technology

For the design of the filter link, it is proposed to use the T / 4 delay method to separate the positive sequence and negative sequence components of the grid voltage, but the T / 4 used is a fixed value. Once the grid frequency fluctuates, this method will not be able to accurately separate the grid Positive-sequence and negative-sequence components; for the design of the regulator, it is proposed to use a PI regulator and a phase-locked loop control method with variable PI parameters. This type of method has a defect: when the grid frequency fluctuates greatly, the phase-locked loop exists oscillation problem

At present, the method of reducing the closed-loop bandwidth of the soft phase-locked loop is generally used in engineering to suppress the 100Hz fluctuation of the phase, but it will reduce the response speed of the SPLL, and it is easy to cause overcurrent or overvoltage of the grid-side converter during a severe asymmetric fault in the grid.

Therefore, at this stage, the soft phase-locked loop cannot realize the functions of smooth and fast phase tracking, suppression of fluctuations, strong anti-interference ability, and good flexibility

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