Method for realizing software phase-locked loop with unfixed sampling frequency

Abstract

The invention discloses a method for realizing a software phase-locked loop with an unfixed sampling frequency. The method comprises the following steps: firstly adopting an analog phase-locked loop digital controlled oscillator of the DSP period counter to obtain digital controlled oscillator output signals; then working out the phase error between the mains voltage and a reference signals in the DQ-transformation phase demodulation mode by using the digital controlled oscillator output signals as the reference signals; and establishing a closed loop transfer function secular equation of a phase-locked loop system and determining the parameters of the designed loop filter based on the digital controlled oscillator output signals and the phase error between the mains voltage and the reference signals. The invention can maintain the fixed number of the sampling points in the primitive period, and is used for repeatedly controlling various grid-connected converting devices, such as active electric filters, new energy-powered grid-connected converters and the like. By adopting the DQ-transformation phase demodulation mode, the invention can well inhibit the harmonic and unbalanced mains, resist the fluctuation of the mains voltage, and ensure the reliable operation of the phase-locked loop under the conditions of multiple mains voltage zero passage, voltage harmonics, voltage fluctuation and mains voltage imbalance.

Description

technical field [0001] The invention relates to a method for realizing a phase-locked loop, in particular to a method for realizing a software phase-locked loop with a non-fixed sampling frequency, and belongs to the technical field of signal processing. Background technique [0002] The initial phase angle and frequency of the fundamental wave of the power grid are important information for the operation of power system FACTS, new energy grid-connected power generation converters, and uninterruptible power supplies (UPS). At present, the main way to obtain these information is to use analog phase-locked loop technology, digital phase-locked loop technology and DSP-based software phase-locked loop technology. [0003] Both the analog phase-locked loop and the digital phase-locked loop need to be implemented with additional hardware. The analog phase-locked loop has DC zero drift, component saturation, initial calibration is required, and there are problems such as false lock...

AI Technical Summary

Problems solved by technology

The repetitive controller is a new type of control strategy based on the internal model principle. Applying it to the active power filter can greatly improve its static compensation accuracy; the repetitive control is generally implemented by digital control, and requires the system to The internal (or internal model period) has a fixed number of sampling points to ensure the correct update of the internal model, otherwise, it will cause an error in the internal model update, making the repetitive control not work properly

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