Software phase locked loop improving method

Abstract

The invention relates to a software phase locked loop improving method. The software phase locked loop improving method is characterized by comprising the following steps that sampling is carried out on power grid voltage, and voltage components ualpha and ubeta under a two-phase coordinate system are obtained through Clarke conversion; accurate delayed signals ualpha-D and ubeta-D of the voltage components ualpha and ubeta are calculated through a weighted average method; power grid voltage positive-sequence components u and u are extracted according to a delayed signal cancellation principle; rotation axis conversion is carried out on the power grid voltage positive-sequence components u and u so as to obtain u (n) and u (n), wherein n represents the current nth control period; the frequency of the power grid voltage is calculated; digital integration is carried out on the frequency of the power grid voltage so as to obtain a power grid voltage phase angle used for calculation of rotation axis conversion, and closed loop feedback is formed. The weighted average method of two sets of delayed signals is adopted to approach the expected delayed signals, and therefore signal delaying is more accurate, direct current offset and fluctuation in the phase locked angle and amplitude are effectively restrained, accuracy of power grid fundamental wave voltage phase locking is improved, and the method can be widely applied on the occasions high in requirement for the PLL response speed.

Description

technical field [0001] The invention belongs to the technical field of phase-locked loops, in particular to a method for improving software phase-locked loops by using a signal delay cancellation (Delayed Signal Cancellation, DSC) technology. Background technique [0002] Voltage source grid-connected converters are widely used in the fields of active filtering, UPS uninterruptible power supply, variable frequency drive and renewable energy power generation, and are an important type of power electronic conversion device. It is very important to quickly and accurately obtain the positive sequence information of the grid voltage fundamental frequency for the control of such devices, and this task is usually realized by software phase-locked loop (Phase Locked Loop, PLL) technology. [0003] There are many types of software phase-locked loops. At present, the most commonly used one in the three-phase voltage source grid-connected converter is the Synchronous Reference Frame PL...

AI Technical Summary

Problems solved by technology

[0009] The purpose of the present invention is to overcome the deficiencies of the prior art, provide an improved method for the software phase-locked loop, and solve the problem that the traditional DSC-PLL is difficult to obtain accurate signals when the digital controller control cycle and the signal delay time are not in integer multiples. Delay, resulting in poor phase-locking effect

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