Research On Synchronization Signal Extraction Method Based On SOGI In The Presence Of Harmonics

With the rapid development of modern industrial technology,the increase of nonlinear load in power grid leads to a large number of harmonics,which seriously affect the stable operation of power system and accurate extraction of synchronous signal.The rapid and accurate extraction of synchronous signal(voltage positive and negative sequence component,frequency,amplitude and power etc)is also of great significance in improving the power quality.At present,accurate extraction of the synchronous signal in the present of harmonincs and unbalanced non-ideal grid voltage conditions has become a big challenge of power system.The paper firstly researched on the second order general integrator-frequency locked loop based frequency locked method,proposed enhanced SOGI-FLL and SSOGI-FLL by considering the problem of DC-offset and harmonics to the SOGI-FLL's performance.The proposed methods can realize frequency locked rapidly and accurately with the DC-offset and unknown harmonics.Also researching on dual second order general integrator-frequency locked loop and improving it,proposed enhanced DSSOGI-FLL extract fundamental frequency positive/negative sequence voltage vectors rapidly and accurately even with high asymmetry of three-phase voltage and unknown harmonics.The improved methods are further researched by simulation,and the results proved the accuracy of the proposed methods.On the other hand,the paper combine MSOGI-FLL and the instantaneous power theory,the new active and reactive power measurement methods are proposed.The fundamental,each harmonic contained in the voltage and current and their orthogonal components are separately extracted by MSOGI-FLL.Then the fundamental and each harmonic active power and reactive power are respectively calculated by the instantaneous power theory.Finally,the experimental platform of synchronous signal extraction based on the core of STM32F407 is built,both the hardware circuits and software programs are designed.On the basis of the above experimental platform,experiments about the proposed related SOGI algorithm in presence of harmonics is performed.The experiment results are given and analyzed todemonstrate that the proposed related SOGI algorithm can rapidly and accurately estimate and extract synchronous signal in presence of harmonics,the rightness and effectiveness of the proposed algorithm are proved.