| Summary: | With the development of new energy, three-phase grid connected converter has been widely applied. In order to meet the requirement of synchronous signals extraction under the condition of asymmetry, dc components and harmonic distortion, the positive and negative sequence components, amplitude and fundamental frequency of the voltage signal need to be extracted accurately. Based on dual second order generalized integrator frequency locked loop (DSOGI-FLL), the synchronization signal can be extracted under voltage asymmetry and distortion. But when the three-phase voltage is asymmetrical, dc components and multiple harmonics are influenced by the DSOGI-FLL method, the synchronous signal cannot be extracted accurately. In this paper, the structure of second order generalized integrator (SOGI)is improved, and the difference node and adaptive filter are added on the basis of SOGI, and the method of synchronous signal extraction based on improved dual self-turning second order generalized integrator frequency locked loop (DSSOGI-FLL) is proposed. This method can eliminate the effect of asymmetrical, dc components and multiple harmonics, and can extract the positive and negative sequence components, phase and frequency information accurately and quickly. The accuracy and effectiveness of the improved DSSOGI-FLL method are verified by simulation analysis.
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