Research on frequency adaptive of fans based on harmonicextraction technology

Abstract

In order to solve the problem of voltage distortion and frequency fluctuation caused by harmonic interference of wind turbines which affects the stable operation of wind turbines connected to the grid,a frequency adaptive phase lock methodwas proposed.Based on the harmonic extraction circuit,the NSOGI (new second-order generalized integrator) phase locked loop was designed.Firstly,the fundamental resonance circuit was added to the harmonic extraction circuit to verify the frequency locking accuracy of the phase-locked loop before and after the harmonic extraction.Secondly,a DC suppressor was added to the traditional phase-locked loop for tracking the frequency of the input signal.Finally,the theoretical and simulation analysis were conducted and the frequency deviation in the circuit before and after DSOGI-FLL harmonic extraction was compared to verify the frequency locking accuracy of the two phase-locked loops.The results show that the addition of the fundamental resonance circuit to the harmonic extraction circuit reduces the influence of harmonics on the fundamental wave source and improves the effect of harmonic extraction.In terms of suppressing wind turbine voltage distortion and DC harmonics,the NSOGI phase-locked loop has good effect and high frequency locking accuracy,which verifies the feasibility and correctness of the method.Using NSOGI to control voltage and frequency can improve power supply reliability and improve grid-connected power quality,which provides theoretical reference for the stable operation of wind turbines connected to the grid.

Keywords

• wind energy; harmonic interference; voltage distortion; frequency adaptation; harmonic extraction circuit; frequency deviation; fundamental resonance circuit