New Grid-connected Phase-locked Loop Design under DC Offset and Harmonic Distortion
The Synchronous Reference Frame Phase-Locked Loop(SRF-PLL)is the most widely used grid synchronization technology.However,it does not perform well when there are non-ideal conditions such as grid imbalance,harmonic distortion,and DC offset.In order to improve the filtering ability of SRF-PLL,a traditional second-order generalized integrator(DSOGI)is used to extract and separate the positive and negative sequence components of the voltage.The effect of dc offset cannot be eliminated by improving the multivariable filter(MVF),and the MVF is retained that the positive sequence component of the input voltage fundamental does not produce voltage amplitude changes and phase shifts.By introducing the improved MVF structure into DSOGI,a new PLL is designed,which can effectively improve the ability to filter out harmonic components.Finally,Matlab/Simulink simulation is carried out,and the simulation results show that the PLL can quickly lock in under voltage imbal-ance,DC offset,harmonic distortion and frequency mutation.
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