A method for extracting fundamental-frequency positive-sequence signals based on delayed signal cancellation and low-pass notch filter PLL

A novel scheme for obtaining the fundamental-frequency positive-sequence signals based on a combination of delayed signal cancellation (DSC) method and low-pass notch filter phased-lock loop (LPN-PLL) is proposed in this paper. DSC working in the stationary reference frame is used to obtain the fundamental-frequency positive-sequence voltage vector, while LPN-PLL is used to obtain pulsation and phase angle of the vector, instead of using a conventional synchronous reference PLL, which requires a d-q transformation of three-phase voltage and a proportional-integral controller. The proposed structure can be used to estimate the fundamental positive-sequence component in distorted and asymmetric three-phase systems. The performance of the proposed structure is verified through simulations and experimental cases by using distorted and unbalanced signals, containing fundamental-frequency as well as positive- and negative-sequence harmonic components.