An Arbitrary Harmonic Detection Method Based on Delayed Signal Cancellation and Low-pass Notch Filter PLL

This paper proposes a novel structure based on a combination of delayed signal cancellation (DSC) method and low-pass notch filter phase-locked loop (LPN-PLL) for any individual harmonic detection. Through a cascaded DSC operator, arbitrary harmonic component can be obtained in stationary reference frame, and then the extracted component is input to a LPN-PLL for detecting the magnitude and phase angle of the desired harmonic voltage vector. Compared to conventional synchronous reference frame PLL (SRF-PLL), LPN-PLL does not require a d-q-axis transformation of three-phase voltage and a proportional-integral controller. The resulted detection system is very simple and robust. Meanwhile, it can detect the fundamental signal and arbitrary harmonic components with zero steady-state error in complicated harmonic scenarios. The good performance of the proposed structure is verified with experimental cases, using a grid set of distorted and asymmetric signals.