Open-Loop Approach for Robust Detection of Selective Harmonic in Single-Phase System

This paper proposes an open-loop approach for selective harmonic detection from the single-phase power system under changeable frequency environment. It consists of a frequency tracking algorithm relying on a fixed tuned demodulation method and a selective harmonic detection scheme based on an adaptively tuned cascaded delayed signal cancellation (CDSC) strategy. It can be easily arranged to detect one or several harmonic(s) from the input signal contaminated by different harmonics. The open-loop configuration makes the proposed technique robust, free of interdependent loop, easy tuning, and unconditionally stable. The real-time utilization of trigonometric and inverse trigonometric functions is also avoided in the technique. When compared with the discrete Fourier transform and CDSC-based technique reported in the technical literature, it demands less computational effort and can create faster dynamics and better steady-state accuracy in the estimated frequency. The usefulness of the technique is confirmed by simulation and real-time experimental results.