Improving Harmonic Rejection Capability of OSG Based on n-th Order Bandpass Filter for Single-Phase System

Abstract

The second-order generalized integrator based orthogonal signal generator (SOGI-OSG) is commonly used to produce direct and quadrature axis ( $dq$ -axes) signals in stationary reference frame for single-phase systems. Fast and robust OSG with harmonic rejection capability is required for parallel operation of power generation systems. The frequency response function (FRF) of classical OSG does not show robustness towards DC offset and grid harmonic disturbances compared to the direct signal of SOGI. This paper presents OSGs based on $n^{th}$ order bandpass filter with a phase shifter using a scaled $Q$ factor as a design variable. The frequency and time-domain performance analysis will be performed based on the scaled $Q$ factor to simplify the design process of the proposed OSGs. The −3dB frequency and settling step time will be matched in higher order OSGs selecting a scaled $Q$ factor. The proposed method will show enhanced harmonic rejection ratio of an additional −20dB with increasing OSG order with tradeoff in computational burden.

Keywords

• SOGI
• DC offset
• harmonic distortion
• quadrature signal generator