A harmonic suppression strategy for grid-connected inverters based on quadrature sinewave extractor

Abstract

Grid-connected inverters need to reduce current harmonics as much as possible. After introducing the input signal’s fundamental and main harmonic quadrature components, a discrete state model is created, and the discrete observer design method is used to propose a harmonic extraction algorithm called quadrature sinewave extractor (QSE). The QSE is a stable recursive operator with the advantages of no phase displacement and the ability to eliminate mutual influence between harmonic components. Compared to the widely used proportional multi-resonant controller, QSE can reduce current harmonics and improve system stable performance by using it in the current control of grid-connected inverters. Finally, comparative experiments on a three-phase grid-connected inverter are used to verify the proposed method’s effectiveness.

A control method for the single-phase three-leg unified power quality conditioner without a phase-locked loop

“…Second, the series compensation terminal needs the realtime phase angle of the grid voltage to obtain an accurate compensation voltage reference (Srinivas et al, 2019). Moreover, the extraction of reactive current and harmonic current from the system also relies on the real-time phase angle of the grid voltage (Zhang et al, 2022b;Xia et al, 2022). However, the PLL not only increases the complexity of the control algorithm but also fails to respond promptly to phase variations in the grid voltage, leading to overcurrent issues in the compensation device (Mishra and Lal, 2022;Mohammed et al, 2023).…”