Input filters for THD minimization and power factor improvement in rectifier-fed systems: A review

Rectifiers are widely used in modern electronic equipment and electrical power systems (EPS) and constitute one of the primary sources of harmonic currents in distribution networks. These harmonics can distort the voltage at the point of common coupling (PCC), degrade the power factor (PF), reduce overall system efficiency, and adversely affect sensitive electrical equipment. To mitigate these effects, the IEEE 519-2022 standard imposes stringent limits on the total harmonic distortion (THD) of currents drawn by nonlinear loads, including rectifiers. Input filters are among the widely adopted solutions for reducing harmonic distortion and improving power quality at the front end of rectifiers. Although numerous passive, active, and hybrid filter topologies have been reported in the literature, a comprehensive comparison of all of these approaches in terms of operating principles, harmonic mitigation capability, PF improvement, implementation complexity, cost, and application suitability remains limited. This paper addresses this gap through a structured literature review and a comprehensive assessment of passive, active, and hybrid filtering approaches. In addition, a unified two-port network formulation based on inverse hybrid (g-) parameters is developed and demonstrated through a design example. The proposed framework reveals fundamental-frequency PF degradation that may not be captured by conventional single-frequency THD or impedance-based analyses, thereby providing an additional practical tool for filter evaluation and selection. By combining a comprehensive review of the literature, quantitative performance assessment, and a unified analytical framework, this work provides a reference for the understanding of the design consideration, evaluation, and selection of filters while also identifying some directions for future research.