This chapter provides a comprehensive overview of power quality issues, their causes, impacts, and the importance of current quality compensation. It covers power quality standards and introduces two types of current quality compensators: the LC-Hybrid Active Power Filter (LC-HAPF) and the Transformer-Coupled LC-Hybrid Active Power Filter (TCLC-HAPF). The circuit configurations and operating principles of these compensators are presented. The chapter also explores advanced control strategies for LC-HAPF and TCLC-HAPF systems, aimed at optimizing performance, stability, and dynamic response under various operating conditions. An overview of the book's organization is provided, serving as a roadmap for readers interested in the theoretical foundations, design considerations, simulations, and practical applications of current quality compensators for harmonic mitigation and power quality improvement.