This book focuses on the urgent demand for high-quality and efficient development of active distribution networks, which aims to address the bottleneck issues such as single functionality, low equipment utilization, and poor reliability encountered in the practical process of the commercialization of series-connected voltage-quality controllers. The book primarily conducts research on the expansion of functions and performance improvement of series-connected voltage-quality controllers, which summarizes some achievements and experiences of the authors in the new topology, new technology, new methods, and engineering application cases of advanced series-connected voltage-quality controllers. This book serves as a guidelines for scholars, students, engineers, and equipment manufacturers in the fields of power electronics technology and advanced power quality control technology.