Supercapacitor management system: A comprehensive review of modeling, estimation, balancing, and protection techniques

Recent advances in energy storage systems have speeded up the development of new technologies such as electric vehicles and renewable energy systems. In this respect, supercapacitors have gained interest due to their unique features such as high power density, long lifespan, and wide operating range. To achieve the high-voltage levels required for vehicular or utility applications, a supercapacitor pack should contain hundreds of high-capacity series-parallel cells. The internal states of these cells cannot be obtained by direct measurements and these states are usually affected by operating conditions such as temperature and noise. In addition, due to the uncertainty in the manufacturing processes, the characteristics between different batches or even the same batch of supercapacitor cells will be unavoidably different, which will impose significant challenges in terms of uniformity, functional safety, and durability of the system. Therefore, the supercapacitor pack will require a management system to effectively monitor, control, and protect the cells along all performance boundaries. Based on a comprehensive review of the latest articles and achievements in the field, as well as some useful previous experiences of the authors, this paper provides an overview of the key technologies, functionalities, and requirements for Supercapacitor Management Systems (SMSs). To the best of the author's knowledge, this is the first survey that provides an inclusive collection of key requirements for the SMS, including issues related to the modeling, estimation, control, and protection of the supercapacitors. The supercapacitor is a relatively new technology and no international standard about SMSs and their functional requirements are available up to date. The present survey will perfectly fill these gaps. In the survey, the key SMS requirements are broadly divided into the software and hardware functions, and several key issues including modeling and state estimation functions, control and balancing circuits, etc. Are covered. A comprehensive review of the supercapacitor/SMS vehicular applications is also provided in this paper.