Reviews of supercapacitor cell voltage equalizer topologies for EVs

Supercapacitors (SCs) are also known as Electric Double-layer Capacitor (ELDC) or Ultracapacitors. In the high voltage applications, the supercapacitors are connected in series, so that the voltage imbalance will occur because the SCs are not identical. This different parameters of the cells caused by many factors for instance the internal parameters of supercapacitors (Capacitance, Equivalent Series Resistor, Self-discharge rate). To avoid imbalance problems, balancing or equalizer circuit are required. There have been several cell voltage equalization techniques which are proposed. Generally, these cell voltage equalization methods can be categorized in two groups, dissipative cell voltage equalization method and non-dissipative cell voltage equalization methods. This paper reviews the existing topologies of supercapacitor cell voltage equalizations, compares and provides sample simulation.