Fast two-stage charge equaliser based on state-of-charge (SOC) balancing for series-connected supercapacitors

Abstract

New energy storage vehicles which use supercapacitors (SCs) as the unique source of traction power are developing rapidly recently. To satisfy the operating voltage requirement of energy storage vehicle, hundreds of SCs are needed to be connected in series. In this case, there is a voltage imbalance between the energy storage cells during rapid charging, resulting in reduced energy efficiency and service life of the energy storage device. A layered equalisation scheme is proposed to solve the problem of voltage imbalance. A single-input multiple-output synchronous rectification equalising circuit is proposed to ensure voltage consistency of series supercapacitor monomer in bottom module. The proposed circuit resolves the existing slow balancing speed and low-voltage balancing precision problems in the current supercapacitor equalising circuits. Meanwhile, an equalisation strategy based on module SOC is adopted to solve voltage imbalance problem of the upper supercapacitor module. The results of MATLAB/Saber co-simulation and experiment demonstrate that the layered equalisation system achieves the target of fast equilibrium and high precision balance.

Keywords

• rectification
• supercapacitors
• energy storage
• traction power supplies
• fast two-stage charge equaliser
• series-connected supercapacitors
• traction power
• operating voltage requirement
• energy storage cells
• reduced energy efficiency
• service life
• energy storage device
• layered equalisation scheme
• multiple-output synchronous rectification equalising circuit
• voltage consistency
• series supercapacitor monomer
• low-voltage balancing precision problems
• current supercapacitor equalising circuits
• equalisation strategy
• module SOC
• voltage imbalance problem
• upper supercapacitor module
• layered equalisation system
• high precision balance
• state-of-charge balancing
• energy storage vehicles
• slow balancing speed