Research Of Voltage Self-Balancing Topologies For Energy Storage System Based On Switched-Capacitor Reutilization

In energy storage systems,a large number of energy storage cells which are connected in series and parallel are required to meet the voltage and power requirements of the load.However,due to the limitation of manufacturing processes,there will be differences in the characteristics of energy storage cells,resulting in the voltage gap between cells,which reduces the energy utilization rate of the energy storage system and decreases the life of energy storage cells.Therefore,it is necessary to introduce voltage equalization technology.However,energy storage circuits and equalization circuits are often designed separately,leading to the introduction of a large number of additional equalization devices,which increases the volume and cost of the system.Therefore,this paper is based on the principle of switched-capacitor,and realizes the voltage self-equalization of energy storage cells by reusing switched capacitors,which avoids the introduction of a lot of equalizing capacitors.The paper research interests are as follows:First of all,this paper proposes a novel voltage self-balancing topology for super capacitor arrays.Only by reusing the first column of super capacitors as equalizing devices,the voltage self-balancing of the array can be realized.Firstly,the working modes of the topology are introduced in detail,and the equivalent capacitors are used to replace the parallel capacitor banks to further obtain the voltage/current characteristics and energy loss of the super capacitors.Secondly,a comparative analysis of multiple modules is carried out through simulation to verify that the proposed topology has good scalability.Finally,a 4-series 2-parallel super capacitor array is built to complete a voltage self-equalization experiment,which verifies the feasibility of the topology.Secondly,a novel voltage-balancing topology is proposed for the hybrid energy storage system composed of lithium batteries and super capacitors.The voltage balance of the hybrid energy storage system can be realized by reusing super capacitors.The equilibrium is analyzed in detail,and obtain the voltage /current characteristic of the energy storage cells.Based on the analysis,the equivalent circuit of the equilibrium process is deduced.The software is used to simulate the typical working mode of the hybrid energy storage system,and an experimental platform composed of lithium titanate batteries and super capacitors is built to verify the feasibility of the topology.Finally,based on switched-capacitor reutilization,this paper proposes three novel topologies for lithium battery system,to achieve lithium battery voltage balance and multi-level inverter output.With the goal of improving the equalization process and increasing the number of inverter levels,three topological structures are gradually improved.The paper introduces the working modes and working principles of the three topologies in detail.And the advantages and disadvantages of the three topologies are discussed through simulation.Under the guidance of the simulation results,the second topology is selected for experimental verification,and the experimental results show that the topology is feasible.