Researchon Modular Equalization Circuit Based On Zero-voltage Switching

With the function of improving the stability and equality of power generation andincreasing energy efficiency, energy storage system plays a growing rolein fields such asnew energy power generation, electric vehicles as well as UPS. At present energy storagesystem generally adopts battery or super capacitor to storage energy except hydropower. Ahigh-power energy storage system contact series of battery or super-capacitor for thelownominal voltage of energy storage unit commonly used. Inconsistent in performanceand parameters of the energy storage unit will result in excessive charge or excessivedischarge of monomer in the system, which may hurt energy storage unit and even damagethe whole energy storage system.Thus, the voltage balancing technology is of greatsignificance to the development of energy storage system.Different equalization methodsare studied in this thesis. Based on analysis of workingmechanism are and summarize for advantages and disadvantages of equalization methods, anew type of advances equalization method based on zero-voltage switching is proposed.Detailsof working principle and control method for the equalization method is introduced,conditions to realize zero-voltage switchingof equalization circuit are given.Methods ofexpansion for equalization module are explained and basic features of equalization systemare introduced in this thesis. Basic Simulinkmodules are built in PSIM simulation softwareand results of simulation are used to analyses the performance of equalization circuit underdifferent statesof energy storage unit. Simulation of extensionstructure of equalizationmodule is completed, and results demonstrate effectiveness of extension for equalizationmodule.Hardware experiment circuitsare designed according to the simulation model ofzero-voltage switching equalization method. Experimental results are analyzed andcompared with the simulation to prove performance and effectiveness of extensions ofequalization module. Experimental results of different equalization method are comparedand analyzedAtthe end, The zero-voltage switching equalization method proposed in thisthesis has superiority in equalization error and efficiency.A voltage balancing technology based on zero-voltage switching is proposedin thisthesis. By realizing soft switch of switching devices in equalization process, theequalization circuit can reduce the switching loss and improve the efficiency. Modularity degree of the zero-voltage switching equalization circuit is high and could form variousforms of expending structure, which is convenient forapplication in large-scale energystorage system.