Research On State-of-Health Estimation And Balance For Power Battery

The energy crisis,environmental pollution and many other factors make electric vehicles again onto the historical stage,which has become the focus of global attention.China electric vehicle industry has been listed as a key point on the development of new strategic industries.The Chinese government hopes that through the development of electric cars to boost its industry structural adjustment and technological progress,finally realizes electric the auto industry overtaking around the curve.Power battery as the main power sources of electric vehicles,its performance directly affects the vehicle’s performance,economy and safety.At present,the battery technology is one of the three key technologies of electric vehicle,including state monitoring and estimation and group technology is the key of the key.In this paper,power lithium-ion battery for electric cars as the research object,the main work includes the following aspects of content:Based on the chemistry of lithium-ion batteries work principle and the theory of the electron motion understanding,the second-order RC model is selected.In the process of model parameter identification,A method based on M sequence signal for battery model parameter identification is proposed from the perspective of parameter identification theory,simulation experiment is also carried out.The results show that feasibility and validity of the method by compared the pulse test.At the same time with forgetting factor recursive least square online parameter identification method is deduced and simulation test is done,the accuracy,applicability of second-order RC model also verified.Based on lithium-ion battery cycle life test data,the influence factors of lithium ion battery capacity and cycle characteristics were analyzed,and the results show that the factors that affect monomer battery capacity existing coupling effect,which makes SOH estimation based on the number of life cycles is difficult.And for the lithium-ion battery charge and discharge cycle test process features showed a strong regularity is studied;Based on the second-order RC model have been established,SOH estimation model based on charging voltage curve is deduced,the method of model parameter extraction is also given;SOH were estimated by the battery cycle life test data,the estimated results verified the precision and reliability of the proposed estimation method.To solving series battery pack capacity uncertainty problems,the maximum available capacity of series battery pack with different equilibrium function and energy consumption were analyzed in detail,the results show that using a dynamic balancing without energyconsumption of the battery pack,to maximize capacity and energy utilization can reach.The specific definitions of maximum available capacity,SOC and SOH for series battery pack are put forward,which lay favorable conditions for the battery state estimation and provide theoretical guidance for the establishment of equilibrium solution.For the inconsistency between before and after the series power battery group,based on the analysis of series battery maximum available capacity,the series battery capacitor balanced system topology structure were researched,a series of new balance topology structure based on four monomer is proposed,and simulation circuit model is built,the results show that the proposed equilibrium topological structure has better equilibrium effect,providing a new solution for capacitive balanced application in series battery pack.