Development Of Half-bridge Cascade Energy Storage System For Secondary Use Battery

The problems of battery recovery and the secondary use which are brought about by the rapid development of the new energy vehicle industry need to be solved urgently.Using the returned power battery in the energy storage system can effectively alleviate the recovery pressure and reduce the life cycle cost of the power battery.Compared with the new battery,the problem of battery safety maintenance and parameter inconsistency of the secondary use battery for the energy storage system is particularly prominent.In particular,the problem of low capacity utilization of the battery pack due to inconsistent capacity needs to be solved.In view of the above problems,the secondary use of battery energy storage systems is studied in this thesis.The detailed research is as follows:According to the use scenario of the secondary use battery,the characteristics and application scenarios of several common flexible battery group energy storage topologies are compared.And the research is conducted on the half-bridge cascaded topology with simple control,modular independent control and redundant control.The working principle is analyzed and combined with the topological characteristics,a hierarchical distributed control architecture of "local control and secondary regulation"is established.In order to realize the stable operation of the system under distributed control and independent control of battery power,an integrated control strategy based on ?-? drooping between submodules is proposed.A half-bridge cascaded simulation model was built for simulation verification and waveform analysis.To solve the problem that the utilization of battery capacity is low due to the big difference of battery capacity,the control strategy research on batteries balance of the half-bridge cascade energy storage system is studied based on the independent control of submodule power.A two-stage equalization control strategy which is suitable for the utilization of different types of batteries is proposed to realize the balance control of battery modules with different specifications/capacities.The balance capability of the half-bridge cascaded energy storage system is analyzed,which provides a theoretical basis for setting the operating parameters of the actual energy storage system.Combining with the characteristics of the system topology and the security protection problems in the actual operation of the energy storage device,the protection and redundancy control strategies of the system are designed.Focusing on the problem of deterioration of inductor ripple current after redundancy,the control strategy of coding and carrier reconstruction is proposed.For the problem of inductor ripple current deterioration caused by battery module capacity difference and balance control,the combination of theoretical derivation,simulation calculation and model verification is adopted.The influence of the relative relationship between different sub-modules and phase shift angle on the inductor ripple current under carrier phase-shift modulation is analyzed.Under a certain capacity distribution,a carrier phase shifting method with smaller ripple coefficients is established,which provides some reference for the design of inductance and the optimization of operation and maintenance management of energy storage system.A cascaded half-bridge energy storage systems experimental prototype with 15 sub-modules is developed.The distributed integrated control strategy,balance control strategy and redundant control strategy are verified by experiments.Through the analysis of experimental data and waveforms,the effectiveness of the proposed control strategy is verified.The established energy storage system is suitable for the secondary use of battery and meet the actual needs.