Research On Construction And Control Technology Of Electrochemical Hybrid Energy Storage System Based On Impedance Source Topology

With the increasingly prominent environmental problems and the need of energy transformation,the proportion of new energy power generation represented by photovoltaic and wind energy in the total power generation is increasing.Because renewable energy is generally characterized by volatility and randomness,and the microgrid is small in scale,changes in either power supply or load in the grid may bring stability problems to the microgrid.In response to this problem,energy storage units are generally introduced to stabilize power fluctuations and achieve ’peak load shifting’.However,it is difficult for a single energy storage mode to meet the needs of high power output and high energy density at the same time.Therefore,the combination of various types of energy storage methods to construct a hybrid energy storage system has become one of the effective ways to solve the above problems.In this paper,the electrochemical hybrid energy storage system including supercapacitor and battery is taken as the research object,and the construction and control technology of the system are studied.The main research contents are as follows:Firstly,based on the construction method of the conventional non-isolated impedance source DC-DC converter,a high gain impedance source converter is constructed as the power interface circuit of the electrochemical hybrid energy storage system studied in this paper.The working mode of the proposed hybrid energy storage system based on impedance source converter is analyzed,and the power stage circuit parameters are designed.Then,the state space average model of the hybrid energy storage system based on impedance source converter is established,and the open-loop frequency domain characteristics and relative stability of the system are analyzed.According to the power demand of the DC side,and based on the state of charge of the supercapacitor unit and the battery group obtained by sampling,the charging and discharging logic of the two electrochemical energy storage units is designed,and the control strategy of stabilizing the DC side power/voltage fluctuation based on the double closed-loop charging and discharging control is designed.By substituting the adjusted controller parameters,the closed-loop frequency domain characteristics of the system are analyzed.In addition,based on the equivalent circuit model of various components in the system,the power loss and power transmission efficiency of the proposed hybrid energy storage system based on impedance source converter are analyzed.Finally,a simulation and experimental platform is built to verify the feasibility and superiority of the proposed scheme.Under the condition of power shortage and power surplus,the electrochemical energy storage system including battery,supercapacitor and only battery is compared respectively.It is proved that the proposed hybrid energy storage system based on impedance source can stabilize the bus voltage fluctuation and realize ’peak shaving and valley filling’ under the condition of DC side power shortage or surplus.In addition,under the condition of large fluctuation of DC side power,the supercapacitor and the battery group in the proposed scheme jointly respond to the power demand.Therefore,compared with the electrochemical energy storage system using only the battery group,the charging and discharging depth of the battery group in the proposed scheme is reduced,and the charging and discharging current of the battery group is low,which is beneficial to prolong the cycle life of the battery group.