Research On High Power Density Multifunctional Energy Storage Device For High Power Fluctuation Suppression In Power Grid

With the projects such as UHV AC transmission in northern Zhejiang,Lingshao and Binjin UHV DC transmission,Zhoushan flexible DC transmission have been put into operation successively,Zhejiang Power Grid has become a large-scale AC and DC hybrid power system.Due to the existence of the failure probability of the large-capacity transmission channel,the problem of voltage stability and the power oscillation between regions in electric power system need to be solved urgently.In order to ensure the safe and stable operation of the grid after HVDC fault,this paper proposes to develop a high-power density multi-function energy storage device which combines supercapacitor and STATCOM to adjust active and reactive power independently.The device can restrain super power fluctuation,stabilized voltage,and can also improve the power quality of the grid.Firstly,this paper introduces the main circuit topology and working principle of high power density multi-function energy storage device.By analyzing and comparing the topology of current multi-level inverters,the cascaded H-bridge topology is selected as the main circuit of the system.Simultaneously,the mathematical model and control strategy of the circuit after dq decoupling in the two-phase rotating coordinate system are deduced,which can make the device realize four-quadrant operation in the grid.Additionly,the main circuit parameters of the high power density multi-function energy storage device are designed based on the capacity requirements of the device,.Then the LCL filter parameters suitable for the device are determined based on the previous research results.Based on the mathematical model in dq rotating coordinate system,the paper designs a current tracking controller of PI control strategy and proposes the shortcomings of PI control strategy in this system.Finally,combined the advantages of PI control strategy and the repeated control strategy,a series-type composite current tracking controller based on PI control and repetitive control is designed.In this paper,PSCAD/EMTDC simulation software is used to simulate the design scheme of the system,which verifies the feasibility and correctness of the control strategy of high power density multi-functional energy storage device.