Research On 100 Megawatt Battery Energy Storage System

Power battery is one of the core parts of the battery energy storage system.In order to reduce the storage cost,retired power battery in electric vehicle can be made full use of to establish a mode of echelon use of storage battery.Another core part of the energy storage system is the power conversion system,which is the bridge between the system and the power grid.This paper stands on the application of large-scale energy storage system and focuses on the topology and control method of cascaded H bridge structure.First,the structure and working mode of the modularized cascaded H bridge converter are studied.The sub module structure is decided as the three level converter.The working principle of sub module and the three phase system is analyzed.Then the suitable modulation principle and reference wave generation method for the cascade H bridge converter are studied.Carrier phase shift modulation principle can achieve a better balance between the control complexity and harmonic reduction in the structure of multi-level output;direct current control principle can track grid fluctuations and battery voltage.It also can achieve the four quadrant running mode.The neutral point balance algorithm is added to the control mode to solve the neutral point balance problem of the sub module structure.The simulation experiment of the system is carried out in MATLAB/SIMULINK.Then the equilibrium problem of the sub module is calculated.Considering the equilibrium method,the SOC equilibrium boundary to satisfy the requirement of grid voltage is proposed,and the boundary condition is instantiated according to the typical case.Finally,master-slave control model is applied--a master controller and multiple sub module controllers--as our system control mode.Under this control mode,the whole process of coordinating sub modules is clear.The main controller is composed of DSP and FPGA,and DSP is mainly responsible for the digital calculation of reference waveforms;the work of FPGA is information transmission and overall planning.The sub module controller is composed of FPGA,and the main work is to receive signal and drive IGBT.The PCB board is designed.The function of the FPGA part of the master and slave module is programmed by Verilog.