Design And Control Strategy Research Of Matrix Power Balance System Applied To DC Microgrid

Given the escalating degradation of the ecological environment and the increasing scarcity of fossil fuels,there has been a growing emphasis on renewable energy and its associated technologies.Among these technologies,the DC microgrid has emerged as an effective and dependable solution for the generation and consumption of renewable energy.Renewable energy sources such as wind power,distributed photovoltaic power generation,and other methodsexhibit inherent characteristics of uncertainty,volatility,and intermittency.To accommodate these characteristics and establish a stable DC microgrid platform,this research delves into the design and investigation of a matrix power balance system specifically tailored for new energy DC microgrids.The proposed system utilizes renewable energy generation as its energy input port and integrates a two-way hybrid energy storage connection port to achieve balanced compensation for the bus voltage within the DC microgrid,along with rational distribution of power flow across the bus.Moreover,a hierarchical operation mode switching is adopted to ensure bus voltage stability and power balance functions of the microgrid.Addressing the interface challenge between the DC microgrid and AC/DC loads,this study employs an integrated solid-state transformer to facilitate power output from the DC bus to AC loadsof varying voltage levels.By employing a 40 k Hz solid-state transformer as the core,the working principle is examined,and conclusions are drawn regarding the system power characteristics.By employing small signal theory,a mathematical model of the solid-state transformer is formulated,and a simulation model of the solid-state transformer subsystem is built in PSIM for open-loop scanning to obtain steady-state characteristics.Subsequently,a closed-loop simulation model is established in the MATLAB/Simulink environment to evaluate the effectiveness and stability of the control system through closed-loop simulations of the output voltage.In order to suppress DC bus voltage fluctuations under multi-port conditions,a hybrid energy storage system comprising a conventional battery and supercapacitor,along with their corresponding DC/DC matching converter,is employed to connect to the DC bus.The system adjusts its operational mode based on the level of DC bus voltage fluctuations,allowing control of power flow direction for each matching converter and achieving compensation for bus voltage fluctuations using the hybrid energy storage unit.An open-loop simulation model of a multi-port bus voltage balance subsystem,consisting of photovoltaic input,a single energy storage battery,and dual supercapacitors,is constructed in PSIM.Open-loop simulations are conducted to analyze different power flows at each port under varying bus voltage fluctuations.Furthermore,a closed-loop simulation model is developed in MATLAB/Simulink to assess the stability and effectiveness of mode switching control at each port of the subsystem under different bus voltage fluctuations.Finally,an overall simulation model of the system is constructed in the MATLAB/Simulink environment,and closed-loop control simulations are performed for each subsystem to verify the effectiveness of the control system during the operation switching of each subsystem.The system’s hardware experimental platform is built using the dsPIC33FJ64GS606 digital controller as the core,and experimental verification is conducted.The results obtained confirm the stability of the designed system and the effectiveness of the control system.In conclusion,this research contributes to the development of a robust DC microgrid system that effectively integrates renewable energy sources,addresses interface challenges,and ensures stability and power balance within the microgrid.