Large Signal Stability Analysis Of Photovoltaic Interface Converter In Photovoltaic-Energy Storage System DC Microgrid

As a key part of renewable energy harvesting and utilization in Photovoltaic(PV)-Energy Storage System DC microgrid,PV interface converter is crucial to stable operation of the whole network.However,the PV power supply has strong intermittency,the load of the microgrid is also characterized by randomness and large fluctuations,and in the meanwhile PV interface converter has control mode switching in the coordinated operation of microgrids,these factors combined make the interface converter a typical multi-input large signal operation system.In this regard,this thesis focuses on the large signal stability for the PV interface Boost converter by the Lyapunov theory.Firstly,the PV interface converter is modeled,and the main circuit is designed.Based on the small signal model,the Maximum Power Point Tracking(MPPT)controller is designed for the converter.At the same time,the influence of the load type on the controller design is considered to ensure the stable operation of the system.Based on the three mainstream Lyapunov functions,i.e.,Quadratic Lyapunov Function(QLF),Mixed Potential Function(MPF)and Lyapunov-Like Function(LLF),the large signal stability of the PV interface converter under MPPT mode operation is analyzed,and the stability region of the converter is estimated,and preliminary comparison results are given.Secondly,considering the mode switching characteristics under the coordinated operation of the DC microgrid,the stability of the large signal switching of the converter is analyzed from the perspective of switching dynamic systems for the problem of the PV interface converter switching between MPPT and Constant Voltage(CV).With the help of the Linear Matrix Inequality(LMI)solving tool,the switching stabilities based on the Common Lyapunov Function(CLF)and Multiple Lyapunov Function(MLF)is discussed respectively.Finally,the simulation model of the PV-Energy Storage System DC microgrid was established,and a laboratory prototype of a 120 W PV interface Boost converter was designed and implemented.The analyses results are verified by simulation and experimental results.