Research On System Structure And Control Strategy Of Photovoltaic Series-Connected Power Optimizer Without Communication

Greenhouse gas emissions,global warming and other issues make extreme weather frequent,environmental challenges become more and more serious,facing the strong demand of sustainable development of human society,the development and utilization of clean energy becomes more urgent.Among the many renewable energy sources,solar energy is considered as an important way to solve the future energy demand because of its clean,safe,widely distributed and abundant resources.In the photovoltaic power generation system with series power optimizer structure,each photovoltaic module is connected with a power optimizer.The output terminal of the optimizer is connected in series to form a DC bus.The latter converter transmits the energy from the DC bus to the latter system.The structure can effectively utilize the energy of each module,and has the characteristics of high efficiency and modularity.It meets the requirements of distributed photovoltaic system and has become a research hotspot in recent years.In this paper,the structure of series power optimizer and the coordinated control strategy without communication are deeply analyzed and studied.The first chapter introduces the application background and development direction of photovoltaic grid-connected system,briefly analyses and summarizes the work of predecessors,and puts forward some views on this basis.In the second chapter,the structure and control strategy of series power optimizer are analyzed.The power optimizer completes the maximum power point tracking of each component,and solves the problem of heat spot effect and power loss caused by partial occlusion.Based on the analysis and comparison of the topologies of series photovoltaic power optimizer,the conditions for the realization of MPPT in series system are given.Based on this,Boost circuit is selected as the main power topology of power optimizer,and the circuit parameter design,small signal analysis and double-loop controller design are completed.Finally,through the analysis of the startup problem of series power system,the startup strategy of series power optimizer without communication is given.Chapter 3 introduces a power supply system of UAV based on series power optimizer.Because of its special application environment,UAV platform has put forward the application requirements of high efficiency,high power density and high reliability for power supply system.The UAV power supply system described in this chapter is composed of two stages.The front stage is a series optimizer structure to achieve maximum power tracking of photovoltaic modules.The latter stage is Buck converter,which realizes the functions of energy balance,battery charging control and overvoltage protection.The post-stage converter greatly improves the efficiency of the whole system by changing bus voltage mode and through mode.It is worth noting that the control strategy of the system is non-communication control strategy,the startup strategy of non-communication is adopted between the series optimizers,and the coordination control strategy of non-communication is adopted between the front and rear systems.In the fourth chapter,the simulation results and experimental results of power supply system of UAV are given,and the experimental waveforms are analyzed.