| With the use of traditional fossil energy,more and more problem has been brought to human beings.People pay more attention to the research and utilization of new energy sources.With a wide range of applications,clean,easy to maintain and other advantages,photovoltaic power generation has been a hot spot among the field of new energy.But we are still facing some technical problems which are not solved in the field of photovoltaic application.And during the research process,a set of practical photovoltaic experimental platform is also a powerful tool to study the photovoltaic system and verify the theories.In this paper,some problems about photovoltaic power generation technology are studied.Aim to use in laboratory environment,a single phase photovoltaic grid connected system experimental platform is designed.First of all,two-stage grid connected system is selected to be the main structure of the system.We focus to research the first-stage of photovoltaic system.Solar panels and DC/DC circuit are researched.The characteristics of solar panels are analyzed.Construction and simulation of engineering model are established.Double-Boost circuit is selected to realize MPPT and voltage regulator function.The model of solar panels is established and characteristics are studied.Then,three common MPPT methods used in engineering are analyzed.Their advantages and disadvantages are summarized.Their tracking speed is slow and accuracy is not high.In disturbance observation method and incremental conductance method variable step length method have their problems like search speed is not balanced at two side of MPP and working point shock.When the system is working in the changing state,the working point will jump among these different characteristic curves which will cause false judgement.Consider the above problems,variable step length combined with power prediction MPPT control method is proposed.With this method,the optimization speed and precision are improved effectively.Solve the problem of false judgement under dynamic conditions.Finally,the design of hardware and software of the experimental platform of photovoltaic system is designed.Hardware aspect,power circuit like Double-Boost circuit and inverter are designed.The related power components are selected.The Controller of the system is also designed.Software aspect,Controller program is designed.Program block diagram is finished.The thought of the Program is summarized.Then the host computer system is designed in order to realize the monitoring of the platform and online parameter adjustment.Communication protocol is developed and the host computer system interface is designed.After completing the design of system,the system is tested. |
