Research And Design Of Small PV Grid-connected Power Generation System

With the increasing problem of energy crisis,the urgency of finding alternative energy has become higher and higher.As a renewable and clean energy,solar energy is inexhaustible and has been widely developed and utilized as an alternative energy source for fossil energy.At present,the use of solar energy is mainly power generation.Solar power generation can be converted into electric energy by photovoltaic grid-connected power generation system and then incorporated into the power grid.Therefore,the research and design of photovoltaic grid-connected power generation system is of great significance.The purpose of this paper is to study and design a small photovoltaic grid-connected power generation system,including the following aspects:(1)The array form and circuit topology of photovoltaic cells are introduced,compared and studied,from which centralized array,boost chopper,voltage-isolated inverter and LCL filter circuit are selected.On this basis,the overall design scheme of the system is given directly,and the working process of photovoltaic grid-connected power generation system is described."(2)Starting from the PN junction inside photovoltaic cells,the working principle of photovoltaic cells is explored in detail by using power electronics.Equivalent circuit model is established,the output characteristics of photovoltaic cells are derived by using the model,and the significance of maximum power point tracking(MPPT)is revealed.Through the study of MPPT principle,the interference observation method is chosen as the MPPT algorithm in this paper.(3)The hardware design frame is given,and the main circuit,control circuit and auxiliary power supply circuit are designed in detail.In the design of the main circuit,the design index is given,and the chopper circuit,inverter circuit,filter circuit and transformer are designed accordingly.The calculation formula and results are given,and the device selection is determined.In addition,the control circuit includes power drive circuit,protection circuit,voltage and current sampling circuit.(4)The coordinate transformation is derived and the double closed loop parameters of the control system are designed according to the coordinate transformation.The main program and interrupt subroutine are introduced.Moreover,the main program,MPPT,double closed loop and SVPWM interrupt subroutine are designed.(5)The Simulink simulation model is built and the simulation analysis is carried out.Simulation results show that the DC output voltage under MPPT control can rise to a stable value quickly and the overshoot is small.Even if the light intensity changes,the DC voltage can quickly return to a stable value.In addition,the AC voltage and current waveforms of inverter AC side and transformer high voltage side are very sinusoidal,and the phase and amplitude also meet the design requirements.Therefore,the simulation results verify the correctness of the design of photovoltaic grid-connected power generation system.