The Research And Implementation Of A Micro-photovoltaic Inverter

With the highly development of human civilization,the demand for energy will be larger and larger.There will be a very prominent contradiction between the increasingly depletion of traditional fossil energy and the deterioration of the ecological environment.As a clean,pollution-free and renewable energy,photovoltaic is getting widely attention.Small or micro photovoltaic power generation is an important development direction of solar energy utilization.It has advantages such as lower voltage,safer,higher reliability,modular design and so on.Micro grid-connected inverter is the core equipment,its performance directly affects the quality and efficiency of the entire photovoltaic solar power generation system.So it is very important to study how to improve the performance of micro inverter.In this paper,the isolated grid-connected inverter is regard as the main research object,the inverter system topology,the maximum power point tracking,grid-connected control strategy is analyzed and studied in detail,including the following:(1)The advantages and disadvantages of the common topology of isolated micro inverter are analyzed and compared,and the rationality of choosing the isolated Cuk structure is clarified.Combined with the working principle of grid connected inverter,a mathematical model is built,the two stage MPPT control method and the LCL based sliding mode control strategy are proposed,they are verified by the simulation results.(2)The hardware circuit of the micro inverter is designed,including the main circuit and control circuit.The control circuit mainly includes DSP chip and its peripheral circuit,voltage and current signal sampling and conditioning circuit,PWM drive circuit and so on.The main component parameters are calculated,and the selection of the device is established.The inverter system control software is designed mainly as the main control program and the interrupt service program.The main control program is used to complete initialization of each function module,and the interrupt service routine mainly completes the signal sampling and processing,pulse width modulation,MPPT control,grid current control function.(3)The experimental prototype of micro inverter is built.Experimental results show that the proposed control strategy is correct and the design of hardware and software is reasonable.The design of the micro grid inverter proposed in this paper has the advantages of high safety,small volume,small harmonic grid,it has certain theoretical and engineering reference value.