| As the core component of solar power generation,photovoltaic inverters have attracted much attention for their technological innovation and reform.At present,the pursuit of high frequency,high efficiency,high power density and miniaturization is becoming a new development trend.Based on this objective,this paper presents a squirrel algorithm to optimize MPPT system,a staggered parallel Boost structure to improve DC-DC efficiency,and a high frequency GaN switch to improve the power density of the inverter.A 500W two-stage photovoltaic micro-inverter is designed.The main work is as follows:Firstly,the development status and main trends of photovoltaic power generation are introduced,and the wide application of micro-inverters in distributed power generation system is introduced.The application characteristics and main structure of the micro-inverters are analyzed,and the applicability of the two-stage structure of the front step-up and the rear step-down to the design of the photovoltaic micro-inverters is emphasized.Secondly,the development and characteristics of GaN power devices are introduced,and the differences between GaN materials and traditional semiconductive materials are compared.By analyzing the applications of GaN power devices in various circuits,the advantages of using a new wide band GaN power device instead of a traditional Si based power switch device in the design of inverters are illustrated.Then,the common topology types of boost and invert circuits are analyzed in detail,their advantages and disadvantages are combined with the applicable scenarios,and the overall structure of the two-stage photovoltaic micro-inverters in this paper is determined,that is,the Boost topology for the front boost and the SPWM modulation for the back boost.For the problems caused by low input voltage and large fluctuation range of photovoltaic panels,the staggered parallel Boost structure and the MPPT control system based on the squirrel algorithm are designed to function in the front step boost circuit.The rationality of the above micro-inverter design is verified by simulation with MATLAB/simulink.Finally,the software and hardware of the whole micro-inverter are designed,using STM32H743 as the main control chip,and the control system including MPPT and double closed-loop of voltage and current is designed.For the application characteristics of GaN power switch,a special high frequency drive circuit is designed,and its driving theory is analyzed in detail.After the above foundation is completed,a two-stage GaN photovoltaic micro-inverters physical prototype with maximum power up to 500W is designed,and its performance is tested by setting up an experimental platform.The experimental results show that the frequency of the switch is 100 kHz,the output voltage is 220 V AC power frequency,and the efficiency of the inverter is 94%,which meets the requirements of the high frequency and high efficiency target design of the micro-inverter.Figure[58]Table[2]reference[75]... |
