Development Of Photovoltaic Micro-inverter Based On SiC Power Device

The environmental pollution and the exhausted of fossil energy has become one of the important factors of restricting the development of human society today.However,The development of green renewable energy such as solar energy,wind energy will be the key to solve the problem of environment and energy security.Because of its abundance in resources,widely distributed,pollution-free,and many other advantages,solar energy receives people's favor.Compared with the centralized photovoltaic grid connected system,distributed photovoltaic(pv)grid tied system has advantages no matter in terms of reliability,efficiency,or in the occupied area.So the distributed photovoltaic grid tied system has developed rapidly in recent years.And micro-inverter is the core of distributed photovoltaic grid tied system.Its reliability and efficiency will play an important role in the whole photovoltaic system.Power switching device is an important component of micro-inverter,and its performance will directly affect the efficiency of the inverter.With the advantages of bearing higher temperature and voltage,lower losses,new silicon carbide(SiC)material power device is more suitable for application in high frequency,high efficiency occasion compared with traditional silicon(Si)materials switching devices.Based on the above background,this paper developed a micro-inverter based on SiC power devices,aiming to improve the efficiency of the micro-inverter.Firstly,the development and present status of micro-inverter and SiC power device are discussed in this paper.In this paper,we mainly introduce the two level topology micro-inverter,and the working principle of DC/DC and DC/AC is analyzed.The active-clamp flyback topology and the full bridge inverter topology are selected as the main power circuit of the micro-inverter.At the same time,the characteristics of SiC power device and Si power device are compared and analyzed.According to the characteristics of SiC MOSFET,the design of its driving circuit is presented in this paper.In this paper,the hardware design and the system control strategy are studied,including the SiC MOSFET drive circuit,DC/DC,DC/AC main circuit and the corresponding control circuit.Control strategy includes maximum power point tracking(MPPT),SPWM modulation technology,voltage and current double closed-loop control.Finally,through the SiC inverter prototype,this paper presents the results of the grid connected experiment and the efficiency comparison experiment,and the data analysis is carried out.Experimental results show that the experimental prototype can achieve UPF(unity power factor)grid-connected.Efficiency comparison test results show that in the case of the same power input,the efficiency of the SiC inverter is higher than that of the Si inverter and the inverter efficiency is raised from 93.4% to 94.3%.At last,the experimental results show that the efficiency of the micro inverter prototype using SiC power device has been effectively improved.