Research On High Frequency Model And EMI Suppression Of High Frequency Isolation Quasi-Z-Source Photovoltaic Inverter

At present,China is the largest coal consuming country in the world.The huge consumption of coal causes serious pollution to the environment and leads to excessive consumption of non-renewable resources,which violates the social pattern of sustainable development in China.Solar power generation and wind power generation have gradually occupied more market share in the field of power generation because of their advantages of minimal environmental pollution and direct access to energy from nature.In the field of new energy generation,the role of inverters is indispensable.The role of inverters is to convert the DC generated by solar panels into AC that can be transmitted in the grid.Inverters are one of the most core components of photovoltaic power generation system.Isolated quasi-Z-source inverter is a new topology.It can be used in photovoltaic power generation system because of its high boost ratio,high efficiency and electrical isolation.By increasing the working frequency of the inverters,the volume of the components of the inverters can be reduced,and the power density of the inverters can be increased.However,the high frequency switching tubes will produce a lot of electromagnetic noise.This kind of electromagnetic noise not only seriously affects the normal operation of the surrounding electrical equipment,but also poses a serious threat to the stable operation of the power grid.Therefore,researching and rectifying the electromagnetic compatibility of inverters will gradually become an important branch of power electronics industry.In this paper,the research status of conduction EMI suppression for isolated quasi-Z-source inverters is summarized firstly.The EMI modeling of the inverters,the EMI suppression method of the inverters and the research status of the isolated quasi-Z-source inverters are analyzed.The research on conduction EMI suppression of the isolated quasi-Z-source inverters is of great value.Then,the modeling method based on device behavior is used.The high-frequency model of isolated quasi-Z-source inverters including power MOSFET,power diode,inductor,capacitor and high-frequency transformer is built.The high-frequency model of isolated quasi-Z-source inverters is built by using the high-frequency model of each device.The chaotic modulation technology is used to suppress the conduction EMI of the inverters,in which Chua's chaos,multi-coil chaos of Chen system and grid are introduced.Multi-coil chaos is analyzed,and chaotic model is built in Simulink.The mechanism of chaotic spread spectrum modulation to suppress conduction EMI is deduced.The working principle of isolated quasi-Z-source inverters is analyzed,and the influence of transformer leakage inductance and hardswitching state on circuit waveform is proposed.In view of these two points,the circuit topology is improved,and an active clamp soft-switching isolator is designed.The off-type quasi-Z-source inverters are analyzed and their modes are analyzed.Finally,the improvement of switching waveform and DC-link waveform is verified by simulation.The main circuit,peripheral circuit and DSP software system of the isolated quasi-Z-source inverters are designed,and the physical model of the inverters is built.The Chua's chaos,Chen's chaos and grid multi-coil mixing are realized by computer simulation.Chaos suppresses conduction EMI of isolated quasi-Z-source inverters.The effects of different modulation coefficients and chaotic attractor orders on conduction EMI suppression are analyzed.Finally,experiments are carried out on a real model to verify the correctness of theory and simulation.On the one hand,this paper provides two feasible methods for conduction EMI suppression of isolated quasi-Z-source inverters,and at the same time,it plays an important role in promoting the research of EMI suppression technology of power electronics.