Modeling And Suppression Of Electromagnetic Radiation Of Photo-Voltaic Power Optimizer

Switching power supply has been widely used in the industrial field due to its small loss,good reliability,and greatly reduced volume and weight compared with conventional power supplies.Most of the current switching power converters adopt the PWM control mode.The switching devices generate high dv/dt and di/dt at the moment of switching operation,thus causing a large electromagnetic noise,which seriously affects the reliability and electromagnetic compatibility of the switching power converter.Therefore,it is of great theoretical and practical significance to study the electromagnetic interference problem of power converters and suppress them.In photovoltaic power generation system,the appearance of photovoltaic power optimizer has solved the problem of output power reduction caused by external environment changes such as local shadow occlusion.In this paper,a 750W dual-channel power optimizer is taken as the research object,its EMI modeling,simulation and suppression technology are studied.Based on the research of radiation emission mechanism of power converter at present,the high frequency EMI model of power circuit,MOSFET,photovoltaic cable and other main components of power optimizer is established,and the corresponding parameter extraction method is introduced.The EMI model of low-voltage MOSFET is established by using Simplorer device parametric feature modeling tool,and the high-frequency distributed parameter model of photovoltaic cable is established by using impedance analyzer test and ANSYS Q3D simulation method.Finally,EMI time domain circuit simulation model of power optimizer based on ANSYS Simplorer is built.Through the model,some interference characteristics of the power optimizer and the influence of the high frequency model of the key components on the interference spectrum characteristics are analyzed.Based on the established high-frequency circuit model of photovoltaic power optimizer,the common mode current on the photovoltaic cable is obtained by simulation,and it is used as the radiation excitation source to realize radiation simulation of "field-circuit coordination".Based on the established equivalent common-mode radiation model of PCB board and cable,a prediction method of far-field radiation of PCB with cable is proposed combining simulation with theoretical calculation.Finally,the board-level EMC optimization design and filtering rectification scheme were carried out for this power optimizer.Among them,by optimizing the area of high-frequency ring road and parasitic inductance,the radiation emission of this product has been greatly improved and passed the standard of EMC standard EN55022 Class A.At the same time,for the two-wire floating power optimizer system with two-way mirror buck-boost cascade topology,a filtering scheme based on "π-type filter" is proposed,which enables the products to pass the electromagnetic compatibility standard EN55022 Class A and Class B.