Control System Design And Parasitic Parameters Influence For A Multimode Resonant Converter

The new energy generation unit has the characteristics of low output voltage,wide range and so on.High frequency,high efficiency,low input voltage and wide voltage input range converter have become a hot spot in the field of new energy generation.In this paper,the soft switch resonant topology suitable for high frequency circuit is discussed with the front end boost converter in the new energy generation system as the research object.The full bridge LLC resonant converter has good soft switching characteristics,and it can realize the soft switch of power device in full power range.The requirement of wide voltage range input can be realized by the deformation of the topology and the expansion of the working mode.In this paper,the basic principle of multi mode resonant DC converter is introduced.By drawing phase trajectory diagram,the stress of switch tube under three working modes is obtained,and the mathematical relationship between control volume and gain ratio under different modes is obtained.According to the output characteristics of the front stage of the converter and the soft switching characteristics of the three working modes,the voltage range of the working mode is reasonably partitioned.The circuit parameters are designed based on the application background of photovoltaic power generation.By modeling and analyzing the small-signal in s domain containing parasitic parameters of the circuit,the influence of the parasitic parameters on the high frequency is studied.The influence of high frequency parasitic parameters on the soft switch of the circuit is carried out.Based on the energy storage characteristics of the electric field between the windings,the mathematical modeling is carried out to extract the parasitic parameters of the magnetic components.By analyzing the equivalent circuit containing parasitic parameters,the parasitic parameters of the soft switch and the time constraints of dead time are not affected.Finally,a two stage photovoltaic grid connected inverter is designed,and the system design of the two stage grid connected inverter is completed.The MPPT tracking strategy and multi mode control strategy for the former multi mode resonant DC converter are studied.The grid connection strategy of the post stage double buck grid connected inverter is studied.Complete an experimental prototype of 30VDC/220VAC 500W.The maximum efficiency is 96.08%,which verifies the feasibility of the theoretical analysis.