Research On High Voltage Gain Soft-switching DC-DC Converter Based On Switched Capacitor And Coupled Inductor

In recent years,with the gradual exhaustion of primary energy,renewable energy power systems such as wind energy,photovoltaics,and fuel cells have developed rapidly.However,photovoltaic,fuel cell and other new energy power generation systems usually output a wide range of low-voltage direct current.Therefore,a DC-DC converter with high voltage gain is required to boost it to a higher voltage to meet the requirements of grid connection or load.This paper will use switched capacitor technology and coupled inductor technology to study a new type of high-efficiency high-gain soft-switching DC-DC converter.Although the switched capacitor converter can obtain high gain by superimposing the switched capacitor unit,its gain is not adjustable and the structure is complicated.Therefore,this paper combines traditional Boost and Buck-Boost converters with switched capacitor units,and proposes four switched capacitor converters with inductive energy storage units,whose voltage gain is more than doubled compared with traditional Boost and Buck-Boost converters.In order to further improve the voltage gain,the coupling inductor technology is introduced,which is similar to the flyback structure to form a superimposed boosting unit,and the composite I-type switched capacitor converter based on the coupling inductor is obtained.The voltage gain was further improved and verified based on PSIM simulation software.Based on the compound I-type switched capacitor converter based on coupled inductors,three-winding coupled inductors are introduced.And a new high gain soft switching DC-DC converter based on switched capacitor and coupled inductor is proposed.The working principle and static operating characteristics of the converter are analyzed in detail,and the key parameter design is given.Looking further at the switching conditions of the converter,the freewheeling of the coupled inductor allows all switches to achieve zero voltage turn-on in a larger range.At the same time,because the function of the active absorption circuit unique to the switched capacitor can reduce the switch off voltage spike and reduce its voltage stress,therefore,a switch with a lower withstand voltage can be selected.The on-state impedance of this type of device is very small.The loss is further reduced.The above analysis was verified by PSIM simulation software.In order to obtain more excellent dynamic performance,the state-space averaging method is used to model the converter proposed in this paper,and its stability is studied in the frequency domain.According to the obtained open loop system Bode diagram,the design of the controller is completed,and the stability of the closed loop system is achieved.T The digital control scheme is selected for closed-loop control,and the dead time under light load is optimized.This paper builds a 100 W experimental prototype.When the input voltage is 25 V DC,the output is a stable 380 V DC,the operating frequency is 100 k Hz,and the efficiency is 96% at rated power.The experimental results are basically the same as the simulation results and theoretical analysis,which verifies the correctness of the theory.