Research On High Gain DC-DC Converter Based On Switched Capacitor

In recent years,in order to release the serious situation of fossil fuels and environmental pollution,photovoltaic generation has become a hot field of research.The input voltage of photovoltaic generation is low and variable(approximately25-50 V),which greatly depends on weather conditions.As a result,high-voltage gain DC-DC converters are needed to convert it to high bus voltage(380 V).This paper studied the high-gain DC-DC conversion technology based on switched capacitors,and proposed a high-gain switched capacitor DC-DC converter based on coupled inductors.First,this paper proposed a novel high-gain switched capacitor DC-DC converter based on coupled inductors to meet the requirement of photovoltaic generation。The proposed topology improves the traditional switched capacitor energy storage structure,and solves the problem of insufficient voltage on the switched capacitor of the traditional switched capacitor energy storage structure.This paper analyzes the working principles of the optimized switched capacitor energy storage structure,and uses simulation to verify its correction.The proposed topology combined with coupled inductors to further improve the voltage gain and reduce the stress of the switching device.Next,the working principle of the proposed switched capacitor DC-DC converter is analyzed in detail,and the method and example of parameter design are given.This paper analyzes the working principle of the proposed converter in current continuous mode and current discontinuous mode,derives the voltage gain in the corresponding mode,and obtains the boundary conditions between different modes.To meet experiment requirement,this paper provides specific design methods and reference values,verifying the above theoretical analysis by simulations.In order to make the proposed converter based possess good dynamic response and steady-state characteristics,this paper adopts the state space averaging(SSA)method to establish the small signal model of the whole system.According to the open-loop Bode diagram of the system,the K-factor method is used to compensate the system.With the designed controller,the closed-loop system obtained a good dynamic response.This paper has completed a 200 W principle experimental prototype.When the input voltage varies from 25-45 V,it proposed converter outputs 380 V DC stably at the rated frequency of 100 k Hz.In rated conditions,the efficiency is over 90%,and the closed-loop control experiment verified it possessed a good dynamic response.The experimental results have verified the theoretical analysis and simulation results.