Study On High Gain DC-DC Convrter With Coupled Inductor

In recent years,fossil fuels caused by air pollution is more and more serious,so people started looking for new energy to replace it.At present,the application of relatively common and relatively mature technologies of clean energy mainly include:fuel cells,photovoltaic(PV)etc.However,the output voltage of these systems is often low and can not be directly applied to other energy systems.It needs a boost process,which is the DC-DC transform.The conventional Boost converter,which the voltage gain only determined by the duty ratio,so often in order to achieve high gain,had to switch to limit occupied ratio of air,sometimes even close to 1,so that not only increase the turn-on time,also tend to cause greater voltage and the current spike.Switch inductance,switch capacitor and coupling inductance and other new circuit structure emerge at the historic moment,greatly improve the voltage gain of the circuit.Based on the study of quasi Z source circuit,several improved DC-DC converters based on coupled inductors are proposed.In this paper,based on quasi Z source circuit,a new topology structure is proposed by applying the coupling inductance,clamping circuit and voltage doubling unit to the circuit,which is called quasi Z source circuit with coupled inductors.The converter formed by applied the coupling inductor,the voltage doubler capacitor and the clamping circuit to the quasi Z-source converter.The main features of the circuit are: the input inductor current is continuous,and the circuit is common ground structure;the high voltage gain can be achieved with a lower duty cycle,thus avoiding the circuit operating at the extreme duty cycle,and reducing the loss of the circuit;the passive clamp circuit limits the voltage stress of the switch and absorbs the leakage inductance energy.Then,the working principle,voltage and current stress of the circuit are analyzed.Finally,the simulation platform is built by Pspice software to verify the analysis,and build an experimental platform to further verify the feasibility of the analysis of the structure and circuit.Secondly,in order to further improve the voltage gain,the passive clamp structure、the two times voltage unit and the three winding structure are applied to the quasi Z source circuit based on coupled inductor.A series of new topologies are proposed,and the specific static operation process is analyzed.Moreover,the voltage gain of the circuit is analyzed and compared;Then,one of the circuits is taken as an example to analyze the voltage and current stresses of the related components in the circuit;Finally,a simulation model is built to verify the theoretical analysis,and the experimental verification of the circuit is carried out to verify its feasibility.Finally,the closed loop analysis based on sliding mode control is proposed for the quasi Z source circuit based on the coupled inductor.The small signal model of the circuit is obtained by the space averaging method of the clearance state.Then,the transfer function between the output voltage and duty cycle of the circuit is obtained by using Matlab and draw the Bode diagram of the system.The amplitude margin andphase angle margin of the open loop are obtained.Finally,the closed-loop design of the circuit is analyzed.First,the PD correction is used to analyze the system,and it is found that the corrected result is not up to maturity.Therefore,closed loop control is designed for the system by means of the theory of fixed frequency sliding mode.The switching function and the parameters of the sliding surface are calculated.The simulation platform is built by using Matlab software.Adjusting parameters to realize closed-loop control verification theoretical analysis.