Research On Multiple Input High Step-up DC/DC Converter

As one of the renewable energy sources for solving the fossil energy crisis,photovoltaic(PV)power generation has been developed rapidly in recent years and is expected to become one of several major power generation modes by the middle of the 21 st century.However,typical output voltage range from a single PV panel is about 24 to 48 V dc.while the voltage of dc bus is 380V-760 V.At this time,the traditional boost converter has been difficult to be applied to PV power generation systems due to low input-output voltage gain,low converter efficiency and high device stress.In this context,a large number of high-voltage-gain DC/DC converters have been proposed in recent years.Compared to traditional boost converters,they have the advantage of high input-output voltage gain,but the existing solutions are single-input converters mostly.which has the disadvantages of high cost and low economic efficiency,because every single PV panel required a converter.Therefore,multi-input high-voltage-gain DC/DC converters have received much attention in view of power generation costs and power generation efficiency.This paper proposes two kinds of dual-input zero-voltage turn-off(ZVT)high-voltage-gain DC/DC converters.The main contents of the paper are as follows:Firstly,the background of multi-input high-voltage-gain DC/DC converters are introduced briefly,and the research status of multi-input high-voltage-gain DC/DC converter is analyzed.Based on this analysis,two kinds of dual-input ZVT high-voltage-gain DC/DC are derived.through theoretical analysis,simulation model and experimental prototype,the converter shows that the two kinds of dual-input ZVT high-voltage-gain DC/DC converters have low voltage stress,controllable input-output voltage gain,simple control and low cost.At the same time,according to the analysis of performance characteristics,the output capacitor of the first converter is composed of two series capacitors and the voltage are equalized,therefore,there is an advantage in grid connection through a half bridge circuit.In the second converter,the voltages of all the voltage multiplier(VM)units are equal,which has an advantage in reducing the cost.Then,the general-purpose reduced-order model construction method for high-voltage-gain DC/DC converter based on VM unit is analyzed in this paper.It takes a high step-up DC/DC converter as an example.First of all,the equivalent linearized small-signal model of the converter is established,and the transfer function is introduced.By comparing the theoretical simulation and physical simulation of the transfer function in PSIM,the accuracy of the proposed method is proved,then the controller was designed,finally the simulation verification and closed-loop dynamic test were carried out.The simulation and experimental results verified the stability and dynamic response speed of the proposed converter.In addition,in order to promote the proposed generalized reduced-order model construction method,the reduced-order model parameters of different converters based on VM units are calculated.Finally,the two kinds of dual-input ZVT high-voltage-gain DC/DC converters mentioned in this paper are compared with other common solutions in the literature for performance,component usage,and economic benefits.