Analysis And Design Of DC-DC Power Converters Based On Impedance Modulation

With the development and application of power electronic converters,DC-DC converters play an important role in many applications like renewable energy power generation,electric vehicles,and electrochemical industries.However,the emergence of most existing converters depends on the designers’ inspiration and experience.In order to systematically design a converter,scholars have proposed many converter design methods in recent years,e.g.,basic cells method,graph theory method,and TRIZ theory.Nevertheless,they are still with some limitations that they are not systematic and cannot be widely applied.Moreover,scholars only pay attentions to the performance without considering the impact of the load on the converters.Aiming at solving above problems,main contributions of this dissertation can be listed as follow.(1)Based on Telligent’s Theorem and Two-Port network,novel concepts of impedance strengthening,impedance weakening(ISW)and dynamic voltage gain are proposed in this dissertation,which can be used to describe the essential reasons why the converters can realize boost/buck functions.In addition,the various effects of different loads on the voltage gain are pointed out,and a novel converter design method based on ISW is then proposed.(2)Based on the proposed converter design method,filter capacitors are analyzed to reduce capacitor voltages via realizing impedance weakening.Therefore,a novel extendable single-switch n-cell boost converter(ESSn B)which bears lower voltage stresses for buffer capacitors is proposed.The proposed ESSn B,with high scalability,small volume and low cost,has thus demonstrated its applicability and implementability for industrial applications such as photovoltaic power generation.(3)According to the proposed converter design method,a family of Y-source impedance strengthening networks is proposed and then applied to the conventional half-bridge inverter,which effectively reduces the equivalent input impedance.With the proposed Y-source impedance strengthening network,the inherent shoot-through problem of the conventional half-bridge converter can be avoided.Besides,the proposed converter is with wide output voltage range by adjusting the impedance strengthening network and duty cycle.Conclude that the proposed converters satisfy the wide output voltage requirements of industrial applications such as electroplating.(4)Based on the proposed converter design method,the impedance of different characteristic loads is modulated for impedance strengthening,thereby increasing the voltage gain.Specifically,the converters for capacitive load should be modulated to be inductive;the converters for inductive load should be modulated to be capacitive;the converter for resistive load should be modulated to be resistive.In this dissertation,resistive load is taken as an example,an additional capacitor and diode is added to the existing inductive converter for impedance modulation,which effectively improve the power density and efficiency of the converter.It is applicable for industrial applications that require small volume,such as electric vehicles.The creativity of this dissertation is to redefine the concept of voltage gain from the perspective of impedance strengthening and weakening,and then analyze the boost/buck function of existing converters.Furthermore,a novel converter design method is proposed,which promotes the systematization of converter design to a certain extent.Conclude that the proposal of this dissertation has both good theoretical and industrial application meanings.