Study And Application Of Non-electrolytic Capacitor DC-DC Converters

Electrolytic capacitor is one of the most important components in DC-DC converters.However,drawbacks of electrolytic capacitors,i.e.,short life and large volume,hinder their development.To solve these problems,there are two solutions,i.e.,one is to monitor capacitor features and replace if it is failed;the other one is to replace electrolytic capacitors with non-electrolytic capacitors.The former one is with very complicated process and high economic cost;while the latter one can only be used for low frequency alternative current output converters.Moreover,both methods can only detect or remove some electrolytic capacitors in a converter,they cannot remove all of them.Thus,both methods are difficult to be applied in DC-DC converters,since DC-DC converters are with large number of capacitors and high switching frequency.To well solve above problems,study of non-electrolytic capacitors DC-DC converters is conducted in this dissertation.1.From the perspective of energy storage and filtering,capacitors are divided into two kinds,i.e.,energy storage capacitors and filter capacitors.Then,mathematical models of energy storage capacitor and filter capacitor redundant value are built up.Finally,electrolytic capacitors elimination of DC-DC converters are fully realized.2.Elimination of energy storage capacitor: The traditional capacitor design method of energy storage capacitors is derived by its voltage ripple,however,energy storage capacitor is insensitive to voltage ripple.Thus,the energy storage capacitance derivation by this method is redundant.In order to solve this problem,a redundant capacitance mathematical model is developed based on the energy storage requirement of capacitor,and a non-electrolytic capacitor with small capacitance is used to replace the electrolytic capacitor with large capacitance.3.Elimination of filter capacitor: Filter capacitor is sensitive to voltage ripple and it is with strict voltage ripple requirements.Thus,its capacitance cannot be calculated by the same method as energy storage one.In this dissertation,three filter electrolytic capacitor elimination methods are proposed from two aspects,i.e.,topology and control respectively.For topology,passive filter network method and modular-based phase shift and superposition method are presented;For control,waveform compensation method is presented.4.Based on the above proposed methods,several typical non-electrolytic capacitor DC-DC converters with experimental prototypes are built up to verify the proposed methods.All experiments well agree with the theoretical results.The contributions of this dissertation are listed as follows,i.e.,the classification of energy storage capacitor and filter capacitor are proposed in terms of sensitivities of voltage ripples;their redundant capacitance models ars developed respectively to eliminate electrolytic capacitors and three filter electrolytic capacitor elimination methods are proposed from topology and control aspects,which is significance in both engineering and academic.This method can also be applied in other types of power electronic converters.The proposal of this dissertation can be a new thought and solution for design and applications non-electrolytic capacitor power electronic converters.