Research On Tapped Inductor Based High Gain DC/DC Topology And Mod- Eling

The DC grid technology is one of the key elements to smart grid research. The variety and unstability of microgrid elements pose new demands on the power electronics equipments and thus greatly promote the development of contemporary power electronics technology. Since the alternative sources such as the solar panel, fuel cells and most of the energy storage equipment like batteries and super capacitors generate relatively low dc voltage, while the dc bus requires high dc voltages (typically 380 V), a request of high gain, high efficiency, low input current ripple and low cost DC/DC converter is arised. The tapped/coupled inductor is a popular solution for these applicaions by offering simple circuit and low part count. However, the complexity of these topologies and inherent leakage inductance of tapped inductor pose great chanllenge on analysis, modeling and control of such kind of DC/DC. The main content of this dissertation is given as followed.1. Detailed review of high step-up TI-based (tapped inductor) converter has been present-ed. Accordingly a group of general TI-converter construction methods are summarized which helps to understand and derive new high gain TI topologies. Furthermore a new family of Sepic derived converter topologies suited for alternative energy generation applications is proposed. To optimize the component parameters, State Plane Analysis method has been used for stress analysis and parameter design guidelines are obtained accordingly.Theoretical ex-pectations were confirmed by simulation and experimental results.2. A new TI-based bidirectional DC/DC converter equipped with active lossless snubber is proposed in this research which has low part count, high voltage gain, simple control scheme, and high efficiency. Detailed principle of operation and steady-steady analyses has been pre-sented, while the performance of the proposed converter has been verified by simulations and experiments in this dissertation.3. Based on the research on topology, the dynamic modeling of DC/DC converter is stud-ied and a new unified modeling method for PWM DC/DC converter, TIS-SFG, has been pro-posed. The proposed three terminal switcher (TIS) encountered in regular and tapped inductor converters can be regarded as an invariant block of most PWM converters, which is a non-linear and time varying network and hence presents the primary modeling challenge. Once derived, the rest of the power stage is just a linear circuit. Therefore the switcher equiv-alent model can be embedded into the flow graph of the problem converter regardless of its topology and help obtain a complete averaging flow graph model of any PWM converter. To verify the proposed TIS-SFG method, several examples were presented. The results obtained by TIS-SFG model were identical to simulation and earlier theoretical results.4. To further study the application of the unified TIS-SFG methods, two more complicated examples, TI-CP-Boost and TI Sepic have been studied. The TI-CP-Boost topology is consti-tutive of a charge pump cell and a Boost derived TI (tapped inductor) converter. By using the unified TIS-SFG modeling method, the model of the TI-CP-Boost converter can be obtained by a nonlinear TIS module model connected with a linear network of CP (charge pump) mod-el. Since the TIS module is prefabricated, it is easy to derive the model of the TI-CP-Boost topology. For the TI-Sepic topology which can be deconstructed into a Boost converter inter-leaved with a TI-Boost converter. Thus the model of TI-Sepic can be descripted as two TIS modules connected through a linear network. The modeling results have been verified by simulations. These examples further demonstrate the versability of the proposed unified TIS-SFG modeling methods.5. Finally, a close loop control (DSP) test bed of bi-directional DC/DC is built which es-tablished the foundation for future research work. The preliminary experiment results of the TI-CP-Sepic converter are presented.In this research, the tapped inductor based high gain DC/DC topology has been well stud-ied. A new family of high step-up DC/DC converter and a bidirectional DC/DC converter with soft-switching performance has been proposed. Based on the research on topology, a new unified modeling method for PWM DC/DC converter, TIS-SFG, has been proposed.this method emerges as a viable analysis tool that greatly alleviates the analytical effort and con-siderably simplifies the task of dynamic modeling of switching converters.