Development of a phase-shifted series-resonant converter using robust control and integrated magnetics

Abstract

Phase-shifted series resonant converter is widely used in handling high power in DC/DC converter series due to its inherent characteristics including high power density, soft-switching and high part load efficiency. However, the classical control and considerable amount of magnetic components in the circuit is not good enough for a high performance application. A high frequency robust controlled integrated magnetics converter is needed. Integrated magnetics has the advantage of incorporating magnetic components, such as transformers and inductors, into a single core and consequently the total volume, weight and cost are reduced. In this dissertation the magnetic components used in the phase-shifted series resonant converter including the resonant inductor, the transformer and the filter inductor were proposed to integrate into a single EE core. One leg of the EE core is air-gapped on which a winding is wound as the filter inductor. The resonant inductor and the transformer are connected in series and they are wound on each of the other two legs. The flux through the air-gapped leg of proposed integrated magnetic devices is designed to exhibit the leakage flux which can be easily controlled. Thus the inductance of the resonant inductor can be regulated and the integrated magnetic device is developed. The equations of calculating electrical parameters of the integrated magnetic are deduced using duality theorem. The analysis of the resonant tank of the converter is based on a fundamental approximation. The model of the converter is simplified by making use of the difference in the bandwidth of the resonant tank and the filter tank. The work is to improve the parameters variation of the power converter such that the input voltage and the load resistances under variation of environmental condition and operation condition should be robustly controlled. Firstly the methodology of constructing an auto-disturbance-rejection controller (ADRC) was discussed. All the disturbances could be estimated by an extended-state-observer (ESO), which is the core of the ADRC. Accurate mode and precise parameters are not necessary. An ADRC has been implemented on a PSRC with a single capacitor output filter. Experiments show ADRC can overcome the problems caused by these disturbances. However, the ADRC is difficult to be applied to high-order systems, as there are many parameters needed to be regulated. Passivity-based Control (PBC) is investigated in order to work against disturbances. A procedure of design PBC controller has been presented. The attractive features of this approach are the enhanced robustness and the lack of controller calculation singularities. Based on the reduced model, the PBC controller and its adaptive version have been derived with which the load resistance can be estimated. Thus the robustness of the closed-loop system based on PBC is ensured in spite of the wide range of variation in load resistance. Only the feedback of output voltage is required to implement the PBC algorithm. The PBC algorithm deduced has been simulated using MATLAB SIMULINK and implemented on a DSP system. Experiments and simulations up to 1.4kW under disturbances have been carried out and successful results are obtained. It illustrates the advantages of the proposed control methodology.