Research On Control Strategies Of Phase-shifted Series Resonant High-voltage Capacitor Charging Power Supply

With the development of science and technology, pulsed power technology plays animportant role not only in military and scientific research field but also in the field ofenergy，flue gas purification, environmental science, medical and bio-engineering. As themost common form of the energy storage unit, it is particularly important to study the mostsuitable topology and control strategy for charging high voltage capacitor.The Series Resonant Converter is the most commonly used converter topology forcapacitor charging power supply. When operated in discontinue mode, it exhibits manyadvantages such as zero voltage switching, easy to control, the characteristics of constantcurrent source, strong anti-short-circuit capability, etc. The wide excursion of switchingfrequency when catering for a wide range of charging current makes the optimal design ofmagnetic components and filters somewhat difficult and increase magnetic core losses andnoise. Working in the DCM also has many disadvantages such as increased peak current ofresonant current and difficult to increase the power.In order overcome these problems, this thesis studies The Series Resonant Convertercontrolled by the operating frequency fixed but varying the duty cycle. Such an SRC iscalled the Phase Shifted Series Resonant Converter (PS-SRC). It possesses all theadvantages of the classical SRC in addition to fixed frequency and light load operationcapability. Therefore, the PS-SRC is well suited for capacitor charging application.This thesis studies the PS-SRC for use in capacitor charging power supply.Completesteady state analysis of the converter for operation above the resonant frequency ispresented. Three different operating modes are identified and the representative equationsderived. The ideal analysis results which are derived through numerical simulation are usedto identify favorable operating points and their boundaries. In particular, the high voltagetransformer parasites affect the normal operation of the converter; often pushing theoperation into unfavorable operating modes. Their effects on the operating mode2areanalyzed.Analysis of the implementation mechanism of the soft-switching of PS-SRC is done byconsidering Commutation process. Though a suitable operating point facilitating ZVS canbe chosen for a fixed load, ZVS is invariably lost for a changing load. The ZVS range ofthe PS-SRC is studied and a new circuit to considerably extend the ZVS range is introduced. Design relations for the new circuit are given.Due to the difficulty of establishing accurate mathematical model of the PS-SRC andthe fact that capacitor charging power supply is a large inertial system, this thesis studiestwo kinds of control strategies including output voltage feedforward control and fuzzycontrol, and designs controllers respectively. The simulation and comparison of two controlstrategies are done.Finally, the relevant parameter of the power supply is designed and the relatedexperiments are carried out on a prototype. The experimental results validate thecorrectness and availability of the design.