| With the development of power electronics,dc-dc converters have become an important part of electrical systems and equipments,and its reliability requirements are also increasing.To deal with N faults,N redundant circuits are needed in conventional fault-tolerant converter,resulting in high cost and large volume.In order to reduce cost and volume,in this paper proposes an LLC converter is proposed which obtains twice fault-tolerant capabilities by modular redundancy and topology reconfiguration.Firstly,the topology and operation principle of the proposed converter are introduced.The redundant circuit is utilized to keep the whole system working normally after first fault occurrence,and with the two additional diodes,second fault-tolerance is achieved through the auto-reconfiguration of the remaining healthy half-bridge part of original and redundant LLC converters.And its operation process can be divided into 3 modes.The steady-state characteristics shows the voltage and current stress of switches and diodes are not increased after failures,contributing to simplified circuit design.The reliability analysis based on Markov model is also given in this paper.Secondly,small-signal models of the proposed converter in different modes are built by extended describing function and related compensation in feedback control is designed.According to the results,models for different modes are similar,thus only one PI compensation is needed,which help simplify the control design.Thirdly,the scheme of driving signal generation in different mode is put forward to deal with the mode switching process.In the meantime,a soft mode convertion method is used to suppress the voltage and current overshoot.Finally,design process of a prototype is introduced,including system parameter design,power and control circuit design.Meanwhile,the experiment results of steady state operation,load conversion and mode switching are given,which validate the effectiveness of topology and control strategy. |
PDF Full Text Request