| As an important part of DC power supply network,DC/DC converters can combine with communication technology and realize information transmission between converters by using communication technologies,which can distribute and control the energy of each node in power supply network reasonably.As a result,it can greatly improve power supply efficiency and reliability of systems.Based on traditional cascaded converters,this paper studies power/signal synchronous transmission(PSST)strategies in DC/DC cascaded converters by adopting different modulation methods.Firstly,a PSST system based on bifurcation of converters is constructed by using the characteristic of output voltage ripple variation when bifurcation occurs.After dealing with model equivalently,the state equation and discrete iteration model of system are deduced separately,and the control parameters for signal transmission are determined by taking voltage ripple and bifurcation diagram of inductance current and output voltage into consideration.After finishing the design of demodulation circuit,the feasibility of PSST function is verified by simulation and experiment.Secondly,in order to improve the dynamic response of system,a cascaded converters PSST system based on pulse train(PT)control is designed by introducing capacitor current pulse train(CC-PT)control.The working principle of PT controlled cascaded converter is analyzed and studied.The causes and suppression methods of low frequency oscillation are discussed.The signal transmission parameters and threshold are also determined.PSST between converters is completed and realized by software simulation and experiment,which verifies the correctness of theoretical analysis.Then,in order to improve the reliability and anti-jamming ability of PSST system,frequency modulation technology is introduced,and some key problems in frequency modulation mode of converters are analyzed in detail.In addition,the demodulation principle of zero-crossing comparison method is introduced and the threshold in modulation link is deduced.The feasibility and correctness of PSST based on zero-crossing comparison method are verified by simulation and experiment.Relevant test results show that this method can satisfy PSST well and is less affected by system noise.Finally,in order to further improve the anti-jamming ability of system and reduce the requirement for switching frequency,a PSST strategy based on direct sequence spread spectrum(DSSS)by using frequency shift keying(FSK)technology(DSSS-2FSK PSST)is studied.Basic concepts and characteristics of pseudo random code and correlation function are introduced.The modulation and demodulation mode of DSSS are introduced into cascaded converters.The modulation and demodulation process of system are described in detail.At the same time,the influence of carrier phase delay angle on signal demodulation process is analyzed,and the input capacitance ripple on load side of converters is deduced.Through simulation and experiment,the correctness and feasibility of DSSS-2FSK PSST are verified,and the advantages and disadvantages of this method are summarized. |
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