| As great many distributed energy storage devices are connected to the grid,low-voltage DC distribution network technology has gradually attracted people’s attention.As the core devices in the DC distribution network,the DC/DC converter usually consists of multiple isolated dual-port DC/DC converter.However,the multi-port DC/DC converter does not need an additional circuit,because it is connected with multiple DC sources through multi-winding transformers.The isolated three-port bidirectional DC/DC converter with full bridge cells is more widely studied and applied in multi-port isolated DC/DC converters.After including asymmetric CLLC resonant network in the converter,the circuit can achieve good effect in bidirectional wireless power transmission and high conversion efficiency and has the advantages of soft switching.Therefore,the research targets the isolated three-port bidirectional DC/DC converter with the CLLC resonant circuit.Traditional Pulse Frequency Modulation(PFM)does not take into account the effect of the number of resonance on frequency regulation.It is difficult for the range of voltage gain of three-port energy storage units in the DC distribution network to meet the requirements.Thus a hybrid control strategy of PFM+PWM based on an isolated three-port resonant bidirectional DC/DC converter is proposed with a wide range of voltage gain to reduce voltage ripple while stabilizing voltage output and maximize efficiency transmission.Firstly,based on the equivalent circuit of an isolated three-port bidirectional resonant DC/DC converter,the working model of the circuit is analyzed.Secondly,on the basis of the hybrid control strategy proposed in this paper,the output-input transfer function of the isolated three-port bidirectional DC/DC converter the CLLC resonant circuit is derived,and its stability is analyzed with Bode diagram.After that,the waveforms of steady-state response and transient response of the isolated three-port bidirectional DC/DC converter with the CLLC resonant circuit under hybrid control strategy are obtained through simulation,The comparison with traditional PFM and PFM+PS further illustrates the advantages of PFM+PWM control strategy.Finally,on the experimental platform of the SIC MOSFET 3.2kw isolated three-port bidirectional DC/DC converter with the CLLC resonant circuit,Experimental results show that bidirectional DC/DC converter with the CLLC resonant circuit,Experimental results show that the proposed control method is feasible and effective. |
