Characteristic Analysis And Control Strategy Research Of The Three-Port Isolated Bi-directional DC-DC Converter

As the "New Energy + Energy Storage" microgrid development model becomes more and more advanced,isolated multi-port DC-DC converters are gaining attention as energy routers.Isolated three-port bi-directional DC-DC converters are less coupled and have a relatively simple control design,in addition to having flexible energy management and high power density.Therefore,a triple-active-bridge(TAB)isolated bidirectional DC-DC converter is used as a research object to investigate its operating characteristics and to optimize and improve the transient performance of the system.Derive the relationship between the power transferred at the converter ports and the phase shift angle by using the equivalent circuit of the TAB converter and the ideal current-voltage waveform.Six energy transfer modes and 18 conduction states of the TAB converter are determined.A transformer loss model is established.The conditions for the TAB converter to achieve soft switching are also clarified.The open-loop operation mode of the TAB converter is simulated in MATLAB/Simulink.A small-signal model of the TAB converter is developed and the ensuing problem of odd steady-state operating points is analyzed.New control quantities are defined based on the small-signal model and a differential flat controller is designed to optimize the transient performance of the system output.Volatility exists in the PV input on the DC bus side.Therefore,a bus voltage compensation strategy based on model predictive control is designed to stabilize the bus voltage by controlling the output current reference value at the energy storage side.At the same time,the output current reference is used as a differential leveling feedforward control component to optimize the leveling control.Finally,the dynamic performance of the proposed controller,its immunity to parameter perturbations,and its transfer power(within the maximum phase shift angle)under the loss model is compared and verified in MATLAB/Simulink.The results show that the dynamic performance of the TAB converter is significantly improved,with a transfer efficiency of 94.7% under the simulation model.Figure 56;Table 7;Reference 67...