Research On Three-phase Staggered Parallel Bidirectional DC/DC Converter Based On Sliding Mode Control

In recent years,with the output power of power supply increased,the interleaving parallel technology is introduced in DC/DC converter to reduce the ripple of output voltage and the volume of converter.Meanwhile,the power load characteristics appeared diversified,unpredictable and nonlinear.The effect of traditional linear control strategy thus not guaranteed.Besides,the required regulation performance,dynamic response and stability of the converter cannot be ensured.To improve the performance of the converter,many scholars have studied nonlinear control strategies such as fuzzy control,adaptive control,artificial neural network control,single-cycle control,and sliding-mode control etc..Among these control methods,sliding-mode control can effectively improve the dynamic performance,regulation performance and robustness of DC/DC converters.In this paper,the three-phase interleaved parallel bidirectional DC/DC converter was studied based on sliding-mode control.The main research work including the following three parts:(1)Elaboration of the background and significance of this research,summarization of the current situation of the converter control strategy.And also the research status expoundation on the application of sliding mode control in DC/DC converters at home and abroad.The Buck and Boost working mode principles of three-phase interleaved parallel bidirectional DC/DC converters were analyzed.After then,the theoretical basis for the small ripple of three-phase interleaved parallel converters was provided.The Boost mode and Buck mode mathematical models of interleaved parallel bidirectional DC/DC converters were established at the same time.Finally,calculation were carried out on the component parameters of the main circuit according to the performance indicators of the converters.(2)Several solutions were provided to the problems existing in sliding-mode control of dithering after introduction of the sliding-mode control principle.The fixed frequency sliding-mode control controller was designed respectively according to the mathematical model of Buck and Boost mode.The digital simulation model of Buck and Boost mode was built in Simulink before simulation of the possible input back-voltage,overload,light load and other operating conditions of the circuit.The simulation results showed that the converter system could quickly adjust and return to the preset output state.It could effectively eliminate the steady-state error of inductance current,which improved the practicability of sliding-mode control and verified the feasibility of the control strategy.(3)Hardware design of three-phase interleaved parallel bidirectional DC/DC converter,including the main controller selecting,current and voltage sampling circuit,driving circuit,protection circuit,etc.The software design was based on PI sliding mode control strategy,which mainly includes main program,AD sampling program,protection program,PWM generation program,etc.Finally,we built an experimental platform to simulate the actual operating conditions of converter such as undervoltage,light load,and overload.The experimental results were basically consistent with the simulation results,which further proved that the three-phase interleaved parallel bidirectional DC/DC converter based on sliding-mode structure control had good steady-state and dynamic performance.It verified the effectiveness of the design.