Research On The Three-port Power Converter Based On Digital Control

The three-port converter has played an more and more important role in many fields,such as photovoltaic system,aerospace system,automobile electronics and so on.The three-port converter is usually used to connect voltage source or current source,battery and load,and to manage the power uniformly.However,most three-port topologies tend to have complex circuit structure,without effective battery charging circuit and high efficiency.In addition,traditional analog power supplies typically use many analog devices,resulting in large system dispersion and poor stability.At the same time,the control mode is single,and the design lacks flexibility,which is not easy to modify and debug.A new kind of three-port converter and a multi-mode,multi-frequency control strategy is proposed in this dissertation.The flexible loop control is achieved through digital control,which solves the problem that the control logic of the switch is complicated and the competition of the loop is nested.This allows any flow of energy at any port with a wide range of input/output voltage ratios.On this basis,by optimizing the duty cycle distribution and the control loop,the mode switching is more smooth and stable.Against disadvantages of general three port converter,a new type of three-port topology is studied in this dissertation.This topology not only has the advantages of simple structure and high efficiency,but also enables arbitrary flow of energy between multiple ports.By discussing the working state of the converter in stages,the working principle of the converter is studied.Use the state space method to establish a small signal model,and then bring the parameters of the actual circuit into the model for numerical solution analysis.After obtaining the transfer function of the output volt age of each port to the duty cycle,stability analysis and compensator design are performed.In order to make the control more flexible,the digital control method is applied and the modulation method of 13 modes is given.By simulation and analysis of the duty ratio distribution,the modulation parameters and control loop are optimized to make the mode switch more smooth and stable.At the same time,the realization of soft switch and the modular architecture are discussed.The key issues of digital control are analyzed,including the limit cycle oscillation,A/D sampling error,intrinsic time delay and so on.The control effects of the three discrete methods are compared through experiments,and the optimal control method is selected to design the system software.At the same time,the digital soft start program is designed,which can suppress the surge current without adding any new elements in the circuit.The physical system is built for debugging and experimentation.Through experiments,the energy flow that in any direction between ports and a wide range of input/output voltage ratios can be verified.Through the mode switching experiment,the given control strategy flexibility can be verified.By comparing the mode switching process before and after op timization,the effectiveness of the loop takeover can be verified.Finally,the stability of the system can be verified by carrying out load experiments.