Research On PI-Model Predictive Control Of Quasi-Z Source Bidirectional Full-Bridge DC-DC Converters

With the rapid development and progress of society,the demand for energy is increasing day by day,and new energy power generation technology is developing rapidly.As the key to energy management in new energy storage systems,the development of bidirectional DC-DC converters has also received extensive attention.The quasi-Z-source bidirectional full-bridge DC-DC converter studied in this thesis has the advantages of strong boosting ability,simple control method,and high transmission efficiency compared with the traditional bidirectional full-bridge DC-DC converter.In the current research on this topology,PID single-loop control is mainly used.When the input voltage of the system changes in a large range or when the load is increased or decreased,the controller has poor steady-state performance and slower adjustment speed.For this reason,a PI-MPC control strategy was used in this thesis,and used PSO to optimize the objective function of MPC controller,to make the system achieved the goal of stable output and rapid response.This thesis mainly conducted the following research:Firstly,The topology and working principle of the quasi-Z source impedance network and the quasi-Z source bidirectional full-bridge DC-DC converter were introduced.According to the difference of the switch tube conduction conditions of the converter in the three working modes,the PWM modulation mode was determined.Through MATLAB/Simulink,the adopted PWM modulation method was simulated and verified,and the simulation results were consistented with the theoretical analysis.Secondly,the state-space averaging method was used to establish the mathematical model of the system and derived various transfer functions.Considering the influence of the inductance and capacitance parameters on the stability of the system,a small signal analysis was carried out.According to the design requirements of the MPC controller,the obtained inductor current transfer function was discretized,and the current prediction model of the converter was derived.Thirdly,The double closed-loop control logic based on the average current control method and three controllers were designed.First,PI double closed-loop controllers were designed using PI control for both the inner and outer loops,and then the inner loop used MPC to obtain the PI-current MPC controller,and the simulation models were respectively built for steady-state simulation.The results show that PI-current MPC control had a faster response speed and a smaller overshoot,but the output fluctuated significantly before stabilization.Therefore,the PSO algorithm was used to optimize the objective function of the MPC controller,and the PI-PSO-based current MPC controller was obtained.It was verified by simulation that the use of this controller can further improve the output characteristics of the system.Finally,The PI-PSO-based current MPC controller was used to control the system,and the input voltage range is large and the input or load sudden change is simulated,and the overall system plan and the design of the controller's software and hardware were completed.Simulation results showed that the use of the controller can make the system have good dynamic and static performance,stable output and rapid response even when the input and load change suddenly.