Research On Charging Pile Based On T-type Three-level Electric Vehicle

Arising from the research status at home and abroad,this paper discusses the importance and technical issues of the current promotion of electric vehicles,and leads the content of this paper—the charging system of electric vehicles.With the development of battery materials and technologies,electric vehicles will require higher power output charging piles in the future.For this reason,a new topology converter—T-type three-level converter—is introduced in this paper.Electric vehicle charging and discharging systems have medium or large power output.First,the charger is a DC type output in this paper.Referring to the structure of two-level converter in the past,T-type topological three-level converter and half-bridge DC/DC converter were proposed.Regarding the control technology of the T-type three-level converter,the traditional method is the double-loop PI control.This control structure is simple,but the anti-interference is poor,and the PI parameter calculation is too much trouble.To this degree,a new intelligent control algorithm is introduced—Model Predictive Control(MPC),this algorithm is the transformation of the current inner loop in the double-loop PI control strategy.It can also be called model predictive current control.Regarding the half-bridge DC/DC converter,according to the characteristics of the existing charging mode,the constant current and constant voltage control modes under double-loop control are selected.Secondly,detailed researches on T-type three-level converter and two-way half-bridge DC/DC converter are carried out in this paper.Their working principles,mathematical models,control strategies,and modulation strategies are respectively introduced.And the simulations were respectively built on a MATLAB 2017 a environment at last.In the simulation,the system output effects of the T-type three-level converter under double-loop PI control and model predictive control are first compared.After comparing,it is found that the traditional double-loop PI control has poor anti-interference ability,and it is parallel to the load side.Capacitor pressure equalization control is not as good as predictive control;however,predictive control also has its own drawbacks,and harmonic components are more complex.In addition,the simulation of the bi-directional half-bridge DC/DC converter under constant current and constant voltage charging is also introduced.The simulation results show that such a charging mode can be well implemented.Finally,the overall simulation of the pre-stage T-type three-level rectifier circuit and the post-stage half-bridge DC/DC buck circuit were integrated in this paper.In order to make the system output Satisfy with the set technical standards,the main circuit parameters under both control strategies are modified,and finally to achieve the system's constant voltage charging.Because the parameters are inconsistent,there is no way to make a comparison,however,the predictive control has a better effect on the voltage-sharing control of the capacitors.The system power factor under the double-loop PI control can be 1,So different methods have their own advantages,and the specific application can be selected according to the specific situation.