The Research On Power Electronic Transformer With Supercapacitors Energy Storage System

In modern power systems,with the types of loads increase and the form of power supplies changes,the demand for power supply reliability is increasing.Power Electronic Transformer is an emerging power conversion device in recent years.It has revolutionized the traditional transformer and has the ability to cope with some voltage interruption and voltage drop in modern power grid systems.However,since the Power Electronic Transformer itself does not contain a device for storing electrical energy,there is no way to interrupt or drop of the voltage in the power grid.In order to solve the phenomenon that the Power Electronic Transformer can't resist the grid voltage interruption and drop,this thesis combines the super capacitor and the Power Electronic Transformer to study,so that the Power Electronic Transformer has the ability to resist the grid voltage interruption and drop,so that all types of electrical equipment in the power grid can operate safely,efficiently and stably.This thesis first expounds the definition,development process and domestic research status of the Power Electronic Transformer,and summarizes the research on the use of Super capacitors on the Power Electronic Transformer.After a more comprehensive analysis of the working principle of Power Electronic Transformer,according to its working principle,the topology of AC/AC type and AC/DC/AC type Power Electronic Transformer is studied.Then,according to the specific use scenario,a three-phase four-wire Power Electronic Transformer is selected as the type of transformer used in the system.The Super capacitor and the Power Electronic Transformer are connected to each other through a bidirectional DC/DC converter to form a novel energy storage type Power Electronic Transformer system.Based on the research of the Power Electronic Transformer topology,this thesis analyzes the mathematical model of three-phase four-wire Power Electronic Transformer and Super capacitor,and discusses the input stage,intermediate isolation stage and output stage of the Power Electronic Transformer.Super capacitor control strategy.The main parameters of the main circuit of the Power Electronic Transformer and the Super capacitor were designed.Finally,the Power Electronic Transformer without Super capacitor and the Power Electronic Transformer simulation experiment with Super capacitor were established in MATLAB/Simulink software.Through the simulation of five conditions of full load operation,voltage interruption and drop state without Super capacitor compensation and Super capacitor compensation,it is proved that the Power Electronic Transformer containing Super capacitor as electric energy storage device can be interrupted and dropped in voltage.Under the circumstances,the normal operation of the power grid is still ensured,so that the Power Electronic Transformer with the Super capacitor as the energy storage link has the ability to resist voltage interruption and drop,and improves the reliability of the power supply.