Research On Power Electronic Transformer And Its Control Strategy

The shortcomings of the traditional transformers currently in use are becoming more obvious.For example,the relatively large size has shown that it is insufficient to apply it to equipment with high space requirements,high no-load losses,and single function.Excitation inrush current will also pollute the power grid.With the rapid development of power electronic technology,the power electronic transformer PET came into being.As an important supporting device of the smart grid,it has unique advantages that traditional transformers do not have,so it has good development advantages.The power electronic transformer not only has the functions of traditional transformer voltage conversion and energy transfer,but also has the function of effectively controlling the voltage amplitude and phase of the primary and secondary sides of the transformer.And can be interconnected with various AC and DC distributed power supplies.It meets the needs of future power grid construction,therefore,it is necessary to carry out in-depth research.In view of this,this paper will focus on ensuring that the input voltage and current at the high-voltage AC side of the input link are in phase,the unit power factor operation,improving the output voltage and current stability and response speed at the low-voltage AC side of the output link to design the overall implementation plan,and establish a reasonable and effective control strategy direction for research.First of all,the background significance and research status of power electronic transformer are summarized in detail,and its basic working principle is analyzed in depth.Several typical topological structures of power electronic transformer are analyzed and compared,and the general equivalent mathematical model of voltage source converter and power electronic transformer is established.Secondly,the input link,isolation link and output link of the power electronic transformer are modeled respectively,and the control methods of each link are analyzed in detail,and the voltage and current control strategies of the input link are established;the control technology of the virtual synchronous generator used in the output link is discussed in depth,and the research status of the control technology of the virtual synchronous generator is summarized In this paper,the mathematical model of synchronous generator is built,and the double loop control strategy of outer loop active frequency and reactive voltage,inner loop voltage and current control based on virtual synchronous generator technology is established.Finally,the simulation model of power electronic transformer system is built in Matlab/Simulink simulation environment,and the simulation analysis is carried out for the steady-state environment of resistance inductive load and the dynamic environment of load sudden change,aiming at the results of input voltage,phase and power factor of current,output link output voltage,current stability,response speed,harmonic content,power factor and so on Line analysis verifies the rationality of the overall scheme of power electronic transformer and the effectiveness of the control strategy.The research work of this paper can provide valuable reference for the development of key technologies of power electronic transformer.