Research On Control Strategy Of Power Electronic Transformer

Power electronic transformer is a new transformer that can combine the power electronic transform technology and the high frequency electric energy conversion technology.Compared with the traditional transformer,it can not only realize basic roles,such as the transformation of traditional transformer voltage grade and electrical isolation,but also has small volume and weight.In addition,it can provide effective control for the former vice edge to transformer voltage phase and amplitude,By doing so,it can inhibit the fault and the flow of harmonic.Will power electronic transformer applied in power system can guarantee the quality of electric energy,at the same time it makes the system controllability for promotion,what's more,it is helpful for distributed power grid,and in accordance with the smart grid construction.So the power electronic transformer has important significance both in theory and practical application.This paper first introduces the principle of electric transformer and some classical topological structures,next then have a research of AC/DC/AC type power electronic transformer particularly,and the control strategies for input,isolation,and output levels are also studied.The input stage uses a voltage current dual closed-loop control of the feed forward decoupling,at the same time,the isolation stage uses open-loop control directly,and the output stage uses the voltage closed loop control.In order to accelerate the dynamic response speed and cater to occasions requiring fast dynamic response,this paper applied predict direct power control into the input stage of power electronic transformer,besides,combine with space vector pulse width modulation(SVPWM)in order to fixed switching frequency.Apart from,improved predict direct power control to eliminates the steady-state error and can adapt to higher requirements.A simulation model is built for the input stage,isolation stage and output stage of power electronic transformer by Matlab/Simulink,moreover,the input stage uses double closed loop decoupling control and improved predictive direct power control,and have a simulation of the whole of a power electronic transformer under different working conditions.Finally,having a design of the hardware and the software of a power electronic transformer system,what's more,an experimental platform is built.The simulation and experimental results demonstrate the advantages of power electronic transformer,the feasibility of direct power control strategy is applied to power electronic transformer and the correctness of the control strategy in other links.