Fault Analysis And Current Limiting Method On Output Side Of Electronic Power Transformer

With the in-depth transformation of the world's energy structure in recent years,the development of the modern power industry is becoming more green,intelligent and sustainable,while the smart grid can adapt to various types of clean energy,such as flexible access and a series of adjustments to the peaks.The advantages can realize the diverse needs of users,thus become the key of change.Electronic Power Transformer is known as EPT,has good controllability,and can provide AC and DC ports,which can also facilitate the access of various AC-DC distributed power sources and overcome the weight and volume of traditional transformers,which have disadvantages such as excessive no-load loss,so EPT is indispensable for the construction of smart grids.The EPT is located in a key position in the smart grid,so its safe and stable operation is of vital importance to the grid.This thesis firstly elaborates the background and research status of EPT and its fault protection.The topology and control of the EPT system are compared and selected,and the different topological structures of the input stage,the high-frequency isolation stage,and the output stage are also compared and analyzed.The topological structure is established the mathematical model,and selects the corresponding control strategy to obtain the good performance.Then several types of faults on the output side of the EPT are analyzed,such as device faults,port faults and so on,and it focus on the simulation of the short-circuit fault on the output side.Then seven typical faults are simulated through the MATLAB simulation software.Finally,the effect of each fault on EPT by simulating waveforms can be observed.Then several existing current-limiting protection measures are analyzed and the concept of solid-state current limiter in the EPT is introduced.The background and research status of solid-state current limiter are briefly introduced,and its basic principle is analyzed.Then circuit topology and control strategy used in this thesis are proposed.Comparing and analyzing several commonly used current-limiting protection measures and solid-state current limiters at the time of faults,the two typical faults of single-phase grounding short circuit and two-phase phase-to-phase short-circuit are selected and simulated in MATLAB to verify the solid-state current limiter.Compared with the traditional current limiting measures,the solid-state current limiter has good dynamic characteristics and can maintain a good voltage output at the event of a fault.