Design And Electromagnetic Characteristics Analysis Of Superconducting Mobile Emergency Transformer With Air Gap Cor

With the increasing demand for power supply security and the requirement for uninterrupted power supply hours,especially in special situations such as maintenance,emergency power supply,and temporary backup power supply,the use of mobile substations for rapid power supply emergency deployment is an ideal technical solution.However,under the current technological framework,it is very difficult to significantly increase the capacity of mobile transformers due to limitations in road transportation conditions.Therefore,applying superconducting technology to transformer coils is undoubtedly a better choice.Although the large current-carrying capacity of superconducting windings results in a reduction in volume and weight compared to copper windings,a large portion of the transformer’s weight still comes from the iron core.Therefore,the idea of using partially iron core design for superconducting transformers has gradually come into researchers’ view.However,a partially iron core or hollow design may result in significant no-load losses,which is not economical for transformers that are hanging on the grid for a long time.To address these challenges,this article proposes a technical solution that combines mobile transformers with high-temperature superconducting technology.By combining the characteristics of mobile emergency transformers without the need for long-term hanging on the grid,the efficiency loss of partially iron cores and the need for complex low-temperature systems for superconducting equipment are no longer contradictory and can be tolerated.The lightweight characteristics of the newly designed iron core and coil can break through road transportation bottlenecks,and the advantages of superconducting transformers can be raised to new heights.In this study,firstly,based on the current research status of high temperature superconducting transformers,as well as the principle,structure and characteristics,a lightweight emergency mobile superconducting power transformer with an air gap core which capacity is 40 MVA designed and its basic parameters are determined.Compared with the conventional transformer,the weight of the core column is reduced by about 25% due to the presence of the air gap in the core column,in addition to the reduction in the weight of the winding as well as the volume.Secondly,finite element method is used to model and analyze high-temperature superconducting tapes.The article uses the H-method with fewer variables,faster iteration speed,and higher convergence to perform simulation analysis,and expands the H-equation in the 2D model.Based on the H-method,the model of a single YBCO superconducting tape is established using the mfh in large finite element software AC/DC module to quickly apply the superconducting E-J characteristic,providing a modeling foundation for subsequent chapters.Next,using the modeling method of a single tape,a 2D model of a high-temperature superconducting double pancake coil is established,and the magnetic flux distribution maps of three-turn and six-turn high-temperature superconducting double pancake coils are compared.Simulation results show that the modulus of the magnetic flux density at both ends of both the single tape and the double pancake coil is larger than that in the middle.Moreover,due to the close relationship between AC losses and magnetic flux distribution,the AC losses at the ends are also larger.After that,based on the double pancake coil model,an optimization model for the distance between superconducting windings and iron core is established,and three groups of models are established where the superconducting windings are inserted into the air gap,the superconducting windings are flush with the upper and lower iron cores of the air gap,and the superconducting windings are away from the air gap.Simulation results show that the strong magnetic field is located inside the air gap,at both ends of the winding,and at the edge of the iron.When the injected current exceeds the critical current,the superconducting coil quench leading to an exponential increase in losses.