The Calculation Of Magnetic And Temperature Field In New Type Of Photovoltaic Transformer With Split-winding

As a important equipment of photovoltaic power station,the photovoltaic transformer with split windings appropriately boosts the AC power delivered in the inverter and delivers it to the corresponding grid.Therefore,research on the photovoltaic transformer with split windings plays a very important role in the safe and reliable operation of the entire power grid.The dynamic and thermal stability problems of the transformer during operation directly affect the power supply and even threaten the service life of the transformer.Based on reading a large number of domestic and foreign literatures,this thesis simulates the leakage magnetic field,temperature field and winding force of 10 kV photovoltaic split transformer under full traverse operation state and transient state.Through the comparison between theory and simulation,the magnitude and distribution of the stress in the axial and radial directions of the transformer winding are obtained,which provides a reference for the subsequent research and design of the photovoltaic transformer with split windings.In this thesis,the SCB10-GF-1260 kVA photovoltaic transformer with split windings is taken as the research object,the three-dimensional calculation model of the transformer is established.The finite element analysis software Magnet is used to simulate the leakage magnetic field.The distribution of the internal leakage magnetic field and the vector diagram and the low-voltage winding axis and radial magnetic density distribution of the split transformer under full traverse operation are obtained.The maximum position of the leakage magnetic flux is found,and the distribution of the leakage magnetic field of the split transformer winding is obtained.At the same time,the force analysis of the split transformer winding is simulated,and the stress cloud diagram of the winding shaft and the amplitude direction is obtained.At the same time,the axial and radial stress distributions of the low-voltage windings with weak points are calculated,and the position,size and direction of the maximum stress received by the transformer windings are found.The operating parameters of the split transformer under full traversing operation are obtained to determine whether the transformer is in normal operation.Then using the electromagnetic-thermal-flow coupled field analysis method,the fluid-solid coupling model considering the air flow field is applied to calculate and analyze the three-dimensional temperature field of the PV split transformer under full traverse operation.The internal temperature distribution of the split transformer and the axial temperature distribution of the iron core,high voltage winding and low voltage winding are obtained,and the internal temperature distribution law and the maximum temperature point position are found.Finally considering the complexity of the on-site operating condition of the split transformer for photovoltaics,this paper focuses on the split transformer in the transient state(that is,the split transformer is suddenly transformed from the high-side excitation to the low-side excitation due to the work.The internal excitation current is simulated by the conversion to the operating state of the high-side excitation.The size and distribution of the leakage magnetic field inside the transformer under transient conditions are analyzed,and the dynamic stability of the split transformer is analyzed and calculated.The operating parameters of the split transformer in the transient state are obtained,and the deformation method of the winding deformation is calculated by the energy method.