Study On Structural Optimization Design Of Dry-type Air-core Reactor

With the increasing scale of power grids,dry-type air-core reactors are being widely used in reactive power compensation,filtering,and current limiting.However,dry-type air-core reactors have large volumes and heavy weights,resulting in high production and transportation costs.Due to factors such as imprecise manufacturing processes and aging insulation layers,the reactors are prone to inter-turn short-circuit faults,which can lead to fires and cause economic losses in severe cases.Therefore,it is of great significance to optimize the structure of dry-type air-core reactors to reduce costs and mitigate the risk of accidents occurring after inter-turn short-circuit faults.This thesis takes dry-type air-core reactors with a rated voltage of 35 k V as the research object.The electromagnetic parameters such as busbar current and equivalent inductance under normal operating conditions are taken as performance constraints.The active power loss caused by inter-turn short-circuit faults under different encapsulating conditions of the reactors is added as a reliability constraint.Through optimizing the structural parameters of the reactor,the minimum quality of the reactor conductor is achieved to reduce production costs.The optimized results are validated through multiphysics field coupling simulation of electromagnetic-thermal-fluid,ensuring the rationality of the design and the reliability of the reactor operation.The main research content of this thesis is as follows:Firstly,taking a single multi-turn coil as an example,three electromagnetic field models,including a 3D helical model,a 3D cylindrical model,and a 2D model,are constructed.The simulation results are compared and analyzed,and the applicability range of the 2D model is determined through parameter scanning,providing a basis for using the 2D model for subsequent analysis.Then,combining with the parameterized modeling method,the change trends of various electrical parameters of the reactor under different fault locations and different numbers of short-circuit turns are analyzed.The change regularities of various electrical parameters of the dry-type air-core reactor under inter-turn short-circuit faults are summarized,providing data basis and selection criteria for the model expression of the constraint conditions in the optimization model.Secondly,a bi-directional coupled electromagnetic-thermal-fluid model is established to discuss the temperature distribution of the reactor.The influence of each encapsulating surface radiation on the temperature is analyzed to reduce the radiation boundary of the temperature calculation model.The encapsulating of the model is simplified to improve the efficiency of temperature calculation.The reason for the difference in the calculated active power in the electromagnetic field is analyzed to verify the correctness of the bi-directional coupled model.Based on time cost,active power is selected as a constraint for optimization,and then temperature is checked for validation.Based on the above research,the optimization module of finite element software is used to optimize the structural parameters of the reactor.To reduce the computational cost of optimization,a method of multiple electromagnetic fields sharing the same geometry model and mesh is employed.To speed up the convergence of the algorithm,some design variables are fine-tuned,and the optimal fine-tuning range and solution are determined by comparing the temperature and the influence of different fine-tuning ranges on the optimization results.Finally,the optimal solution is revised according to the practical requirements of the project.The feasibility of the optimization method is demonstrated by verifying that all performance indicators,active power loss after inter-turn short-circuit fault,and the highest temperature of the revised optimal solution meet the requirements.