Optimal design and electromagnetic performance analysis of dual-rotor hybrid excitation generator for vehicles

Abstract Under the trend of electrification and intelligence development, the power requirement of electrical systems of vehicles is constantly increasing. Hybrid excitation generators have the advantages of high-power density, high efficiency and adjustable output voltage, so it is the main method to meet the requirement. The paper proposes a topological mechanism of an axially consistent dual-rotor hybrid excitation generator. According to the requirements of electrical systems of vehicles, the performance indicators are determined and the structural parameters are preliminarily estimated. To verify the correctness of the operation principle, the magnetic circuit is qualitatively and quantitatively analyzed by the magnetic circuit analysis method and the finite element method. The expressions of magnetic flux and permeance of each part are derived by the equivalent magnetic circuit method, and the calculation results of the equivalent magnetic circuit method are verified by finite element method, further confirming that the magnetic field analysis is correct. Based on the axial consistency of the dual-rotor structure, an optimization method from local to overall is adopted and sensitivity analysis of the permanent magnet part and the electro-magnetic part is conducted respectively. According to the comprehensive sensitivity, the level of the variables is determined. For the variables of the high sensitivity level, the genetic algorithm is used, combining with the parameter matching coefficient, to determine the Pareto front point. The coefficient of determination is introduced; it is verified that the predicted values are highly consistent with the actual values. For the electro-magnetic part and the medium-sensitivity level variables of the permanent magnet part, the response surface method is adopted to obtain the optimal point, and ultimately the optimal combination of parameters is obtained. From simulation analysis, the no-load induced electromotive force (NEMF_Max) after optimization has increased to 87.1 V, which is 15.5% higher than that before optimization. Harmonic distortion rate (THD) has decreased to 0.2198, a decrease of 39.39%, and the cogging torque (Tcog_Max) has decreased to 0.284N·m, a decrease of 58%. It proves that the optimized design is reasonable. Finally, it is proved by tests that the no-load characteristics and external characteristics meet requirements. It provides theoretical references and practical guidance for the design of hybrid excitation generators for vehicles.