Research On Hybrid Excitation AC And DC Multi-winding Synchronous Generator

AC and DC coexisted power supply system is widely used in military and civil field, and it develops towards the high quality, high stability and miniaturization. The conventional AC and DC electrical excitation synchronous generator and permanent magnet synchronous generator both have their limitations. The magnetic field of AC and DC electrical excitation synchronous generator can be adjusted while permanent magnet synchronous generator can’t. The efficiency of AC and DC electrical excitation synchronous generator is lower while permanent magnet synchronous generator higher. Based on it, combining the hybrid excitation with AC and DC synchronous generator, hybrid excited AC and DC multi-winding synchronous generator is designed in this paper. This designed generator has five sets of winding on the stator. One set of winding directly outputs AC power. After rectifying separately, other four sets of winding parallel output DC power. The permanent magnet of rotor provides main magnetic field. Excitation windings play the role of excitation regulation. This generator combines the advantages of AC and DC electrical excitation synchronous generator and permanent magnet synchronous generator, which is a high power density, high quality AC and DC dual purpose synchronous generator.According to the theory of machine design, basic dimensions and parameters of hybrid excitation generator are designed, and the 2D hybrid excitation generator model is firstly built by Ansoft Maxwell. Finite element method is used to analyze the magnetic field. Based on it, optimization of the generator is made. By the simulation of no-load operation, no-load induced electromotive force is obtained and analyzed by Fourier method. By the comparison of effect of different skewed slots’ slope on tooth harmonics, the optimum slope of skewed slot is obtained. By the simulation of load operation, the external characteristic curve under 3 different load operations is obtained. In order to improve external characteristic, by the adjustment of electrical different load operations is obtained. By the excitation adjustment curve, the excitation current is adjusted, which makes generator have more flatter external characteristic.The comparison of effect of taking full-wave rectifier and half-wave rectifier mode on output DC voltage is made. The simulation results show that output DC voltage wave is more ideal under full-wave rectifier mode. Aiming at the distribution mode of excitation winding of rotor, the comparison of concentrated winding placement mode and distributed winding placement mode is made. The results show that taking distributed winding placement mode can decrease tooth harmonic content of induced electromotive force and thus makes generator have more better performance. Because of the existence of sets of winding on stator and excitation winding on rotor, the calculation of inductance becomes very difficult. Based on two-reaction theory, the self-inductance and mutual-inductance of winding on stator and rotor is deduced. The inductance of generator is calculated by combination of Ansoft simulation.The mathematical model of generator under ABC coordinate system and dq0 coordinate system is deduced. Under the dqO coordinate system, the inductance of generator is constant when excitation current is constant. When neglecting the mutual leakage reactance of different Y winding, d axis and q axis are completely uncoupled, which makes the mathematical model of generator much simpler. Based on the simpler mathematical model, the model of generator is built by Matlab/Simulink and thus the operating characteristic under different load conditions is analyzed.