Basic Research On Hybrid Excitation Synchronous Generator Based On Induced Excitation

Hybrid excitation is the combination of permanent magnet excitation and electrical excitation. The hybrid excitation synchronous machine (HESM) has received wide attention since it was firstly put forward in the 1980s. Since it combined the convenience of excitation regulation in the electrical excitation synchronous machine (EESM) and the specific advantages of the normal permanent magnet synchronous machine (PMSM), such as the high efficiency and torque-mass ratio, and at the same time, the shortcomings of the two former types of synchronous machines have been diminished to the largest extent. However, the electric performance of the hybrid excitation schemes having been proposed as so far is still in imperfection. Even though tandem HESM has simple structure, the reluctance of the magnetic circuit is large, and it belongs to brush excitation structure and it needs electric brush slip-ring device, which makes it easier to produce sparks with inappropriate use; Parallel HESM can achieve brushless excitation, but it needs special brushless excitation system, leading to complex structure of the machine. On this basis, a new type of hybrid excitation machine which integrates the induced excitation and the permanent magnet excitation is discussed in this paper. It is called induced excitation hybrid excitation synchronous generator. The generator has simple structure and it does not need electric brush slip-ring and special exciter. In addition, it can realize brushless excitation of the hybrid excitation synchronous machine based on rotor excitation.This paper comes up with a new type of hybrid excitation synchronous generator based on induced excitation and presents its structure features and fundamental principles. The performance of magnet field can be analyzed by the equivalent magnetic circuit method and two-dimensional finite element method. The prototype has been developed and the no-load magnetic properties have been operated. The researches mainly cover the following aspects:(1) On account of the brush structure excitation scheme of the existing hybrid excitation synchronous machines, this paper takes the brushless improvement, which proposes the hybrid excitation synchronous generator based on the regulation of induction excitation. This kind of machine is able to overcome the shortcomings of the Induced excitation synchronous generator and the permanent magnet synchronous generator, and at the same time, to obtain the maximum combination of the advantages of the two former machines, which makes it easier to regulate the excitation and to achieve the brushless structure.(2) This paper gives a detail introduction of the structural features and the fundamental working principles of the proposed generator, and the designation of the windings is held according to the standards. Main structural parameters have been introduced, including rated operation parameters and the design of stator and rotor slot. We can give full play to the advantages of permanent magnet excitation and induced excitation by reasonable design of structure.(3) Equivalent magnetic circuit model of IE-HESG is established. The relationship of the current of stator auxiliary windings and the current of rotor induced field windings has been analyzed. So we can obtain the expression of the rotor excited magnetic potential. According to the practical flux paths, the equivalent flux path model is established by combining the rotor excited magnetic potential and permanent magnet magnetic potential. It is beneficial to analyze the adjustment principle of magnetic field initially from the angle of the magnetic circuit.(4) Two-dimensional finite element model is built by Ansoft Maxwell. Finite element method is used to analyze the magnetic field of IE-HESG and working characteristic curve. And working characteristics of common induced excitation synchronous generator and permanent magnet synchronous generator are compared under the condition of the same size. The results fully show that the machine in this paper has the advantages of convenient to regulate excitation and high efficiency.(5) According to the requirement of design, a prototype is developed, and the experimental platform is established. On this basis, no-load magnetic experiment is operated. Thus the no-load characteristics of experiment and 2D finite element simulation are compared. Comparison results are basically identical and further verify the rationality of the generator in this paper.