Research On Doubly Salient Electromagnetic High Voltage Direct Generator System

The 270V high voltage DC power system has the advantages of less weight, higher efficiency and easier to realize uninterrupted and is attractive for next generation airplanes. And the doubly salient electromagnetic brushless DC generator, with the characters of simple structure, flexible control, and easy to be integrated with, is the best choice for the power system mentioned. Therefore it is significant to research on the doubly salient electromagnetic brushless DC generator power system.The static character of the 12/8 pole doubly salient electromagnetic generator is researched based on the simplified equivalent magnetic circuit method. The magnetic field in different operational situations is analyzed employing the 2D finite element method, with flux linkage, inductance and no-load voltage calculated. The principle of the inductance and flux linkage vs. the magnetic current and phase current are given.The nonlinear modeling method for the 12/8 pole doubly salient electromagnetic DC generator is researched based on the nonlinear flux linkage calculated by the finite element method. The nonlinear models of the DC generator are built with three methods, named Adaptive-Network-Based Fuzzy Inference System, Support Vector Machine and Spline, respectively. The modeling precision and forecasting capabilities of these three methods are analyzed and compared. Both the advantages and disadvantages of the methods mentioned are summarized with the choice principle given. The non-load voltage waveforms and characters of the doubly salient electromagnetic brushless DC generator are analyzed, based on the three nonlinear models obtained, and compared with the test results. The validity and feasibility of the three modeling method are verified theoretically and experimentally.The 12 operation modes of the output full-bridge rectifier are analyzed with voltage equations built for every mode, respectively. The nonlinear MATLAB model of the DC generator is developed. The generator performances are evaluated based on both the simulation and experiment results. The properties of the flux linkage, inductance, voltage waveform, output DC voltage and the voltage ripple versus exciting and load current, are investigated.In order to solve the problem of the difficulty in breaking arc of 270V DC mechanical switch under high voltage and high altitude, a mechanical-electrical Hybrid DC Power Controller is developed. A new circuit topology with the inverse current protection function is proposed to overcome the shortage of the traditional circuit. It is proved by the experiment results that the 270V DC hybrid power controller effectively keeps the static state characters of the mechanical switch and the dynamic characters of the solid switch and can closes and breaks arc-less rapidly. The inverse current protection function is verified experimentally. The digital voltage regulation for the doubly salient electromagnetic brushless DC generator is researched. The nonlinear PI excitation control algorithm, with the nonlinear characteristics of the doubly salient electromagnetic brushless DC generator considered, is developed and design method given. To improve dynamic performances of the DC generator system furthermore, a real time nonlinear PI algorithm with load-current forward control is developed. Experimental results verified that the proposed algorithm offers not only faster dynamic response, but also less voltage surge during load switched on and off, over a wide load range.