Research And Design Of Digital Excitation System For The Synchronous Generator

In synchronous generators, the excitation system plays an important role, and theexcitation regulator affects the stability of the electric power system. With thedevelopment of the power system, the performance of the excitation regulator made agreat progress in stability and power level. In recent years, as the rapid developmentof computer control technology, the analog control system of excitation regulator isgradually replaced by the digital control system, and digital excitation becomes thedevelopment trend of the modern excitation system. Digital excitation regulator usesthe software program to control, so the control performance of the excitationcontroller has been significantly upgraded and the intelligent control algorithm can beachieved. In summary, digital excitation regulator has the advantages of preciselycontrol, powerful function, compact, easy of debugging and so on.With the development of power electronics technology, the voltage rating andcurrent capacity of the full-controlled devices have been greatly improved.Full-controlled devices can be controlled by the PWM, while the half-controlledthyristor device cannot. The purpose of using full-controlled three-phase voltage-typerectifier (VSR) instead of the traditional silicon controlled rectifier is to reduce theharmonic content of the rectifier input and to improve the power factor. Thethree-phase VSR in the three-phase ABC coordinate system, the two-phase stationarycoordinate system and the two-phase rotating coordinate system mathematical modelis introduced in the paper. The three-phase full-controlled rectifier is controlled byvoltage space vector pulse width modulation (SVPWM) method, and the SVPWMconcrete step to achieve is described in detail. Self-parallel excitation system isapplied in the generator excitation regulator, and the generator terminal voltage meetthe network conditions through adjusting the excitation current network ring beforeconnected grid, and then added feedback quantity relative with power to adjust thereactive power factor.Excitation system is a nonlinear system, and there is no exactly mathematicalmodel between generator power factor and the excitation current or the rectifieroutput voltage, therefore Fuzzy-PI control algorithm is used for power factor control.Fuzzy and PI control system is combined to achieve better control performance. The excitation current can be better tracking system changes in the excitation current ringwith improved PID algorithm.MATLAB/Simulink is used in system modeling and simulation, and thesimulation results verified that the excitation controller could meet the requirementsof the system. This paper completed the hardware design of the Self-parallel digitalexcitation regulator. TMS320F28335DSP is the main control chip, and which fastcomputing power is used to improve the real-time control performance of the system.Part of the hardware system design logic block diagram, circuit schematics andsoftware flowchart are given in the paper.