Modeling And Simulation Of The Alternating Current Excitation Generator With The Matrix AC-AC Converter As An Exciter

The structure of alternating current excitation generator (ACEG) is same as wound rotor induction machine. The stator of ACEG is connected to the grid and the three symmetrical excitation windings in the rotor are fed by converter. The magnitude and frequency and phase and phase sequence of excitation voltage can be controlled, so the magnitude and position of excitation MMF as well as the speed of rotor can be controlled. Therefore, ACEGs have superior performances by contrast with conventional synchronous generators and induction generators, such as upstanding stability, power generation of variable speed constant frequency (VSCF), adjusting active power and reactive power independently, and absorbing lag reactive power deeply. So there are good prospects for alternating current excitation generators.In this thesis, the operation principle of ACEG and the excitation control strategy based on dynamical synchronous reference frame are analyzed, the simulation models of the generator and excitation controller are established based on the Saber simulator. According to the requirement of ACEG , the converter should have regeneration capability, and the input and output currents of converter should be sinusoidal. Matrix AC-AC converter (MC) has good input and output performances. MC as the exciter is proposed in this thesis. According to the space vector modulation method of the equivalent structure of the AC-DC-AC transformation, the transformation relations of the matrix converter are deeply investigated. The AC-AC direct conversion control and the double-space-vector PWM scheme of the matrix converter are deduced, the four-step current commutation strategy of matrix converter is expatiated, the design method of input filter and over voltage protection circuit is analyzed, and the modeling and simulation of a three-phase matrix converter are implemented. The steady state and transient characteristics of the ACEG system are simulated, the harmonics of the EMF and stator current and rotor current as well as MC's input current are researched. The operation characteristics of ACEG with MC as an exciter are compared to those of ACEG with AC-DC-AC converter and cycloconverter as an exciter.The results in this thesis will be helpful to the design of the ACEG excitation control system...