Control of a variable speed DFIM using a matrix converter

Abstract

This dissertation examines the performance of a variable speed doubly-fed induction machine, interfaced to the electrical grid through a direct matrix converter. The power converter is connected between the stator and the rotor windings. Statorflux orientated vector control and a space vector modulated matrix converter are used for the control of the doubly-fed induction machine rotor currents. The system provides optimum rotor current control under fluctuating rotor shaft speeds. The scheme is experimentally verified on a 2kW variable speed test rig where a prototype l.5kW doubly-fed induction machine was investigated. A DSP and an FPGA based controller is used for the control algorithms and a standard 7 .5kW matrix converter was built and tested. The experimental rig was designed and constructed as part of the research. Experimental results are presented for transients of operation below and above the synchronous speed. Both motoring and generating modes are considered.