Improvement of the stability of electrical drives fed by matrix converters

In this paper the stability of an electrical drive fed by a three-phase to three-phase matrix converter is analyzed considering two different control schemes. In the former the duty-cycles of the switching configurations are calculated on the basis of the instantaneous input voltage values, whereas in the latter they are calculated applying a digital low-pass filter to the input voltage. A state average model of the whole system, which takes into account the parameters of the power supply and the input L-C filter, is proposed. The stability of the system is evaluated by analyzing the migration of eigenvalues of the system, which is linearized around a steady-state operating point. The analytical approach allows the determination of the maximum voltage transfer ratio for a stable operation of the matrix converter as function of the time constant of the digital low-pass input voltage filter. Theoretical considerations are supported by simulation results showing the different behavior in terms of stability of the two control schemes. (12 pages)