Matrix Converters: Evaluation of a Technique for the Common Mode Voltage Reduction Aimed at Long Cable Motor Drive Systems

Motor drive systems in mining facilities usually require long cables to connect the converter to the motor. The result is the widely known occurrence of transient overvoltages on the motor terminals, in both differential and common voltages, as such this (i) increases the dielectric stress over the windings and (ii) produces the voltage induced in the motor shaft, which goes on to generate EDM discharges and damage to the motor bearings. In this context, to deal with (ii), in this paper, a modified modulation technique for the common mode voltage reduction in matrix converters is evaluated. Simulations were developed in MATLAB/Simulink employing sophisticated models for the converter, cable, motor and transformer, which are able to represent their behaviors in a wide frequency range. From the obtained results, the advantages and drawbacks of the modulation method under investigation are highlighted and discussed. One of the conclusions is that the differential transient overvoltages are magnified when the modified modulation control is used, in contrast to the common mode reduction provided by it. Due to this trade-off between these two undesired phenomena, the intended application is what will go on to define the feasibility of the investigated technique.