Estratégias de modulação PWM para a redução da tensão de modo comum em máquina pentafásica

Abstract

With the advancement of power electronics and control techniques, alternating current motors, mainly induction motors, have been replacing direct current motors in drive systems. The three-phase machine is the most used, but alternating current machines with a number of phases greater than three have advantages over three-phase machines, such as, for example, extra degrees of freedom in the drive system; increase in useful torque per effective current value; among others. The static converters used to drive the machine introduce high-frequency voltage components, which find a low-impedance path to ground through the machine’s parasitic capacitances. Among the associated problems, mechanical failures in the bearings can be mentioned; increased levels of electromagnetic emissions; among others. A reduction of these problems can be achieved by reducing the common mode voltage in the drive system, considering that this is the supply voltage for the parasitic circuits of the machine. Among the solutions proposed in the literature for reducing common mode voltages and circulating eddy currents, the use of passive filters associated with the topology of the inverter and/or the use of appropriate PWM modulation strategies can be mentioned. In this work some PWM modulation strategies with common-mode voltage reduction in five-phase machines are presented. Two new techniques for mitigating this voltage are proposed, one being a hybrid that obtains significant reductions in common mode voltage, about 80% in relation to the strategy said to be natural or standard, and eddy currents, where it stands out as the strategy that the more it is possible to reduce these currents operating in the entire range of modulation index. The confirmation of these reductions took place through simulations using the MATLAB software. This hybrid strategy is the main technique proposed in this dissertation, it is composed of two techniques already known in the literature and another technique that is also proposed in this work, the CVPWM.