Guest Editorial Special Issue on Integrated Control and Modulation for Electric Drives

Abstract

Green energies and electric mobility are considered exciting solutions to help reduce the emissions of greenhouse gases into the atmosphere. This scenario has significantly promoted the use of electric drives; consequently, higher technical requirements are assumed as mandatory. Focusing on the required high-performance electric drives, the direct control of power converters and the use of integrated modulators, namely, control techniques that avoid the pulse-width modulation stage, can be an attractive alternative to conventional linear controllers. For example, Model Predictive Control (MPC) presents inherent flexibility in defining control objectives, while Direct Torque Control (DTC) provides a fast dynamic response. Unfortunately, unacceptable harmonic distortion can appear in the system if single control action is applied per control cycle. This scenario promotes a higher current ripple in three-phase electric drives when a control scheme using a standard integrated modulator is implemented. The situation is even worse when multiphase drives are used since several orthogonal subspaces need to be regulated with a single control action. In addition, the characteristic low value of the equivalent impedance of the secondary subspaces may lead to enormous harmonic currents. Considering the previous scenario, although the dynamic response is very fast in direct controllers (control scheme based on integrated modulators), these control strategies could be discarded due to their high harmonic distortion. Fortunately, the disadvantages of direct control strategies can be mitigated by using enhanced integrated modulators, such as multi-vector solutions as control actions. On the other hand, as these control techniques’ performance is founded on the nature of the available voltage vectors, the use of some specific electric drives, such as symmetrical six-phase machines, can allow taking advantage of their desirable skills.