PWM Inverters and Double Star Asynchronous Machine drive - Sliding mode solution

The PWM inverters and double star asynchronous machine (DSAM) drive shows drawbacks concerning stator currents quality which depend directly on the inverter´s control law, phase-shift between the two stars, and stator leakage inductance. The machine model is established based on the vectorial formalism. It shows that only the voltages and currents in the alphabeta plane are related to electromechanical energy conversion. The non sequential (xy) current components don´t contribute to electromechanical energy conversion and cause losses. Therefore the control of DSAM has a double objective; better control of torque and minimization of the non sequential current amplitude. The variable structure system (VSS) approach for the design of a control of this drive type appears to meet these two criteria thanks to the possibility to attract the variable on the sliding surface and to maintain it on this surface. A mathematical model of the DSAM and of the supply are derived in form suitable for analysis. And a set of simple surfaces have been chosen for each variable. Then, the following problems are discussed: selection of the switching functions in the form that allows clear optimization of twelve configurations and the algorithm to choose the suitable configuration regarding to different parameters. Simulation and few experimental results are presented