Torsional vibrations in medium voltage electrical drives : analysis and control design

Nowadays variable speed drive systems-VSDS are preferred to constant speed drives in the industry because they can improve the efficiency of the process while avoiding the use of complex mechanical mechanisms. However, the reputation of VSDS has not always been favorable since they can be a cause of torsional vibration problems. This is mainly due to the intrinsic nature of switching-based converter that produce as side-effect a pulsating torque ripple on the shaft. In addition, closed-loop electromechanical interactions could lead to system instability by the intrinsic latency, processing and estimation delays. The aim of this thesis is to discuss the difference in control behavior between open-loop solution, scalar control, and closed-loop solution, full DTC. It will be also introduced a new combined approach to deal with latency-damping relation that affect the overall process, especially in high shaft-power applications. Further a control tuning of the speed control for demanding applications will be discussed. It is also proposed a passive damping solution in order to avoid these kind of oscillations. A simple simulator is provided for manage this kind of issues and it is validated through the ABB full simulator and the ABB full emulator. Greater consideration is referred to low computational structure, aiming to a feasible industrial application.