Appunti di Electrical drives for industrial applications

Inverter-fed Induction machine Dynamic model of the IM and instantaneous torque; different reference system and transformation matrices; vector representation of three-phase variables; Field Oriented Control: direct and indirect implementaion, reconstruction of flux and torque variables, field weakening operation. Doubly Fed Induction Machine: rotor current limit and torque control. Direct Torque Control: selection of the inverter configuration & modulation strategies; Direct Self Control: hexagonal stator flux path. A.C. current control Control of the currents of a three-phase system (i.e. motor) in different reference systems (abc, αβ, dq); PI regulators; Hysteresis regulators; predictive control; compensation of dq coupling terms. Controlo of an Induction machine fed from Current Source Inverter. Space Vector PWM and a.c. current control Inverter configurations, voltage reference and basic principles of the method, limit voltage exagon and overmodulation, optimal sequence of inverter states, switching frequency and current ripple; effect of dead-times and common mode voltage. Active Front-End Converter: block diagram and basic operation. Open- and closed-loop control; current control on different reference frames with linear (PI) and hystereisi regulators, voltage saturation, decoupled current control. Brushless Drives Use of Permanent magnets, different types of rotor design and rotor saliency, elctromagnetic force induced on the stator windings (d.c. and a.c. BL), effect of saliency on torque; cogging; regulation schemes; steady-state operation and geometrical loci in the field-weakening region. BL with prapezoidal cemf: current waveforms and torque ripple.