Dynamic analysis and experimental evaluation of delta modulators for field-oriented AC machine current regulators

Implementation of field-oriented control requires regulation of the temporal orientation of flux and current vectors in AC machines. The orientation is generally achieved via instantaneous control of stator current relative to either the measured flux or the indirectly estimated flux terms. In either case, the instantaneous control of current is critical. A novel approach for current regulation is presented, based on the use of a nonlinear discrete-time delta modulator which offers the potential for reduced parameter sensitivity and more accurate command tracking than either classical or state-space linear system controllers. A power electronic topology, the resonant DC link is ideally suited to implement this controller. Experimental data on a field-oriented induction machine controller using a resonant DC link inverter topology demonstrate the command tracking performance of this induction-machine current regulator