Control of open-end winding induction machine based on indirect matrix converter

Abstract

The aim of this thesis is to study the application of an Indirect Matrix Converter (IMC), with two inverter output stages, to supply energy to an induction machine with opened stator winding (so-called open-end winding connection). This type stator winding connection presents several advantages, compared with a conventional wye or delta connected machines, such as: equal power input from both machine winding ends, thus each inverter is rated at half the machine power rating; each phase stator current can be controlled independently; possibility to have twice the effective switching frequency (depending on the modulation strategy); extensibility to more phases, therefore multiphase induction machines can be considered if current reduction is required; possibility of reducing common-mode voltage; and certain degree of fault tolerance, as there is voltage space vector redundancy. However, an open-end winding induction machine drive can have some drawbacks, such as: possibility of zero sequence current flow through the machine, this because of the occurrence of zero sequence voltage; increased conduction losses; higher complexity in the power converter requirements, i.e. more power devices, circuit gate drives, etc. On the other hand, the use of an IMC to drive this machine presents the following features: sinusoidal input and output currents, bidirectional power flow capability and controllable input power factor, without using bulky energy storage elements. In this thesis, different Pulse Width Modulation (PWM) strategies described in the literature are adapted to the proposed power converter topology. The issues of common-mode voltage and zero sequence voltage are reviewed and addressed with these modulation strategies. The performance of the drive is tested via simulations in PSIM/MATLAB platform and experimentally verified with a laboratory prototype. Results for open and closed-loop operation of the system are presented and discussed.