Discontinuous SVPWM-Based Speed Control of Unsymmetrical Two-Phase Induction Motor Using a Multifunctional Drive System

Abstract

This paper proposes a multifunctional drive system for closed loop speed control of an unsymmetrical two-phase induction motor. A two-phase three-leg voltage source inverter providing constant Volts/Hz and slip regulation control for a machine end converter employs time-based discontinuous space vector pulse width modulation in order to reduce switching loss. A hysteresis current control technique of a single-phase full bridge regenerative PWM rectifier as a front-end converter utilizes source current as a feedback signal instead of converter current. The front-end converter offers multi-functionality of not only bidirectional real power flow but also acting as an active power filter responsible for reactive power and harmonic compensations for various types of nonlinear loads in conjunction with the drive system. As a result, the grid current waveform is nearly sinusoidal and the grid power factor is near unity power factor. With the proposed discontinuous unbalanced space vector pulse width modulation (DUSVPWM) method, the two-phase three-leg inverter provides optimum unbalanced two-phase voltages with orthogonal displacement appropriate for the unsymmetrical two-phase induction motor which is able to improve the converter efficiency. The overall control system is implemented on a low-cost DSP board. The validity of the proposed system is verified by both simulation and experimental results. The capability of the drive under various conditions is satisfactory.