A simple indirect field-oriented control scheme for multiconverter-fed induction motor

In multiconverter topology, several voltage-source pulsewidth modulation (PWM) inverters using common sinusoidal modulating signals and phase-shifted triangular carrier are operated in tandem with their outputs coupled through current sharing inductors, with an objective of increasing the overall rating to megawatt range, reducing the harmonic current and torque ripples, increasing the reliability with phase-redundant operation under various fault conditions. The individual PWM voltage-source inverter (VSI) operates with the devices switching at their optimum switching frequency and behaves as a linear power amplifier (LPA). The overall multiconverter exhibits an improved quality of alternating currents (ac) due to the multiplied carrier effects in PWM. This paper, therefore, presents a simple indirect field-oriented control scheme for the muiticonverter-fed induction machine. Necessary experimental and simulation results are presented to show the effectiveness of the proposed indirect field-oriented control scheme. In the study, on-line analysis has been performed using [C.sup.++], while MATLAB/Simulink has been used to perform the off-line analysis. The paper also discusses the design philosophy of the two well-known topologies of the converters used for high-voltage and high-current applications to facilitate the design and development of near-future megavolt ampere rating power converters/conditioners. Index Terms--Induction motor, multiconverter, sinusoidal pulsewidth modulation, sinusoidal reference wave, triangular carrier wave.