Optimal pulse-width modulated algorithms for inverter control of induction motor

摘要

Pulse-width modulated (PWM) strategies concerned with thecontrol of the frequency, voltage and harmonic content ofthe three-phase output of a voltage-source inverter areincreasingly being used for industrial applications ofvariable speed induction motor drives. The control of theseparameters is provided by the switching informationcontained in the PWM wave.This thesis describes the detailed development of anoptimal sum of harmonics (SOH) pulse-width modulatedalgorithm for induction motor control. The designphilosophy of this algorithm is based on the desire tomaintain a well defined modulating process to easeimplementation by either software or hardware techniquesand yet still reproduce the desirable characteristics of anoptimized PWM strategy. An off-the-shelf IBM PC/ATcompatible, in conjunction with a timer/PIO board designedspecially for modulation algorithms, is used to develop andtest this strategy. With this microprocessor-baseddevelopment system, the control requirements forpractical control of the induction motor are implemented insoftware.It is shown experimentally that this optimal SOH strategyexhibits the desirable characteristics of both theasymmetric sampling and optimized PWM strategies.