A Unified Time Ratio Recursion (TRR) Algorithm for SPWM and TEHPWM Methods: Digital Implementation and Mathematical Analysis

摘要

An efficient algorithm is designed for digital implementation of any regular sampled SPWM (sinusoidal pulse width modulation) switching pattern for single phase full-bridge inverter application. The hardware and software of the scheme are built around the 8-bit general-purpose microprocessor. Complete mathematical analysis of meeting points and duty cycle for SPWM is developed for the performance verification of the algorithm. The suggested time ratio recursion (TRR) algorithm generates the PWM patterns with close agreements with theoretical results, and is a universal one applicable to the modified PWM patterns viz. HPWM (hybrid pulse width modulation), TEHPWM (thermal equalization hybrid pulse width modulation), etc. TRR takes reduced number of comparisons as compared with the linear search (used in many microprocessor-based control circuits) and hence converges at a faster rate.