Analysis of Nonlinear PWM Control System using Subharmonic Describing Functions

Abstract

In this paper, the stability analysis of a pulse width modulated control system with a linear compensated type 3, fourth order plant is investigated using the multiple input describing function. The characteristic of the modulation process is essentially nonlinear and gives rise to odd harmonics in the output, the lowest order harmonic being the third. System design and compensation based on linearization or fundamental frequency describing function technique might not be enough. The possibility of oscillations or instability in the presence of the most significant harmonic ought to be investigated.

Indexing Terms:

• PWM Control System
• Stability
• Describing Function