Modern design of classical controllers: Digital PI controllers

In this paper we describe a new approach to the design of digital Proportional-Integral (PI) controllers. The approach consists of first parametrizing constant magnitude and constant phase loci in the space of controller gains. These loci consist of ellipses and straight lines respectively. The set of stabilizing controllers S is then computed using methods described in [1]. The final step is to specify the desired closed-loop stability margins and crossover frequencies and determine the sets of controllers achieving these specifications that lie in S. The design procedure is simple and graphical and is illustrated by a numerical example and a power electronics application of a voltage source inverter.