A Computer-Aided Design Tool for Developing Digital Controllers

Design, development, and implementation of a com- puter-aided design (CAD) tool for developing digital controllers and relays is presented in this paper. The development includes modeling A/D converters, software, and the necessary logic. Procedures for modeling A/D converters and simulating the software are described. Application of the CAD tool is demon- strated by evaluating and comparing three different designs of a digital overcurrent relay. The designs are evaluated to determine both the speed and accuracy of the relays. The effects of the size of the A/D converters, the word-size used in computations, and the effects of truncation/rounding are included in the simula- tion. The paper also describes the algorithm used in the relay design.