Introduction

Abstract

Use of digital computers for power system simulations gained importance during the early fifties. Load flow analysis [Ward and Hale, 1956] was one of the first computer applications in power system analysis. Before the digital computers era, analog computers and scaled physical models were used for power system computation and simulations. For example, analog computers were used to implement load flow like computations. They were called ac network analyzers and used to occupy a large floor area. The sixties and the first half of the seventies witnessed many important breakthroughs in computational methods for power systems like Optimal Power Flow (OPF) algorithm [Dommel and Tinney, 1968], the electromagnetic transients program [Dommel, 1969], power system state estimation [Schweppe and Wildes, 1970], transient stability [Dommel and Sato, 1972], and fast decoupled load flow [Stott and Alsac, 1974]. Since then, the field of power system computations has grown rapidly. In the last five decades, power system computational techniques have evolved dramatically and have achieved a high level of sophistication and maturity. In tandem with the digital computer revolution, many traditional barriers and constraints which existed earlier have been overcome.

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