Coordination of voltage control in a power system operated by multiple transmission utilities

This paper addresses the problem of coordinating voltage control in a large-scale power system partitioned into control areas operated by independent utilities. Two types of coordination modes are considered to obtain settings for tap changers, generator voltages, and reactive power injections from compensation devices. First, it is supposed that a supervisor entity, with full knowledge and control of the system, makes decisions with respect to long-term settings of individual utilities. Second, the system is operated according to a decentralized coordination scheme that involves no information exchange between utilities. Those methods are compared with current practices on a 4141 bus system with 7 transmission system operators, where the generation dispatch and load demand models vary in discrete steps. Such a discrete-time model is sufficient to model any event of relevance with respect to long-term system dynamics. Simulations show that centrally coordinated voltage control yields a significant improvement in terms of both operation costs and reserves for emergency control actions. This paper also emphasizes that, although it involves few changes with respect to current practices, the decentralized coordination scheme improves the operation of multi-utility power systems.