On the inter-area optimal voltage and reactive power control

Scheduling voltage and reactive power is one of the major problems and concerns of the Transmission System Operators (TSOs) especially after deregulation of power market. Due to locally provision of the reactive power resources, each TSO has developed its own specific method. Hence, the voltage and reactive power coordination in the interconnected system has got less attention. In this respect, current practices of different TSOs in Europe and North America, as examples of interconnected power systems, are investigated in this paper. Afterwards, it focuses on the inter-area optimization of the voltage and reactive power. Instead of performing the studies around one particular optimization, different aspects of the mathematical formulation of the optimization problem in the interconnected power system, including objective function, constraints and appropriate modeling of neighboring areas, are revisited more in depth. Various possible implementations of coordinated approaches, including centralized and decentralized structures, as well as non-coordinated approach in collaborative and non-collaborative environments are studied. In this respect, new contributions are proposed in this paper by using the distributed slack bus model and the limitation of the voltage and reactive power in the interconnections links. The comparative analysis between the available and proposed methods are discussed in terms of sub-optimality and time to convergence. The discussions are based on New England 39 bus system and the presented results in the literatures.