In this paper, we review the functions and architectures of control centers: their past, present, and likely future. The evolving changes in power system operational needs require a distributed control center that is decentralized, integrated, flexible, and open. Present-day control centers are moving in that direction with varying degrees of success. The technologies employed in today's control centers to enable them to be distributed are briefly reviewed. With the rise of the Internet age, the trend in information and communication technologies is moving toward Grid computing and Web services, or Grid services. A Grid service-based future control center is stipulated.

This paper presents an application of noncooperative game theory to generation expansion planning (GEP) in a competitive electricity industry. We apply the Cournot model of oligopoly behavior to formulate a GEP model that may characterize expansion planning in a competitive regime, particularly in pool-dominated generation supply industries. Numerical experiments are conducted on a test system to analyze generation investment and market participation decisions of candidate expansion units that vary in costs and forced outage rates. The numerical results point to: 1) greater industry expansion and system reliability, under Cournot competition than under centralized expansion planning; and 2) higher probabilistic measures of reliability from multi-player expansion than from expansion by a traditional monopolist with an equivalent reserve margin requirement. Furthermore, we summarize analytical results involving a simplified version of the GEP game.

The study of a decentralized coalition formation scheme in a specific power systems transmission expansion scenario is the purpose of this paper. We define first who are the agents in the t:xpansion game and provide a decentralized coalition scheme based on Bilateral Shapley values. Finally, we allocate the total costs of expansion amongst the agents, based on the coalition history, and we compare our method with a centralized scheme.

An improved approach based on sequential method for the AC-DC power flow calculation is proposed in this paper. This approach solves the convergence problem caused by voltage violations at AC buses during the power flow calculation for the DC subsystems. The convergence property can be significantly improved by adjusting the converter transformer tap position flexibly. In order to adjust the tap position of the converter transformer flexibly, three mainly modifications are proposed. Firstly, the equations for whole DC systems are decoupled into individual DC systems so as to easily figure out which DC system's tap position needs adjustment. Secondly, the tap ratio of a converter transformer is selected as an alternative state variable to replace the cosine of the control angle when necessary. Thirdly, the Newton-Raphson method is utilized to solve DC subsystems instead of the method using the linear equations. Furthermore, a theoretical analysis of the advantages of the proposed approach is also presented. Numerical simulations and practical applications show that the proposed approach meet the requirement of different system operating conditions and has advantages in terms of convergence and speed. The proposed approach has been successfully integrated into the Energy Management System (EMS) for China Southern Power Grid. Index Terms-AC-DC, HVDC transmission, multi-infeed DC systems, Newton-Raphson method, power flow analysis. I. INTRODUCTION C HINA has made remarkable strides in high voltage direct current (HVDC) transmission implementation. At present, there are more than ten HVDC lines in operation in China. By 2020, the power grid of China will become a robust AC-DC system with ultra high voltage links. China will have 33 HVDC lines by then. North China Grid and Central China Grid will become AC-DC hybrid power systems with multi-infeed DC systems. Furthermore, the complexity of East China Grid,