Sung-Hwan Song

FACTS operation scheme for enhancement of power system security

This paper presents a FACTS operation scheme to enhance the power system security. Three main generic types of FACTS devices are introduced. Line overloads are solved by controlling active power of series compensators and low voltages arc solved by controlling reactive power of shunt compensators, respectively. Especially, the combined series-shunt compensators such as UPFC are applied to solve both line congestions and low voltages simultaneously. Two kinds of indices that indicate the security level related to line flow and bus voltage are utilized in this paper. They are iteratively minimized to determine operating points of the devices for security enhancement. The sensitivity vectors of the indices are derived to determine the direction of minimum. The proposed algorithm is verified on the IEEE 57-bus system with FACTS devices in a normal condition and in a line-faulted contingency.

Preventive and corrective operation of FACTS devices to cope with a single line-faulted contingency

This paper presents how to find proper operating points of FACTS devices to enhance the steady-state security level considering line contingency analysis. Three generic types of FACTS devices such as series controllers shunt controllers, and series-shunt controllers are introduced and applied to enhance a security margin and to minimize security indices. Quantities (MW) of security margin are depicted in a PV curve and security indices related to line flows and bus voltages are utilized and minimized iteratively in this paper. Contingency analysis is performed to detect the severest line fault in a power system. In this system condition, FACTS devices are tested to establish appropriately preventive or corrective action without generation re-dispatching or load shedding. The FACTS operation scheme is verified on the 9-bus system and the IEEE 57-bus system in a line-faulted contingency.

Cluster design compatible with market for effective reactive power management

Recent progresses in the restructuring of power systems show that voltage control of large-scale power system and zonal reactive power market are an important issue because of local property of voltage and reactive power control. This paper proposes the cluster design compatible with a localized reactive power market. For the cluster design, so-called system performance-based cluster is implemented through the concept of electrical distance, and pilot voltage buses (descriptive nodes) are chosen at each cluster for effective reactive power management. And the validity of system performance-based cluster is ensured by price-based approach which yields zonal procurement of reactive power according to voltage level at each pilot bus. Eventually this may lead to the market-based clustering, grouping the region where the changes in reactive power pricing analogously respond to the variation of system operating condition. A sample case study is given to illustrate concepts and proposition

Model of Information Exchange for Decentralized Congestion Management

The present study examines an efficient congestion management system compatible with the evolving environment. The key is to build an information model shared and exchanged for marketbased solutions to alleviate congestion. Traditional methods for congestion management can be classified into two categories, i.e., the centralized scheme and the decentralized scheme, depending on the extent to which the independent system operator (ISO) is involved in market participants’ (MPs) activities. Although the centralized scheme is more appropriate for providing reliable system operation and relieving congestion in near real-time, the decentralized scheme is preferred for supporting efficient market operation. The minimum set of information between the ISO and MPs for decentralized scheme is identified: ⅰ) congestion-based zone, ⅱ) Power Transfer Distribution Factors, and ⅲ) transmission congestion cost. The mathematical modeling of the proposed information is expressed, considering its process of making effective use of information. Numerical analysis is conducted to demonstrate both cost minimization from the MP perspective and the reliability enhancement from the ISO perspective based on the proposed information exchange scheme.

A Proposal for Congestion Management System and the Information Exchange Protocol

Transmission congestion management is critical for reliable system operation by keeping the system within the security constraints. In this paper we examine an efficient congestion management system compatible with evolving market environment; the key is building an information exchange protocols between the independent system operator (ISO) and market participants (MPs) that integrate market-based solutions to alleviating congestion. New market mechanisms are proposed for temporally interlinking the short-term market and the long- term market managed through the centralized scheme and the decentralized scheme, respectively. Mathematical formulations for the proposed scheme are presented including the congestion distribution factors for clustering and the stochastic optimal power flow for computing expected congestion costs. For illustration purposes a numerical analysis is conducted on the 39-bus system assuming various system contingency conditions.