Tae-Kyoo Oh

New design of PMU for real-time security monitoring and control of wide area intelligent system

Security monitoring and control are very important for stable operation in wide area intelligent system. Electrical power grid is one of a wide area system and is progressing to intelligent system. For real-time security monitoring and control of electrical power grid, measurement of control variables such as voltage, current, real power, reactive power, power factor and system frequency must be synchronized because sub-control sites are distributed widely. Global Positioning System (GPS) is used for synchronization. In this paper, we introduce the new design concept of Phasor Measurement Unit (PMU) for security monitoring and control of electrical power grid, which is one of the wide area intelligent systems. PMU is applied d-q transformation and Phase Locked Loop (PLL) to improve the robustness of measurement. PMU is tested on three-phase 380V distribution line with resistor load.

Status and perspective of transmission pricing scheme in Korean electricity market

This paper thoroughly investigates how best it would be to send an adequately accurate locational price signal with the congestion costs incorporated into the transmission pricing rule when the electricity market, in which costs are recovered from all transmission users on an equivalent basis, is not unduly maintained. This paper attempts to make a supportive and self-explanatory proposal that it could fit the Korean cost-based pool (CBP) that satisfactorily sharpens the locational price signal.

Transmission-security constrained optimal dispatch scheduling using generalized Benders decomposition

For the secure power system operation, we introduce a decomposition technique that separates a transmission-security constrained dispatch scheduling problem into a master problem (MP) and several subproblems (SPs) using Benders decomposition. The MP solves a general optimal power flow (OPF) problem while the SPs inspect the feasibility of OPF solution under respective transmission line contingencies. If a dispatch scheduling solution given by the MP violates transmission-security constraints, then additional constraints corresponding to the violations are imposed to the MP. Through this iterative process between the MP and SPs, we derive an optimal dispatch schedule incorporating the post-contingency corrective rescheduling. Numerical example demonstrates efficiency of the proposed approach.

Stabilizing scheme application for improving power system security in Korea

This paper describes the characteristics of electric power system and special stabilizing control schemes applied to improve system stability in Korea. As additional units of large generators were added to the existing generation sites with the reinforcement of the transmission facilities being delayed because of the difficulty of acquiring new sites and right-of-way, the system characteristics such as short circuit current, voltage regulation, and transient stability show the tendency of degradation. Among them, out-of-step problems of the large capacity generation stations were identified to be solved for improving the system security. This paper presents some typical special stabilizing control schemes that were applied to prevent loss of synchronism of all the generators at a site in Korea.

An Approach to Optimal Dispatch Scheduling Incorporating Transmission Security Constraints

The introduction of competition in electricity markets emphasizes the importance of sufficient transmission capacities to guarantee effective power transactions. Therefore, for the economic and stable electric power system operation, transmission security constrains should be incorporated into the dispatch scheduling problem. With the intent to solve this problem, we decompose a dispatch scheduling problem into a master problem (MP) and several subproblems (SPs) using Benders decomposition. The MP solves a general optimal power flow (OPF) problem while the SPs inspect the feasibility of OPF solution under respective transmission line contingencies. If a dispatch scheduling solution given by the MP violates transmission security constraints, then additional constraints corresponding to the violations are imposed to the MP. Through this iterative process between the MP and SPs, we derive an optimal dispatch schedule incorporating the post-contingency corrective rescheduling. In addition, we consider interruptible loads as active control variables since the interruptible loads can participate as generators in competitive electricity markets. Numerical examples demonstrate the efficiency of the proposed algorithm.

Optimal voltage and reactive power control of local area using genetic algorithm

To improve the voltage profile and to reduce system losses, many switched shunt capacitors are used in a power system. It is necessary to coordinate them for operating the system effectively. In this study, a genetic algorithm (GA) is used to find optimal coordination of switched shunt capacitors within a local area of a power system. To verify the effectiveness of the proposed method, a simulation is performed of KEPCO (Korea Electric Power Corporation) power system.

Bifurcation Control Application to-Voltage Collapse in a Model Power System

Abstract In this paper, we have proposed bifurcation control of voltage collapse in the model power system. Bifurcation theory is applied to analyze the voltage collapse in a model power system. Controls using existing power system facilities have suggested to mitigate voltage collapse phenomena. Nonlinear control law is designed to stabilize periodic solutions which emerges after voltage collapse phenomena. Moreover, a control law, which achieves reducing amplitude of the bifurcated periodic solution, is designed