Sang-Seung Lee

A Reliability-Centered Approach to an Optimal Maintenance Strategy in Transmission Systems Using a Genetic Algorithm

Electric power transmission utilities try to maximize profit by reducing electricity supply costs and operation costs while maintaining their reliability. Developing maintenance strategies is one of the effective ways to achieve these profitable goals. The reliability-centered maintenance approach is a key method in providing optimal maintenance strategies. It considers the tradeoffs between the upfront maintenance costs and the potential costs of reliability losses. Since a transmission system is a group of different kinds of equipment and the reliability of the electric facilities varies with time, an equipment state model using a modified semi-Markov chain is proposed. In addition, a genetic algorithm is used to find the optimal maintenance strategies from a large class of possible maintenance scenarios. These optimal maintenance strategies have been tested on an IEEE 9-bus system and an IEEE 118-bus system; the results show that the proposed method minimizes the total expected costs.

North-East Asia interconnection scenario map, and power reserve strategy in South Korea

The purpose of This work is to obtain the reserve power for the future power shortages faced by the metropolitan areas of the Korean Peninsula and by the southeastern area of the South Korea in North-East Asia. The assumed scenarios will be proposed in the cases of without or with connection to the Sinpo nuclear power plant which is to be constructed with 2,000 MW capacity in the future. In this connection, the types of a power transmission for interconnection consist of the 765 kV HVAC and the HVDC. Here, the various scenarios for providing the interconnection of the power systems among Far-East Russia, North-East China, North Korea, South Korea, and Japan are presented, and the resulting interconnected power systems are simulated by means of a power flow analysis performed with the PSS/E tool. The power flow map is drawn from the data simulated and the comparative study is done.

Northeast Asia interconnection, and power flow considering seasonal load patterns

This paper presents the effects of an increase or a decrease of a power reserve by load flow calculations under seasonal load patterns of each country for the future power shortages faced by the metropolitan areas or by the southeastern area of the South Korea in North-East Asia. In these connections, the types of a power transmission for interconnection consist of the 765 kV HVAC and the HVDC. In this paper, the various cases of the power system interconnections in Far-East Asia are presented, and the resulting interconnected power systems are simulated by means of a power flow analysis performed with the PSS/E 28 version tool. The power flow map is drawn from data simulated and the comparative study is done. In this future, a power flow analysis was considered to reflect the effects of seasonal power exchanges. And the plan of assumed scenarios was considered with maximum or minimum power exchanges during summer or winter in North-East Asia countries.

Nonlinear adaptive back-stepping controller design for power system stabilizer in multi-machine power systems

This paper proposes a nonlinear adaptive back-stepping controller to damp the oscillations and improve the transient stability in multi-machine power systems. The designed controller is adaptive to unknown generator parameters. The proposed controller is designed based on a fourth order nonlinear model of a synchronous generator and the automatic voltage regulator model is considered so as to decrease the steady state voltage error. The construction of both control law and associated Lyapunov function is consistently systematic within the design methodology. A 3-machine power system is used to demonstrate the effectiveness of the proposed controller over other two controllers: one is the conventional damping controller (power system stabilizer) and the other is the one designed by the feedback linearization technique.

Compressed Air Energy Storage Units for Power Generation and DSM in Korea

In this paper, we discuss compressed air energy storage (CAES) units, and reflect on a demand-side management (DSM) technique including six generic load shape objectives in the Korea electric power corporation (KEPCO). The CAES technology has been considered for substitute energy utilization not only in regards to the management of large or small loads but also for use by emergency generators during a power failure. Recently, in the energy storage field, countries with CAES have developed small, medium and large units for storage roles. These units can be used for the dual-purpose applications of supplementary power generation and district heating supply systems. These units have an underground cavern or a modular-type pressurized vessel with large and small, micro containers. The storage and utilization time of the CAES are determined by the power between the lower limit and upper limit by the KEPCO load curve patterns over an entire day.

Northeast Asia interconnection, and technical & market considerations

This paper proposes technical and market considerations for the power system interconnection in Northeast Asia (NEA). In technical sides, the effects of an increase or a decrease of a power can compensate reserve power by the utilization under seasonal load patterns of each country for the future power shortages faced by the metropolitan areas or by the southeastern area of the South Korea in NEA. The transmission voltage for interconnection between South Korea and North Korea may be used 345 kV or 765 kV HVAC, and also the transmission voltage between North Korea and North China or Far-East Russia may be used 500 kV HVAC or HVDC. In market sides, we firstly deal with a monopoly electric power market, and secondly a competitive electric power market with complexity because the transition from the regulated monopoly to a free electricity market in NEA countries radically changes the situation with ISET substantiation and financing. In this paper, in the various cases of the power system interconnections in Far-East Asia, technical and market considerations are presented

Demand response prospects in the South Korean power system

This paper describes demand response prospects for South Korea. To manage the increasing electric power demand, the way to increase power generation has reached a limit becoming a social, economic and environmental problem. To solve this problem by managing the supply side, demand response (DR) has become an important solution. As seen in other countries, the Korean electricity community plans to improve the DR in order to solve the generation problem. But the conventional DR program in Korea has a history of contracts being conducted over the transom, so the DR program has many disadvantages. This is one of the more important problems in the Korean DR program. Because of this, this paper proposes a more effective DR program than the conventional one to protect the participant returns. This paper also designs a DR the information and control structure suitable for the electrical environment.

Northeast Asia Power Interconnection Studies; Trends and Prospects in South Korea

In this paper, we present recent representative studies about technical and economical considerations for the power system interconnection in Northeast Asia (NEA). These activities on interconnection between countries or areas in a NEA have been considered and presented from many sides including considering political and economical situations. In South Korea, recent studies of power system interconnection are trending toward specific technical and economical considerations for each of several scenarios. We include reliability studies and power flow studies on technical sides. Also, we introduce an economic feasibility study.

Northeast Asia Interconnection-based integration of DG, DR, HVDC, and nuclear load-following under Smart Grid in the South Korean power system

This paper, based on the Northeast Asia (NEA) power system interconnection, presents an integration of renewable generation (RG), demand response (DR) or distributed generation (DG), high-voltage direct-current (HVDC), and nuclear power plant load-following operation under Smart Grid (SM) in the South Korean power system. The reliable power system depends on considering the reliability that affect after the system is connected or disconnected. The land-to-land power system interconnection in NEA countries will use as the back to back (BTB) technique for power transmission lines; whereas the point-to-point (PTP) will be used for over-sea interconnection, such as a Jeju Island and South Korea-Japan submarine transmission. In this paper, we will suggest how to design and analyze the operation mechanism/algorithm of the reliability side for the NEA, and an integration of RG, DR, HVDC, and nuclear power plant load-following operation under SM in the South Korean power system. Also, we present an inter-area power flow map for a power flow analysis for NEA countries to relieve the possible future power imbalances within the metropolitan areas or the southeastern area of Korea.

Generalized Reliability Centered Maintenance Modeling Through Modified Semi-Markov Chain in Power System

The purpose of power system maintenance is to prevent equipment failure. The maintenance strategy should be designed to balance costs and benefits because frequent maintenance increases cost while infrequent maintenance can also be costly due to electricity outages. This paper proposes maintenance modeling of a power distribution system using reliability centered maintenance (RCM). The proposed method includes comprehensive equipment modeling and impact analysis to evaluate the effect of equipment faults. The problem of finding the optimum maintenance strategy is formulated in terms of dynamic programming. The applied power system is based on the RBTS Bus 2 model, and the results demonstrate the potential for designing a maintenance strategy using the proposed model.