Jaegul Lee

Design of Advanced Voltage Management System Including Manual Operation Mode via Real-Time Digital Simulator

This paper presents the design of the advanced voltage management system (AVMS) including manual operation mode in order to control reactive power generation in a practical power system. The existing secondary voltage controller (SVC) has a demerit occurring as a large transient phenomenon shortly after the SVC begins to work. This malfunction results from the difference of the operation statuses before and after the SVC operates. For solving the problem and implementing the voltage control safely, the AVMS including the manual operation mode is developed by Korea Electric Power Corporation. Aside from the fact that the AVMS overcomes the drawback, it can also execute the coordination control of both continuous voltage controller (CVC) and discrete voltage controller (DVC). The CVC controls reactive power generation sources such as generator and flexible ac transmission system devices which can generate reactive power continuously and linearly. On the other hand, the DVC controls the discrete reactive power sources such as switched shunt capacitors and reactors. The performances of the proposed AVMS are carried out by time-domain simulation in the Jeju Island power system with real-time digital simulator.

Design of advanced voltage management system including manual operation mode via real-time simulation

This paper presents the design of the advanced voltage management system (AVMS) including manual operation mode in order to control reactive power generations in practical power system. The existing secondary voltage controller (SVC) has a demerit occurring large transient phenomenon shortly after the SVC begins to work. This malfunction results from the difference of the operation status before and after the SVC operates. For solving the problem and implementing the voltage control safely, the AVMS including the manual operation mode is developed by Korea Electric Power Corporation (KEPCO). As well as the AVMS overcomes the drawback, it can execute the coordination control of both continuous voltage controller (CVC) and discrete voltage controller (DVC). The CVC controls reactive power generation sources such as generator and FACTS devices which can generate reactive power continuously and linearly. Otherwise, the DVC controls the discrete reactive power sources such as switched shunt capacitors and reactors. The performances of the proposed AVMS are carried out by time domain simulation in the Jeju Island power system with real-time digital simulator (RTDS).

A Practical Power System Stabilizer Tuning Method and its Verification in Field Test

This paper deals with parameter tuning of the Power System Stabilizer (PSS) for 612 MVA thermal power plants in the KEPCO system and its validation in a field test. In this paper, the selection of parameters, such as lead-lag time constants for phase compensation and system gain, is optimized using linear and eigenvalue analyses. This is then verified through the time-domain transient stability analysis. In the next step, the performance of PSS is finally verified by the generators on-line field test. After the field test, measured and simulated data are also compared to prove the effectiveness of the models used in the simulations.

A Tuning Method for the Power System Stabilizer of a Large Thermal Power Plant and Its Application to Real Power System : Part I-Selection of Parameters by Off-line Simulation

This paper, which consists of two parts, dealt with the parameter tuning of the power system stabilizer for a 612[MVA] thermal power plant in KEPCO system and its validation in field test. In Part 1 of the paper, the selection of parameters such as lead-lag time constants for phase compensation, system gain was optimized by using linear & eigenvalue analyses and they were verified through the time-domain transient stability analysis. In part 2, the performance of PSS was finally verified by the generator`s on-line field test. Through the comparisons of simulation results and measured data before and after tuning of the PSS, the models of generator and its controllers including AVR, Governor and PSS used in the simulation are validated and confirmed.

A Tuning Method for the Power System Stabilizer of a Large Thermal Power Plant and Its Application to Real Power System : PART II - Field Tests and Verification of PSS Performance

【This paper, as the second part of the paper, dealt with the field test and test results to validate PSS(Power System Stabilizer) parameters which are previously tuned in Part 1 paper. In Part 1 of the paper, the selection of parameters such as lead-lag time constants for phase compensation and system gain was optimized by using linear & eigenvalue analyses and they were verified through the time-domain transient stability analysis. In part 2, the performance of PSS was finally verified by the generators on-line field test. Through the comparisons of simulation results and measured data before and after tuning of the PSS, the models of generator and its controllers including AVR, Governor and PSS used in the simulation are verified and confirmed.】

Application of Multi-step Undervoltage Load Shedding Schemes to the KEPCO System

This paper deals with improvements to the special protection schemes (SPS) which have been applied to the low probability and high impact contingencies in the Korea Electric Power Corporation (KEPCO) system since 2004. Among them, the SPS for voltage instability in the Seoul metropolitan area is considered in this paper, and is a form of event-based undervoltage load shedding with a single-step scheme. Simulation results based upon a recent event that occurred on 765kV lines show that the current setting values of the SPS have to be revised and enhanced. In addition, by applying response-based multi-step undervoltage load shedding (UVLS) schemes to severe contingencies in the system, more effective results than those of the existing single-step SPS can be obtained. Centralized and distributed UVLS schemes are considered in the simulation. ULTC-based load recovery models and over excitation limiters (OXL) for the KEPCO system are also included in the long-term voltage instability studies.

Web based Online Outage Cost Assessment and Information System of Electrical Energy

This paper proposes a Web Based Online Outage Cost Assessment and Information System(WOOCAIS) for power system outage cost assessment. The proposed WOOCAIS is a kind of web based survey method for outage cost assessment. While conventional survey methods have done outage cost assessment based on survey paper lists collected by post mail or visiting customers, the proposed WOOCAIS is a web based online survey operation and assessment system. Therefore, it can curtail expenditure for survey and also is more convenient than conventional method. It will be set up for actual outage cost assessment system of KEPCO in South Korea in the near future. The WOOCAIS will be applied in various research and actual planning and operation areas. First of all, the assessed results may be not only applied as one of objective function for generation system and grid expansion but also operational planning problems in power system.

A Study on the Method to Evaluate Minimum Capacity of Energy Storage System(ESS) for Micro Grid(MG) Design

In this paper, we propose a probability method to determine minimum capacity of energy storage system(ESS) for Micro-grid Because of high capital cost of ESS, It`s very important to determine optimal capacity of ESS and for stable operation of Micro grid(MG), we should determine minimum capacity of ESS. The proposed method has abilities to consider forced outage rate of generators and intermittent of non-dispatchable generators and minimum capacity make MG keep energy balancing by oneself.

Study on the Estimation of Seasonal Ambient Current for the Application of Ambient Adjusted Line Rating(AAR) in Overhead Transmission Lines Using Risk Tolerance(RT) Method

Ambient Adjusted line Rating(AAR) method for overhead transmission lines considering Risk Tolerance(RT) was proposed in this paper. AAR is suitable for system operators to plan their operation strategy and maintenance schedule because this can be designed as a seasonal line rating. Several candidate transmission lines are chosen to apply the proposed method in the paper. As a result, it is shown that system reliability was significantly enhanced through maximizing transfer capability, solving the system constraints.

Field Implementation of Voltage Management System (VMS) into Jeju Power System in Korea

This paper presents the results of field tests on Voltage Management System (VMS) using hybrid voltage control, which utilizes coordinated controls of various reactive power resources such as generators, FACTS and switched shunt devices to regulate the pilot bus voltage in a voltage control area. It also includes the results of performance test on RTDS-based test bed in order to validate the VMS before installing it in Jeju power system. The main purpose of the system is adequately to regulate the reactive power reserve of key generators in a normal condition with coordination of discrete shunt devices such as condensers and reactors so that the reserves can avoid voltage collapse in emergency state in Jeju system. Field tests in the automatic mode of VMS operation are included in steady-states and transient states. Finally, by the successful operation of VMS in Jeju power system, the VMS is proved to effectively control system voltage profiles in steady-state condition, increase system MVAR reserves and improve system reliability for pre- and post-contingency.