Jeonghoon Shin

Fast and Reliable Estimation of Composite Load Model Parameters Using Analytical Similarity of Parameter Sensitivity

This paper proposes a computationally efficient technique for estimating the composite load model parameters based on analytical similarity of parameter sensitivity. When the model parameters are updated in the optimization procedure to best fit the actual load dynamics, i.e., measurements, parameters of similar sensitivity representation in the given mathematical model structure are updated in the same manner at every iterative step. This research allows for practically reducing the number of load model parameters to be identified in the estimation process and the overall computational cost while preserving the desired complexity and accuracy of the original model. This approach consequently facilitates the parameter estimation in the optimization process and helps manage increased number of parameters often criticized for adopting the dynamic composite load model via measurement-based approach. Case studies for the real power system demonstrate the computational efficiency and intact accuracy of the proposed method with reference to the existing methods of estimating all the parameters of the given composite load model independently.

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.

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.

Application of dual-input PSS to 343 MVA pumped storage unit and its validation

This work describes practical tuning methods and testing of a dual-input prototype PSS, which uses both frequency and power, with the 343 MVA Muju P/P #2 in the KEPCO system to enhance the damping of both local and inter-area modes. A Bode plot was drawn to tune the PSSs time constants to compensate for phase lag. In addition, eigenvalue analysis was used to determine a reliable PSS gain, Ks, and a time-domain transient program was used to verify safe operation of the PSS in the presence of predictable disturbances, such as the AVR step test and generator unloading. In the on-site test, the AVR step tests at 300 MW loading at Muju P/P #2 were implemented with a dual-input prototype PSS to check to what extent the PSS damped the power oscillation of the disturbances. The recorded data showed that power oscillations were reduced considerably as the PSS gain was increased.

A study on the application of the DVR system using EMTDC program

Voltage sag(Instantaneous voltage drop) of the grid system is the most frequent power quality problem. The impact of sag to the sensitive loads is severe. And load disruptions by sag bring about substantial economic losses up to millions of dollars. DVR is one of the CPD(Custom Power Device) that can mitigate the voltage sag. It operates as a series connected compensator whose output voltage can control the voltage of the system. And the magnitude of compensation voltage of DVR is limited by the characteristics of system and load. We simulate the compensation capability of DVR by EMTDC. Also we test the effect of DVRs compensation at ‘Power quality test center’ which is composed of SSFG(Sag, Swell, and Flicker Generator) SSTS, DVR, DSTATCOM, and loads.

Development of long-term simulator for the large-scaled power system

This paper presents a development of program in long-term dynamic stability. The long-term voltage instability is caused by reactive-power reserves. The reactive-power reserve problems are especially determined by Over-excitation limiter(OXL) and Under Load Tap Changer(ULTC), etc., which are the power device having a few to 10s minutes of time periods. The previous method estimating Long-term voltage stability is the Full-time domain simulation. The Full time simulation methods can compute the exact results, but it may take an amount of time to simulate. And it may have the numerical error in long-term time scale. Thus, the alternative methods to calculate the appropriate results are needed. This paper deals with the Long-term voltage stability using Quasi-Steady-State (QSS) Analysis. QSS can provide good results and improve the speed of simulation. This fast time simulation method (QSS) assumes that the short-term dynamics or transient stability are stable after the contingency and can be replaced by their equilibrium equations. The concept of singular perturbation is applied on focus on long-term dynamics.

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.