Naebboon Hoonchareon

A new coordinated control scheme of PSS and FACT devices for improving power system oscillations in multi-machine system

This paper presents a new coordinated control scheme based on wide-area signals to coordinate local controllers The coordinated controller transmits the supplementary signals to the local controllers. The proposed scheme uses the energy function based on Lyapunovs stability theory for modeling a coordinated controller. In this study, the coordinated controller which is installed at system control center utilizes remote measurements and compensates the interactions between the local controllers. When the coordinated controller is implemented, it provides an additional oscillation damping and also improves the global stability of the power system. A two-area power system which is installed with PSS and SVC is selected to simulate and investigate in this study. The simulation results in different operation conditions and contingencies indicate that implementation of coordinated control scheme can heighten the efficiency of power system and can enhance power oscillation damping for multi-machine power system. Moreover, this scheme can be used to improve the stability of the large power system with multi local controllers.

Fault Data Synchronization Using Wavelet for Improving Two-terminal Fault Location Algorithm

Fault data synchronization for improving Two-terminal fault location algorithm is proposed. Conceptually, employing Wavelet technique, the instantaneous currents of both ends, sampled by Digital Fault Recorders (DFR), will be used to determine a transient reference point for synchronizing the DFR data before applying the Two-terminal algorithm. In the study, both symmetrical and unsymmetrical faults have been simulated for a simplified 230 kV transmission system. The case studies of applying Two-terminal fault location algorithm to the simulated unsynchronized sampled data with assumed phase-shift error varying from -180 to 180 degree, and to the corresponding synchronized data using the proposed Wavelet technique with fixed threshold are conducted for performance verification. Additionally, the effect of fault resistance in the range of 0.01 50 ohm has been investigated. In all test cases, the proposed synchronization method yields satisfactory results such that the error of fault location is independent of the phase-shift error.

Transmission network reconfiguration algorithm considering short-circuit curtailment and voltage stability index

In order to limit high short-circuit currents in the transmission system of the large cities, this paper proposes a network reconfiguration by bus splitting and line removal. Maximum value of fast voltage stability index (FVSI) [6] from all evaluated lines is used in order to indicate the voltage stability condition in the system after reconfiguring the network. The proposed method is tested on the modified IEEE 24-bus reliability test system. The numerical results evidently show its performance to limit short-circuit current of the system while the major system operating constraints are maintained in their limits.

Fault recorder data refinement for accurate fault location in a transmission system

This paper presents a data refinement process for fault data recorded by a group of associated digital fault recorders (DFR) for improving accuracy in line fault location in a transmission system. The refinement process employs weighted least square state estimation technique to compute calibration factors, using the measurements of pre-fault data of voltage and current from multiple correlated DFRs. The factors then are applied to correcting the corresponding during-fault data. To verify the effectiveness of the proposed refinement method, both simulated data from the IEEE 14 bus test system and field measured data from the Thailands transmission system have been tested using the standard two-terminal fault location algorithm. Test results strongly confirm that the improved accuracy in locating fault on a transmission line can be obtained when compares to the respective unrefined cases.

Fault current limitation in metropolitan power system using HVDC link

In this paper, the solution for limitation of short-circuit current using High Voltage Direct Current (HVDC) transmission has been examined. The HVDC is used to replace some AC lines considering two major impacts in a test system. In the first solution, the maximum short-circuit current location is considered. The AC lines connected to the maximum short-circuit bus are chosen to be replaced by HVDC line. In the second solution, the lines with maximum power flow location is considered. The investigation has been conducted on a modified Electricity Generating Authority of Thailand (EGAT) metropolitan area power system. Comparison of short-circuit current and voltage stability index are provided for the two locations to examine feasibility of the proposal method to curtail the fualt currents.

State estimation based enhanced one-terminal algorithm for fault location in a transmission network

This paper proposes an enhanced one-terminal fault-location algorithm in which its salient performance is to combine the advantage of minimal fault data requirement for standard IEEE one-terminal algorithm with the advantage of superior accuracy for two-terminal algorithm. Assuming that voltage phasor at any bus can be easily obtained, and that fault impedance can be treated with resistive characteristic, an optimization problem is then formulated, and solved by a well-known SQP routine, to estimate the fault current contribution from the other terminal with no measuring device such as digital fault recorder. Performance of the proposed technique has been validated by comparing against respective performances of the two aforementioned IEEE standard algorithms as well as another enhanced one-terminal proposed by Takagi, et. al, testing on an IEEE 14-bus network for three-phase and single-phase-to-ground short-circuits with fault resistance varying from 0.1–5 ohm and fault position varying over the entire line length. Test results show impressive accuracy performance, especially for the cases with fault resistance above 1 ohm and fault position within 0.7 per-unit line length. The optimization formulation will be further refined in the future, in an attempt to even improve the accuracy closer to the level obtained from the two-terminal algorithm.

On-line Estimation of Power System Low Frequency Oscillatory Modes in Large Power Systems

In order to evaluate the small signal stability of power system, eigenvalue analysis is an important method to implement. However, there are some disadvantages for example it cannot analyze in on-line condition and is effective for calculating in limited operation conditions. This paper aims to investigate the performance of online oscillation mode estimation techniques for large power systems. Autoregressive and moving average (ARMA model) with least-square and kalman filter algorithms are employed and compared. The performance of both algorithms is tested in term of calculation time and mean square error. The results present ARMA model with both algorithms can provide the satisfied performance. However, ARMA model with kalman filter algorithm has more advantages such as faster calculation time and more accurate calculation results. Thus, this algorithm can be utilized in online oscillation mode estimation and can be used in design the control system for enhancing the damping in power system.

Implementation of Adaptive Neuro-Fuzzy Inference System in Fault Location Estimation

This paper proposed a new scheme using hybrid intelligent technique that combines artificial neural network and fuzzy inference system. This technique, known as Adaptive Neuro-Fuzzy Inference System (ANFIS) has associated with the advantage of wavelet transform as a pattern recognition method. The algorithm used to identify the type of fault either single line to ground, double line, double line to ground or three phase occur on a power transmission line. Other than that, this scheme is capable to analyze the fault location without the knowledge of line parameters. A power clustering algorithm called Gustafson Kessel is implemented for better performance. Alternative Transient Program/Electromagnetic Transient Program (ATP/EMTP) is used for simulation purposes and Matlab for further analysis. Outcomes indicated that the scheme is efficient and has a high percentage of accuracy.

Generalized sagittal diagram for fault equipment identification within a transmission system

There have been many intelligent approaches proposed for fault equipment identification within a transmission system. In particular, the fuzzy relation implemented in a form of sagittal diagram can associate various alarm patterns with the fault equipment, even in the case of malfunction of protective relays or protection device failure. However, such a method requires that a specific sagittal diagram for each equipment be constructed, with respect to a power system configuration. It is also rather difficult to apply the method for a transmission system of which its service stations are breaker-and-a-half type. This paper proposes the concept of generalized sagittal diagram for fault equipment identification with no requirement of the detailed system configuration information. Rather, an outage configurator program (OCP) has been devised for detecting a set of outage elements, that are buses and nodes, within a breaker-and-a-half station. Performance of the proposed algorithm has been verified using actual digital data from the digital fault recorders (DFR) installed within a Thailands 230-kV transmission network. Case studies include those complex fault events with one or two circuit breaker failure.

Controller design for DFIG-based wind power generation using Zakian's framework

In this paper, a real power controller design for wind power generation has been conducted. The wind power station is assumed to be a type of doubly-fed induction generator (DFIG). Zakians framework has been employed to maximize power output and to limit the system frequency negative impact, concurrently. Under fluctuation of wind speed in two-machine test system, the performances of the design controller are examined. Simulated test results show that the proposed method is effective.