Komsan Hongesombut

Stabilization of Tie-Line Power Flow by Robust SMES Controller for Interconnected Power System With Wind Farms

This paper presents the use of superconducting magnetic energy storage (SMES) with robust controllers for stabilization of tie-line power flow in a longitudinally interconnected power system with wind farms. The high penetration of wind power with abrupt changes causes fluctuations of tie-line power flow and significantly affects the effective use of transmission lines. A simultaneous active and reactive power control scheme of SMES including a characteristic of SMES coil current is employed for realizing a permissible range of SMES operation. Moreover, a multiplicative uncertainty model is considered in the parameter optimization of robust SMES controllers by using a heuristic method. Finally, simulation results are carried out to show the effectiveness and robustness under various situations.

Application of power line communication with OFDM to smart grid system

Recently, power distribution grid is moving toward a smart grid where energy generation is decentralized and the grid adapts to demands. Due to the most cost-effective way for two-way communication, the use of power line distribution grid for data communication of smart meters has gained higher interests by utility companies. This paper presents the smart grid system with power line communication (PLC). The system serves as the communication infrastructure linking smart meters through the PLC network. The characteristics of PLC multipath channel and the noise model are presented. The smart meters and PLC are modeled based on the actual distribution grid data to set the model for analyzing the feasibility and performance of a smart grid. Orthogonal Frequency Division Multiplexing (OFDM) modulation technique is used to improve better performance and higher efficiency. Simulation results on different loading conditions have confirmed the performance of OFDM when operating in a power line channel in smart grid system.

Rice (Oryza sativa L.) Seed Sterilization and Germination Enhancement via Atmospheric Hybrid Nonthermal Discharge Plasma

We designed a system to produce atmospheric hybrid cold-discharge plasma (HCP) based on microcorona discharge on a single dielectric barrier and applied it to inactivate microorganisms that commonly attach the rice seed husk. The cold-plasma treatment modified the surface of the rice seeds, resulting in accelerated germination and enhanced water imbibition. The treatment can operate under air-based ambient conditions without the need for a vacuum. The cold-plasma treatment completely inactivated pathogenic fungi and other microorganisms, enhancing the germination percentage and seedling quality. The final germination percentage of the treated rice seeds was ∼98%, whereas that of the nontreated seeds was ∼90%. Microcorona discharge on a single dielectric barrier provides a nonaggressive cold plasma that can be applied to organic materials without causing thermal and electrical damage. The hybrid nonthermal plasma is cost effective and consumes relatively little power, making it suitable for the surface sterilization and disinfection of organic and biological materials with large-scale compatibility.

Tuning the ballistic electron transport of spatial graphene–metal sandwich electrode on a vacuum-silicon-based device

Future high-speed electronic devices rely on the integration of hot-carrier generation and short transit time. Graphene is an attractive material because of its exceptionally high electron mobility along a 2D honeycomb lattice (in-plane transport). Here, we demonstrate the atomic and electrical interactions of graphene–metal (G–M) and metal–graphene–metal (M–G–M) sandwich electrodes on a vacuum-solid-state-based device (i.e., metal-oxide-Si (MOS) with a void channel) forming G–MOS and M–G–MOS, respectively. The combination of a graphene–metal electrode can produce an extremely high ballistic electron emission (∼106 A cm−2 at 1 V bias), traveling along the vertical direction perpendicular (out of plane) to the graphene mesh. The electron emission process is found to be very robust under low-voltage operation, even for emitters at ambient conditions. In addition, the proposed configurations exhibit electrostatic tuning of ballistic electron transport, governed either by space-charge-limited current or field-emission current, having the potential to significantly contribute to various nanoelectronic applications.

Optimal DG Placement in a Smart Distribution Grid Considering Economic Aspects

The applications of Distributed Generation (DG) in a smart distribution grid environment are widely employed especially for power balancing and supporting demand responses. Using these applications can have both positive and negative impacts on the distribution system. The sizing and location of their installations are the issues that should be taken into consideration to gain the maximum benefit from them when considering the economic aspects. This paper presents an application of the Bat Algorithm (BA) for the optimal sizing and siting of DG in a smart distribution power system in order to maximize the Benefit to Cost Ratio (BCR), subjected to system constraints including real and reactive power generation, line and transformer loading, voltage profile, energy losses, fault level as well as DG operating limits. To demonstrate the effectiveness of the proposed methodology and the impact of considering economic issues on DG placement, a simplify 9-bus radial distribution system of the Provincial Electricity Authority of Thailand (PEA) is selected for the computer simulation to explore the benefit of the optimal DG placement and the performance of the proposed approach.

Wide Area Robust TCSC Controller using Phase-Plane Fuzzy Logic Control

This paper presents a robust control of Thyristor Controlled Series Capacitor (TCSC) using the phaseplane fuzzy logic to improve the power oscillation damping of a wide-area power system. First, the TCSC is installed in series with transmission lines of two-area four-machine interconnected power system. Then, the phase-plane fuzzy logic control is adopted so as to control the power oscillations robustly and to improve the power system stability due to uncertainty from the delay time of a wide area control. The performance of the proposed phase-plane fuzzy logic controller is compared with the lead-lag compensator optimally tuned by GA. The simulation results reveal that the proposed phase-plane fuzzy logic control can achieve higher performance and more robustness under the large communication delay. Phase-Plane Fuzzy Logic Control , Thyristor Controlled Series Capacitor, Robust Control, Wide Area Control

New heuristic-based design of robust power system stabilizers

This paper proposes a new robust design of power system stabilizers (PSSs) in a multimachine power system using a heuristic optimization method. The structure of each PSS used is similar to that of a conventional lead/lag stabilizer. The proposed design regards a multimachine power system with PSSs as a multi-input multi-output (MIMO) control system. Additionally, a multiplicative uncertainty model is taken into account in the power system representation. Accordingly, the robust stability margin can be guaranteed by a multiplicative stability margin (MSM). The presented method utilizes the MSM as the design specification for robust stability. To acquire the control parameters of PSSs, a control design in MIMO system is formulated as an optimization problem. In the selection of objective function, not only disturbance attenuation performance but also robust stability indices are considered. Subsequently, the hybrid tabu search and evolutionary programming (hybrid TS/EP) is employed to search for the optimal parameters. The significant effects of designed PSSs are investigated under several system operating conditions.

Coordinate operation of fuzzy logic voltage regulator and Bi-2212 SFCL for enhancing fault ride through capability of DFIG wind turbines

With penetration of wind turbines, fault ride through capability is unconditionally considered as one of the most remarkable research area. Hence, this paper proposes the fault ride through capability improvement of DFIG wind turbines by using cooperative operation of fuzzy logic voltage regulator and Superconducting Fault Current Limiter (SFCL). BSCCO (Bi-2212) superconducting coil material is fully introduced to investigate in this paper. Under large disturbances such as faults, fuzzy logic voltage regulator is directly utilized to enhance a voltage dip at the DFIG terminal. Nevertheless, a high peak fault current cannot be deducted. For this reason, the Bi-2212 SFCL is used for fault current reduction simultaneously. As the simulation results, the proposed fuzzy logic voltage regulator and Bi-2212 SFCL combinative operation have a superior performance to diminish a peak current and improve fault ride through capability for Swedish grid code requirement.

Modeling of rate of change of under frequency relay for microgrid protection

This paper presents the permutation of rate of change of under frequency (ROCOUF) relay to avoid the frequency instability and voltage collapses in microgrid. When some of distributed generators (DGs) in a microgrid are disconnected from the main grid, the system may be imbalance between the power supply and the power demand, resulting in a rapid frequency decline that causes frequency instability in a microgrid. To solve this problem, this paper proposes the development of a modified conventional load shedding scheme using ROCOUF relay. The modeling and simulation of ROCOUF relay is applied and designed for inspection and identification of the severity of disturbance in a microgrid to improve the digital logic of ROCOUF relay so that preventing the frequency and voltage instability in microgrid. The simulation results in this paper are verified by using DIgSILENT PowerFactory software.

An efficient method of automatic distance relay settings for transmission line protection

This paper presents a method for automatic distance relay setting to overcome the overlapping problem of the protection zones. The proposed method is developed as a program aimed at enhancing the calculation of the setting values of the digital distance relay for each protection zone more effectively. The program is developed by using the DPL script (DIgSILENT Programming Language) that is a tool for the analysis of industrial, utility and commercial electrical power systems. In order to validate the performance, the developed program is used for the protection design of closed-loop and radial power system of the Provincial Electricity Authority (PEA), Thailand. From the validation results, it is found that the developed program can ensure that the distance relay operates correctly in its protection zone, leading to higher reliability of the primary protection system of PEA and the shorter of the time spent on the protection design.