Weerawoot Kanokbannakorn

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.

The modeling of AC magnetic contactor for immunity studies and voltage sag assessment

This paper presents the parametric model of AC magnetic contactor to study behavior of contactor during voltage sags. The model derived from contactor structure and its operation so that electrical, magnetic and mechanical equations can be obtained. The model was simulated using electromagnetic transient program. The results show dynamic behavior and immunity of contactor during sag. Additionally, how the sag characteristics, such as point on wave, impact to contactor can study through the model. For voltage sag assessment, the voltage sag ride-through capability curves of AC contactor were constructed and field-test data were also applied. The model reveals that although sag does not cause contactor to disengage, it can cause decreasing in contactor operation lifetime.

Unbalanced voltage sag source location identification based on superimposed quantities and negative sequence

This paper presents a new method to effectively identify the unbalanced sags source location based on negative sequence and superimposed quantities concept. Many previous proposed methods have shown good performance for balanced voltage sag cases. However, their performance reduces for the unbalanced voltage sags, which are the major sag events in power system. The proposed method was derived mathematically and verified by computer simulations and field data from voltage sag survey. The results show the good performance of proposed method. Moreover, the method can locate the sag source in both transmission and radial system.

Microcorona Discharge-Mediated Nonthermal Atmospheric Plasma for Seed Surface Modification

By exploiting the physical effect of a highly nonuniform localized electric field and electron-initiated impact ionization on space charge, we generated homogeneous nonthermal plasma under ambient atmosphere. We evaluated the physical characteristics and evolution of microcorona discharge-induced nonthermal atmospheric plasma (NAP) based on a point-to-plane electrode in open air with two distinct configurations. High-voltage pulses were employed as the primary power source of corona discharge generation to reveal the fundamental mechanism, polarity effect and feasibility of using NAP for organic surface modification. Consequently, we employed NAP to modify the surface of rice (Oryza sativa L.) seeds to improve their wettability. The surface modification of the rice seeds was investigated via water apparent contact angle (ACA) and water imbibition (WI) measurements. The ACA and WI measurements revealed not only the improvement in the wetting properties but also the mutual relationships between and limitations of ACA and WI analysis. We found that the WI time reached saturation after a certain treatment time, called the threshold treatment time. Because vacuum conditions are not required, well-established NAP technology will garner interest in many fields, ranging from the life, environmental, and biomedical sciences to solid-state electronics applications.

The improvement of LVRT criteria for wind generation in PEA transmission grid

This paper presents the improvement of Low Voltage Ride-Through (LVRT) criteria for wind generation interconnection in Provincial Electricity Authority (PEA), Thailand. The existing LVRT is investigated. The intensive studies are carried out by simulations. The results show the existing LVRT should be revised. Finally, LVRT criteria is proposed and the procedures for the future developments are discussed.

An evaluation of voltage variation and flicker severity in micro grid

This paper evaluates the effects of voltage fluctuation in a micro grid. The micro grid is modeled and simulated using the DIgSILENT software. The voltage flicker due to the variation of power productions from renewable sources in microgrid during off-grid and grid-connected mode are presented. The results indicate that the main sources of voltage fluctuation in the studied micro grid are PV and wind generations. The situation becomes worse when the microgrid is operated in off-grid mode. The renewable sources can improve voltage profiles in some cases.

The study of reactive power control strategies of PV plant in PEA distribution system

Due to the significantly increasing of Photovoltaic generations in distribution system, many utilities have reported about the adversely impact of high penetration PV on voltage variations. The various reactive power control strategies have been proposed to solve this issue. The aim of this paper is to study the performance of the implementation of three reactive power control strategies i.e. cosφ, cosφ(P) and Q(U) in Provincial Electricity Authority (PEA) distribution system. The large-scale PV Plant in this study built by DIgSILENT PowerFactory is used to perform simulation. The simulations are shown the voltage improvement and feeder losses on the different reactive power control strategies, by comparing with the base case (PV is generating the maximum active power and not injecting reactive power). The results are expected to use as a guideline for further development of PEA grid code.

The voltage sags correlations between transmission and distribution system of PEA region 1

This paper presents the correlations of voltage sags between the transmission system and the distribution system. The studies included the effect of the transformer connections. Rotchana substation of Provincial Electricity Authority (PEA) has been selected as the case study. It receives power from 115 kV transmission systems and distribute to customers in 22 kV distribution systems. The studied network is simulated by PSCAD/EMTDC program and also the voltage sags data recorded by the power quality meters are used in the analysis. Finally, the results are proposed and discussed.

The studies of a transmission system and distribution system voltage sags correlations

This paper presents the correlation of voltage sags between two sides of difference types of transformer winding connections. We study the propagation of voltage sag down to low voltage and reverse up to high voltage. This study performs on network of provincial electricity authority (PEA), a utility in Thailand. The network is modeled using PSCAD/EMTDC. The faults are applied on this network to generate voltage sags. The types of transformer winding connection are varied to study its influence on voltage sag. Finally, the results are discussed.