-This paper presents a multiagent system for microgrid operation in the grid-interconnected mode. An energy market environment with generation competition is adopted for microgrid operation in order to guarantee autonomous participation and meet the requirements of participants in the microgrid. The modified Contract Net Protocol (CNP) is used as a protocol for interactions among agents. The multiagent system for microgrid operation based on the modified CNP and the energy market environment is designed and implemented. To verify the feasibility of the suggested multiagent system, experiments on three operation conditions are carried out.
Abstract:A microgrid is an eco-friendly power system because renewable sources such as solar and wind power are used as the main power sources. For this reason, much research, development, and demonstration projects have recently taken place in many countries. Operation is one of the important research topics for microgrids. For efficient and economical microgrid operation, a human operator is required as in other power systems, but it is difficult because there are some restrictions related to operation costs and privacy issues. To overcome the restriction, autonomous operation for microgrids is required. Recently, an intelligent agent system for autonomous microgrid operation has been studied as a potential solution. This paper proposes a multiagent system for autonomous microgrid operation. To build the multiagent system, the functionalities of agents, interactions among agents, and an effective agent protocol have been designed. The proposed system has been implemented by using an ADIPS/DASH framework as an agent platform. The intelligent multiagent system for microgrid operation based on the proposed scheme is tested to show the functionality and feasibility on a distributed environment through the Internet.
Abstract:One of the most important requirements of microgrid operation is to maintain a constant frequency such as 50 Hz or 60 Hz, which is closely related to a power balance between supply and demand. In general, microgrids are connected to power grids and surplus/shortage power of microgrids is traded with power grids. Since islanded microgrids are isolated from any power grids, the decrease in generation or load-shedding can be used to maintain the frequency when a power imbalance between supply and demand occurs. The power imbalance restricts the electricity use of consumers in the case of supply shortage and the power supply of suppliers in the case of supply surplus. Therefore, the islanded microgrid should be operated to reduce power imbalance conditions. Meanwhile, the microgrid is a small-scale power system and the employment of skillful operators for effective operation of its components requires high costs. Therefore, automatic operation of the components is effective realistically. In addition, the components are distributed in the microgrid and their operation should consider their owners' profits. For these reasons, a multiagent system application can be a good alternative for microgrid operation. In this paper, we present a multiagent system for autonomous operation of the islanded microgrid on a power market environment. The proposed multiagent system is designed based on a OPEN ACCESSEnergies 2010, 3 1973 cooperative operation scheme. We show the functionality and the feasibility of the proposed multiagent system through several tests.
Water motion over a 200-mm diameter wafer surface rotating in a single-wafer wet cleaner was studied, using the water flow visualization technique with a video camera and blue-colored ink as the tracer. When the tracer was injected from the wafer center, it was seen to symmetrically spread over the rotating wafer surface from its center to the edge. The radial velocity of the water showed a negligibly small change over the wafer surface except at its center area. The water layer thickness in the rotation rate range between 500 and 1400 rpm was approximately 0.1 mm; it gradually decreased with the increasing rotation rate. The tracer injected from non-center positions showed that the water flow tended to be localized in the peripheral region of the wafer, particularly at the high rotation rates.The process of fabricating semiconductor silicon microelectronic devices requires a very clean silicon surface. Because various contaminants are present during the device fabrication, they must be removed by cleaning techniques, such as wet cleaning using a single-wafer-type and a batch-type wet cleaner. 1,2 The single-wafer wet cleaner using wafer rotation has various advantages, such as no cross-contamination between the wafers and a small footprint. 1 In order to study and optimize the wet cleaning process condition from the viewpoint of the transport phenomena and the chemical reaction, the fluid flow on and around the rotating wafer surface should be clarified. 3,4 Thus, the water motion and etch rate were studied by many researchers 3,5 based on numerical calculations. For further developing the numerical calculation model, the water motion should be clarified by experiment using a fluid visualization technique.In this study, the typical water motion over a wafer surface rotating in a single-wafer wet cleaner was studied by the flow visualization technique using a blue-colored ink tracer and a video camera. The water velocity and the water layer thickness were evaluated when the water was injected at the wafer center. Additionally, the water motion injected from positions other than the wafer center was studied. Figure 1 shows the single-wafer wet cleaner used in this study. This cleaner uses a 200-mm diameter wafer rotating at the rate of 100-1400 rpm in a cylindrical-shaped vessel. Water was supplied through a tube from the pump, and was injected downward from the water nozzle normal to the wafer surface at the flow rate of 1 l/min. After the injection, the water was transported along the wafer surface from the injected position to the wafer edge, then finally sputtered off from the wafer edge to the outside. ExperimentalIn order to obtain the water motion, the mass transport should be directly visualized and traced. For this purpose, a water-soluble colored ink can be a suitable tracer, because it is perfectly dissolved and transported with the water. Additionally, the ink is harmless and very low cost.At a specified time after starting the water injection for forming a steady state of water flow, 1 cm 3 of the blu...
Abstract:A microgrid is an eco-friendly power system because renewable sources are used as main power sources. In the islanded operation mode of a microgrid, maintaining the balance between power supply and power demand is a very important problem. In the case of surplus supply, decreased generation output and/or charge of distributed storages can be applied to solve the imbalance between power supply and demand. In the case of supply shortages, increased generation output and/or discharge of distributed storages can be applied. Especially in the case of critical supply shortages, load shedding should be applied. In a distributed load-shedding approach, microgrid components need to make decisions autonomously. For autonomous microgrid operation, a multi-agent system has been investigated. In this paper, a distributed load-shedding system for agent-based autonomous operation of a microgrid is designed. The designed system is implemented and tested to show the functionality and feasibility of the proposed system.
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