Causes Of Disconnection Research Articles

Voltage Control Architectures for the Universal Operation of DPGS

The future concept of universal operation embraces those distributed power generation systems (DPGS) capable of getting disconnected from the main grid to start operating within an island. Once the cause of disconnection is solved, the DPGS is able to resynchronize and reconnect with the grid. In these conditions, the universal operation can be successfully implemented through a voltage control. Voltage control is manly adopted in uninterruptible power supply (UPS) and island applications. However, a study that solely focused on the universal operation is missing. The goal of this work is to help in the selection of the most suitable control structure as function of: 1) power dynamics, power quality, and robust stability in grid-connected; 2) voltage regulation and performance under local load steps in island mode; and 3) behavior during the reconnection with the grid. For that purpose, five architectures have been reviewed within a general mathematical framework and with experimental results.

STATCOM and Capacitor Banks in a Fixed-speed Wind Farm

Wind Farms are the viable solution for delivering clean energy in near future. There are many difficulties in ensuring higher quality power into the grid, as demanded by the more and more stringent grid codes. The solution of these problems could be solved by Flexible Alternate Current Transmission Systems (FACTS) devices in the system and particularly the Statatic synchronous condenser (STATCOM). Which uses the principle reactive power (injection or absorption).One of the main causes of disconnection of wind network is the variation of voltage (drop voltage or over voltage) at the bus bar connection. The use of STATCOM, allows regulating the voltage and maintaining the grid connected wind even under certain severe conditions of disturbance.In this paper, we propose a study of the importance use of STATCOM when it installed in a wind farm and we will try to see the effect of injecting reactive power in order to maintain the voltage at the nominal value. This opportunity offers the possibility of connecting the wind farm to the grid. The choice of this study is justified by simulation in MATLAB.

Discovering periodic patterns of nodal encounters in mobile networks

Routing in Delay Tolerant Networks is very challenging because of frequent disconnections. One cause of disconnection is node movement. Disconnections can be overcome by finding a set of sequential opportunistic encounters between pairs of mobile nodes. These encounters can be used for message forwarding and delivery. In this context, understanding user mobile behaviour is essential to design effective and efficient network protocols. This paper presents a generic methodology to model and find periodic encounter patterns by using the auto-persistence function and detection techniques derived from it. From the studies on four real mobility traces, we are able to detect strong weekly periodic encounter patterns with an accuracy of up to 100%. The experimental results show that periodic encounter patterns in real mobility traces do not last long, e.g., years, because they are interrupted by unexpected events from time to time. Nonetheless our experimental results show that those periodic encounters can still last up to a few months. Furthermore, we show that, for some of the mobility traces, the network formed by periodic encounters forms a small-world structure.

FRT Control Method Including Islanding Detection in PCS Model for Photovoltaic Generation

In this study, we made experiments by the simulated PV system for understanding the cause of disconnection when instantaneous voltage sag occurs. Moreover, it is understood that the PCS with the voltage phase jump detection method which is one of the main causes of the disconnection. We modeled it in the simulation. When fault occurs, even though the residual voltage is more than 20 % and the voltage sag time is within 1.0 sec, the PCS disconnected by the voltage phase jump detection was confirmed in the simulation results. If a large number of PV systems are interconnected in the power system, we verified through the simulation that the interaction caused by the disconnection which generated by the voltage phase jump detection. We proposed threshold limit value of islanding detection. The validity of proposed method was verified through the simulation in this study.