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Seamless formation and robust control of distributed generation microgrids are essential requirements to facilitate powerful and flexible control infrastructure in future smart power grids. Motivated by this objective, this paper presents a control structure for microgrid converters based on direct-voltage control and optimized dynamic power sharing. The salient features of the proposed scheme are 1) minimum switching actions between grid-connected and isolated microgrids systems to minimize internal microgrid formation disturbances; 2) active damping control performance in the converter control voltage vector to effectively reject both voltage magnitude disturbances and power angle swings associated with mode transition and load disturbances; and 3) high bandwidth direct voltage control loop in both grid-connected and isolated microgrid modes to improve the dynamic response and disturbance rejection performance. Theoretical analysis and comparative experimental results are presented to validate the effectiveness of the proposed control scheme. [ABSTRACT FROM AUTHOR]

Although active islanding detection techniques have smaller nondetection zones than passive techniques, active methods could degrade the system power quality and are not as simple and easy to implement as passive methods. The islanding detection strategy, proposed in this paper, combines the advantages of both active and passive islanding detection methods. The distributed-generation (DG) interface was designed so that the DG maintains stable operation while being grid connected and loses its stability once islanded. Thus, the over/undervoltage and over/underfrequency protection method would be sufficient to detect islanding. The main advantage of the proposed technique is that it relies on a simple approach for islanding detection and has negligible nondetection zone. The system was simulated on PSCAD/EMTDC and simulation results are presented to highlight the effectiveness of the proposed technique. [ABSTRACT FROM AUTHOR]

Wind generation is considered one of the most rapidly increasing resources among other distributed generation technologies. Recently, wind farms with considerable output power rating are installed. The variability of the wind output power, and the forecast inaccuracy could have an impact on electricity market prices. These issues have been addressed by developing a single auction market model to determine the close to real-time electricity market prices. The market-clearing price was determined by formulating an optimal power flow problem while considering different operational strategies. Inaccurate power prediction can result in either underestimated or overestimated market prices, which would lead to either savings to customers or additional revenue for generator suppliers. [ABSTRACT FROM AUTHOR]

Integration of wind facilities into power system grids have several impact on power system related issues including; transmission congestion, optimum power flow, system stability, power quality, system economics and load dispatch. Consequently, wind farm control strategy, location across the distribution network and its penetration level could have an impact on electricity market prices. This paper addresses these issues, by developing a single auction market model. An optimal power flow problem was formulated for determining the close to real time electricity market-clearing price and the total cost of generation. Simulation results, considering different operational cases, are presented to highlight the impact. [ABSTRACT FROM AUTHOR]

An active islanding detection technique for an inverter-based distributed generator (DG) is presented. Two control strategies are studied: one in which the DG only supplies active power and one in which the DG supplies both active and reactive power to improve the power factor. The nondetection zone (NDZ) of the over/under voltage and frequency protection (OVP/UVP and OFP/UFP) method for each control strategy is determined. For the presented interface control, it is observed that the NDZ of the OVP/UVP and OFP/UFP is larger when the DG interface is designed to improve the power factor. In order to decrease the NDZ, an islanding detection method is designed that is based on creating a mismatch between the load and DG reactive power, thus forcing the frequency to deviate outside the OFP/UFP limits. It is shown that the proposed islanding detection technique is robust and has a negligible NDZ. [ABSTRACT FROM AUTHOR]

Islanding detection of Distributed Generation (DG) is considered as one of the most important aspects when interconnecting DGs to the distribution system. With the increasing penetration and reliance of the distribution systems on DGs, new interface control strategies are being proposed. Aside from its main task of supplying active power, the DG could provide voltage support, improve the power factor, or mitigate other power quality problems. This paper examines the impact of the interface control strategy of inverter based DGs on islanding detection. The Non-detective Zone (NDZ) for over/under voltage and over/under frequency is derived analytically for each interface control and validated by simulation. [ABSTRACT FROM AUTHOR]

The battle for electricity customers in an increasingly competitive and deregulated market environment is one of the challenges facing the electric power utilities of today. Customers expect a reliable and efficient supply of power from their utilities. One of the advantages that a distributed generator (DG) can provide to the electric utility and to customers is the possibility of improving the continuity of supply by implementing safe intentional islands in the event of upstream utility supply outage. Implementing intentional islanding of DG in a deregulated era will have an impact on electricity market prices. This problem is considered in this paper by solving the optimal power flow problem while accounting for islanded operation. [ABSTRACT FROM AUTHOR]

Abstract-The Sandia frequency-shift (SFS) method is one of the active islanding detection methods that possesses small nondetection zones (NDZs). The effectiveness of the SFS depends to a great extent on its design parameters (cf[subo] and k). In this letter, a formula is derived to aid protection engineers to determine the optimal parameter setting for the SFS islanding detection method. It is concluded that the parameter (k) has a significant effect on the NDZ and a modified version of the SFS is proposed that relies only on this parameter. [ABSTRACT FROM AUTHOR]