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The rapid increase in installed distributed generation (DG) has led to concerns about the impact on the proper operation of the protection system. In particular, the limited fault current capability of inverter interfaced distributed generation (IIDG) could lead to malfunctioning of the distribution network protection system which largely relies on overcurrent based protection techniques. The absence...
A small scale distributed generation system was designed, built and evaluated over the past 23 years at the University of Massachusetts Lowell (UML). This paper highlights both previous and current research that is being done on the system.
This panel paper presents some outlines on the energy management of electric power microgrids with hybrid components. The hybrid nature of the microgrid is attributed to renewable energy sourced generation, energy storage, schedulable loads and information enabling technology such as smart meters. The panel paper and the accompanying presentation aim to describe the electric energy management visà-vis...
This paper proposes an approach for the control and optimization of power flow by integrating Plug-In Hybrid Vehicles (PHEV) to an existing residential photovoltaic system. Optimization of Power flow reduces the dependency for electric power from the grid and control involves determining the source from which residential load will be catered. The system built to achieve the goal is a combination of...
Microgrids can be viewed as a group of Distributed Generation (DG) units with the capability of operating connected or isolated from the main grid. Most of the work conducted in the area of microgrids focused on developing new control schemes that can maintain the voltage and frequency within standard limits during grid connected and islanded mode of operation. An issue of equal importance is the...
This paper describes the design of 1MVA 4.16kV Medium-Voltage motor drive using Hexagram inverter, and is compared to Cascaded H-bridge inverter motor drive system. System design and component selection is elaborated for motor drive system using both topologies. Power loss and reliability is also estimated for comparison purpose. Fault tolerant control is a feature for both motor drive system and...
This paper addresses the control design for a three-stage solid stage transformer (SST). When two or more independently controlled converter stages are cascaded, which is the case for the three-stage SST, the interaction among the stages can lead to instability. Normally, the input and output impedances of the cascaded stages need to be examined according to the impedance criterion to ensure stability...
With more and more photovoltaic (PV) panels, energy storage devices and other small generators being put into service, it is necessary to integrate them into power systems. Grid integration provides a reliable means for customers to use renewable energy such as solar at its maximum and to use other sources as backup. Inverters are widely used as interfaces for these distribution resources. In this...
The increasing presence of single-phase distributed generators and unbalanced loads in the electric power system may lead to unbalance of the three phase voltages, resulting in increased losses and heating. To decrease this voltage unbalance problem three-phase four-wire inverter-connected distributed generation units may be used. In this paper, the influence of the control strategy of three-phase...
In this paper, a comparison of six representative topologies for the implementation of Solid State Transformers (SST) is performed. The objective is to help identify the most suitable topology capable of supporting additional functionalities as compared to a regular transformer, e.g. on-demand reactive power support to grid, voltage regulation, and current limiting. The comparison is based on switch...
The control algorithms proposed in the literature so far for the Double Output Induction Machine Based Variable Speed Constant Frequency (VSCF) stand alone generators suffer from the disadvantage of loss of `field orientation' during sudden load disturbance at the machine terminal. As a result, undesirable transients are observed in the load voltage during such transients. This paper presents a new...
This paper deals with modeling, control and co-simulation of a single-phase single-stage Grid-interactive photovoltaic (PV) system with active filter functions. Single-phase PV systems are the most prevalent in roof-top configurations. In this paper, the modeling of a PV array with maximum power point tracking is performed in MATLAB/Simulink. The developed PV array model may be directly connected...
In recent years, various types of gas-fueled combined heat and power (CHP) systems have been developed and introduced into sites such as hospitals, hotels, commercial buildings, district heating & cooling centers, factories, etc., to increase energy savings and reduce greenhouse gases. Typical components integrated into CHP systems are gas engines (GE), gas turbines (GT), and fuel cells (FC);...
In recent years, installation of renewable energy into load supply systems has drastically increased. Load modeling considering dispersed generators is indispensable to improve the accuracy of power system analysis. Most of the installed capacity of dispersed generators currently consist of synchronous generators equipped with excitation controllers with Automatic Q Regulator (AQR) or Automatic Power...
The National Renewable Energy Laboratory (NREL) conducts a variety of research in the area of hybrid power system integration and microgrids. NREL is studying hybrid (stand-alone) power systems incorporating photovoltaic power in the United States and assessing the characteristics and status of government-installed hybrid systems greater than 2 kW over the last 30 years. This research provides information...
The number of installed distributed generation (DG) in residential areas rapidly increases, specifically in the form of photovoltaics (PV), causing some undesired side effects such as voltage rise. Overvoltage can damage critical loads, but is also disadvantageous for the owner because inverters switch off in case of overvoltage, resulting in output loss. Since grid connected inverters essentially...
This paper presents an approach to coordinate Distributed Generation (DG) such that quantities in an unbalanced distribution system are balanced and power factor corrected. Models for the DG and three-phase distribution network are combined to form a set of Differential Algebraic Equations (DAE) that represent the behavior of the distribution system. Two state-feedback controllers with reference inputs...
This paper describes the development of a 3-phase line-interactive DVR with a new sag detection algorithm. The developed detection algorithm has a hybrid structure composed of an instantaneous detector and the RMS-variation detectors. The source voltage passes through the sliding-window DFT and RMS calculator, and the instantaneous sag detection part. If instantaneous sag is detected, the RMS variation...
Basic, stage 1, MicroGrids combine distributed generation, intelligent load control, and in many cases energy storage, to form a well-behaved aggregate load or generator. This allows more straight-forward and widespread integration of distributed generation. More advanced MicroGrids (stage 2) can further add the capability to isolate such small sections of the network and continue to operate them...
The dynamic behaviour of a PWM voltage source inverter based voltage generator with an output LC filter is analyzed in this paper. This converter is able to participate to frequency regulation either in connected mode or in an islanded mode with minor modifications in the control algorithm. Thanks to a droop control, it is possible to achieve power sharing between this converter and a classical synchronous...
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