Are Power Line Communications (PLC) a good candidate for Smart Grid applications? The objective of this paper is to address this important question. To do so, we provide an overview of what PLC can deliver today by surveying its history and describing the most recent technological advances in the area. We then address Smart Grid applications as instances of sensor networking and network control problems and discuss the main conclusions one can draw from the literature on these subjects. The application scenario of PLC within the Smart Grid is then analyzed in detail. Because a necessary ingredient of network planning is modeling, we also discuss two aspects of engineering modeling that relate to our question. The first aspect is modeling the PLC channel through fading models. The second aspect we review is the Smart Grid control and traffic modeling problem which allows us to achieve a better understanding of the communications requirements. Finally, this paper reports recent studies on the electrical and topological properties of a sample power distribution network. Power grid topological studies are very important for PLC networking as the power grid is not only the information source but also the information delivery system-a unique feature when PLC is used for the Smart Grid.

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For the Grid and Through the Grid: The Role of Power Line Communications in the Smart Grid

This report describes the various methods and circuits that have been developed to detect an islanding condition for photovoltaic applications and presents three methods that have been developed to test those methods and circuits. Passive methods for detecting an islanding condition basically monitor parameters such as voltage and frequency and/or their characteristics and cause the inverter to cease converting power when there is sufficient transition from normal specified conditions. Active methods for detecting the island introduce deliberate changes or disturbances to the connected circuit and then monitor the response to determine if the utility grid with its stable frequency, voltage and impedance is still connected. If the small perturbation is able to affect the parameters of the load connection within prescribed requirements, the active circuit causes the inverter to cease power conversion and delivery of power to the loads. The methods not resident in the inverter are generally controlled by the utility or have communications between the inverter and the utility to affect an inverter shut down when necessary. This report also describes several test methods that may be used for determining whether the anti-islanding method is effective. The test circuits and methodologies used in the U.S. have been chosenmore » to limit the number of tests by measuring the reaction of a single or small number of inverters under a set of consensus-based worst-case conditions.« less

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Evaluation of Islanding Detection Methods for Utility-Interactive Inverters in Photovoltaic Systems

This paper presents an active islanding detection method for a distributed resource (DR) unit which is coupled to a utility grid through a three-phase voltage-sourced converter (VSC). The method is based on injecting a negative-sequence current through the VSC controller and detecting and quantifying the corresponding negative-sequence voltage at the point of common coupling of the VSC by means of a unified three-phase signal processor (UTSP). UTSP is an enhanced phase-locked loop system which provides high degree of immunity to noise, and thus enable islanding detection based on injecting a small (3%) negative-sequence current. The negative-sequence current is injected by a negative-sequence controller which is adopted as the complementary of the conventional VSC current controller. Based on simulation studies in the PSCAD/EMTDC environment, performance of the islanding detection method under UL1741 anti-islanding test is evaluated, and its sensitivity to noise, grid short-circuit ratio, grid voltage imbalance, and deviations in the UL1741 test parameters are presented. The studies show that based on negative-sequence current injection of about 2% to 3%, islanding can be detected within 60 ms even for the worst case scenario.

Negative-Sequence Current Injection for Fast Islanding Detection of a Distributed Resource Unit

This paper presents an overview of power system islanding and islanding detection techniques. Islanding detection techniques, for a distribution system with distributed generation (DG), can broadly be divided into remote and local techniques. A remote islanding detection technique is associated with islanding detection on the utility side, whereas a local technique is associated with islanding detection on the DG side. Local techniques can further be divided into passive techniques, active techniques and hybrid techniques. These islanding detection techniques for DG are described and analyzed.

Review of islanding detection methods for distributed generation

The mainly used islanding detection techniques may be classified as active and passive techniques. Passive techniques don't perturb the system but they have larger non-detection zones, whereas active techniques have smaller non-detection zones but they perturb the system. In this paper, a new hybrid technique is proposed to solve this problem. An average rate of voltage change (passive technique) has been used to initiate a real power shift (active technique), which changes the real power of distributed generation (DG), when the passive technique cannot have a clear discrimination between islanding and other events in the system. Simulation results show that the proposed method is effective in detecting islanding of distribution systems with DGs.

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A Hybrid Islanding Detection Technique Using Average Rate of Voltage Change and Real Power Shift

Islanding of grid-connected photovoltaic (PV) power systems jeopardizes personnel and equipment and must therefore be prevented. Existing islanding prevention schemes are undesirable because they fail for certain relatively common customer loads and when more than one PV power system is present, degrade PV power quality, reduce system efficiency, and increase system complexity. These problems can be overcome using power line carrier communications. (PLCC) and an inexpensive, purpose-designed receiver. The use of PLCC for islanding prevention is discussed. In this paper, including considerations for maximum anti-islanding effectiveness. Also, a low-cost receiver for a commercial PLCC system is described and demonstrated. This receiver demonstrates the feasibility of PLCC-based islanding prevention.

Using power line carrier communications to prevent islanding [of PV power systems]

Islanding of grid-connected photovoltaic (PV) systems jeopardizes personnel and equipment and must therefore be prevented. Existing islanding prevention schemes are undesirable because they fail for certain relatively common customer loads and when more than one PV system is present, degrade PV power quality, reduce system efficiency, and increase system complexity. These problems can be overcome using power line carrier communications (PLCC) and an inexpensive, purposedesigned receiver. The use of PLCC for islanding prevention is discussed in this paper, including considerations for maximum anti-islanding effectiveness. Also, a low-cost receiver for a commercial PLCC system is described and demonstrated. This receiver demonstrates the feasibility of PLCC-based islanding prevention.

K. Aaker

Papers

Using power line carrier communications to prevent islanding [of PV power systems]

Using power line carrier communications to prevent islanding