References of "Margossian, Harag 50002292"
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See detailTopology and Parameter Estimation in Power Systems through Inverter Based Broadband Stimulations
Neshvad, Surena UL; Margossian, Harag UL; Sachau, Jürgen UL

in IET Generation, Transmission & Distribution (2016)

An increasing number of inverter based power generators have been connected to the distribution network in recent years. This phenomenon, coupled with the adoption of open energy markets has significantly ... [more ▼]

An increasing number of inverter based power generators have been connected to the distribution network in recent years. This phenomenon, coupled with the adoption of open energy markets has significantly complicated the powerflows on the power network, requiring advanced and intelligent parameter knowledge to optimize the efficiency, quality and reliability of the system. This paper describes a method for identifying parameters associated with the power system model. In particular, the proposed algorithm in this paper addresses the line parameter and topology identification task in the scope of state estimation. The goal is to reduce the a priori knowledge for state estimation, and to obtain online information on the power system network. The proposed parameter estimation method relies on injected stimulations in the network. Broadband stimulation signals are injected from distributed generators and their effects measured at various locations in the grid. To process and evaluate this data, a novel aggregation method based on weighed least-squares will be proposed in this paper. It combines and correlates various measurements in order to obtain an accurate snapshot of the power network parameters. In order to test its capabilities, the performance of this algorithm is evaluated on a small-scale test system. [less ▲]

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See detailDistribution Network Line Protection in the Presence of Distributed Generation
Margossian, Harag UL

Doctoral thesis (2015)

The evolution of the distribution network from a passive grid with unidirectional power flows to, in the presence of distributed generation (DGs), an active grid with bidirectional power flows can lead to ... [more ▼]

The evolution of the distribution network from a passive grid with unidirectional power flows to, in the presence of distributed generation (DGs), an active grid with bidirectional power flows can lead to some technical challenges in its operation as well as some opportunities for greater control and grid support. This dissertation studies the impact of high levels of penetration of DGs into the power system on the operation of distribution network line protection. The contribution of DGs during faults results in varying short circuit current levels that are hard to predict. This complicates the design of distribution network line protection. If the DGs are located in between the protection device and the fault, the device sees a lower current than it would see in the absence of the DGs. Conversely, if they are connected upstream of the device, the device sees a higher current than before. This means that the reliability, selectivity and speed of the protection devices can be negatively or positively affected. This dissertation analyzes what can be expected from the DGs and how the protection devices themselves can be enhanced in order to avoid these potential problems. In the planning stage, it is possible to control the outputs of DGs during faults in a way that enhances the operation of the protection devices instead of hampering it. This can be done by enforcing regulations through distribution network grid codes. There are two main grid code requirements that directly impact the fault current levels in the network: fault ride through requirements that specify how long and for what voltages the DGs need to remain connected and dynamic voltage support curves that regulate their reactive current output during faults. From these requirements, three parameters are of particular interest: the voltage threshold above which the DGs need to remain connected, the maximum current that they should be capable of producing and the maximum reactive current that they are required to produce below a certain voltage. Using these three parameters, it is possible to control the fault current levels in the network and consequently increase the maximum amount of DGs that can be connected, without endangering the operation of the protection system. In the operating stage, it is possible to enhance the protection devices themselves so that they can deal with the varying fault current levels. Here, adaptive protection is considered. By gathering information about the changes in the network, including the status of switches and DGs and changing the settings of the protection relays accordingly, the reliability, selectivity and speed of the protection system can be maintained while increasing its complexity and cost. To get the information needed from the network, a modified state estimation is proposed. The distribution network is characterized by low observability due to the low number of measurements available. For this reason, load estimates and zero injection buses are added as measurements. To account for the additional uncertainty introduced by the presence of DGs, information about the DGs and their controls are used to add additional measurements that support the state estimation. When calculating the fault current levels in the network to choose the protection relay settings, it is important to correctly account for the fault contributions of inverter based DGs that represent a significant proportion of DGs connected to the distribution network. Unlike synchronous and asynchronous generators, inverter based DGs have a controlled current output during faults. By using an iterative process where the outputs of inverter based DGs are changed based on the calculated voltage at their terminals, a more accurate calculation of the short circuit current levels can be made. Employing these methods in the planning and operating stages, it will be possible to increase the amount of DGs that can be connected to the distribution network, while avoiding cascading faults, slower operation times and the unnecessary loss of load associated with protection mal-operation. The methods should be applied in reasonable steps and whenever needed in combination with each other to ensure the practicality of their implementation and to avoid unnecessary costs. [less ▲]

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See detailDistribution Network Protection Considering Grid Code Requirements for Distributed Generation
Margossian, Harag UL; Deconinck, Geert; Sachau, Jürgen UL

in IET Generation, Transmission & Distribution (2015), 9(12), 1377-1381

The amount of inverter based distributed generation (DG) connected to the low and medium voltage levels is increasing rapidly. Their growing impact on the power system has already driven some distribution ... [more ▼]

The amount of inverter based distributed generation (DG) connected to the low and medium voltage levels is increasing rapidly. Their growing impact on the power system has already driven some distribution network operators to start imposing requirements on their operation similar to those described in transmission grid codes. This paper studies how different grid code requirements can affect the fault current levels in the distribution network and explores the possibility of using the grid code requirements to ensure the reliability and selectivity of the protection of distribution feeders. [less ▲]

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See detailShort Circuit Calculation in Networks with a High Share of Inverter Based Distributed Generation
Margossian, Harag UL; Deconinck, Geert; Sachau, Jürgen UL

Scientific Conference (2014, June 24)

Conventional short circuit calculation programs do not consider the actual behavior of inverter based distributed generation (DG). Several techniques to consider them have been suggested in literature and ... [more ▼]

Conventional short circuit calculation programs do not consider the actual behavior of inverter based distributed generation (DG). Several techniques to consider them have been suggested in literature and are briefly described in this paper. A tool is developed with the combination of these techniques. The approach uses standard short circuit calculation tools and accommodates inverter based DG with different fault responses. The approach is evaluated and compared against other techniques using a realistic test distribution network model. [less ▲]

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See detailAssessing the Potential of Network Reconfiguration to Improve Distributed Generation Hosting Capacity in Active Distribution Systems
Capitanescu, Florin UL; Ochoa, Luis; Margossian, Harag UL et al

in IEEE Transactions on Power Systems (2014), 30(1), 346-356

As the amount of distributed generation (DG) is growing worldwide, the need to increase the hosting capacity of distribution systems without reinforcements is becoming nowadays a major concern. This paper ... [more ▼]

As the amount of distributed generation (DG) is growing worldwide, the need to increase the hosting capacity of distribution systems without reinforcements is becoming nowadays a major concern. This paper explores how the DG hosting capacity of active distribution systems can be increased by means of network reconfiguration, both static, i.e., grid reconfiguration at planning stage, and dynamic, i.e., grid reconfiguration using remotely controlled switches as an active network management (ANM) scheme. The problem is formulated as a mixed-integer, nonlinear, multi-period optimal power flow (MP-OPF) which aims to maximize the DG hosting capacity under thermal and voltage constraints. This work further proposes an algorithm to break-down the large problem size when many periods have to be considered. The effectiveness of the approach and the significant benefits obtained by static and dynamic reconfiguration options in terms of DG hosting capacity are demonstrated using a modified benchmark distribution system. [less ▲]

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See detailFeeder Protection Challenges with High Penetration of Inverter Based Distributed Generation
Margossian, Harag UL; Capitanescu, Florin UL; Sachau, Jürgen UL

in Proceedings of the EUROCON 2013 conference (2013, July)

The increasing proportion of inverter based distributed generation (DG) in the power system may limit the short circuit power available at distribution substations and consequently cause significant ... [more ▼]

The increasing proportion of inverter based distributed generation (DG) in the power system may limit the short circuit power available at distribution substations and consequently cause significant troubles for the protection of distribution feeders where DG are connected. In this paper, the current practices of distribution network operators in dealing with higher penetration levels of DG are investigated and evaluated using a realistic 31-node distribution network model with limited short circuit supply. The paper discusses the challenges for the protection system related to the integration of increasingly significant amounts of DG and highlights the need for more sophisticated protection systems. [less ▲]

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See detailDistributed Generator Status Estimation for Adaptive Feeder Protection in Active Distribution Grids
Margossian, Harag UL; Capitanescu, Florin UL; Sachau, Jürgen UL

in Proceedings of the CIRED2013 conference (2013, June)

This paper proposes a framework for adaptive feeder protection in distribution grids with a high amount of distributed generators (DGs) installed. The scheme adapts the feeder protection relay settings ... [more ▼]

This paper proposes a framework for adaptive feeder protection in distribution grids with a high amount of distributed generators (DGs) installed. The scheme adapts the feeder protection relay settings according to the changes in the connection status of those DGs that have a significant impact on the fault current. The core of the method consists in the identification of the connection status of the DGs using an iterative modified state estimation (SE) program. The approach is illustrated using a realistic 31-node distribution network model. [less ▲]

Detailed reference viewed: 121 (21 UL)