Taha Selim Ustun

Modeling of a Centralized Microgrid Protection System and Distributed Energy Resources According to IEC 61850-7-420

Microgrids have been proposed in an effort to handle the impact of distributed generators (DGs) and make conventional grids suitable for large scale deployments of DGs. However, the introduction of microgrids brings some challenges such as the protection of a microgrid and its entities. Due to the existence of generators at all levels of the distribution system, the fault currents vary substantially. Furthermore, grid connected and islanded modes introduce two different sets of fault currents. Consequently, the traditional fixed current relay protection schemes need to be improved. The authors developed a new protection system which utilizes extensive communication to monitor the microgrid and update relay fault currents according to the variations in the system. This system is designed to respond to dynamic changes in the system such as connection/disconnection of DGs. This paper presents the modeling of a microgrid protection system with logical nodes provided in IEC61850 and IEC61850-7-420 communication standards. It also demonstrates how the proposed communication takes place through logical nodes. Firstly, models for different DGs are provided to detail the implementation of the said logical nodes. Then, a case study is given on a sample microgrid to show how the proposed protection scheme can be run based on these models.

Fault current coefficient and time delay assignment for microgrid protection system with central protection unit

With growing numbers of distributed generators (DGs) getting connected to the network, new protection schemes are required. These schemes are aimed at responding to the changing fault current values, bi-directional current flow and distributed generation (DG) at all levels of the grid. For this purpose these schemes utilize comprehensive protection systems with extensive communication and coordination between DGs and protection devices such as relays. This paper details the assignment of two parameters which are critical for proper operation of a microgrid protection system. The first parameter, the fault current coefficient, represents the fault current supplied by any DG to any point inside the network whereas the second parameter is the adjustment of relay hierarchy for selective operation of relays. The automated assignment of these parameters serves the notion of self-operating microgrid protection system. Furthermore, elimination of manual design and calculation facilitates deployment of new DG units and thus makes it possible to design plug-and-play DGs and protection devices.

Implementing Vehicle-to-Grid (V2G) Technology With IEC 61850-7-420

Electric Vehicles (EVs) have become very popular due to climate change concerns and carbon emission reduction schemes. Accordingly, in recent years the awareness of people about EVs has increased significantly. In addition to the well-known advantages such as cleaner environment, less oil-dependency, cheaper fuel, more silent operation etc., through smartgrids, EVs offer a unique benefit called vehicle to grid (V2G) technology. In order to define the role of EVs as distributed storage devices, simulation works undertaken in Paladin Designbase 4.0 are presented in this paper. It is shown that through V2G, EVs can support better operation of smartgrids in terms of reliability and storage. In order to achieve these, the components of smartgrids shall communicate and share information via communication lines. Having a universal communication standard is vital for implementing the plug-and-play concept in smartgrids. IEC 61850, the substation automation standard, could be used for this purpose. However, it is insufficient and must be expanded to cover missing links. In this paper, authors propose an extension to the IEC 61850-7-420 standard by defining the information model for controlling the charging and discharging of EVs.

A microgrid protection system with central protection unit and extensive communication

Microgrids have been proposed in order to handle the impacts of Distributed Generators (DGs) and make conventional grids suitable for large scale deployments of distributed generation. However, the introduction of microgrids brings some challenges. Protection of a microgrid and its entities is one of them. Due to the existence of generators at all levels of the distribution system and two distinct operating modes, i.e. Grid Connected and Islanded modes, the fault currents in a system vary substantially. Consequently, the traditional fixed current relay protection schemes need to be improved. This paper presents a conceptual design of a microgrid protection system which utilizes extensive communication to monitor the microgrid and update relay fault currents according to the variations in the system. The proposed system is designed so that it can respond to dynamic changes in the system such as connection/disconnection of DGs.

A central microgrid protection system for networks with fault current limiters

Large deployments of Distributed Generators (DGs) have substantial impacts on the structure of existing networks. In order to tackle these issues, it has been proposed to divide the network into smaller manageable sets which can be more effectively and efficiently operated. This very concept is called the ‘Microgrid’. However, due to their unprecedented structure, these smaller grids experience very significant protection issues. Conventional fault current protection schemes cannot be used and should be modified due to the existence of generators at all levels of the distribution system. Furthermore, two distinct operating modes (grid connected and islanded modes) exist in microgrids causing the fault currents in a system to vary substantially. It is also a challenge to operate Inverter Interfaced DGs (IIDGs) and estimate their fault currents. Fault current limiters have thus been proposed for proper operation of DGs in a network. This paper presents a conceptual design of a microgrid protection system which makes use of current limiters in fault current estimation. It utilizes extensive communication to monitor the microgrid and update relay fault currents according to the variations in the system. The proposed system is designed so that it can respond to dynamic changes in the system such as the connection/disconnection of DGs.

Electric Vehicle Potential in Australia: Its Impact on Smartgrids

The availability of the technology and the promising acceptance of hybrid electric vehicles (HEVs) has encouraged car manufacturing companies to take solid steps toward the electric vehicle (EV) market. As it is spread over a vast surface area, Australia has high car usage and ownership rates, and the inefficiency of the public transportation system contributes to this. Therefore, Australia has a very large potential market for EVs. In addition to the well-known advantages, such as zero direct emissions, reduced dependency on oil, cheaper fuel, and more silent operation through smart grids, EVs also offer a unique benefit called vehicle-to-grid (V2G) technology. Through V2G technology, EVs can support better operation of the smart grids in terms of reliability and storage. Based on reliable statistics and social studies, this article studies the EV potential of Australia and envisages the impact of large EV utilization therein. The statistics indicate that the growing population will demand more cars, and acceptance of EVs could also benefit other areas, such as environmental conservation, finance, and energy production. Accordingly, a microgrid system with V2G technology has been modeled and simulated in three different conditions: islanded, IEEE-T14-bus system, and IEEE-34-bus system. The results are presented to forecast the necessary changes in the power networks for the large deployment of EVs.

Implementation of Dijkstra's algorithm in a dynamic microgrid for relay hierarchy detection

Unlike conventional utility grids, microgrids comprise generators, storage devices and loads at all levels of the system. Power generation, distribution and consumption levels are not discrete and power flow may occur at any direction. At any point in time, microgrid may be disconnected from the utility grid and continue its operation under islanding conditions. Furthermore, some microgrids may have changing structures with alternative paths and the coupling point for a device or a part of the microgrid may change due to the altering conditions. Considering all of these challenges, it is required to develop a new protection concept/scheme for a safe and secure operation. Maintaining proper selective operation of relays in these new systems and new dynamic microgrid structures is also a challenge in itself. This requires monitoring the connections and updating time delays of the relays to ensure the desired protection hierarchy in the system. In this paper, a microgrid system is modeled according to the graph theory where the components are represented as nodes. Dijkstras algorithm, which is famous for shortest-path calculation purposes, is run over the microgrid to determine the relay hierarchy at any point in time. In this manner, regardless of the dynamic changes occurring in the system the hierarchy of network components can be extracted. The implemented algorithm not only ensures proper selective operation under fault conditions but also facilitates the introduction of new connections and new devices to the system. Since the relay hierarchy is detected automatically, even with new connections, this algorithm serves for plug-and-play concepts in electrical networks.

Simulation of communication infrastructure of a centralized microgrid protection system based on IEC 61850-7-420

Recently `Microgrid concept has been proposed where the networks are divided into smaller manageable sets which can be more effectively and efficiently operated. This concept allows conventional grids to be made suitable for large scale deployments of distributed generation. The dynamic structures of micro-grids change very often depending on various network factors. This dynamic behavior of micro-grids to alter operation under various network conditions is an area that needs to be more thoroughly investigated and understood in moving forward with the integration of the micro-grid concept to existing power supply grids. This paper presents one embodiment of a protection system which employs a microgrid central protection unit (MCPU) to coordinate differential current protection. The communication infrastructure of the proposed protection system has been modeled according to IEC 61850 international communication standard for power networks as well as its recent extension for distributed generators (DGs) IEC 61850-7-420. The system is implemented in Matlab/Simulink Environment where the signals and their attributes are adjusted according to these standards.

Investigation of micro-grid behavior while operating under various network conditions

The proposed solution to handle the impact of Distributed Generators is the micro-grid concept. This concept allows conventional grids to be made suitable for large scale deployments of distributed generation. The dynamic structures of micro-grids change very often depending on various network factors. This dynamic behavior of micro-grids to alter operation under various network conditions is an area that needs to be more thoroughly investigated and understood in moving forward with the integration of the micro-grid concept to existing power supply grids. This paper presents the detailed modeling of a typical micro-grid when operated in islanded mode or when connected to a Standard IEEE T14 Bus system or when connected to an IEEE Standard 34 Bus system. Various power/load flow studies conducted give a detailed outline of the operation of the micro-grid under various conditions such as: islanded operation, operation when connected to transmission and distribution networks.