The Role of Smart Transformers within Microgrids February 2016

Key Questions What are Smart Transformers? How do Smart Transformers fit into the Smart Grid? What are the potential benefits of having Smart Transformers? What are foreseen challenges?

Microgrids Generation, storage and loads that form an entity The building blocks of the Smart Grid Single, controllable entities Single point of connection with the larger grid Components within the microgrid (generators, loads and storage) posses “microgrid agents” that provide them with monitoring and communication capabilities. Stability within a microgrid can be maintained by ensuring the microgrid voltage remains stable

Smart Transformers There are 40 times more transformers than generators on the grid How are we utilizing them? Definition not “set in stone” Transformers with intelligence and remote control capabilities Intelligence consists of monitoring and communication capabilities In the research, it is suggested that the smart transformer be placed at the point of connection between a microgrid and the larger grid.

Smart Transformers in Microgrids Smart transformers act as microgrid and market managers They are in constant communication with other microgrid agents, and are capable of gathering data from, and issuing instructions to other microgrid agents Smart Transformers: Monitor the operations of microgrid agents Issue generation set-points to generators to maintain voltage stability Monitor and orchestrate interaction between various microgrid agents Monitor and control interaction between the microgrid and the larger power grid.

SRAPET Transformer Developed in 2006 Has a OLTC for voltage regulation on the LV side For application in deep-rural areas, where LV feeder can be extended by LV voltage regulation Possesses data monitoring capabilities

Eskom Remote Data Retrieval Released in 2013, applicable on all remote data-retrieval devices Required DNP3 for data retrieval of non-substation based devices Required various other protocols to achieve uniformity in functionality (SNMP, FTP, HTTP-based web interface, NTP, SSH etc.) A device (the STCD) was created to interface with the SRAPET transformer and allow it to meet this specification This equips the SRAPET with “Smart Grid” technologies, thus, moving towards a Smart Transformer

The STCD An open-source solution built on the hardware foundation of the Beaglebone black Interfaces with the SRAPET controller board to gather monitoring data and issue commands Interfaces with a modem (GRPS / 3G) to communicate with central data servers Allows for the remote monitoring and control of transformers

The STCD Measurements include: Voltages, currents, temperatures, tap position of OLTC etc. Employs a monitoring strategy based on both periodic, and event- based monitoring Periodic readings are taken every 5 minutes (or user-defined time) Event readings are triggered when user-defined events occur

The STCD Graphs showing monitoring

Smart Transformers as Market Manager Smart Transformers communicate with generators, loads and storage within the microgrid It monitors the measurements taken at these key points and can control them in various ways Generators: Gives generation set points that limit the possible generation Storage: Controls the charging and decharging of storage via a Battery Management System (BMS) Loads: Controllable loads can be offset in their electricity usage

Microgrid Simulation A simulation was conducted to investigate the management of interactions between microgrid agents by the Smart Transformer A generation and load agent was simulated using raspberry PI development boards. These boards were connected in a network, and web services were used as a common language between devices over the network Electricity bids are manually entered into the load agent over a web interface hosted on it. The bid is communicated to the Smart Transformer, that checks with generators within the microgrid to determine the possibility of meeting the bid The Smart Transformer decides how the bid should be met (by the utility and local generators), and records the interaction as well as the financial implications thereof. The Smart Transformer keeps track of relevant tariff information to perform such actions.

Future Considerations Utility and DG agreements Sustainable design Communication security and reliability Full benefits of remote monitoring and control Self-healing grids, demand-response, condition monitoring / predictive maintenance, electric vehicle integration etc.

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