- Olav B. Fosso
- Institutt for elkraftteknikk, Fakultet for informasjonsteknologi og elektroteknikk, NTNU
The objective of WP4 is to develop concepts, technologies and models for microgrids and their interaction with the distribution system.
The expected impact is a contribution to cost-efficient and robust integration of microgrids with the distribution grid, and a contribution to the integration of more distributed and renewable energy resources (DER) in the system.
- Interaction between microgrids and distribution system operators
- Microgrid energy management and protection
- Ancillary services and energy routers
- Modelling and analysis of microgrids
Activities related to assess the state of the art internationally and relate this to challenges within the setting of CINELDI were initiated in 2017. These activities were concluded in 2018 in the memos:
• Mikronett i Norge – Muligheter og utfordringer
• Microgrid protection – challenges and solutions
• Fault responses of inverter-interfaced DER – literature review
Development of laboratory infrastructure
An essential part of the activities within WP4 in 2018, has been the development of a laboratory infrastructure to be used to facilitate research and development activities within CINELDI as well as to do externally funded projects. A setup in the smart grid lab that is a building block for the proposed "Real-time power hardware-in-the-loop simulation platform to evaluate ancillary services in microgrids" has therefore been implemented. The setup is two parallel inverters operated in island mode for feeding a linear load. The load is emulated using the grid emulator and the real time simulator for providing more flexibility in terms of the feeder impedance/load that can be connected to the system. At the moment, the setup is able to operate one converter with an emulated load, a synchronisation mechanism is needed to connect the other converter. A figure is provided for illustration.
PhD/Post Docs – internally and externally funded
WP4 currently has two PhD-students funded from CINELDI where one is working on the task Microgrid Protection with the perspective of communication and use of 5G technologies, while the other is in the task on Ancillary Services and Energy Routers. The candidates are progressing well and have publications accepted and under review. To strengthen the activities within WP4, externally funded PhD and Post docs have been recruited to work with Microgrid related topics. One PhD-student and one Post doc are working within dynamic interaction in systems with high penetration of Power Electronic converters. Both positions are on strategic funding from NTNU. One PhD-student funded through SINTEF Energy Research/ Norwegian Research Council is working within planning in systems with distributed intermittent resources and storage devices. The experience with techniques developed for large-scale hydro scheduling is a core for the activities. An exchange PhD-student funded by the Norwegian Research Council coming from Shanghai Jiao Tong University, China, working within planning and operation of microgrid systems is on a one year stay at NTNU while a PhD-student from Universidad Tecnica de Pereira, Colombia, is working on control strategies for non-linear systems during his seven-month stay at NTNU. The external resources have made it possible to work on a broader scope and to build a more solid foundation for the future work within WP4 Microgrids.
MSc and project students – WP4 relevant activities
A priority within WP4 has been to have a close collaboration with MSc-students at NTNU to provide interesting and challenging research activities within microgrids. The activity of one student is equivalent to eight months full-time work. Five MSc-projected were concluded in the spring 2018. In the autumn 2018, seven students were recruited for the project continuing in a MSc-project finishing in 2019. These projects cover all major activities of WP4.
Dissemination and publications
Several conference and journal papers have been published related to the WP4 from researchers and internally and externally funded PhD-students and Post docs. Additionally, a significant number of papers are in the review process in internationally recognised journals. Five MSc theses were completed in June 2018 and seven student projects completed in December 2018. The student projects are continued in the spring 2019 and will be completed as MSc-thesis in June 2019.
Demonstrating simplified reference system for microgrids on the smart grid laboratory
A simplified reference system for studying isolated microgrids has been defined. The reference system has been used for developing and testing primary control strategies, a droop control that ensures cooperative power sharing and harmonic sharing. One of the challenges is deriving a droop controller that works when the line feeder impedances change dynamically and varies from largely resistive to more inductive characteristics, and still obtain proper sharing of power and current harmonics.
This research has been driven forward through collaboration between PhD candidate Fredrik Göthner and two master students. The simplified reference converter system and associated cascaded controllers have been successfully implemented in simulation environment, supporting master thesis and PhD thesis work. A related paper entitled Considerations of Virtual Impedance Implementation in the Synchronous Reference Frame was authored by Fredrik Göthner and Raymundo E. Torres-Olguin, and accepted for IEEE Environment and Electrical Engineering conference.
Two contributing master projects are Improved Power Sharing in AC Microgrids by Using Decentralised Virtual Impedance Control, and Advanced Harmonic Sharing Techniques for Microgrid Applications. The research is in collaboration and supervision by Professor Dr. Olimpo Anaya-Lara from University of Strathclyde. Extensive laboratory activities are planned starting March 2018, the previous simulation work and promising results are input for a hardware-in-the-loop implementation at the Norwegian Smart Grid Laboratory. The plan is to utilize and demonstrate the advanced facilities available at the laboratory, with the help from research partners at NTNU and SINTEF Energy Research.
State-of-the-art review of protection in microgrids
Through the work WP4 is creating high-level use cases identifying important challenges for relay protection custom to microgrids. One use case description has been proposed Adaptive microgrid protection, and a state-of-the-art review on protection in microgrids has been started, forming the basis for further research. The WP4 microgrid work package will partly run in cooperation with WP2 supporting research of a PhD candidate focusing on 5G for Low-Latency, Secure and Dependable Communication Services for Fault Handlings.