By Miles Stepniewski, Global Sustainable Energy Solutions (GSES) project manager
As concern for climate change and energy security grows and electricity prices continue to rise, renewable energy technologies are presenting as a viable alternative.
With the increased penetration of renewable generation sources, the ageing grid infrastructure often struggles to cope with the challenges presented by these new technologies, such as intermittency, voltage rise and oversupply. A solution being employed to deal with these challenges is a relatively new grid structure known as a microgrid.
Monitoring and control Systems
Microgrids require complex monitoring and control systems to maintain grid stability and to ensure that demand is met. These systems must be able to monitor all generation sources and loads, as well as other factors such as weather, battery state of charge (if present) and main grid demand.
To ensure this modelling and data collection can work in both grid-connected mode and island mode, locally available information should be used (Lasseter, 2001). If in island mode, a microgrid should also be able to establish and regulate the main grid voltage and frequency as well as acceptable power quality.
There are several different co-operation approaches that can be used for microgrids in island mode which are affected by power quality and stability, installed storage capacity, types of generation units and microgrid ownership (Pedrasa & Spooner, 2006). These are explored further in the expanded version of this article on the GSES website.
Case Study: Wildpoldsried, Germany
Wildpoldsried utilises microgrid technologies and produces up to 500 per cent more energy than it requires. Wildpoldsried utilises 6MW of solar PV, 1MW of biogas, 12MW of wind, hydro, biomass heating, solar thermal and geothermal heating.
The Integration of Regenerative Energy and Electric Mobility (IRENE) project was set up to attempt to automate the stabilisation of the microgrid. Some of the challenges recognised by IRENE was the integration of renewables, bidirectional power flows, power asymmetries and harmonics and electric vehicle (EV) charging integration. These were overcome by implementing a closed loop control system, voltage regulated transformers, installing Li-Ion battery storage and controlling PV inverters and EV charging.
The IREN2 project was then set up to qualify the system to become a topological power plant, ensure safe re-synchronisation, prove grid stability, test ancillary services provision and prove blackstart capability.
This will be achieved by improved control and automation systems, adjustment of energy storage and other modifications (Becker, 2015).
The future of micro-grids in Australia
The success story of Wildpoldsried should give the Australian energy sector confidence the challenges of integrating distributed energy are being solved.
With an excellent solar and wind resource, Australia could be a main player in the future of the microgrid market. A combination of improvements in solar PV technology and the introduction of generous feed-in tariffs has seen the solar PV industry in Australia grow significantly; Australia currently has 4.2MW of solar PV installed (APVI, 2015).
This provides a strong foundation for microgrid implementation. As battery storage technologies continue to improve and prices continue to fall, the once major barrier of energy storage is quickly being removed.
This combination of Australia’s suitability to distributed energy generation and the improvement of battery storage will see the implementation of microgrids in Australia within the next decade.