THOUGHT LEADERSHIP

What have we learnt about renewable microgrids and remote area power systems?

With the evolution of modern inverter and renewable energy technologies, it’s become possible to build microgrids with very high renewable penetration. These renewable solutions are revolutionising electricity sustainability, reliability and access in many far-flung locations – such as Pacific islands, remote locations around Australia, and on mining sites.  

High renewable penetration allows operators of off-grid microgrids to extract maximum value from their installed solar, wind or other renewable generation while minimising the use of fossil fuels, such as diesel. It’s a win-win for the financial bottom line and emissions-reduction goals. If the microgrid connects with a broader power system, the benefits of reducing reliance on externally sourced energy are significant too.   

Establishing a relatively simple microgrid with modest fuel-saving targets doesn’t have to be particularly complex. It’s within the reach of current technology and practice to be able to optimise microgrids to all but eliminate the use of fossil fuel (with the related advantages of eliminating fuel handling, shipping, etc.). However, careful thought must be given to the distinct nature of the microgrid: its customers, energy sources and storage options. 

To make a microgrid successful, some technical challenges will need to be managed. Resolving these challenges in a cost-effective way becomes more difficult as the renewable energy balance approaches 100% – but they’re not insurmountable. Let’s explore. 

Challenge 1: Ensuring quality of supply and an acceptable customer experience 

The small size of microgrids and the fact that they are usually dedicated to a single ‘customer’ makes engineering a microgrid a sensitive task. While larger grids can operate with tight voltage and frequency tolerances and multiple levels of redundancy, microgrids often cannot. This inevitably means negotiating acceptable system standards for islanded operation that are within the tolerance of customers’ equipment and expectations. Microgrids powered by fossil fuels typically have more difficulty maintaining tight frequency and voltage tolerances than renewables-based microgrids. 

Understanding customer and stakeholder expectations relating to reliability and robustness (energy availability and the ability to ride-through faults) is key to the establishment of a successful microgrid. Where the microgrid exists with no possibility of interconnection to another power network (i.e. in an ‘island’), there is more flexibility and less operational complexity. Discerning acceptable standards and practices is still not easy but it can be a more productive discussion than when the microgrid must comply with less tailored standards due to interconnection. 

When the microgrid is interconnected, many of the technical requirements for the microgrid will be specified and/or mandated by the network service provider, electricity code requirements, and some operational requirements for electrical safety. If additional communication and inter-tripping with network equipment remote to the microgrid are required, these can add further complexity. 

Challenge 2: Managing different modes of operation requiring different controls 

In the previous section, we discussed how complicated it is to determine system standards. A great deal of care is also needed when contemplating which standards and controls are most appropriate to the microgrid’s specific characteristics. This is where cookie-cutter solutions could under-deliver and a more insightful approach is required. 

A microgrid must manage the voltage, frequency and quality of supply while it is islanded as well as during periods of interconnection. Islands can remain satisfactory for longer if there are energy sources, storage and load controls within the island. Each of these elements comes at a cost and, depending on the frequency and duration of islanded operation, must have a value outside of the islanded scenario. 

Our experience with microgrids is that semi-autonomous operation of each of the power sources using standard power system control approaches (solar, BESS and other power sources on voltage and frequency droop control) leads to the simplest and most secure response to transients (load or generation trips, network or network faults). Slower controls can be put in place to balance generation and rates of battery charge or discharge. If the battery power rating is large enough relative to the largest disturbance, it can manage most frequency disturbances within acceptable limits. If the battery energy capacity is large enough, it can always maintain a state of charge that allows fast reaction to variations in customer demand or VRE. Alternatively, auxiliary plant such as switched resistors, synchronous condensers and customer-level load control can be used to minimise battery power, storage and other energy inputs.  

Operating microgrids in different modes requires careful engineering of the controls and equipment. The solutions and approaches described above have proven successful across multiple projects, but the key is to always be open to new solutions as new problems arise or new technologies emerge. 

Challenge 3: Understanding the marginal value of resistors, synchronous condensers and/or demand management 

Auxiliary equipment can help to extend the range and effectiveness of a microgrid to rely solely on renewable energy. The challenge is to understand the actual value of extension in this context. Where it has a direct bearing on fossil fuel use, the benefits are clear. Where it might cause an incremental improvement in the robustness of the islanded operation only, it’s important to consider whether any operational benefits or security benefits gained from the additional capital investment are valuable enough to justify the cost. 

If the robustness of islanded operation is to be increased by managing customer demand, customer storage and/or embedded generation (e.g. rooftop solar), the value of the extended island longevity should be weighed against the perceived cost (direct or indirect) to the customer. This requires careful consideration of the diversity within the community, their openness to energy management, and the relationship between true costs and benefits. 

Microgrids that maximise local use of renewable resources represent a relatively cost-effective option for lowering carbon emissions and/or reducing energy costs. Isolated communities, remote industrial sites, unreliably connected rural communities and others could benefit greatly from considering microgrid opportunities.  

Entura has a long history of design, formation and operation of microgrids throughout Australia (such as King Island, Flinders Island, Rottnest Island, and at mining sites such as the Agnew gold mine) and in the Pacific region (including the Cook Islands, the Federated States of Micronesia, Tonga, and the Solomon Islands, to name just a few). We’ve seen the real benefits these systems bring to our clients and communities.  

Contact us if you’re interested in unlocking the full potential of microgrids for your operation or community, or if you’re interested in ways to increase your use of renewable energy.  

ABOUT THE AUTHORS

Donald Vaughan has over 20 years’ experience providing advice on regulatory and technical requirements for generators, substations and transmission systems. He has worked for all areas of the electrical industry, including generators, equipment suppliers, customers, NSPs and market operators. Donald specialises in the performance of power systems. His experience in generating units, governors and excitation systems provides a helpful perspective on how the physical electrical network behaves.

Greg Koppens is Entura’s Principal Control Engineer Hybrid Renewable Systems and has led Entura’s secondary electrical engineering team. Greg’s experience spans power, oil and gas, and mining, including onsite roles. With over a decade of detailed design experience, Greg facilitates collaboration between engineering disciplines and other stakeholders to solve complex problems. He regularly shares his extensive expertise with the mining sector to advance their decarbonisation goals. Find out more about Greg in our podcast series here.

26 March, 2025