Caterpillar has been servicing microgrids for decades, In Australia we have over 200 Service locations and more than 2,000 technicians working within the service network that captures microgrids as well as other Cat products. We have an extensive range of power generation products, from Diesel and Gas Generators to Gas Turbine technology. Cat is in many cases the equipment of choice for microgrid operators across Australia and the world. Microgrid design is being revolutionised right now with the world wide roll out of high penetration, low cost renewable energy being integrated into many projects. This integration of generation assets like Solar and Wind pose some very unique and tricky challenges that can be difficult to resolve.
The 2 main challenges for designers are:
1. the issues of Transient response of the generation plant during a cloud flyover or significant load increase.
2. the ability to deliver fault contribution when the generators are switched off.
Transient response challenges on a microgrid are a difficult engineering challenge, for decades the typical approach has been for designers to simply oversize the generation capacity of a site to handle the load steps. For example, when a large ball mill comes on line the load transient can be huge and difficult to handle. This method of oversizing a generation plant facilitates the load step with a spinning reserve and provides a huge amount of inertia into the system that helps the generators smooth out the frequency deviation and keeps the voltage within acceptable limits.
To help reduce the number of generators required on this type of system Cat has developed the Grid Stability module, a series of batteries and inverters that use the Cat Patented “Non-Linear Droop controller” This GSM can act as a virtual spinning reserve and the performance of the droop controller dramatically improves the transient capability of the site.
A serious limitation of many systems is the ability to completely switch off generators and still safely operate the facility, Cat Has developed the Bi-Directional Power inverter to enable this operating scenario. The BDP has a very high overload rating, high enough to generate a fault current in this type of operating condition. Where other systems require a synchronous alternator to be inline the Cat PGS does not. This greatly improvs the overall fuel offset with renewable energy, making a more efficient and reliable system.
During my talk I will explain the methods behind these improvements and show some case studies of projects that are using this equipment right now to improve the reliability of their Microgrids.