It’s not a big surprise that existing electric power transmission and distribution systems were not designed to manage the possibility of large numbers of distributed energy resources (DERs), such as solar and wind installations, that produce variable power. But now, a new Industrial Internet Consortium (IIC) testbed report is documenting progress on a goal to develop and demonstrate techniques for a 100% DER power-generation-based microgrid with the smarts to be “both operationally feasible and support a variety of business models.”
The IIC Microgrid testbed group has developed a tiered communication and control architecture for microgrid and distribution grid management. (Image source: Industrial Internet Consortium)
Microgrid Cost Issues
The key takeaway from the report is that there is a pressing need to bend the cost curve and provide more cost-competitive solutions when it comes to the generation of power using DERs. Many believe a day is coming when this type of power will be cheaper than fossil fuel-based generation. DERs are working under a mandate to become more cost efficient.
The group concludes that microgrids with DERs are a solution with definite commercial viability. Taking advantage of the latest advances in communication technology and embedded systems, microgrids can be increasingly competitive in terms of cost per megawatt generation by addressing synchronization requirements effectively. The key and technological challenge is how to respond to streams of external data (weather forecasts and real-time pricing and demand, for example) and create solutions that mitigate supply-demand fluctuations.
The report states as its final summary that “the generation, distribution and transmission operators must rethink their technical and business models to stay relevant and continue to keep the grid as reliable while having a feasible business model. By providing a unified communication technology among DERs and installed equipment, the solution presented here meets flexible business models and helps utilities manage their assets and networks optimally.”
The technical group determined that a key challenge in microgrid development is synchronizing the voltage, and particularly the phase-angle, of the power in a microgrid distributed from the main grid. Since reconnection of the two can only happen when the phase angles of the two systems match closely, they determined that “the simplest solution is to shut off power on the islanded microgrid, reconnect to the main grid and then turn everything back on. To avoid losing power, microgrid controllers often use phase-locked loops or similar control methods to synchronize the microgrid power signal frequency and phase with the main grid’s, but these methods are cumbersome and error-prone.”
The resulting system architecture implements intelligent control at the edge of the grid combined with peer-to-peer, high-performance communications for local autonomy. Third-party data and cloud analytics are deployed in a tiered architecture by integrating the microgrid control and its real-time databus with cloud-based management, analytics, and visualization tools.
TSN technology is envisioned as providing the peer-to-peer, high-performance communications that these distributed control systems will require to synchronize and coordinate multiple inverters by transmitting real-time measurements of grid power, frequency, and phase-angle among inverters.
The system is also being designed to gather data about the operating conditions of the grid. Intelligent analytics is used to estimate power supply and integrate with the local balancing authority for grid stability, along with integration with utility back-end systems to provide an integrated dashboard for operators and/or end users.
The report is worth a full reading. It discusses additional topics including potential smart grid enhancements and thoughts on commercializing the technology via the IIC testbed. Engineers at Wipro, National Instruments, RTI, and Cisco collaborated on the testbed report, which summarizes the activity and conclusions of the group. A copy of the full report can be found on the IIC website at https://www.iiconsortium.org/microgrid.htm.
Al Presher is a veteran contributing writer for Design News, covering automation and control, motion control, power transmission, robotics, and fluid power.
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