We are currently witnessing a 1-in-50-years opportunity to transform today’s T&D into infrastructure for the 21st century. However, I have a hard time being optimistic about the prospects of large-scale investments in fast, smart T&D switches, essential to direct line-flow control.
We will begin to overcome these hurdles when T&D owners realize that the value of T&D technology depends on the needs and preferences of the grid users. For example, for quite some time, I have been advocating a natural evolution of today’s planning and operating practices into what I call dynamic monitoring and decision systems (DYMONDS).
DYMONDS are fundamentally different because operators and planners make decisions based on proactive and binding information exchange with system users. This makes it possible to account for choice at value while, at the same time, meeting difficult societal goals. Although many others have advocated this commonsense idea, not much progress has been made in implementing it. This is because managing the system, by using such diverse information about vastly diverse, constantly changing grid users, becomes overwhelmingly complex and beyond the human ability to do.
One way out is to no longer use industry nomograms based on what is assumed to be the worst-case system condition, because it is simply impossible to predict. Instead, it is critical to rely on data-driven information exchange and dynamic decision making enabled by robust software that should be embedded into the platforms of system users (generation and demand), T&D smarts, and system operators and planners.
Software outputs become necessary binding signals to be exchanged with system users and planners. This information exchange process must be repeated periodically, as decisions are being made for the long term or closer to real time. The process becomes a win-win situation for all, and future uncertainties are distributed over many stakeholders according to the risks they are willing to take and according to the
expected value from the selected technologies.
The uncertainties lead to qualitatively new reliable and efficient services. The right stakeholders pay and are paid for their services, and the technologies that bring value survive beyond subsidy stages.
Using real-world data in two Azores Islands, we’ve shown it is possible to use DYMONDS framework to make islands green without increasing the long-term cost of electricity service. Throughout this project, we have discovered that learning a bit more about likely load characteristics and preferences, intermittent resources and limited rates of responses by the conventional power plants could set the basis for much more flexible, multi-temporal on-line adjustments of available resources as conditions change. The following were shown to be key smarts on T&D:
- Voltage-controllable equipment that helps deliver the lowest cost and cleanest power as conditions vary, including variations in solar and wind power and seasonal changes in hydro
- Grid reconfigurations to serve most customers during contingencies
- Delivery of power to clusters of electric vehicles and responsive demand.
Big Lessons Learned
A big lesson learned is that on-line data-driven scheduling of controllable equipment (smarts) could and, therefore, should be used even during non-time-critical contingencies. The wind and sun are going to vary all the time. In addition, hard-to-predict persistent fluctuations require phasor measurement units (PMUs) to ensure quality of frequency, voltage and line flows; inter-area oscillations can be avoided, in particular. Finally, we showed the critical role of fast-automated FACTS and flywheel control for avoiding transient stability problems during sudden wind gusts.
We concluded that careful model-based data processing — provided by today’s supervisory control and data acquisition, by producers of wind power, solar power and electric vehicles, and by synchronized PMUs — may make it possible to dream of sustaining beautiful green islands.
In my view, the world of T&D should be changing as we speak. I believe the same principles shown for the Azores Islands can be used for making continental power grids sustainable. Perhaps one exception is, in large systems, T&D flow control will become even more critical to directing available power to where it is needed, instead of letting power follow Ohm’s law blindly.
I believe this not-so-distant dream could become a reality. If done right, the on-line scheduling of most effective controllable equipment will reduce generation standby reserve. The long-term cost and quality of electricity services will depend, in major ways, on how well we reposition our practices to embrace the potential offered by on-line data availability.
Marija Ilic is a professor of electrical and computer engineering at Carnegie Mellon University.