Driving Complexity out of Microgrid Design

In this week’s Industry PerspectivesScott Manson, of Schweitzer Engineering Laboratories, explains why we need simpler microgrid design and more “elegant” control strategies. 

microgrid design

Scott Manson, SEL Engineering Services technology director at Schweitzer Engineering Laboratories

About two decades ago, one of the first programmable logic controller (PLC) systems I coded was controlling an expensive machine called a sheeter. This machine created square sheets of paper out of a continuous roll of craft paper moving 60 mph. My PLC code was over 5,000 lines (rungs) of ladder logic, and the six-axis motion controllers and dc drive system programming were over 1,000 lines more. The second sheeter PLC required half the code, produced significantly more product, and was far easier to maintain. The third and fourth machines required even less code and the machines were simpler, more reliable, less expensive, and required even less maintenance.

Nearly every improvement achieved in this work was the result of first solving a physics problem, then mathematically simplifying the result, coming up with a better control algorithm, designing revisions, and experimenting. These analysis techniques brought great elegance and simplicity to the code, and they also drove revisions to both the mechanical and electrical systems. Gearboxes, motors, sensors, controllers, encoders, resolvers, drives, communication systems, mechanical structures and more were changed.

This experience taught a crucial lesson: to solve a problem, first observe, guess a solution, prove it mathematically, then experiment, test, analyze, and repeat. To engineers, this technique is called “getting back to first principles.” Others refer to this as “the scientific method” or “applied research.”

Our forefathers in the power industry truly understood the concept of first principles. Engineers 80 years ago didn’t have computers, terabytes of data storage, word processing, email, the Internet, or even calculators. They had chalkboards, slide rules, hands-on experience, a solid grasp of physics, and—most important of all—intuition. The designs they worked out for the electric power system were remarkable.

The designs of the slide-rule age are still functioning today. Insulators, cables, synchronous machines, induction machines, gearboxes, turbines, reciprocating engines, governors, exciters, and protective relays designed decades ago are still functioning today in our electric power grid. These designs brought low-cost, reliable electric power to most homes in the United States. As shown in Figure 1, energy prices dropped as these innovations matured. Along with this proliferation of reliable, low-cost power came a quality of life never before experienced by mankind.

Fifteen years ago, I was fortunate enough to tackle the problem of islanded power grids in the oil and gas industry. In this industry, the ability to seamlessly island ensures operational continuity and process uptime during power system disturbances. Within a year we had invented revolutionary control methods that allowed multiple grid segments to seamlessly transition to islanded mode and which dispatched generation to reach an equilibrium state in a process now known as load sharing. The process beautifully managed all forms of voltage, frequency, and intertied and reactive power flows, and it resynchronized the islanded grid segments with ease. The entire system was designed on a whiteboard before a single line of code was ever written.

In this industry, the ability to seamlessly island ensures operational continuity and process uptime during power system disturbances.

Real price of electricity in the United States (in cents per kilowatt-hour, adjusted to 2016 values).

Today we call such islanded power systems microgrids. We have committees, working groups, task forces, government funding, and private funding driving research and development to improve the efficacy and reliability of microgrids. These efforts all strive for a future in which microgrids provide energy independence, reduced environmental impact, lower costs, higher reliability, and improved human safety. All of these works are ultimately aimed at bringing the next revolution in quality of life to our descendants.

Through all of this din, there is a cry for simplicity in microgrid design. We need microgrid power systems that don’t take a team of Ph.D.s to assemble. We need fewer lines of code. We need more elegant control strategies. We need simplified distributed energy resource interfaces. We need simplified and comprehensive cybersecurity measures. We need innovative protection methods.

Scott Manson - There is a cry for simplicity in #microgrid design. Click To Tweet

If our forefather’s results are to repeated, then let us go back to the proverbial chalkboard and find elegant, simplified ways to solve our challenges. This will require leadership, math, physics, experience, intuition, and a firm belief that this is possible. By going after these challenges with both passion and rigor, we will soon have microgrid systems that define a new age of reliable, low-cost power for our world.

Scott Manson is the SEL Engineering Services technology director at Schweitzer Engineering Laboratories

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