Advancing Clean Energy

Preparing the Grid to Let the Sun Shine In

May 19, 2016

Industry-Leading ComEd Study Supports Smart Integration of Renewable Energy

Dimitra Apostolopoulou, a Ph.D. engineer on ComEd’s Smart Grid & Technology team, spends a lot of time thinking about the sun – perhaps more than the native of Greece would have thought upon leaving her Mediterranean homeland!

Dimitra is leading an effort to prepare ComEd’s power grid in northern Illinois for the integration of solar energy. At the heart of that effort is hosting capacity research, which is helping ComEd understand the capacity of each of its more than 5,000 power lines – or “feeders” – to accommodate extra power generated at the “ends” of the grid, as with rooftop solar installations. Ultimately, this work will help ComEd guide the most effective integration of solar and other distributed generation into its system.

ComEd’s work on this front is industry-leading and has garnered international attention.

“The challenge of integrating distributed energy resources (DER) into the system stem from the fact that the distribution network has been designed assuming one-way power flows,” said Dr. Math Bollen, Chair Professor in Electric Power Engineering at Luleå University of Technology, Sweden.  “Through its hosting capacity research, ComEd engineers are taking the utility’s more than 5,000 distribution feeders, studying them under multiple conditions, and then organizing them into different categories based on unique  characteristics and behavior.  This type of data will enable ComEd to make much quicker and smarter decisions when evaluating proposals to bring DER onto its system.”

Here, Dimitra – who holds a doctoral degree from the University of Illinois at Urbana-Champaign and an undergraduate degree from National Technical University of Athens, Greece – shares more about the research and how it will help ComEd drive a cleaner energy future in Illinois.


Q: Decreasing costs associated with distributed generation technologies like solar panels, a growing interest among customers for control over consumption and costs, and government incentives all bode well for the growth of renewable energy. But what are some of the issues and challenges associated with integrating renewables into the electric system?

A:  At ComEd, we’re doing everything we can to set the stage for the smart, sustainable growth of solar power on our system. Making sure our power grid is ready to accommodate solar and other renewables is essential to meeting the needs of residents and businesses that want to “go green.”

Power grids have been predominantly designed for one-way power flows and this design creates challenges. To a certain point, the current network can accommodate the multi-directional energy flows associated with rooftop solar and other so-called “distributed generation,” or power generation at the “ends” of the grid rather than at central generating stations. Beyond that point, however, network performance is negatively impacted. With the increased penetration of distribution generation, some utilities have begun to experience challenges such as over voltages, over currents and equipment overload, which can negatively impact the operation and reliability of the system and impair power quality – so at ComEd, we want to prepare well.

We’ve been making great progress in recent years to improve reliability and we want to continue doing so while integrating more renewables into the system.

Q: What is the focus of your research?

A: We’re focused on the challenges created by the increasing adoption of distributed generation as it transforms the power grids from passive, steady and radial systems to active, dynamic and complex networks.

Hosting capacity addresses two of the major challenges that utilities are faced with when considering the integration of distributed generation:  overvoltage and overloading.  In fact, we’re looking at ways to determine the hosting capacity for distributed generation of each individual feeder, or power line. The best indicator for capacity is the point at which a feeder reaches overvoltage and is damaged – and that’s influenced by a lot of things, such as feeder design, customer behavior and load.

Q: What are you learning?

A: We’ve developed an approach for evaluating distributed generation impacts on specific feeders. The key advantages of the proposed method include the overall scalability by running automated simulations that take into account the uncertainty in the size and location of potential installed distributed generation units. This approach may be used to:

  • Provide an estimate for the amount of distributed generation that a system can accommodate without upgrades
  • Identify the potential locations for distributed generation installations to minimize grid impacts
  • Study the impacts of different distributed generation technologies, including intermittent sources such as photovoltaic (PV) solar systems
  • Determine optimal locations and settings for smart inverters for voltage regulations and control
  • Predict where and when issues might arise as well as how often they might occur

Q: What’s the next step in your research on hosting capacity? And what else would you want customers to know about this?

A: The current methodology determines the hosting capacity for a specific feeder. Our system contains around 5,000 feeders. The computational intensity to determine all the feeders’ hosting capacity is a cumbersome task. In this regard, we will group the feeders with “similar” characteristics into categories and calculate the hosting capacity of the category’s representative feeder. We may argue that all the feeders in the same category have the same hosting capacity as the representative feeder. In this way, we may calculate the hosting capacity of all our feeders and approximate a system-wide hosting capacity.

In addition, we plan on further investigating the value of distributed generation at specific locations in a given feeder. We need to better understand and quantify the location and sizing of distributed generation, e.g., PV solar systems, and the impact on the hosting capacity of a feeder. To do that, we plan on building an algorithm for calculating the locational sensitivity of a feeder with respect to the size of installed distributed generation.

Through this analysis we’ll develop a way to quantify the locational impact of distributed generation and the optimal location for distributed generation on the system. This will enable us to develop targeted incentive programs to encourage installation of distributed generation in a more optimal and sustainable manner.