A new approach to ensuring stability in renewable power systems

As the world pushes towards cleaner energy solutions, the integration of renewable energy sources like wind and solar power into the grid has presented significant challenges. One of the major concerns is the risk of power system instability caused by oscillations, which could result in power outages or other disruptions. Associate Professor LYU Jing and doctoral candidate GAO Lei from the Wind Power Research Center of Shanghai Jiao Tong University, together with other researchers, have developed a cutting-edge method for assessing these oscillations in renewable power systems, using a frequency-domain modal analysis approach.

The findings, published online in the Journal of Shanghai Jiao Tong University on December 5, 2023, offer a novel way to evaluate and mitigate the risks posed by sub-synchronous and super-synchronous oscillations in systems with a high penetration of renewable energy.

Understanding the Challenge

In traditional power systems, the presence of synchronous generators provides inherent stability. However, renewable power sources, particularly wind and solar, often operate asynchronously and introduce complex dynamics that can make the grid more susceptible to oscillations. These oscillations, which occur at frequencies above or below the system's natural frequency, can propagate through the network, potentially leading to power system instability.

In recent years, incidents of power system oscillations have caused significant disruptions, including a well-known event in 2009 at a U.S. wind farm that resulted in a mass disconnection of turbines. Similar occurrences have been documented in China's wind farms.

A New Method for Stability Assessment

The research team developed a more accurate and flexible method for assessing oscillations, based on frequency-domain modal analysis (FDMA). It combines the strengths of existing techniques to give a clearer view of system stability.

By modeling key components like wind farms, solar stations, and generators, the proposed method creates a system-wide network that reflects the real grid. Analyzing this network identifies weak spots and potential instability, pinpointing areas most at risk for oscillations.

GAO Lei, the first author, emphasized, "This approach allows us to identify where the system is weakest and where interventions, such as oscillation suppression measures, would be most effective."

Real-World Applications

To test their method, the researchers applied it to a renewable power system in East China, which included offshore wind farms, a solar power station, and thermal and nuclear plants. Using frequency-domain analysis, they assessed the system's stability under varying conditions, like different levels of renewable energy input.

The findings were clear: as more renewable energy was added, the risk of oscillations increased, especially when offshore wind farms operated at full capacity, causing oscillations between 40 and 60 Hz. However, with the proposed method, the team identified weak points in the system and proposed solutions to reduce these risks.

Looking Forward: Towards a More Stable Future

This research has big implications for the future of renewable energy. As more countries aim for carbon neutrality, maintaining stable power systems becomes crucial. This new method provides a reliable tool to manage the risks of system oscillations, paving the way for safer, more stable grids that can handle larger amounts of renewable energy.

Next, the team plans to refine their approach by studying energy storage control strategies. By pairing energy storage with advanced control algorithms, they hope to further minimize oscillation risks, making large-scale renewable energy integration even more feasible.

As Associate Professor LYU noted, "Our work is just the beginning. By better understanding how oscillations occur and how to prevent them, we can ensure that renewable power systems not only provide clean energy but also operate in a stable and reliable manner."