In the rapidly evolving landscape of power systems, the integration of renewable energy sources is both a challenge and an opportunity. As the proportion of new energy connected to the grid increases, so do the issues related to power system stability, particularly in weak grids. A recent study published in the journal Dianli jianshe (Power Construction) sheds light on a critical aspect of this challenge: the sub- and super-synchronous interactions (S²SI) caused by Static Var Compensators (SVCs) in weak AC grids.
SVCs are crucial devices for enhancing the dynamic response of power systems, but they can inadvertently trigger oscillations in weak grids, leading to potential system instability. This is where the work of WEN Cao, lead author and a researcher at the Ultra High Voltage DC Center of State Grid Sichuan Electric Power Company, comes into play. Cao and his team, including collaborators from State Grid Sichuan Electric Power Company, Sichuan University, and State Grid Sichuan Electric Power Research Institute, have delved deep into the mechanisms behind these interactions and proposed an effective strategy to suppress these oscillations.
The research team employed a frequency-coupled impedance model (FCIM) to analyze the frequency coupling characteristics between SVCs and weak grids. Their findings revealed a strong coupling relationship between sub-synchronous and super-synchronous frequencies. “We found that the oscillation frequency is closely related to the controller parameters of the SVC,” Cao explained. “This understanding is crucial for developing effective control strategies to mitigate these oscillations.”
The team’s innovative approach involved studying the influence of controller parameters on oscillation modes based on the stability criterion of impedance crossing. They proposed a supplementary sub-synchronous damping controller (SSDC) designed to optimize these parameters and suppress oscillations. To validate their theoretical analysis, the researchers conducted electromagnetic transient time-domain simulations using the PSCAD/EMTDC platform. The results were compelling: the proposed SSDC control strategy significantly reduced the amplitude of sub-super-synchronous oscillations, thereby enhancing system stability.
The implications of this research are far-reaching for the energy sector. As the integration of renewable energy sources continues to grow, ensuring the stability of weak grids becomes increasingly important. The findings of Cao and his team offer a practical solution to a pressing problem, with significant engineering application value. By optimizing SVC controller parameters, power system operators can improve the dynamic response of their grids, ensuring a more stable and reliable energy supply.
This study not only reveals the underlying mechanisms of S²SI triggered by SVCs but also provides a roadmap for future developments in power system stability. As the energy sector continues to evolve, the insights gained from this research will be invaluable in shaping the next generation of power system technologies. The work published in Dianli jianshe, which translates to Power Construction, underscores the importance of ongoing research and innovation in maintaining the integrity and reliability of our power systems.
As we move towards a more sustainable energy future, the challenges posed by weak grids and the integration of renewable energy sources will only become more pronounced. The research conducted by Cao and his team represents a significant step forward in addressing these challenges, paving the way for a more stable and resilient power system.
