In the quest for stable and efficient energy systems, researchers have long grappled with the challenge of subsynchronous oscillations (SSOs), particularly in weak grid conditions. A recent study published in *Southern Power System Engineering*, led by Yuxin Sun of Jiangsu University’s School of Electrical Information Engineering, offers a promising solution to this persistent problem. The research focuses on Virtual Synchronous Generators (VSGs), which, despite their benefits, can exhibit negative damping characteristics that trigger SSOs, leading to system instability.
Sun and his team have developed a method to determine the feasible domains for adding virtual impedance on the grid side to suppress these oscillations. “The virtual impedance can effectively suppress the subsynchronous oscillations, but different parameter values result in varying suppression effects,” Sun explains. By analyzing the suppression mechanism through amplitude, phase angle, and electrical vectors associated with electrical resonance, the researchers introduced virtual impedance to alter the system’s impedance characteristics.
The study establishes a VSG sequence impedance model and determines the feasible domain of the virtual impedance under the constraints of output power and system stability. “Ensuring that the virtual impedance lies within the feasible domain can provide sufficient power output capability and suppress subsynchronous oscillations, thereby guaranteeing stable system operation,” Sun notes.
The effectiveness of this method was verified through MATLAB/SIMULINK simulations. By selecting different virtual impedance values and observing voltage, current, power, and frequency responses, the team demonstrated that introducing virtual impedance at the grid side can effectively suppress SSOs under weak grid conditions. The simulations also revealed that better suppression is achieved when the virtual inductance is relatively large and the virtual resistance is relatively small within the feasible domain.
This research has significant implications for the energy sector, particularly in regions with weak grid infrastructure. By providing a method to suppress SSOs, it paves the way for more stable and reliable energy systems. “This study offers a practical solution to a longstanding challenge in the field,” Sun says. “It has the potential to shape future developments in VSG technology and contribute to the overall stability of the grid.”
As the energy sector continues to evolve, the need for innovative solutions to ensure system stability becomes increasingly critical. This research by Sun and his team at Jiangsu University represents a significant step forward in addressing this need, offering a promising approach to suppressing subsynchronous oscillations and enhancing the reliability of energy systems worldwide.