Research on broadband oscillation characteristics and additional damping control of new energy grid-connected systems

The large-scale grid connection of new energy sources makes the power system highly electronic. The resulting broadband oscillation problem is the main challenge hindering the safe and stable operation of current high-proportion new energy power systems. To ensure the safe operation of the power grid, it is important to carry out systematic research on broadband oscillation suppression measures. At present, an additional damping controller method is often used in broadband oscillation suppression, but the parameter optimization problem for the additional controller of new energy units and flexible DC transmission systems must still be further explored. This article first establishes a state–space model of direct-drive permanent magnet wind farms connected to the AC and DC grid systems and uses eigenvalue analysis to analyze the broadband oscillation modes involved. Then, additional damping controllers are designed for wind turbines and flexible DC transmission systems, and a parameter optimization model is established with the maximum damping ratio of the coupled oscillation mode as the optimization goal. The Improved Plant Growth Simulation algorithm (I-PGSA), based on cloud model theory with good global search and a fast calculation speed, is used to optimize and solve the additional damping controller parameters. In addition, considering that adjusting the controller parameters during the optimization process may cause the target mode frequency to change too much, so it is impossible to continue to optimize it, this article further introduces mode tracking technology to track the target mode to ensure that no target offset occurs during the optimization process. Finally, through eigenvalue analysis and power systems computer-aided design/electromagnetic transients, including DC (PSCAD/EMTDC) time domain emulation, the system is compared before and after governance, and it is verified that the proposed controller parameter optimization strategy can effectively suppress the system broadband oscillation problem.