Modeling and Simulation on the Hybrid Solution of Static Var Generator and Synchronous Condenser for Unlocking Power Output Limitation of Wind Farms Integrated into Weak Grid

The issues of low inertia, overvoltage, and wide-frequency oscillations in high-proportion renewable energy systems have become prominent, posing major challenges to renewable energy integration and threatening grid stability. Currently, many wind-rich areas ensure grid safety and stability by reducing wind farm output. To enhance the active power delivery capability of wind farms, this paper proposes a hybrid solution of a small synchronous condenser (SC) and static var generator (SVG) within wind farm stations to optimize reactive power and voltage at the point of grid connection. First, it was analyzed that the low short-circuit ratio (SCR) is a key factor affecting the stable operation of wind farms, and the sub-transient reactance of the SC can increase the SCR. Based on this, a method for configuring the capacity of the SC was developed. Next, simulation models for both the SC and the SVG were established, and their reactive power compensation capabilities were verified. The hybrid control approach combined the advantages of both devices, providing comprehensive voltage support across sub-transient, transient, and steady-state conditions for renewable energy stations. Furthermore, based on a practical 50.5 MW wind farm, which has been operating with a power delivery consistently limited to 60% of its capacity, a simulation model and scenarios were set up. A comparison of the simulation results shows that, with only the SVG in operation, the wind farm is prone to oscillations after a grid fault. However, after adopting the hybrid control of the SC and SVG, the wind farm operates stably. Therefore, installing a small SC within wind farms can effectively address the limitations of voltage stability and a low short-circuit ratio, thereby supporting higher levels of renewable energy integration.