Transitioning to renewable energy sources such as wind power involves addressing significant technical challenges, particularly the integration of these sources with existing power systems. Traditional methods often struggle to maintain voltage stability and power balance, especially as renewable energy penetration increases. A new study presents a novel soft grid integration control strategy for self synchronized voltage source doubly-fed induction generator (DFIG) wind turbine generators, which aims to solve these issues effectively.
The research highlights how conventional renewable energy systems typically rely on synchronous generators for integration, which provides inherent stability characteristics. DFIG wind turbines, on the other hand, use power electronic converters for control, leading to different grid-integration characteristics. A primary disadvantage of traditional grid-following strategies for DFIGs is their dependence on phase-locked loops (PLLs), which can become unstable under weak grid conditions, resulting in integration challenges.
The proposed soft grid integration control strategy focuses on enabling mechanical and electrical start-up processes for DFIG wind turbines. Researchers, affiliated with Nanjing Vocational University of Industry Technology, describe how the system strategically controls the rotor-side converter (RSC) and grid-side converter (GSC) to synchronize with the grid without incurring damaging surge currents. This method significantly enhances the frequency stability of the connected power system.
During the mechanical start-up process, the pitch angles of the wind turbine are adjusted to optimize rotor speed before integration with the power grid. This careful coordination ensures the generators can handle changes brought on by load variations. Once at the grid's operational speed, the system transitions to electrical start-up processes, which involve pre-synchronization controls to align the output voltage with grid parameters.
Utilizing simulation results obtained through Real-time Digital Simulator (RTDS), the researchers established the effectiveness of their proposed strategy. The results showed improved integration performance— not only could the DFIG seamlessly connect to the grid, but they also observed no surge current, which is commonplace with traditional methods. This smooth transition mitigates risks associated with grid instability, making their approach significantly advantageous.
One of the key takeaways from the research is the assertion: "The proposed soft grid integration control strategy has its obvious advantage…it can achieve the soft grid integration and virtual inertia response without additional hardware." This statement reflects the study's broader significance as the power sector increasingly moves toward enhancing the reliability and stability of renewable energy systems.
By enabling wind turbine generators to function effectively as additional grid resources, the soft grid integration approach demonstrates its exceptional potential. It not only assures successful integration of wind energy but also plays a pivotal role as current power systems evolve to embrace higher levels of renewable energy sources. The researchers urge organizations involved with power generation to connect higher penetrative levels of wind energy to benefit from this technology.