In the vast landscape of renewable energy, photovoltaic (PV) plants are increasingly integral to our power grids. However, their integration into weak AC networks can sometimes lead to sub-synchronous oscillations (SSO), a phenomenon that can cause significant instability and potential damage to the grid. Enter Fan Zhang, an engineer from Baoding Power Supply Company of State Grid Hebei Electric Power Co., Ltd., who has proposed an innovative solution to this pressing issue.
Zhang’s research, published in ‘Zhongguo dianli’ (China Electric Power), introduces a static var generator (SVG) based supplementary damping control strategy designed to mitigate SSO in large-scale PV plants. The strategy is both elegant and effective: it extracts the voltage at the PV coupling point and produces a sub-synchronous current that aligns with the sub-synchronous voltage. This alignment effectively turns the SVG into a positive resistance at the sub-synchronous frequency, dissipating the oscillatory energy and suppressing SSO.
“The key innovation here is the use of the SVG to act as a damping controller,” Zhang explains. “By designing the supplementary sub-synchronous damping controller (SSDC) to produce a current that is in phase with the sub-synchronous voltage, we can create a system that naturally dissipates the energy causing the oscillations.”
The implications of this research are far-reaching. For the energy sector, this means more stable and reliable integration of PV plants into weak AC networks. This stability is crucial for the commercial viability of large-scale PV projects, as it reduces the risk of grid instability and potential downtime. Moreover, the ability to mitigate SSO can lead to more efficient use of existing infrastructure, delaying the need for costly upgrades.
Zhang’s work doesn’t stop at the theoretical. He and his team have validated the effectiveness of their control strategy through electromagnetic transient simulations, using a PV plant in northwest China as a case study. The results were compelling, showing improved stability margins under various working conditions.
“This strategy not only enhances the stability of the PV system but also ensures that the energy generated is utilized more efficiently,” Zhang adds. “It’s a win-win for both the grid and the PV plant operators.”
As the energy sector continues to pivot towards renewable sources, innovations like Zhang’s will be pivotal. By addressing the technical challenges of integrating large-scale PV plants, this research paves the way for more robust and efficient energy systems. The future of renewable energy integration looks brighter, and it’s researchers like Fan Zhang who are leading the charge.
