In the vast expanse of the ocean, where the wind blows fiercely and steadily, lies an untapped goldmine of renewable energy. Offshore wind power is gaining traction globally, and China is at the forefront of this green energy revolution. However, integrating this power into the grid isn’t without its challenges. A recent study published in the journal *Power Engineering and Technology* has shed light on a significant hurdle and proposed an innovative solution that could reshape the future of offshore wind power transmission.
The study, led by Zhiqiang Yang from NR Electric Co., Ltd. in Nanjing, focuses on the Rudong project, China’s first offshore wind power integration project using a voltage source converter based high voltage direct current (VSC-HVDC) transmission system. The research addresses potential mid-frequency oscillation risks associated with such systems, a phenomenon that could lead to system instability and power outages.
“Mid-frequency oscillations are a critical issue that can hinder the efficient integration of offshore wind power,” Yang explained. “Our study aims to understand the root cause of these oscillations and propose an effective suppression strategy.”
The research team established a mid-frequency impedance model of the offshore VSC converter and discovered that the converter exhibits inductive and positive-resistance characteristics in the mid-frequency band. Combined with the capacitive and negative-resistance characteristics of the wind farm in the same frequency band, the interaction between these components can induce a 320 Hz oscillation, posing a significant risk to the system’s stability.
To mitigate this risk, the team proposed a mid-frequency oscillation suppression strategy based on virtual damping. This strategy involves extracting mid-frequency harmonic currents using a DC-blocking component and a narrow band-pass filter with an adjustable center frequency. These currents are then fed into a virtual damping block, where a reverse suppression voltage is generated, reshaping the positive damping characteristic of the VSC-HVDC system within the target frequency band.
The effectiveness of this strategy was validated through both simulation results and field tests. “Our strategy can rapidly and effectively suppress oscillations while maintaining the steady-state and dynamic performance of the system,” Yang stated. “Since the commissioning of the Rudong project three years ago, no oscillations have reoccurred, demonstrating the robustness of our solution.”
The implications of this research for the energy sector are profound. As offshore wind power continues to gain momentum, the need for efficient and stable integration methods becomes increasingly critical. The proposed strategy provides a replicable technical solution for offshore wind power VSC-HVDC transmission projects, paving the way for more reliable and widespread adoption of this renewable energy source.
Moreover, the study’s findings could influence future developments in the field. By understanding the underlying mechanisms of mid-frequency oscillations and developing effective suppression strategies, researchers can enhance the stability and efficiency of offshore wind power integration, ultimately contributing to a more sustainable and resilient energy infrastructure.
As the world grapples with the challenges of climate change and the transition to renewable energy, innovations like the one proposed by Yang and his team offer a glimmer of hope. By addressing the technical hurdles of offshore wind power integration, we can harness the full potential of this abundant and clean energy source, bringing us one step closer to a greener and more sustainable future.