Dileep Kumar and Wajiha Shireen, researchers at the University of Strathclyde in the United Kingdom, have developed a new energy control strategy aimed at improving the fault ride-through capability of offshore wind farms (OWFs) connected to the grid using Modular Multilevel Converter-based High Voltage Direct Current (MMC-HVDC) systems. Their work, published in the IEEE Transactions on Power Electronics, addresses a critical challenge in the integration of offshore wind energy into the power grid.
Offshore wind farms are increasingly being connected to the grid using MMC-HVDC systems, which are known for their flexibility and efficiency. However, when an AC fault occurs on the onshore side of the system, it can reduce the power transfer capability of the onshore converter station, leading to a surplus of power in the HVDC link. This surplus power can cause a rapid rise in the DC-link voltage, potentially compromising the safe operation of the offshore wind farm.
To tackle this issue, Kumar and Shireen have proposed a new AC fault ride-through scheme. This scheme combines the storage of surplus power in the capacitors of the MMC submodules (SMs) and the dissipation of any residual power in an energy dissipation device (EDD). The proposed control strategy allows for the use of half-bridge MMC SMs with lower capacitance, leveraging their storage capacity to share the surplus power during faults. This approach also enables the use of a lower-rated EDD, making the system more efficient and cost-effective.
The researchers tested their proposed scheme on a 640kV/420MW MMC-HVDC system. The results demonstrated that the control scheme effectively maintains DC link voltages, ensuring the continued connection of OWFs during AC faults. This enhancement in fault ride-through capability is crucial for the reliable and stable integration of offshore wind energy into the power grid.
The practical applications of this research are significant for the energy sector. As the world increasingly turns to renewable energy sources, the reliable integration of offshore wind farms into the grid is becoming more important. The proposed energy control strategy can help ensure the stable operation of MMC-HVDC systems, facilitating the wider adoption of offshore wind energy. This, in turn, can contribute to the global transition towards a more sustainable and low-carbon energy future.
This article is based on research available at arXiv.