Fault Current-Limiting Control and Isolation Strategy of All-DC Offshore Wind Transmission System

As a key research object of renewable energy generation, offshore wind power is playing a vital role to reduce carbon emission. Aiming at developing distant offshore wind power, a novel all-DC transmission system which incorporates DC collection and DC transmission together was put forward. Due to its low inertia characteristic, the fault current develops rapidly, which adds to the difficulty of fault clearing in a short time. Therefore, in order to reduce the fault impact on unfaulty zones while balancing the economy and reliability together, an optimized fault isolation strategy based on a new current-limiting control method was proposed. The operation principle and fault characteristics of the all-DC transmission system are firstly analysed. The current-limiting method based on the changing of the bridge arm voltage reference value combines the inner-loop and outer-loop control together. Simulation verification shows that the fault current can be reduced to zero and the isolation process takes less than 10ms in total, proving the effectiveness and rapidity of the strategy.