Control and Protection Strategies of Parallel De-icing Operating Mode for UHVDC Power Transmission System

The topology of parallel de-icing operation mode is described,and the existing control strategy of parallel de-icing operation mode is analyzed.Then a new unified control strategy of two parallel converters is proposed based on mature single converter control theory and strategy,with the implementation of the new control strategy elaborated.A comprehensive overview about the influence of the parallel de-icing operation mode on DC protection is given,and the coping strategies of the relevant protection are proposed.The new protection criterion logic on the key protection function is put forward.The new control and protection strategies have passed the real-time digital simulator(RTDS)test and on-site tests as proof of its feasibility and reliability.