Protection Scheme for Hybrid Cascade HVDC Transmission Line Based on Current Control Adjustment Deviation

Hybrid cascaded high voltage direct current (HVDC) transmission adopts the form of modular multilevel converter (MMC) and line-commuted converter (LCC) in series, which not only reduces the investment cost, but also reduces the fault current. In this paper, the topology and control strategy of the hybrid cascade HVDC transmission system is introduced firstly. Then, the fault characteristics of current control signal in converter is analysed. The polarity of current control signal adjustment deviation is different in AC/DC faults. Thus, this paper proposes a protection scheme for hybrid cascade HVDC transmission based on current control adjustment deviation. A hybrid cascaded HVDC transmission is modelled in PSCAD\EMTDC. The simulation results show that the proposed method is applicable to different fault circumstances. And the proposed method has strong fault transition resistances and anti-noise abilities.