Dual Phase Shift PWM-CSCs Based Hybrid HVDC Transmission System

In order to reduce the cost of the high voltage direct current (HVDC) transmission system, a hybrid HVDC transmission system adopting line commutated converter (LCC) on the rectifier side and dual phase shift pulse width modulated current source converters (PWM -CSCs) on the inverter side is proposed in this paper. The mathematical model and the output ac current harmonic characteristics of the PWM -CSC are analyzed in detail. A maximum power factor control method is proposed. Finally, a 400 kV/1250 MW PWM-CSC based unipolar HVDC transmission system is built using PSCAD/EMTDC software. The simulation results verify that the proposed control method realizes the maximum power factor operation under normal state and that the proposed hybrid HVDC transmission system can ride through both ac and dc faults smoothly.