Pulse width modulated current-source converter (PWM-CSC) has great prospects in high voltage direct current transmission system (HVDC) due to its attractive features

such as flexible control characteristics

ability to avoid commutation failure

and lower cost. However

valve voltage of the PWM-CSC is the jump value between filter capacitors line-voltage and zero voltage due to its bypass operation

resulting in high peak voltage withstand by the converter for a rated HVDC system and high voltage ripper ratio. In order to solve these issues

an improved modulation method called specific carrier frequency of SPWM is proposed. After adopting the improved modulation method

the number of the reverse blocking integrated gate commutated thyristor (RB-IGCT) in series can reduce by 31.5% under unity power factor operation and the value of the dc choke can reduce by about 78.6% compared to traditional modulation methods

improving practicability of engineering application. Moreover

active power and reactive power operating range are derived under different modulation methods and the relationship of the power factor

modulation in q-axis and DC current are studied. Finally

effectiveness of the improved modulation method and comparisons of power operating range are verified in PSCAD/EMTDC.