System and method for dc power transmission

A DC power transmission system comprising;

• an AC power source for providing AC power;
• a power conversion system comprising:
• an AC-DC converter coupled to receive the AC power and convert the AC power to DC power, and
• DC-DC converters for converting the DC power from the AC-DC converter to a pulse width modulated DC power, wherein the DC-DC power conversion system comprises a plurality of legs, each configured for pulse width modulation;
• a controller coupled to each of the DC-DC converter comprising:
• an analysis module programmed for determining a number of legs for switching for minimizing a cost function based on operating conditions of the power conversion system;
• a switch control module programmed for using the number of legs determined by the analysis module for generating switching commands for the power conversion system;
• and
• a DC transmission bus coupled to the DC-DC converters and configured to receive and transmit the pulse width modulated DC power subsea.

A method for DC power transmission comprising:

• obtaining AC power from an AC power source;
• converting the AC power to DC power;
• converting the DC power to a pulse width modulated (PWM) DC power by determining a number of legs for switching for minimizing a cost function based on operating conditions of the power conversion system and using the number of legs determined by the analysis module for generating switching commands for the power conversion system;
• and
• transmitting the pulse width modulated DC power over a DC transmission bus.