A power transmission system is provided. The power transmission system includes a power source for providing power. The system also includes a power conversion system comprising power converters coupled to receive the power and convert the power to DC power, wherein the power conversion system comprises a plurality of legs each configured for pulse width modulation. The system further includes a controller 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. The controller also includes 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. The system also includes a DC transmission bus coupled to receive the DC power and transmit the DC power.