This paper presents a power supply of an underwater vehicle with AC power transmission via a ropecable. The module of a three-phase voltage source inverter provides the conversion of DC voltage to AC voltage of increased frequency so as to match the power of the energy source with the load power. The inverter modular design allows organizing the connection of different power load types of underwater vehicles. The operation algorithm of the three-phase voltage source inverter module is proposed. The algorithm takes into account the parameters of the cable line that affect the energy transmission to the underwater part of the power supply. Preliminary calculations of the modulation coefficients, including the different operation modes of the power supply, provides the formation of the output AC voltage of increased frequency with minimal dead time at the desired rate. The control method of power transistors is organized using SVPWM with the third harmonic injection. This method allows reducing the dynamic switching losses of power transistors and the harmonic distortion in the output voltage. Moreover, the third harmonic injection provides the increase in the output voltage value relative to the voltage of the DC power supply. For the correct choice of transistors, the ratios of static and dynamic losses are obtained. The value of these losses determines to a greater extent the duration of dead time. To confirm the algorithmic implementation, the circuit solutions of the onboard and underwater parts of the underwater vehicle power supply, as well as the module of the three-phase voltage source inverter are presented. The waveforms of the power transistors control signals for the inverter module are presented, which illustrate the sweep of the modulation coefficients in accordance with the SVPWM and the third harmonic injection.