In this paper, the power electronic for an innovating pasteurization technology is presented. A specific high AC voltage, 120kV at a frequency as high as 800kHz, has to be generated in order to apply an alternating electrical field of 3kV/cm through the liquid. The high voltage generator is based on a modular approach. The module's inputs are paralleled on a DC voltage, while outputs are connected in series to generate the high AC voltage. The modules are made with an H-bridge and a transformer providing the required insulation. The system has been designed to obtain the simplest and most reliable connections. By controlling in real time the number of operating modules, the output voltage of the entire system can be quickly changed. With an accurate model of the system, the output voltage measurement is not necessary and permits to avoid complex and expensive sensors. The electronics have been build and tested. However, due to some air breakdown in high voltage inductances, a reduced voltage of 64kV @ 820kHz has been reached. The system optimization is foreseen for further research activities.