Method for providing thermal protection to a pre-charge unit and electric power conversion system for executing the method

A method for providing thermal protection to a pre-charge unit (PRC) comprising a step-up transformer of an electric power conversion system with a DC link, comprising the steps of

• executing a parameter identification block identifying electrical and thermal parameters of the PRC;
• executing a current estimation block estimating a current flowing through the step-up transformer of the PRC based on a voltage input;
• executing a thermal level estimation block estimating a thermal level at the step-up transformer of the PRC based on the estimated current flowing through the step-up transformer of the PRC;
• executing a protection logic block comparing the estimated thermal level to a pre-determined trip threshold to determine whether a thermal overload has occurred;
• and
• outputting a trip signal if the trip threshold has been exceeded.