A method for controlling a hybrid vehicle electrical system includes driving the vehicle in a first driving mode where the battery pack is connected to the traction voltage DC-link and the battery pack is supplying the electrical auxiliary units with power, shutting down the power electronics unit in order to cease power delivery from the electric machine to the traction voltage DC-link or to the electric machine from the traction voltage DC-link, disconnecting the battery pack from the traction voltage DC-link by opening the relay, and activating the power electronics unit and controlling output voltage of the power electronics unit to a predetermined level.