Robust Active Front End Approach in Crane Applications for Port Competitiveness

Focusing on the ports development, a variety of cranes can be envisaged for the activities in container terminals. Rubber Tired Gantry (RTG) cranes powered by on-board diesel generators represents the common solution. However, the more cost effective approach based on Electrically powered Rubber Tyred Gantry (E-RTG) cranes should be taken into consideration. The latter may constitute a nonlinear load for the electric power system, when the active front end interface is not present. This means that the delivered apparent power from the grid has to be increased in order to achieve the same working power at the load. This problem is emphasized when the container traffic is enlarged due to economic growth or as a consequence of competitiveness between ports. These unwanted energy fluctuations may be properly mitigated by applying an active front end, i. e. bidirectional three-phase AC/DC power converters. By decreasing the peak crane power, more cranes could be installed thereby increasing the speed of container traffic. In order to achieve high power quality, a variable DC link voltage has been initially evaluated by means of simulations. Then, the proposed approach has been tested in a 1kV active front end model based on STM32F407 microcontroller, showing more influence of variable DC link voltage in the single-phase solution.