Control Algorithm Implementation for a Filtering and Regeneration System used in Urban Traction DC Substations

This paper focuses on the design and implementation of the control algorithm of an active filtering and energy recovery system which transforms the classical DC traction substation into a active substation. For this goal, the active power filter control loops must be tuned not only for the proper operation as an active filter, but also to give the APF the ability to generate back to the power grid the energy intake from the DC line to the compensating capacitor. It will be proved that the transition between filtering operation and energy recovery operation is done automatically, without the intervention of the human operator or of a specially designed system. The correct implementation and tuning of the control algorithm was validated on a complete Simulink model which includes in detail all the sections of the active substation. Moreover, the correct implementation was further experimentally verified on a scale model of the active substation based on a dSpace DS1103 platform. The results obtained both by simulation and on the experimental setup proved the correct answer of the tuned regulators and the overall operation of the active substation. The indirect current control approach was adopted, with the computation of the desired power grid current based on a modified synchronous rotating d-q frame.