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This paper is concerned with the possibilities of transformation the DC traction substations with uncontrolled rectifiers into active substation, being able to ensure both the braking energy recovery and active filtering function. There are a lot of approaches on the management of regenerative braking energy, most of them based on energy storage systems or the concept of reversible substation. Few references refer to the addition of complementary functions, such as harmonic filtering, and involve the adoption of specific structures without further argumentation. In this paper, the intention is to analyze and find argumentations on the possibilities of coupling a three-phase active power filter based on voltage source inverter topology in the power structure of a DC traction substation. The most used types of uncontrolled rectifiers, i.e. the three-phase bridge scheme and both 12-pulse parallel and series structures are taken into consideration. Based on correlation between the DCline and AC-line voltages, it is shown that the active power filter can be connected directly in the secondary of the existing traction transformer only in the case of 12-pulse series rectifier. A dedicated recovery transformer is required for the other two schemes of rectifiers and some considerations and results on the compensating power and correlation between the active filtering performance and the voltage in the recovery transformer primary are presented.

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This paper is focused on an adaptive controller for the direct current (DC) voltage in three-phase three-wire shunt active power filters systems. Although the controller structure of the proportional-integral (PI) type is determined off-line and does not change, the prescribed DC voltage and the controller parameters are calculated in an adaptation block, depending on the non-active power to be compensated. The adaptive control is based on the design expressions for the DC circuit of the shunt active power filter found by the authors, based on the detailed analysis of its operation, during the active filtering. The performances of the proposed adaptive control and its advantages compared to the classical control (where the prescribed DC voltage and the controller parameters are constant) were first determined on the virtual model of a laboratory setup. Then, the adaptive control was implemented on the dSPACE 1103 control board, which allowed the experimental determinations that prove and support the results obtained on the virtual model.

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