Abstract
| The attention in this paper is directed to the transformation of an existing DC-traction substationsequipped with 12-pulse parallel uncontrolled rectifier into an active substation. In this manner, the traction substation gains the capability of redirecting the braking energy to the power supply and the power quality indicators during the traction regime are greatly improved. The practical solution lies in adding a shunt active power filter, accompanied by appropriate circuits of connection on both the DC and AC sides, between the DC-traction line and the primary of the traction transformer via a dedicated recovery transformer. To control the current provided by the shunt active filter in both traction/active filtering and regeneration regimes, the indirect method of handling the supply current has been adopted. The reference supply current during the operation in traction regime is calculated based on instantaneous powers provided by the concepts of the instantaneous reactive power theory. Two compensation strategies have been implemented for this operation mode, i.e. the total compensationof the current harmonics and reactive power and the partial compensation (only the current harmonics). In regeneration mode, the traction rectifier is blocked and the reference supply current is given by the voltage controller. Based on the conceived Matlab/Simulink models of the whole system, the proper operation is confirmed and the good performance of the system during both traction/filtering and regeneration regimes is shown. Indeed, the total harmonic distortion of the supply current is always below the limits and recommendations of the power quality standards and the operation in regeneration mode is allowed. |
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