Abstract
| Although the high power DC traction substations are using 12 pulse rectifier which have lower distortion than the classical 6 pulse rectifier, considering the high power, the reactive and harmonic components of the absorbed current are harmful to the power grid. The addition of an active compensator to the classical dc traction substation creates the “active substation”. The active substation allows bidirectional power flow between the power grid and the DC catenary, which means the active power flow from the power grid to the DC catenary and the recovered power flow from the catenary back to the power grid. At the same time, because the compensator acts like an active filter in the first case and like a power inverter in the last case, both the consumed and recovered power are active powers. To achieve this goal the active compensator must inject current to the point of common coupling, and the typical currentcontroller is the hysteresis regulator. At the same time, the typical approach on the injected current regulation is the direct current control, which implies the closed loop controlof the current at the compensator output, i.e. the current through the output inductors. A new approach is the closed loop control of the current absorbed from the power grid, i.e. the indirect control, for which the compensator controls the grid current, and for a given load current, the compensator injected current results from the first two. |
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