Average current-mode control of the 12-pulse rectifier

For comparison purposes, a PI-based controller structure is designed (Fig. 35.36B), taking into account that small mismatches of the line voltages or of the trigger angles can completely destroy the current share of the four paralleled rectifiers, in spite of the current equalizing inductances (l and l′). Output voltage control sensing only the output voltage is, therefore, not feasible. Instead, the slow and fast manifold approach is selected. For the fast manifold, four internal current control loops guarantee the same dc current level in each three-phase rectifier and limit the short-circuit currents. For the output slow dynamics, an external cascaded output voltage control loop ( ...

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