Active Harmonic Reduction Using DC-Side Current Injection Applied in a Novel Large Current Rectifier Based on Fork-Connected Autotransformer

In this paper, a novel large current rectifier using the fork-connected autotransformer and dc-side current injection method is proposed. The fork-connected autotransformer outputs two sets of three-phase voltages with 60° phase difference, and feeds two three-phase half-wave rectifiers. Compared with the isolated line-frequency transformer, the proposed autotransformer has lower kilovoltampere (kVA) rating under the same load power. An optimal designed single-phase full-bridge inverter is used to inject the compensation currents into the dc side of the two three-phase half-wave rectifier, which can reduce the harmonics in input line current to be an acceptable level. The kVA rating of the single-phase full-bridge inverter is very lower, and the proposed large current rectifier draws nearly sinusoidal currents from the ac main after using the dc-side injection. A 4 kW prototype is set up to validate the theoretical analysis and evaluate the performance.