Application of optimal and suboptimal current injection in twelve-pulse three-phase diode rectifiers

Two methods of current injection applied to reduce input current THD of twelve-pulse three-phase diode rectifiers are proposed in this paper. The methods are optimal and suboptimal current injection. In the case of the optimal current injection, THD of the input currents is zero, and the currents are in phase with corresponding input voltages. In the case of suboptimal current injection, THD of the input currents is 1.016%, while the power factor is 0.9999. In comparison to conventional twelve-pulse three-phase rectifiers, that provide THD of the input currents of 15.22%, significant improvement is achieved for the price of two additional transformers with low VA rating, and dissipation of less than 2.5% of the output power in the current injection system. Proposed solutions are analyzed and compared. Both of the methods are verified by simulation. Experimental verification of the suboptimal current injection is performed on an 1.8 kW rectifier model.