Multiloop control of a unity power factor fast switching AC to DC converter

A new three-phase ac to de converter is proposed for inductive loads such as de machines or current fed inverters. The converter consists of a set of fast electronic switches and a small three-phase LC-filter. It permits the control of the load current while maintaining almost sinusoidal currents at zero phase displacement in the mains. An analysis of the circuit leads to the definition of a complex transfer vector k which governs the interaction between the ac side and the de side. During operation the modulus and the argument of the transfer vector are varied using a special amplitude and angle modulation technique for complex quantities. To facilitate closed loop control the state variables of the system are subjected to a coordinate transformation. The transformed variables are processed in a multiloop control system so as to maintain the desired operating conditions.