A high-performance three-phase DC-voltage source-an application to a welding machine

Three-phase current-source PWM rectifiers are becoming increasingly popular as the front-end converter unit in power electronic systems due to tighter EMC regulations. In this paper, the three-phase current-type DC-voltage source with reactive power control is introduced. The control system is realized in the synchronously rotating reference frame, where the active (the DC-link voltage) and reactive power can be independently and very simply controlled with the quadrature axis components of the supply current. Also, the control system includes simple methods to compensate the reactive power drawn by the supply filter and to damp the LC filter resonance. The control methods are realized without supply current measurements, which enables the elimination of the line side current sensors since the supply current measurements are not needed either for protection in the current source converters. The proposed control system is realized using a single-chip Motorola MC68HC916Y1 microcontroller. The prototype has been tested with both a resistor and a welding machine connected to the DC-link.